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Letters

Facile Fabrication of Superomniphobic Polymer Hierarchical Structures for Directional Droplet Movement
Hanmin Jang - ,
Heung Soo Lee - ,
Kwan-Soo Lee - , and
Dong Rip Kim *
We report a facile method for fabricating polymer hierarchical structures, which are the engineered, ratchet-like microscale structures with nanoscale dimples, for the directional movement of droplets. The fabricated polymer hierarchical structures with no surface modifier show hydrophobic, superhydrophobic, or omniphobic characteristics depending on their intrinsic polymer properties. Further treatment with a surface modifier endows the polymer surfaces with superomniphobicity. The fabricated polymer substrates with no surface modifier enable the movement of the water droplet along the designed track at almost no inclination of the substrate.

Injectable Self-Healing Hydrogel with Antimicrobial and Antifouling Properties
Lin Li - ,
Bin Yan *- ,
Jingqi Yang - ,
Weijuan Huang - ,
Lingyun Chen - , and
Hongbo Zeng *
Microbial adhesion, biofilm formation and associated microbial infection are common challenges faced by implanted biomaterials (e.g., hydrogels) in bioengineering applications. In this work, an injectable self-healing hydrogel with antimicrobial and antifouling properties was prepared through self-assembly of an ABA triblock copolymer employing catechol functionalized polyethylene glycol (PEG) as A block and poly{[2-(methacryloyloxy)-ethyl] trimethylammonium iodide}(PMETA) as B block. This hydrogel exhibits excellent thermosensitivity, and can effectively inhibit the growth of E. coli (>99.8% killing efficiency) and prevent cell attachment. It can also heal autonomously from repeated damage, through mussel-inspired catechol-mediated hydrogen bonding and aromatic interactions, exhibiting great potential in bioengineering applications.

Sequential Growth of NaYF4:Yb/Er@NaGdF4 Nanodumbbells for Dual-Modality Fluorescence and Magnetic Resonance Imaging
Hui-Qin Wen - ,
Huang-Yong Peng - ,
Kun Liu - ,
Mao-Hong Bian - ,
Yun-Jun Xu - ,
Liang Dong - ,
Xu Yan - ,
Wei-Ping Xu - ,
Wei Tao - ,
Ji-Long Shen *- ,
Yang Lu *- , and
Hai-Sheng Qian *
Upconversional core–shell nanostructures have gained considerable attention due to their distinct enhanced fluorescence efficiency, multifunctionality, and specific applications. Recently, we have developed a sequential growth process to fabricate unique upconversion core–shell nanoparticles. Time evolution of morphology for the NaYF4:Yb/Er@NaGdF4 nanodumbbells has been extensively investigated. An Ostwald ripening growth mechanism has been proposed to illustrate the formation of NaYF4:Yb/Er@NaGdF4 nanodumbbells. The hydrophilic NaYF4:Yb/Er@NaGdF4 core–shell nanodumbbells exhibited strong upconversion fluorescence and showed higher magnetic resonance longitudinal relaxivity (r1 = 7.81 mM–1 s–1) than commercial contrast agents (Gd-DTPA). NaYF4:Yb/Er@NaGdF4 nanodumbbells can serve as good candidates for high efficiency fluorescence and magnetic resonance imaging.

Ferroelectric Zinc Oxide Nanowire Embedded Flexible Sensor for Motion and Temperature Sensing
Sung-Ho Shin - ,
Dae Hoon Park - ,
Joo-Yun Jung - ,
Min Hyung Lee - , and
Junghyo Nah *
We report a simple method to realize multifunctional flexible motion sensor using ferroelectric lithium-doped ZnO-PDMS. The ferroelectric layer enables piezoelectric dynamic sensing and provides additional motion information to more precisely discriminate different motions. The PEDOT:PSS-functionalized AgNWs, working as electrode layers for the piezoelectric sensing layer, resistively detect a change of both movement or temperature. Thus, through the optimal integration of both elements, the sensing limit, accuracy, and functionality can be further expanded. The method introduced here is a simple and effective route to realize a high-performance flexible motion sensor with integrated multifunctionalities.

Ultrafast Nanofiltration through Large-Area Single-Layered Graphene Membranes
Yanzhe Qin - ,
Yongyou Hu *- ,
Stephan Koehler - ,
Liheng Cai - ,
Junjie Wen - ,
Xiaojun Tan - ,
Weiwei L. Xu - ,
Qian Sheng - ,
Xu Hou - ,
Jianming Xue - ,
Miao Yu *- , and
David Weitz
Perforated single-layered graphene has demonstrated selectivity and flux that is orders of magnitude greater than state-of-the-art polymer membranes. However, only individual graphene sheets with sizes up to tens of micrometers have been successfully fabricated for pressurized permeation studies. Scaling-up and reinforcement of these atomic membranes with minimum cracks and pinholes remains a major hurdle for practical applications. We develop a large-area in situ, phase-inversion casting technique to create 63 cm2 high-quality single-layered perforated graphene membranes for ultrafast nanofiltration that can operate at pressures up to 50 bar. This result demonstrates the feasibility of our technique for creating robust large-area, high quality, single-layered graphene and its potential use as a pressurized nanofiltration membrane.

Reversible Light-Switching of Enzymatic Activity on Orthogonally Functionalized Polymer Brushes
Matthias Dübner - ,
Victor J. Cadarso - ,
Tugce N. Gevrek - ,
Amitav Sanyal - ,
Nicholas D. Spencer - , and
Celestino Padeste *
Copolymer brushes, composed of glycidyl methacrylate and a furan-protected maleimide-containing monomer, were grafted from radical initiators at the surface of irradiation-activated fluoropolymer foils. After postpolymerization modification with enzymatically active microperoxidase-11 and photochromic spiropyran moieties, the polymer brushes catalyzed the oxidation of 3,3′5,5′-tetramethylbenzidine. Exposure to either UV or visible-light allowed switching the turnover by more than 1 order of magnitude, as consequence of the reversible, light-induced spiropyran-merocyanine transition. The modified samples were integrated into an optofluidic device that allowed the reversible switching of enzymatic activity for several cycles under flow, validating the potential for application in smart lab-on-a-chip systems.

Unprecedented Development of Ultrahigh Expansion Injection-Molded Polypropylene Foams by Introducing Hydrophobic-Modified Cellulose Nanofibers
Long Wang - ,
Shota Ishihara - ,
Yuta Hikima - ,
Masahiro Ohshima *- ,
Takafumi Sekiguchi - ,
Akihiro Sato - , and
Hiroyuki Yano
Herein, an ultrahigh 18-fold expansion of isotactic polypropylene (iPP)/cellulose nanofiber (CNF) nanocomposite foams was achieved for the first time using a core-back foam injection molding technique. It was found that CNFs were well dispersed and aligned along the cell wall in the core-back direction. Interestingly, the formations of a hybrid shish-kebab of CNFs and classic shish-kebab of PP were simultaneously achieved in the PP/CNF composites. Finally, we proposed that the combination of local strong melt strength, probably resulting from the strong alignment of CNFs and subsequent formation of hybrid shish-kebab structures, and weak melt strength in the unreinforced PP melt might be the driving force for remarkably enhancing the PP foamability.

Achieving Ultralow Fouling under Ambient Conditions via Surface-Initiated ARGET ATRP of Carboxybetaine
Daewha Hong - ,
Hsiang-Chieh Hung - ,
Kan Wu - ,
Xiaojie Lin - ,
Fang Sun - ,
Peng Zhang - ,
Sijun Liu - ,
Keith E. Cook - , and
Shaoyi Jiang *
We achieved ultralow fouling on target surfaces by controlled polymerization of carboxybetaine under ambient conditions. The polymerization process for grafting polymer films onto the surfaces was carried out in air and did not require any deoxygenation step or specialized equipment. This method allows one to conveniently introduce a nonfouling polymer network onto large substrates.

Synthesis of Multifunctional Cationic Poly(p-phenylenevinylene) for Selectively Killing Bacteria and Lysosome-Specific Imaging
Zhuo Chen - ,
Huanxiang Yuan *- , and
Haiyan Liang
In this work, a cationic polymer was synthesized to bear quaternized N-methyl-imidazole groups in the side chains. Positively charged PPV-M could selectively bind to Gram-negative and Gram-positive bacteria over fungi and exhibit enhanced antibacterial activity with the aid of white light because PPV-M could sensitize oxygen to generate reactive oxygen species (ROS) that would damage bacteria. In addition, green fluorescent and positively charged PPV-M has the ability to enter mammalian cells and be specifically accumulated in lysosome. Moreover, PPV-M could stay in live cells for a relatively long time, which implies that PPV-M has the potential to be a long-term imaging agent.

Collagen-Based Photoactive Agent for Tissue Bonding
Justina Pupkaite - ,
Manuel Ahumada - ,
Sarah Mclaughlin - ,
Maha Temkit - ,
Sura Alaziz - ,
Richard Seymour - ,
Marc Ruel - ,
Irene Kochevar - ,
May Griffith - ,
Erik J. Suuronen *- , and
Emilio I. Alarcon *
Using a combination of methacrylated collagen and the photosensitizer rose Bengal, a new light-activated biomimetic material for tissue sutureless bonding was developed. This formulation was cross-linked using green light. In vivo tests in mice demonstrate the suitability of the material for sutureless wound closure.
Articles

Defects and Charge-Trapping Mechanisms of Double-Active-Layer In–Zn–O and Al–Sn–Zn–In–O Thin-Film Transistors
Youngin Goh - ,
Taeho Kim - ,
Jong-Heon Yang - ,
Ji Hun Choi - ,
Chi-Sun Hwang - ,
Sung Haeng Cho - , and
Sanghun Jeon *
Active matrix organic light-emitting diodes (AMOLEDs) are considered to be a core component of next-generation display technology, which can be used for wearable and flexible devices. Reliable thin-film transistors (TFTs) with high mobility are required to drive AMOLEDs. Recently, amorphous oxide TFTs, due to their high mobility, have been considered as excellent substitutes for driving AMOLEDs. However, the device instabilities of high-mobility oxide TFTs have remained a key issue to be used in production. In this paper, we present the charge-trapping and device instability mechanisms of high-mobility oxide TFTs with double active layers, using In–Zn–O (IZO) and Al-doped Sn–Zn–In–O (ATZIO) with various interfacial IZO thicknesses (0–6 nm). To this end, we employed microsecond fast current–voltage (I–V), single-pulsed I–V, transient current, and discharge current analysis. These alternating-current device characterization methodologies enable the extraction of various trap parameters and defect densities as well as the understanding of dynamic charge transport in double-active-layer TFTs. The results show that the number of defect sites decreases with an increase in the interfacial IZO thickness. From these results, we conclude that the interfacial IZO layer plays a crucial role in minimizing charge trapping in ATZIO TFTs.
Biological and Medical Applications of Materials and Interfaces

Development of Bioactive PEGylated Nanostructured Platforms for Sequential Delivery of Doxorubicin and Imatinib to Overcome Drug Resistance in Metastatic Tumors
Biki Gupta - ,
Thiruganesh Ramasamy - ,
Bijay Kumar Poudel - ,
Shiva Pathak - ,
Shobha Regmi - ,
Ju Yeon Choi - ,
Youlim Son - ,
Raj Kumar Thapa - ,
Jee-Heon Jeong - ,
Jae Ryong Kim - ,
Han-Gon Choi - ,
Chul Soon Yong *- , and
Jong Oh Kim *
Metastasis of cancers accounts for almost all cancer-related deaths. In this study, we report a PEGylated nanostructured platform for coadministration of doxorubicin (DOX) and imatinib (IMT) intended to effectively inhibit metastatic tumors. The DOX and IMT coloaded nanostructured system (DOX/IMT-N) is characterized by an excellent encapsulation potential for both drugs and shows sequential and sustained drug release in vitro. DOX/IMT-N significantly inhibited the in vitro proliferation of MDA-MB-231 and SK-MEL-28 cells. The inhibitory effect on in vitro proliferation of the cells was significantly greater than the effect of free DOX, DOX/IMT cocktail, or the nanostructured system housing DOX only (DOX-N). DOX/IMT-N remarkably enhanced cellular drug uptake, resulting in enhanced apoptosis, caused by significant increases in the expression levels of apoptotic marker proteins. Intravenous administration of DOX/IMT-N to MBA-MB-231 xenograft tumor-bearing mice resulted in significantly improved inhibition of tumor progression compared to that with DOX, DOX/IMT, or DOX-N. Therefore, the nanostructured DOX/IMT-N system could potentially aid in overcoming drug resistance in metastatic tumors and improve the effectiveness of metastatic tumor therapeutics.

Incorporation of Human-Platelet-Derived Growth Factor-BB Encapsulated Poly(lactic-co-glycolic acid) Microspheres into 3D CORAGRAF Enhances Osteogenic Differentiation of Mesenchymal Stromal Cells
Saktiswaren Mohan - ,
Hanumantharao Balaji Raghavendran *- ,
Puvanan Karunanithi - ,
Malliga Raman Murali - ,
Sangeetha Vasudevaraj Naveen - ,
Sepehr Talebian - ,
Mohammad Mehrali - ,
Mehdi Mehrali - ,
Elango Natarajan - ,
Chee Ken Chan - , and
Tunku Kamarul *
Tissue engineering aims to generate or facilitate regrowth or healing of damaged tissues by applying a combination of biomaterials, cells, and bioactive signaling molecules. In this regard, growth factors clearly play important roles in regulating cellular fate. However, uncontrolled release of growth factors has been demonstrated to produce severe side effects on the surrounding tissues. In this study, poly(lactic-co-glycolic acid) (PLGA) microspheres (MS) incorporated three-dimensional (3D) CORAGRAF scaffolds were engineered to achieve controlled release of platelet-derived growth factor-BB (PDGF-BB) for the differentiation of stem cells within the 3D polymer network. Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and microtomography were applied to characterize the fabricated scaffolds. In vitro study revealed that the CORAGRAF-PLGA-PDGF-BB scaffold system enhanced the release of PDGF-BB for the regulation of cell behavior. Stromal cell attachment, viability, release of osteogenic differentiation markers such as osteocalcin, and upregulation of osteogenic gene expression exhibited positive response. Overall, the developed scaffold system was noted to support rapid cell expansion and differentiation of stromal cells into osteogenic cells in vitro for bone tissue engineering applications.

Antibacterial Performance of a PCL–PDMAEMA Blend Nanofiber-Based Scaffold Enhanced with Immobilized Silver Nanoparticles
Fernanda G. Santos - ,
Letícia C. Bonkovoski - ,
Francielle P. Garcia - ,
Thelma S. P. Cellet - ,
Maria A. Witt - ,
Celso V. Nakamura - ,
Adley F. Rubira - , and
Edvani C. Muniz *
In the present study, nanofiber meshes (NFs), composed of polycaprolactone and poly[(2-dimethylamino)ethyl methacrylate] at 80/20 and 50/50 PCL/PDMAEMA blend ratios, were obtained through electrospinning. Silver nanoparticles (AgNPs) formed in situ were then immobilized on NF surfaces through adsorption processes at different pHs. It was possible to observe that the amount of NF-AgNPs can be tuned by changing the pH of AgNPs immobilization and the PCL/PDMAEMA ratio in the blend. The neat NF and NF-AgNPs were characterized with respect to their morphology and mechanical properties. The effects of AgNPs on the antibacterial activities and cytotoxicity of meshes were also evaluated. The antibacterial performance of such NF was improved by the presence of AgNPs. The NF-AgNPs presented good antibacterial effect against S. aureus and partial toxicity against E. coli and P. aeruginosa. Also, compared with neat PCL/PDMAEMA the NF-AgNPs presented lower cytotoxicity against VERO cells, showing their potential for applications in tissue engineering for different types of cell growth.

Tumor Microenvironment Activated Membrane Fusogenic Liposome with Speedy Antibody and Doxorubicin Delivery for Synergistic Treatment of Metastatic Tumors
Hongzhang Deng - ,
Kun Song - ,
Xuefei Zhao - ,
Yanan Li - ,
Fei Wang - ,
Jianhua Zhang *- ,
Anjie Dong - , and
Zhihai Qin *
Metastasis is the principal event leading to breast cancer death. Discovery of novel therapeutic approaches that are specific in targeting tumor metastasis factors while at the same time are an effective treatment of the tumor is urgently required. S100A4 protein is a key player in promoting metastasis and sequestrating the effect of tumor-suppressor protein p53. Here, a tumor microenvironment activated membrane fusogenic liposome was prepared to deliver rapidly anti-S100A4 antibody and doxorubicin into the cytoplasm directly in a fusion-dependent manner in order to bypass the cellular endocytosis to avoid the inefficient escape and degradation in the acidic endosome. After intracellular S100A4 blockage with anti-S100A4 antibody, the cytoskeleton of breast cancer 4T1 cells was rearranged and cell motility was suppressed. In the meantime, the antitumor effect of doxorubicin was enormously enhanced by reversing the effect of S100A4 on the sequestration of tumor-suppressor protein p53. Importantly, both local growth and metastasis of 4T1 cells were inhibited in a xenograft mouse model. Together, the speedy delivery of antibody and doxorubicin into cytoplasm based on a new membrane fusogenic liposome was an innovative approach for metastatic breast cancer treatment.

Modulating Three-Dimensional Microenvironment with Hyaluronan of Different Molecular Weights Alters Breast Cancer Cell Invasion Behavior
Yu-fang Zhao - ,
Shu-pei Qiao - ,
Shu-liang Shi - ,
Li-fen Yao - ,
Xiao-lu Hou - ,
Chun-feng Li - ,
Feng-Huei Lin - ,
Kai Guo - ,
Alaka Acharya - ,
Xiong-biao Chen - ,
Yongzhan Nie - , and
Wei-ming Tian *
Hyaluronan (HA), a polymer with various molecular weights (MW) found in tumor microenvironments, is associated with malignant progression of breast cancer. Reducing the amount of high-MW HA in the microenvironment by hyaluronidase is a promising approach for breast cancer treatment. However, whether the generation of HA fragments negatively affects breast cancer cells remains to be determined. Furthermore, HA forms three-dimensional (3D) networks by cross-linking with other extracellular molecules to function. Therefore, a model mimicking the cross-linked HA network is required to determine the effect of HA fragments on breast cancer cells. To clarify the differential roles of low (HA35) versus high (HA117) MW HA on cancer cell phenotype, a 3D culture system was set up by covalently cross-linking HA with alginate and investigating the behavior of 4T-1 and SKBR3 breast cancer cells alongside a two-dimensional (2D) control. The results show the invasion and migration abilities of 4T-1 and SKBR3 cells are significantly enhanced by the presence of HA35 but inhibited by HA117 in both 2D monolayers and 3D spheroids. The differential effects of HA35 and HA117 on cancer cell epithelial–mesenchymal transition (EMT) phenotype were further confirmed in terms of differential regulation of E-cadherin and vimentin as important EMT markers at both the cellular and mRNA levels. Additional experiments show the CD44–Twist signaling pathway might be involved in the differential effects of HA35 and HA117. These results have important implications with respect to understanding the role of HA in breast cancer development and for the design of therapeutic approaches based on the eradication of HA with hyaluronidase.

Osteogenic Lineage Commitment of Adipose-Derived Stem Cells Is Predetermined by Three-Dimensional Cell Accumulation on Micropatterned Surface
Yuichi Furuhata - ,
Toru Yoshitomi - ,
Yuka Kikuchi - ,
Miho Sakao - , and
Keitaro Yoshimoto *
Lineage commitment of stem cells is mainly regulated by their microenvironments, which comprise soluble growth factors, extracellular matrix, mechanical forces, and cell density. Although numerous studies have investigated stem cell response to these factors in two-dimensional (2D) culture, little is known about that in 3D culture. Here, we studied effects of 3D cell accumulation levels on the differentiation behavior of mesenchymal stem cells (MSCs) by using a micropatterned surface. After induction of 3D-cultured MSCs on the surface, their osteogenic differentiation was significantly promoted, while adipogenic differentiation was not. This differentiation behavior of densely packed MSCs in 3D culture is unlike that in 2D culture. Moreover, to determine the contributing factor of this commitment, the relationship between 3D cell accumulation levels and their differentiation potential was studied before differentiation induction. A series of MSCs with varied 3D accumulation levels were constructed on the micropatterned surface, where the accumulated MSCs were not in hypoxic environment. Interestingly, with increasing 3D accumulation levels, MSCs enhanced their osteogenic potential but repressed adipogenic potential in the gene expression level. These results suggest that preconditioned 3D microenvironments with high cell accumulation levels promote osteogenic differentiation of MSCs and their accumulation levels help in regulating MSC differentiation.

Multifunctional Theranostic Agent of Cu2(OH)PO4 Quantum Dots for Photoacoustic Image-Guided Photothermal/Photodynamic Combination Cancer Therapy
Wei Guo - ,
Zhenyu Qiu - ,
Chongshen Guo *- ,
Dandan Ding - ,
Tianchan Li - ,
Fei Wang - ,
Jianzhe Sun - ,
Nannan Zheng - , and
Shaoqin Liu *
Image-guided phototherapy is considered to be a prospective technique for cancer treatment because it can provide both oncotherapy and bioimaging, thus achieving an optimized therapeutic efficacy and higher treatment accuracy. Compared to complicated systems with multiple components, using a single material for this multifunctional purpose is preferable. In this work, we strategically fabricated poly(acrylic acid)- (PAA-) coated Cu2(OH)PO4 quantum dots [denoted as Cu2(OH)PO4@PAA QDs], which exhibit a strong near-infrared photoabsorption ability. As a result, an excellent photothermal conversion ability and the photoactivated formation of reactive oxygen species could be realized upon NIR irradiation, concurrently meeting the basic requirements for photothermal and photodynamic therapies. Moreover, phototherapeutic investigations on both cervical cancer cells in vitro and solid tumors of an in vivo mice model illustrated the effective antitumor effects of Cu2(OH)PO4@PAA upon 1064-nm laser irradiation, with no detectable lesions in major organs during treatment. Meanwhile, Cu2(OH)PO4@PAA is also an exogenous contrast for photoacoustic tomography (PAT) imaging to depict tumors under NIR irradiation. In brief, the Cu2(OH)PO4@PAA QDs prepared in this work are expected to serve as a multifunctional theranostic platform.

Development of Laser-Structured Liquid-Infused Titanium with Strong Biofilm-Repellent Properties
Katharina Doll *- ,
Elena Fadeeva - ,
Joern Schaeske - ,
Tobias Ehmke - ,
Andreas Winkel - ,
Alexander Heisterkamp - ,
Boris N. Chichkov - ,
Meike Stiesch - , and
Nico S. Stumpp *
Medical implants are commonly used in modern medicine but still harbor the risk of microbial infections caused by bacterial biofilms. As their retrospective treatment is difficult, there is a need for biomedical materials that inhibit bacterial colonization from the start without using antibacterial agents, as these can promote resistance development. The promising concept of slippery liquid-infused porous surfaces (SLIPS) possesses enormous potential for this purpose. In the present study, this principle was applied to titanium, a common material in implantology, and its biofilm-repellent properties were demonstrated. To simplify prospective approval of the medical device and to avoid chemical contamination, surface structuring was performed by ultrashort pulsed laser ablation. Four different structures (hierarchical micro- and nanosized spikes, microsized grooves, nanosized ripples, and unstructured surfaces) and five infusing perfluoropolyethers of different viscosities were screened; the best results were obtained with the biomimetic, hierarchical spike structure combined with lubricants of medium viscosities (20–60 cSt at 37 °C, 143 AZ, and GPL 104). The surfaces exhibited extremely low contact angle hysteresis, as is typical for liquid-infused materials and a reliable 100-fold reduction of human oral pathogen Streptococcus oralis biofilms. This characteristic was maintained after exposure to shear forces and gravity. The titanium SLIPS also inhibited adherence of human fibroblasts and osteoblasts. Toxicity tests supported the explanation that solely the surface’s repellent properties are responsible for the vigorous prevention of the adhesion of bacteria and cells. This use of physically structured and liquid-infused titanium to avoid bioadhesion should support the prevention of bacterial implant-associated infections without the use of antibacterial agents.

Enhanced Fluorescence ELISA Based on HAT Triggering Fluorescence “Turn-on” with Enzyme–Antibody Dual Labeled AuNP Probes for Ultrasensitive Detection of AFP and HBsAg
Yudong Wu - ,
Weisheng Guo - ,
Weipan Peng - ,
Qian Zhao - ,
Jiafang Piao - ,
Bo Zhang - ,
Xiaoli Wu - ,
Hanjie Wang - ,
Xiaoqun Gong *- , and
Jin Chang *
At present, enzyme-linked immunosorbent assay (ELISA) is considered to be the most appropriate approach in clinical biomarker detection, with good specificity, low cost, and straightforward readout. However, unsatisfactory sensitivity severely hampers its wide application in clinical diagnosis. Herein, we designed a new kind of enhanced fluorescence enzyme-linked immunosorbent assay (FELISA) based on the human alpha-thrombin (HAT) triggering fluorescence “turn-on” signals. In this system, detection antibodies (Ab2) and HAT were labeled on the gold nanoparticles (AuNPs) to form the detection probes, and a bisamide derivative of Rhodamine110 with fluorescence quenched served as the substrate of HAT. After the sandwich immunoreaction, HAT on the sandwich structure could catalyze the cleavage of the fluorescence-quenched substrate, leading to a strong fluorescence signal for sensing ultralow levels of alpha fetoprotein (AFP) and hepatitis B virus surface antigen (HBsAg). Under the optimized reaction conditions, AFP and HBsAg were detected at the ultralow concentrations of 10–8 ng mL–1 and 5 × 10–4 IU mL–1, respectively, which were at least 104 times lower than those of the conventional fluorescence assay and 106 times lower than those of the conventional ELISA. In addition, we further discussed the efficiency of the sensitive FELISA in clinical serum samples, showing great potential in practical applications.

Peptide-Decorated Tunable-Fluorescence Graphene Quantum Dots
Bedanga Sapkota - ,
Abdelkrim Benabbas - ,
Hao-Yu Greg Lin - ,
Wentao Liang - ,
Paul Champion - , and
Meni Wanunu *
We report here the synthesis of graphene quantum dots with tunable size, surface chemistry, and fluorescence properties. In the size regime 15–35 nm, these quantum dots maintain strong visible light fluorescence (mean quantum yield of 0.64) and a high two-photon absorption (TPA) cross section (6500 Göppert–Mayer units). Furthermore, through noncovalent tailoring of the chemistry of these quantum dots, we obtain water-stable quantum dots. For example, quantum dots with lysine groups bind strongly to DNA in solution and inhibit polymerase-based DNA strand synthesis. Finally, by virtue of their mesoscopic size, the quantum dots exhibit good cell permeability into living epithelial cells, but they do not enter the cell nucleus.

Transdermal Gene Delivery by Functional Peptide-Conjugated Cationic Gold Nanoparticle Reverses the Progression and Metastasis of Cutaneous Melanoma
Jie Niu - ,
Yang Chu - ,
Yan-Fen Huang - ,
Yee-Song Chong - ,
Zhi-Hong Jiang - ,
Zheng-Wei Mao - ,
Li-Hua Peng *- , and
Jian-Qing Gao *
Permeability barrier imposed by stratum corneum makes an extreme challenge for the topical delivery of plasmid DNA (pDNA), which is widely used in gene therapy. Existing techniques to overcome the skin barrier for bio-macromolecules delivery rely on sophisticated mechanical devices. It is still a big challenge to treat the skin cancer, for example, melanoma, that initiates in the dermal layer by topical gene therapy. To facilitate the skin penetration of pDNA deeply into the melanoma tissues, we here present a cell-penetrating peptide and cationic poly(ethyleneimine) conjugated gold nanoparticle (AuPT) that can compact the pDNAs into cationic nanocomplexes and penetrate through the intact stratum corneum without any additional enhancement used. Moreover, the AuPT is highly efficient in stimulating the intracellular uptake and nuclear targeting of the pDNAs in cells, which guarantees the effective transfection. This study provides evidence that penetrating peptide conjugated cationic gold nanoparticle offers a promising vehicle for both the skin penetration and transfection of pDNAs, possessing great potential in topical gene therapy.

Highly Efficient and Safe Delivery of VEGF siRNA by Bioreducible Fluorinated Peptide Dendrimers for Cancer Therapy
Xiaojun Cai - ,
Haofang Zhu - ,
Yanmei Zhang - , and
Zhongwei Gu *
RNA interference (RNAi) has a great promise in treating various acquired and hereditary diseases. However, it remains highly desirable to develop new delivery system to circumvent complex extra- and intracellular barriers for successful clinical translation. Here, we report on a versatile polymeric vector, bioreducible fluorinated peptide dendrimers (BFPD), for efficient and safe small interfering RNA (siRNA) delivery. In virtue of skillfully integrating all of the unique advantages of reversible cross-linking, fluorination, and peptide dendrimers, this novel vector can surmount almost all extra- and intracellular barriers associated with local siRNA delivery through highly improved physiological stability and serum resistance, significantly increased intratumoral enrichment, cellular internalization, successful facilitation of endosomal escape, and cytosolic siRNA release. BFPD polyplexes, carrying small interfering vascular endothelial growth factor (siVEGF), demonstrated excellent VEGF silencing efficacy (∼65%) and a strong capability for inhibiting HeLa cell proliferation. More importantly, these polyplexes showed superior performance in long-term enrichment in the tumor sites and had a high level of tumor growth inhibition. Furthermore, these polyplexes not only exhibited excellent in vivo antitumor efficacy but also demonstrated superior biocompatibility, compared with LPF2000, both in vivo and in vitro. These findings indicate that BFPD is an efficient and safe siRNA delivery system and has remarkable potential for RNAi-based cancer treatment.

Efficient Enrichment and Analyses of Bacteria at Ultralow Concentration with Quick-Response Magnetic Nanospheres
Cong-Ying Wen - ,
Yong-Zhong Jiang - ,
Xi-You Li - ,
Man Tang - ,
Ling-Ling Wu - ,
Jiao Hu - ,
Dai-Wen Pang - , and
Jing-Bin Zeng *
Enrichment and purification of bacteria from complex matrices are crucial for their detection and investigation, in which magnetic separation techniques have recently show great application advantages. However, currently used magnetic particles all have their own limitations: Magnetic microparticles exhibit poor binding capacity with targets, while magnetic nanoparticles suffer slow magnetic response and high loss rate during treatment process. Herein, we used a highly controllable layer-by-layer assembly method to fabricate quick-response magnetic nanospheres (MNs), and with Salmonella typhimurium as a model, we successfully achieve their rapid and efficient enrichment. The MNs combined the advantages of magnetic microparticles and nanoparticles. On the one hand, the MNs had a fast magnetic response, and almost 100% of the MNs could be recovered by 1 min attraction with a simple magnetic scaffold. Hence, using antibody conjugated MNs (immunomagnetic nanospheres, IMNs) to capture bacteria hardly generated loss and did not need complex separation tools or techniques. On the other hand, the IMNs showed much excellent capture capacity. With 20 min interaction, almost all of the target bacteria could be captured, and even only one bacterium existing in the samples was not missed, comparing with the immunomagnetic microparticles which could only capture less than 50% of the bacteria. Besides, the IMNs could achieve the same efficient enrichment in complex matrices, such as milk, fetal bovine serum, and urine, demonstrating their good stability, strong anti-interference ability, and low nonspecific adsorption. In addition, the isolated bacteria could be directly used for culture, polymerase chain reaction (PCR) analyses, and fluorescence immunoassay without a release process, which suggested our IMNs-based enrichment strategy could be conveniently coupled with the downstream identification and analysis techniques. Thus, the MNs provided by this work showed great superiority in bacteria enrichment, which would be a promising tool for bacteria detection and investigation.

Synergistic Cisplatin/Doxorubicin Combination Chemotherapy for Multidrug-Resistant Cancer via Polymeric Nanogels Targeting Delivery
Haiqiu Wu - ,
Haojie Jin - ,
Cun Wang - ,
Zihao Zhang - ,
Haoyu Ruan - ,
Luyan Sun - ,
Chen Yang - ,
Yongjing Li - ,
Wenxin Qin *- , and
Changchun Wang *
Combination chemotherapy has been proposed to achieve synergistic effect and minimize drug dose for cancer treatment in clinic application. In this article, the stimuli-responsive polymeric nanogels (<100 nm in size) based on poly(acrylic acid) were designed as codelivery system for doxorubicin and cisplatin to overcome drug resistance. By chelation, electrostatic interaction, and π–π stacking interactions, the nanogels could encapsulate doxorubicin and cisplatin with designed ratio and high capacity. Compared with free drugs, the nanogels could deliver more drugs into MCF-7/ADR cells. Significant accumulation in tumor tissues was observed in the biodistribution experiments. The in vitro antitumor studies demonstrated the superior cell-killing activity of the nanogel drug delivery system with a combination index of 0.84, which indicated the great synergistic effect. All the antitumor experimental data revealed that the combination therapy was effective for the multidrug-resistant MCF-7/ADR tumor with reduced side effects.

Facile Preparation of Poly(lactic acid)/Brushite Bilayer Coating on Biodegradable Magnesium Alloys with Multiple Functionalities for Orthopedic Application
Lei Zhang - ,
Jia Pei *- ,
Haodong Wang - ,
Yongjuan Shi - ,
Jialin Niu - ,
Feng Yuan - ,
Hua Huang - ,
Hua Zhang - , and
Guangyin Yuan
Recently magnesium and its alloys have been proposed as a promising next generation orthopedic implant material, whereas the poor corrosion behavior, potential cytotoxicity, and the lack of efficient drug delivery system have limited its further clinical application, especially for the local treatment of infections or musculoskeletal disorders and diseases. In this study, we designed and developed a multifunctional bilayer composite coating of poly(lactic acid)/brushite with high interfacial bonding strength on a Mg–Nd–Zn–Zr alloy, aiming to improve the biocorrosion resistance and biocompatibility of the magnesium-based substrate, as well as to further incorporate the biofunctionality of localized drug delivery. The composite coating consisted of an inner layer of poly(lactic acid) serving as a drug carrier and an outer layer composed of brushite generated through chemical solution deposition, where a facile pretreatment of UV irradiation was applied to the poly(lactic acid) coating to facilitate the heterogeneous nucleation of brushite. The in vitro degradation results of electrochemical measurements and immersion tests indicated a considerable reduction of magnesium degradation provided the composite coating. A systematic investigation of cellular response with cell viability, adhesion, and ALP assays confirmed the coated Mg alloy induced no toxicity to MC3T3-E1 osteoblastic cells but rather fostered cell attachment and proliferation and promoted osteogenic differentiation, revealing excellent biosafety and biocompatibility and enhanced osteoinductive potential. An in vitro drug release profile of paclitaxel from the composite coating was monitored with UV–vis spectroscopy, showing an alleviated initial burst release and a sustained and controlled release feature of the drug-loaded composite coating. These findings suggested that the bilayer poly(lactic acid)/brushite coating provided effective protection for Mg alloy, greatly enhanced cytocompatibility and bioactivity, and, moreover, possessed local drug delivery capability; hence magnesium alloy with poly(lactic acid)/brushite coating presents great potential in orthopedic clinical applications, especially for localized bone therapy.

Enhancement in Sustained Release of Antimicrobial Peptide from Dual-Diameter-Structured TiO2 Nanotubes for Long-Lasting Antibacterial Activity and Cytocompatibility
Yanni Zhang - ,
Lan Zhang - ,
Bo Li - , and
Yong Han *
Novel films on Ti-based orthopedic implants for localized antimicrobial delivery, which comprises dual-diameter TiO2 nanotubes with the inner layers of compact and fluorine-free oxide tightly bonding to Ti, were formed by voltage-increased anodization with F– sedimentation procedure. The nanotubes were closely aligned and structured with upper 35 and 70 nm diametric tubes as nanocaps, respectively, and the underlying 140 nm diametric tubes as nanoreservoirs. Followed by loading ponericin G1 (a kind of antimicrobial peptide (AMP)) into the dual-diameter nanotubes with vacuum-assisted physisorption, the resultant films were investigated for loading efficiency and release kinetics of AMP, antibacterial activity against Staphylococcus aureus, and osteoblastic compatibility, together with the AMP-loaded single-diameter (140 nm) nanotube film. The loaded films had no statistical difference in the loading efficiency of AMP and revealed burst release within 6 h followed by steady release of AMP in phosphate-buffered solution. At day 42, almost all of AMP was released from the single-diameter nanotube film. However, the dual-diameter nanotube films loaded with AMP still showed sustained release at least up to 60 days, and the sustained efficacy was enhanced with decreasing diameter of nanocaps. In the case of nominal AMP loading amount of 125 μg, the resultant 35 nm capped dual-diameter nanotube film exhibited significant short- and long-term (even for 49 days) antibacterial activity not only against planktonic bacteria, which is ascribed to the release-killing efficacy of AMP, but also against adhered bacteria, which is ascribed to the AMP-derived killing efficacy and the nanocaps-derived adhesion resistance. Moreover, this loaded film presented cytocompatibility comparative to that of Ti but higher than that of the other AMP-loaded films. Increasing the nominal loading amount of AMP to 200 μg improved antibacterial activity but gave rise to obvious cytotoxicity of the loaded films.

Microbead-Based Platform for Multiplex Detection of DNA and Protein
Xiangjun Liu *- ,
Tao Bing - , and
Dihua Shangguan *
We present a novel microbead-based detection platform as a simple and universal strategy for simultaneous determination of multiple biomolecules. This platform is composed of streptavidin coated uniform-sized polystyrene microbeads, dye and biotin-labeled ssDNA or aptamer probes, and quencher-labeled complementary sequences. By this method, upon target binding to the probes, quencher strand dissociation is triggered, which results in fluorescence reactivation of the microbead linked probes. The fluorescence variation is readily monitored by flow cytometry and with a high sensitivity. Explicitly, this microbead-based detection platform shows a high sensitivity for target DNA with a detection limit as low as 0.20 nM, alongside good selectivity from one-base mismatched DNA. This novel platform also shows good selectivity and high sensitivity for protein detection when aptamer is used as a probe. The detection limit for lysozyme is as low as 8.56 nM. Moreover, simultaneous detection of multiple targets has been achieved via incorporating different dye-labeled probes on the microbeads concurrently. We have also applied this developed strategy to the detection of target DNA in human serum. This strategy can be easily extended to other targets through simple probe and quencher variation.

Bifunctional Succinylated ε-Polylysine-Coated Mesoporous Silica Nanoparticles for pH-Responsive and Intracellular Drug Delivery Targeting the Colon
Chau T. H. Nguyen - ,
Richard I. Webb - ,
Lynette K. Lambert - ,
Ekaterina Strounina - ,
Edward C. Lee - ,
Marie-Odile Parat - ,
Michael A. McGuckin - ,
Amirali Popat - ,
Peter J. Cabot - , and
Benjamin P. Ross *
Conventional oral drug formulations for colonic diseases require the administration of high doses of drug to achieve effective drug concentrations at the target site. However, this exposes patients to serious systemic toxicity in order to achieve efficacy. To overcome this problem, an oral drug delivery system was developed by loading a large amount (ca. 34% w/w) of prednisolone into 3-aminopropyl-functionalized mesoporous silica nanoparticles (MCM-NH2) and targeting prednisolone release to the colon by coating the nanoparticle with succinylated ε-polylysine (SPL). We demonstrate for the first time the pH-responsive ability of SPL as a “nanogate” to selectively release prednisolone in the pH conditions of the colon (pH 5.5–7.4) but not in the more acidic conditions of the stomach (pH 1.9) or small intestine (pH 5.0). In addition to targeting drug delivery to the colon, we explored whether the nanoparticles could deliver cargo intracellularly to immune cells (RAW 264.7 macrophages) and intestinal epithelial cells (LS 174T and Caco-2 adenocarcinoma cell lines). To trace uptake, MCM-NH2 were loaded with a cell membrane-impermeable dye, sulforhodamine B. The SPL-coated nanoparticles were able to deliver the dye intracellularly to RAW 264.7 macrophages and the intestinal epithelial cancer cells, which offers a highly promising and novel drug delivery system for diseases of the colon such as inflammatory bowel disease and colorectal cancer.

Indocyanine Green Loaded Magnetic Carbon Nanoparticles for Near Infrared Fluorescence/Magnetic Resonance Dual-Modal Imaging and Photothermal Therapy of Tumor
Saijie Song - ,
He Shen *- ,
Tao Yang - ,
Lina Wang - ,
Han Fu - ,
Huabing Chen - , and
Zhijun Zhang *
Malignant tumor incidences have been rapidly rising recently and are becoming a serious threat to human health. Herein, a multifunctional cancer targeted theranostic nanoplatform is developed by in situ growth of iron oxide magnetic nanoparticles on carbon nanoparticles, and then loaded with fluorescent dye indocyanine green (ICG@MCNPs). The loading of ICG on the nanoplatform significantly improves its photostability, and hence facilitates long-term near-infrared fluorescence (NIRF) imaging and efficient photothermal therapy (PTT) of tumor. The in vivo NIRF imaging reveals that ICG@MCNPs can be targeted to the tumor site. Moreover, in vivo magnetic resonance imaging also confirmed the efficient accumulation of ICG@MCNPs in the tumor site. Inspiringly, the subsequent PTT of tumor-bearing mice is achieved, as evidenced by the complete ablation of the tumor and the recovery of the physiological indexes to normal levels. Benefitting from its low-cost, simple preparation, and excellent dual-modal imaging and therapy, the ICG@MCNPs-based theranostic nanoplatform holds great promise in tumor-targeted nanomedicine.

Ultrathin Alumina Membranes as Scaffold for Epithelial Cell Culture from the Intestine of Rainbow Trout
Carolin Drieschner - ,
Matteo Minghetti - ,
Songmei Wu - ,
Philippe Renaud - , and
Kristin Schirmer *
Permeable membranes are indispensable for in vitro epithelial barrier models. However, currently available polymer-based membranes are low in porosity and relatively thick, resulting in a limited permeability and unrealistic culture conditions. In this study, we developed an ultrathin, nanoporous alumina membrane as novel cell culture interface for vertebrate cells, with focus on the rainbow trout (Onchorynchus mykiss) intestinal cell line RTgutGC. The new type of membrane is framed in a silicon chip for physical support and has a thickness of only 1 μm, with a porosity of 15% and homogeneous nanopores (Ø = 73 ± 21 nm). Permeability rates for small molecules, namely lucifer yellow, dextran 40, and bovine serum albumin, exceeded those of standard polyethylene terephthalate (PET) membranes by up to 27 fold. With the final goal to establish a representative model of the fish intestine for environmental toxicology, we engineered a simple culture setup, capable of testing the cellular response toward chemical exposure. Herein, cells were cultured in a monolayer on the alumina membranes and formed a polarized epithelium with apical expression of the tight junction protein ZO-1 within 14 days. Impedance spectroscopy, a noninvasive and real time electrical measurement, was used to determine cellular resistance during epithelial layer formation and chemical exposure to evaluate barrier functionality. Resistance values during epithelial development revealed different stages of epithelial maturity and were comparable with the in vivo situation. During chemical exposure, cellular resistance changed immediately when barrier tightness or cell viability was affected. Thus, our study demonstrates nanoporous alumina membranes as promising novel interface for alternative in vitro approaches, capable of allowing cell culture in a physiologically realistic manner and enabling high quality microscopy and sensitive measurement of cellular resistance.

High-Purity Magnesium Staples Suppress Inflammatory Response in Rectal Anastomoses
Jiazeng Xia - ,
Hui Chen - ,
Jun Yan - ,
Hongliu Wu - ,
Hao Wang - ,
Jian Guo - ,
Xiaonong Zhang - ,
Shaoxiang Zhang - ,
Changli Zhao *- , and
Yigang Chen *
Magnesium-based materials are promising biodegradable implants, although the impact of magnesium on rectal anastomotic inflammation is poorly understood. Thus, we investigated the inflammatory effects of high-purity Mg staples in rectal anastomoses by in vivo luciferase reporter gene expression in transgenic mice, hematoxylin-eosin staining, immunohistochemistry, and Western blotting. As expected, strong IL-1β-mediated inflammation and inflammatory cell infiltration were observed 1 day after rectal anastomoses were stapled with high-purity Mg or Ti. However, inflammation and inflammatory cell infiltration decreased more robustly 4–7 days postoperation in tissues stapled with high-purity Mg. This rapid reduction in inflammation was confirmed by immunohistochemical analysis of IL-6 and TNF-α. Western blot also suggested that the reduced inflammatory response is due to suppressed TLR4/NF-κB signaling. In contrast, MCP-1, uPAR, and VEGF were abundantly expressed, in line with the notion that expression of these proteins is regulated by feedback between the VEGF and NF-κB pathways. In vitro expression of MCP-1, uPAR, and VEGF was also similarly high in primary rectal mucosal epithelial cells exposed to extracts from Mg staples, as measured by antibody array. Collectively, the results suggest that high-purity Mg staples suppress the inflammatory response during rectal anastomoses via TLR4/NF-κB and VEGF signaling.

Small-Sized mPEG–PLGA Nanoparticles of Schisantherin A with Sustained Release for Enhanced Brain Uptake and Anti-Parkinsonian Activity
Tongkai Chen - ,
Chuwen Li - ,
Ye Li - ,
Xiang Yi - ,
Ruibing Wang - ,
Simon Ming-Yuen Lee - , and
Ying Zheng *
Schisantherin A (SA) is a promising anti-Parkinsonism natural product. However, its poor water solubility and rapid serum clearance impose significant barriers to delivery of SA to the brain. This work aimed to develop SA in a nanoparticle formulation that extended SA circulation in the bloodstream and consequently an increased brain uptake and thus to be potentially efficacious for the treatment of Parkinson’s disease (PD). Spherical SA nanoparticles with a mean particle size of 70 nm were prepared by encapsulating SA into methoxy poly(ethylene glycol)-block-poly(d,l)-lactic-co-glycolic acid (mPEG–PLGA) nanoparticles (SA-NPs) with an encapsulation efficiency of ∼91% and drug loading of ∼28%. The in vitro release of the SA-NPs lasted for 48 h with a sustained-release pattern. Using the Madin–Darby canine kidney (MDCK) cell model, the results showed that first intact nanoparticles carrying hydrophobic dyes were internalized into cells, then the dyes were slowly released within the cells, and last both nanoparticles and free dyes were externalized to the basolateral side of the cell monolayer. Fluorescence resonance energy transfer (FRET) imaging in zebrafish suggested that nanoparticles were gradually dissociated in vivo with time, and nanoparticles maintained intact in the intestine and brain at 2 h post-treatment. When SA-NPs were orally administrated to rats, much higher Cmax and AUC0-t were observed in the plasma than those of the SA suspension. Furthermore, brain delivery of SA was much more effective with SA-NPs than with SA suspension. In addition, the SA-NPs exerted strong neuroprotective effects in zebrafish and cell culture models of PD. The protective effect was partially mediated by the activation of the protein kinase B (Akt)/glycogen synthase kinase-3β (Gsk3β) pathway. In summary, this study provides evidence that small-sized mPEG–PLGA nanoparticles may improve cross-barrier transportation, oral bioavailability, brain uptake, and bioactivity of this Biopharmaceutics Classification System (BCS) Class II compound, SA.

Fluorescent Poly(glycerol-co-sebacate) Acrylate Nanoparticles for Stem Cell Labeling and Longitudinal Tracking
Lifeng Wang - ,
Keming Xu - ,
Xiaochun Hou - ,
Yiyuan Han - ,
Shiying Liu - ,
Christian Wiraja - ,
Cangjie Yang - ,
Jun Yang - ,
Mingfeng Wang - ,
Xiaochen Dong *- ,
Wei Huang *- , and
Chenjie Xu *
The stable presence of fluorophores within the biocompatible and biodegradable elastomer poly(glycerol-co-sebacate) acrylate (PGSA) is critical for monitoring the transplantation, performance, and degradation of the polymers in vivo. However, current methods such as physically entrapping the fluorophores in the polymer matrix or providing a fluorescent coating suffer from rapid leakage of fluorophores. Covalent conjugation of fluorophores with the polymers and the subsequent core-cross-linking are proposed here to address this challenge. Taking rhodamine as the model dye and PGSA nanoparticles (NPs) as the model platform, we successfully showed that the synthesized rhodamine-conjugated PGSA (PGSAR) NPs only released less than 30% rhodamine at day 28, whereas complete release of dye occurred for rhodamine-encapsulated PGSA (PGSA-p-R) NPs at day 7 and 57.49% rhodamine was released out for the un-cross-linked PGSAR NPs at day 28. More excitingly, PGSAR NPs showed a strong quantum yield enhancement (26.24-fold) of the fluorophores, which was due to the hydrophobic environment within PGSAR NPs and the restricted rotation of (6-diethylamino-3H-xanthen-3-ylidene) diethyl group in rhodamine after the conjugation and core-cross-linking. The stable presence of dye in the NPs and enhanced fluorescence allowed a longitudinal tracking of stem cells both in vitro and in vivo for at least 28 days.

Sulfated Hyaluronan Alters Endothelial Cell Activation in Vitro by Controlling the Biological Activity of the Angiogenic Factors Vascular Endothelial Growth Factor-A and Tissue Inhibitor of Metalloproteinase-3
Sandra Rother - ,
Sergey A. Samsonov - ,
Stephanie Moeller - ,
Matthias Schnabelrauch - ,
Jörg Rademann - ,
Joanna Blaszkiewicz - ,
Sebastian Köhling - ,
Johannes Waltenberger - ,
M. Teresa Pisabarro - ,
Dieter Scharnweber - , and
Vera Hintze *
Several pathologic conditions such as rheumatoid arthritis, ocular neovascularization, cancer, or atherosclerosis are often associated with abnormal angiogenesis, which requires innovative biomaterial-based treatment options to control the activity of angiogenic factors. Here, we studied how sulfated hyaluronan (sHA) and oversulfated chondroitin sulfate derivatives as potential components of functional biomaterials modulate vascular endothelial growth factor-A (VEGF-A) signaling and endothelial cell activity in vitro. Tissue inhibitor of metalloproteinase-3 (TIMP-3), an effective angiogenesis inhibitor, exerts its activity by competing with VEGF-A for binding to VEGF receptor-2 (VEGFR-2). However, even though TIMP-3 and VEGF-A are known to interact with glycosaminoglycans (GAGs), the potential role and mechanism by which GAGs alter the VEGF-A/TIMP-3 regulated VEGFR-2 signaling remains unclear. Combining surface plasmon resonance, immunobiochemical analysis, and molecular modeling, we demonstrate the simultaneous binding of VEGF-A and TIMP-3 to sHA-coated surfaces and identified a novel mechanism by which sulfated GAG derivatives control angiogenesis: GAG derivatives block the binding of VEGF-A and TIMP-3 to VEGFR-2 thereby reducing their biological activity in a defined, sulfation-dependent manner. This effect was stronger for sulfated GAG derivatives than for native GAGs. The simultaneous formation of TIMP-3/sHA complexes partially rescues the sHA inhibited VEGF-A/VEGFR-2 signaling and endothelial cell activation. These results provide novel insights into the regulation of angiogenic factors by GAG derivatives and highlight the potential of sHA derivatives for the treatment of diseases associated with increased VEGF-A and VEGFR-2 levels.
Energy, Environmental, and Catalysis Applications

Carbon-Coated Silicon Nanowires on Carbon Fabric as Self-Supported Electrodes for Flexible Lithium-Ion Batteries
Xiaolei Wang - ,
Ge Li - ,
Min Ho Seo - ,
Gregory Lui - ,
Fathy M. Hassan - ,
Kun Feng - ,
Xingcheng Xiao *- , and
Zhongwei Chen *
A novel self-supported electrode with long cycling life and high mass loading was developed based on carbon-coated Si nanowires grown in situ on highly conductive and flexible carbon fabric substrates through a nickel-catalyzed one-pot atmospheric pressure chemical vapor deposition. The high-quality carbon coated Si nanowires resulted in high reversible specific capacity (∼3500 mA h g–1 at 100 mA g–1), while the three-dimensional electrode’s unique architecture leads to a significantly improved robustness and a high degree of electrode stability. An exceptionally long cyclability with a capacity retention of ∼66% over 500 cycles at 1.0 A g–1 was achieved. The controllable high mass loading enables an electrode with extremely high areal capacity of ∼5.0 mA h cm–2. Such a scalable electrode fabrication technology and the high-performance electrodes hold great promise in future practical applications in high energy density lithium-ion batteries.

First-Principles Study of the Band Diagrams and Schottky-Type Barrier Heights of Aqueous Ta3N5 Interfaces
Eriko Watanabe *- ,
Hiroshi Ushiyama *- , and
Koichi Yamashita
The photo(electro)chemical production of hydrogen by water splitting is an efficient and sustainable method for the utilization of solar energy. To improve photo(electro)catalytic activity, a Schottky-type barrier is typically useful to separate excited charge carriers in semiconductor electrodes. Here, we focused on studying the band diagrams and the Schottky-type barrier heights of Ta3N5, which is one of the most promising materials as a photoanode for water splitting. The band alignments of the undoped and n-type Ta3N5 with adsorbents in a vacuum were examined to determine how impurities and adsorbents affect the band positions and Fermi energies. The band edge positions as well as the density of surface states clearly depended on the density of ON impurities in the bulk and surface regions. Finally, the band diagrams of the n-type Ta3N5/water interfaces were calculated with an improved interfacial model to include the effect of electrode potential with explicit water molecules. We observed partial Fermi level pinning in our calculations at the Ta3N5/water interface, which affects the driving force for charge separation.

Roles of Fe−Nx and Fe−Fe3C@C Species in Fe−N/C Electrocatalysts for Oxygen Reduction Reaction
Jae Hyung Kim - ,
Young Jin Sa - ,
Hu Young Jeong - , and
Sang Hoon Joo *
Iron and nitrogen codoped carbons (Fe−N/C) have emerged as promising nonprecious metal catalysts for the oxygen reduction reaction (ORR). While Fe−Nx sites have been widely considered as active species for Fe−N/C catalysts, very recently, iron and/or iron carbide encased with carbon shells (Fe−Fe3C@C) has been suggested as a new active site for the ORR. However, most of synthetic routes to Fe−N/C catalysts involve high-temperature pyrolysis, which unavoidably yield both Fe−Nx and Fe−Fe3C@C species, hampering the identification of exclusive role of each species. Herein, in order to establish the respective roles of Fe−Nx and Fe−Fe3C@C sites we rationally designed model catalysts via the phase conversion reactions of Fe3O4 nanoparticles supported on carbon nanotubes. The resulting catalysts selectively contained Fe−Nx, Fe−Fe3C@C, and N-doped carbon (C−Nx) sites. It was revealed that Fe−Nx sites dominantly catalyze ORR via 4-electron (4 e–) pathway, exerting a major role for high ORR activity, whereas Fe−Fe3C@C sites mainly promote 2 e– reduction of oxygen followed by 2 e– peroxide reduction, playing an auxiliary role.

Niobium-Doped (001)-Dominated Anatase TiO2 Nanosheets as Photoelectrode for Efficient Dye-Sensitized Solar Cells
Lei Jiang - ,
Lei Sun - ,
Dong Yang - ,
Jian Zhang - ,
Ya-Juan Li - ,
Kun Zou - , and
Wei-Qiao Deng *
TiO2 nanocrystals with different reactive facets have attracted extensive interest since they were first synthesized. The anatase TiO2 nanocrystals with (001) or (100) dominate facets were considered to be excellent electrode materials to enhance the cell performance of dye-sensitized solar cells. However, which reactive facet presents the best surface for benefiting photovoltaic effect is still unknown. We report a systematic study of various anatase TiO2 surfaces interacting with N719 dye by means of density functional theory calculations in combination with microscopic techniques. The (001) surface interacting with N719 would have the lowest work function, leading to the best photovoltaic performances. To further increase the efficiency, Nb dopant was incorporated into the anatase TiO2 nanocrystals. Based on the theoretical prediction, we proposed and demonstrated novel Nb-doped (001)-dominated anatase TiO2 nanosheets as photoelectrode in a dye-sensitized solar cell to further enhance the open-circuit voltage. And a power conversion efficiency of 10% was achieved, which was 22% higher than that of the undoped device (P25 as an electrode).

Ternary Pt9RhFex Nanoscale Alloys as Highly Efficient Catalysts with Enhanced Activity and Excellent CO-Poisoning Tolerance for Ethanol Oxidation
Peng Wang - ,
Shibin Yin - ,
Ying Wen - ,
Zhiqun Tian - ,
Ningzhang Wang *- ,
Julian Key - ,
Shuangbao Wang - , and
Pei Kang Shen *
To address the problems of high cost and poor stability of anode catalysts in direct ethanol fuel cells (DEFCs), ternary nanoparticles Pt9RhFex (x = 1, 3, 5, 7, and 9) supported on carbon powders (XC-72R) have been synthesized via a facile method involving reduction by sodium borohydride followed by thermal annealing in N2 at ambient pressure. The catalysts are physically characterized by X-ray diffraction, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy, and their catalytic performance for the ethanol oxidation reaction (EOR) is evaluated by cyclic and linear scan voltammetry, CO-stripping voltammograms, and chronopotentiometry. All the Pt9RhFex/C catalysts of different atomic ratios produce high EOR catalytic activity. The catalyst of atomic ratio composition 9:1:3 (Pt/Rh/Fe) has the highest activity and excellent CO-poisoning tolerance. Moreover, the enhanced EOR catalytic activity on Pt9RhFe3/C when compared to Pt9Rh/C, Pt3Fe/C, and Pt/C clearly demonstrates the presence of Fe improves catalytic performance. Notably, the onset potential for CO oxidation on Pt9RhFe3/C (0.271 V) is ∼55, 75, and 191 mV more negative than on Pt9Rh/C (0.326 V), Pt3Fe/C (0.346 V), and Pt/C (0.462 V), respectively, which implies the presence of Fe atoms dramatically improves CO-poisoning tolerance. Meanwhile, compared to the commercial PtRu/C catalyst, the peak potential on Pt9RhFe3/C for CO oxidation was just slightly changed after several thousand cycles, which shows high stability against the potential cycling. The possible mechanism by which Fe and Rh atoms facilitate the observed enhanced performance is also considered herein, and we conclude Pt9RhFe3/C offers a promising anode catalyst for direct ethanol fuel cells.

Synthetic Architecture of MgO/C Nanocomposite from Hierarchical-Structured Coordination Polymer toward Enhanced CO2 Capture
Ping Li - ,
Wen Liu - ,
John S. Dennis - , and
Hua Chun Zeng *
Highly efficient, durable, and earth-abundant solid sorbents are of paramount importance for practical carbon capture, storage, and utilization. Here, we report a novel and facile two-step strategy to synthesize a group of hierarchically structured porous MgO/C nanocomposites using flowerlike Mg-containing coordination polymer as a precursor. The new nanocomposites exhibit superb CO2 capture performance with sorption capacity up to 30.9 wt % (at 27 °C, 1 bar CO2), fast sorption kinetics, and long cycling life. Importantly, the achieved capacity is >14 times higher than that of commercial MgO, and favorably exceeds the highest value recorded to date for MgO-based sorbents under similar operating conditions. On the basis of the morphological and textural property analysis, together with CO2 sorption mechanism study using CO2-TPD and DRIFT techniques, the outstanding performance in CO2 uptake originates from unique features of this type of sorbent materials, which include hierarchical architecture, porous building blocks of nanosheets, high specific surface area (ca. 300 m2/g), evenly dispersed MgO nanocrystallites (ca. 3 nm) providing abundant active sites, and the in situ generated carbon matrix that acts as a stabilizer to prevent the growth and agglomeration of MgO crystallites. The nanocomposite system developed in this work shows good potential for future low-cost CO2 abatement and utilization.

Superhydrophilic In-Situ-Cross-Linked Zwitterionic Polyelectrolyte/PVDF-Blend Membrane for Highly Efficient Oil/Water Emulsion Separation
Yuzhang Zhu - ,
Wei Xie - ,
Feng Zhang - ,
Tieling Xing - , and
Jian Jin *
Because of weak hydrophilicity, membranes always experience fouling problems during separations. This phenomenon seriously impedes the development of membrane technologies for practical industrial-oil wastewater treatment. In this work, we successfully fabricated a superhydrophilic zwitterionic poly(vinylidene fluoride) (PVDF) membrane using a two-part process with an in situ cross-linking reaction during nonsolvent-induced phase separation and a subsequent sulfonation reaction. To prepare this zwitterionic PVDF membrane, a copolymer poly(dimethylaminoethyl methacrylate-co-2-hydroxyethyl methacrylate) (PDH) was synthesized as a zwitterionic polymer precursor and used as an additive in membrane preparation. This zwitterionic additive is well-immobilized in the membrane using in situ cross-linking to ensure the long-term stability of the membrane, and subsequent sulfonation transforms the precursor to a zwitterionic polymer to produce a superhydrophilic membrane. This superhydrophilic zwitterionic PVDF membrane exhibits high water permeation flux and good antifouling properties for separating oil-in-water emulsions with high separation efficiency.

Coating Solution for High-Voltage Cathode: AlF3 Atomic Layer Deposition for Freestanding LiCoO2 Electrodes with High Energy Density and Excellent Flexibility
Yun Zhou - ,
Younghee Lee - ,
Huaxing Sun - ,
Jasmine M. Wallas - ,
Steven M. George - , and
Ming Xie *
Freestanding LiCoO2/multiwall carbon nanotube/nanocellulose fibril (LCO-MWCNT-NCF) electrodes are fabricated by a vacuum filtration technique. The electrode has a high LCO loading of 20 mg/cm2 with excellent flexibility, uniform material distribution, and low surface resistivity. When coated with 2 ALD cycles of AlF3, LCO-MWCNT-NCF has a high specific capacity of 216 mAh/g at 4.7 V. The freestanding AlF3-coated electrode preserves 75.7% of its initial capacity after 100 cycles and 70% after 160 cycles of charge discharge. In contrast, electrodes coated with 2 ALD cycles of Al2O3 cannot be cycled above 4.5 V. By elimination of the unnecessary weight of current collector, and increasing in the working voltage simultaneously, this freestanding LCO-MWCNT-NCF electrode can significantly improve the gravimetric and volumetric energy density of lithium ion batteries.

SnO2@PANI Core–Shell Nanorod Arrays on 3D Graphite Foam: A High-Performance Integrated Electrode for Lithium-Ion Batteries
Feng Zhang - ,
Chengkai Yang - ,
Xin Gao - ,
Shuai Chen - ,
Yiran Hu - ,
Huanqin Guan - ,
Yurong Ma - ,
Jin Zhang - ,
Henghui Zhou *- , and
Limin Qi *
The rational design and controllable fabrication of electrode materials with tailored structures and superior performance is highly desirable for the next-generation lithium ion batteries (LIBs). In this work, a novel three-dimensional (3D) graphite foam (GF)@SnO2 nanorod arrays (NRAs)@polyaniline (PANI) hybrid architecture was constructed via solvothermal growth followed by electrochemical deposition. Aligned SnO2 NRAs were uniformly grown on the surface of GF, and a PANI shell with a thickness of ∼40 nm was coated on individual SnO2 nanorods, forming a SnO2@PANI core–shell structure. Benefiting from the synergetic effect of 3D GF with large surface area and high conductivity, SnO2 NRAs offering direct pathways for electrons and lithium ions, and the conductive PANI shell that accommodates the large volume variation of SnO2, the binder-free, integrated GF@SnO2 NRAs@PANI electrode for LIBs exhibited high capacity, excellent rate capability, and good electrochemical stability. A high discharge capacity of 540 mAh g–1 (calculated by the total mass of the electrode) was achieved after 50 cycles at a current density of 500 mA g–1. Moreover, the electrode demonstrated superior rate performance with a discharge capacity of 414 mAh g–1 at a high rate of 3 A g–1.

3,3′-(Ethylenedioxy)dipropiononitrile as an Electrolyte Additive for 4.5 V LiNi1/3Co1/3Mn1/3O2/Graphite Cells
Chengyun Wang - ,
Le Yu - ,
Weizhen Fan - ,
Jiangwen Liu - ,
Liuzhang Ouyang *- ,
Lichun Yang - , and
Min Zhu
3,3′-(Ethylenedioxy)dipropiononitrile (EDPN) has been introduced as a novel electrolyte additive to improve the oxidation stability of the conventional carbonate-based electrolyte for LiNi1/3Co1/3Mn1/3O2/graphite pouch batteries cycled under high voltage. Mixing 0.5 wt % EDPN into the electrolyte greatly improved the capacity retention, from 32.5% to 83.9%, of cells cycled for 100 times in the range 3.0–4.5 V with a rate of 1C. The high rate performance (3C and 5C) was also improved, while the cycle performance was similar to that of the cell without EDPN when cycled between 3.0 and 4.2 V. Further evidence of a stable protective interphase film can be formed on the LiNi1/3Co1/3Mn1/3O2 electrode surface due to the presence of EDPN in the electrolyte. This process effectively suppresses the oxidative decomposition of electrolyte and the growth in the charge-transfer resistance of the LiNi1/3Co1/3Mn1/3O2 electrode and greatly improves the high-voltage electrochemical properties for the cells. In contrast, EDPN has no positive effect on the cyclic performance of the LiNi0.5Co0.2Mn0.3O2-based cell under high operating voltage.

Urea-Assisted Room Temperature Stabilized Metastable β-NiMoO4: Experimental and Theoretical Insights into its Unique Bifunctional Activity toward Oxygen Evolution and Supercapacitor
Satyajit Ratha - ,
Aneeya K. Samantara - ,
Krishna Kanta Singha - ,
Abhijeet Sadashiv Gangan - ,
Brahmananda Chakraborty - ,
Bikash Kumar Jena *- , and
Chandra Sekhar Rout *
Room-temperature stabilization of metastable β-NiMoO4 is achieved through urea-assisted hydrothermal synthesis technique. Structural and morphological studies provided significant insights for the metastable phase. Furthermore, detailed electrochemical investigations showcased its activity toward energy storage and conversion, yielding intriguing results. Comparison with the stable polymorph, α-NiMoO4, has also been borne out to support the enhanced electrochemical activities of the as-obtained β-NiMoO4. A specific capacitance of ∼4188 F g–1 (at a current density of 5 A g–1) has been observed showing its exceptional faradic capacitance. We qualitatively and extensively demonstrate through the analysis of density of states (DOS) obtained from first-principles calculations that, enhanced DOS near top of the valence band and empty 4d orbital of Mo near Fermi level make β-NiMoO4 better energy storage and conversion material compared to α-NiMoO4. Likewise, from the oxygen evolution reaction experiment, it is found that the state of art current density of 10 mA cm–2 is achieved at overpotential of 300 mV, which is much lower than that of IrO2/C. First-principles calculations also confirm a lower overpotential of 350 mV for β-NiMoO4.

Addressing the Interface Issues in All-Solid-State Bulk-Type Lithium Ion Battery via an All-Composite Approach
Ru-Jun Chen - ,
Yi-Bo Zhang - ,
Ting Liu - ,
Bing-Qing Xu - ,
Yuan-Hua Lin - ,
Ce-Wen Nan *- , and
Yang Shen *
All-solid-state bulk-type lithium ion batteries (LIBs) are considered ultimate solutions to the safety issues associated with conventional LIBs using flammable liquid electrolyte. The development of bulk-type all-solid-state LIBs has been hindered by the low loading of active cathode materials, hence low specific surface capacity, and by the high interface resistance, which results in low rate and cyclic performance. In this contribution, we propose and demonstrate a synergistic all-composite approach to fabricating flexible all-solid-state LIBs. PEO-based composite cathode layers (filled with LiFePO4 particles) of ∼300 μm in thickness and composite electrolyte layers (filled with Al-LLZTO particles) are stacked layer-by-layer with lithium foils as negative layer and hot-pressed into a monolithic all-solid-state LIB. The flexible LIB delivers a high specific discharge capacity of 155 mAh/g, which corresponds to an ultrahigh surface capacity of 10.8 mAh/cm2, exhibits excellent capacity retention up to at least 10 cycles and could work properly under harsh operating conditions such as bending or being sectioned into pieces. The all-composite approach is favorable for improving both mesoscopic and microscopic interfaces inside the all-solid-state LIB and may provide a new toolbox for design and fabrication of all-solid-state LIBs.

Graphene-Embedded Co3O4 Rose-Spheres for Enhanced Performance in Lithium Ion Batteries
Mingjun Jing - ,
Minjie Zhou - ,
Gangyong Li - ,
Zhengu Chen - ,
Wenyuan Xu - ,
Xiaobo Chen *- , and
Zhaohui Hou *
Co3O4 has been widely studied as a promising candidate as an anode material for lithium ion batteries. However, the huge volume change and structural strain associated with the Li+ insertion and extraction process leads to the pulverization and deterioration of the electrode, resulting in a poor performance in lithium ion batteries. In this paper, Co3O4 rose-spheres obtained via hydrothermal technique are successfully embedded in graphene through an electrostatic self-assembly process. Graphene-embedded Co3O4 rose-spheres (G-Co3O4) show a high reversible capacity, a good cyclic performance, and an excellent rate capability, e.g., a stable capacity of 1110.8 mAh g–1 at 90 mA g–1 (0.1 C), and a reversible capacity of 462.3 mAh g–1 at 1800 mA g–1 (2 C), benefitted from the novel architecture of graphene-embedded Co3O4 rose-spheres. This work has demonstrated a feasible strategy to improve the performance of Co3O4 for lithium-ion battery application.

Shape-Dependent Photocatalytic Activity of Hydrothermally Synthesized Cadmium Sulfide Nanostructures
Joyjit Kundu - ,
Santimoy Khilari - , and
Debabrata Pradhan *
The effective surface area of the nanostructured materials is known to play a prime role in catalysis. Here we demonstrate that the shape of the nanostructured materials plays an equally important role in their catalytic activity. Hierarchical CdS microstructures with different morphologies such as microspheres assembled of nanoplates, nanorods, nanoparticles, and nanobelts are synthesized using a simple hydrothermal method by tuning the volume ratio of solvents, i.e., water or ethylenediamine (en). With an optimum solvent ratio of 3:1 water:en, the roles of other synthesis parameters such as precursor’s ratio, temperature, and precursor combinations are also explored and reported here. Four selected CdS microstructures are used as photocatalysts for the degradation of methylene blue and photoelectrochemical water splitting for hydrogen generation. In spite of smaller effective surface area of CdS nanoneedles/nanorods than that of CdS nanowires network, the former exhibits higher catalytic activity under visible light irradiation which is ascribed to the reduced charge recombination as confirmed from the photoluminescence study.

Suppression of Dendrite Formation and Corrosion on Zinc Anode of Secondary Aqueous Batteries
Kyung E. K. Sun - ,
Tuan K. A. Hoang - ,
The Nam Long Doan - ,
Yan Yu - ,
Xiao Zhu - ,
Ye Tian - , and
P. Chen *
Novel zinc anodes are synthesized via electroplating with organic additives in the plating solution. The selected organic additives are cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), polyethylene-glycol (PEG-8000), and thiourea (TU). The synthesized zinc anode materials, namely, Zn-CTAB, Zn-SDS, Zn-PEG, and Zn-TU, are characterized by powder X-ray diffraction and scanning electron microscopy. The results show that each additive produces distinctively different crystallographic orientation and surface texture. The surface electrochemical activity is characterized by linear polarization when the zinc is in contact with the battery’s electrolyte. Tafel fitting on the linear polarization data reveals that the synthetic zinc materials using organic additives all exhibit 6–30 times lower corrosion currents. When using Zn-SDS as the anode in the rechargeable hybrid aqueous battery, the float current decreases as much as 2.5 times. The batteries with Zn-SDS, Zn-PEG, and Zn-TU anodes display the capacity retention of 79%, 76%, and 80% after 1000 cycles of charge–discharge at 4C rate, whereas only 67% obtained from the batteries using the anode prepared from commercial zinc foil. Among these electroplated anodes, Zn-SDS is the most suitable for aqueous batteries thanks to its low corrosion rate, low dendrite formation, low float current, and high capacity retention after 1000 cycles.

Rapid Formation of Metal–Organic Frameworks (MOFs) Based Nanocomposites in Microdroplets and Their Applications for CO2 Photoreduction
Xiang He - ,
Zhuoran Gan - ,
Sergey Fisenko - ,
Dawei Wang - ,
Hani M. El-Kaderi - , and
Wei-Ning Wang *
A copper-based metal–organic framework (MOF), [Cu3(TMA)2(H2O)3]n (also known as HKUST-1, where TMA stands for trimesic acid), and its TiO2 nanocomposites were directly synthesized in micrometer-sized droplets via a rapid aerosol route for the first time. The effects of synthesis temperature and precursor component ratio on the physicochemical properties of the materials were systematically investigated. Theoretical calculations on the mass and heat transfer within the microdroplets revealed that the fast solvent evaporation and high heat transfer rates are the major driving forces. The fast droplet shrinkage because of evaporation induces the drastic increase in the supersaturation ratio of the precursor, and subsequently promotes the rapid nucleation and crystal growth of the materials. The HKUST-1-based nanomaterials synthesized via the aerosol route demonstrated good crystallinity, large surface area, and great photostability, comparable with those fabricated by wet-chemistry methods. With TiO2 embedded in the HKUST-1 matrix, the surface area of the composite is largely maintained, which enables significant improvement in the CO2 photoreduction efficiency, as compared with pristine TiO2. In situ diffuse reflectance infrared Fourier transform spectroscopy analysis suggests that the performance enhancement was due to the stable and high-capacity reactant adsorption by HKUST-1. The current work shows great promise in the aerosol route’s capability to address the mass and heat transfer issues of MOFs formation at the microscale level, and ability to synthesize a series of MOFs-based nanomaterials in a rapid and scalable manner for energy and environmental applications.

Well-Defined ZIF-Derived Fe–N Codoped Carbon Nanoframes as Efficient Oxygen Reduction Catalysts
Yijie Deng - ,
Yuanyuan Dong - ,
Guanghua Wang - ,
Kailing Sun - ,
Xiudong Shi - ,
Long Zheng - ,
Xiuhua Li - , and
Shijun Liao *
A series of ZIF-derived Fe–N codoped carbon materials with a well-defined morphology, high surface area, tunable sizes and porous nanoframe structure was successfully prepared by synthesizing Fe-doped ZIF-8 through the assembly of Zn2+ ions with 2-methylimidazole in the presence of iron(III) acetylacetonate, followed by pyrolysis at a high temperature and in an Ar atmosphere. The prepared optimum catalyst materials exhibited excellent activity for the oxygen reduction reaction (ORR) and outstanding durability in both acidic and alkaline solutions. We found that Fe doping during the ZIF-8 synthesis stage was crucial to achieve the materials’ well-defined morphology, tunable size, good particle dispersion, and high performance. XPS revealed that Fe doping greatly enhanced the fractions of graphitic-N and pyridinic-N and decreased the fraction of oxidized-N. We suggest that the porosity and high surface area of the nanoframe structure originated from the metal–organic frameworks, the high dispersion of Fe in the nanoframe, and the enhanced proportions of active N species, all of which were responsible for the materials’ significantly enhanced ORR performance.

Synthesis of Ultrasmall Platinum Nanoparticles on Polymer Nanoshells for Size-Dependent Catalytic Oxidation Reactions
Licheng Bai - ,
Shumeng Zhang - ,
Qiang Chen *- , and
Chuanbo Gao *
It is highly desirable for the synthesis and stabilization of noble metal nanoparticles of uniform, precisely tunable sizes, especially in the range of angstroms to a few nanometers, for many catalytic applications in pursuit of optimal activity and selectivity. Herein, we report a novel strategy for the synthesis of uniform platinum (Pt) nanoparticles of ultrasmall sizes (average size: 0.9–2.3 nm), which are stabilized on hollow polymer nanoshells formed by polymerization of sodium dodecyl benzenesulfonate (SDBS) at the interface of an ethanol/water emulsion. The resulting composite represents a highly active catalyst for effective oxidation of alcohols under ambient conditions. Strong size-dependent catalytic activity of Pt nanoparticles has been revealed in aerobic oxidation of 1-phenylethanol to yield acetophenone, demonstrating a volcano-shape profile, with Pt nanoparticles of ∼1.7 nm showing the highest activity. The size effect has been attributed to the size-dependent d-band electron structure of the Pt nanoparticles. This work reveals the size effect of Pt nanoparticles in general organic oxidation reactions, and thus provides a general methodology and a lot of opportunities in the design of metal-nanoparticle-based catalysts for fine-chemical production.

Long-Life Nickel-Rich Layered Oxide Cathodes with a Uniform Li2ZrO3 Surface Coating for Lithium-Ion Batteries
Bohang Song - ,
Wangda Li - ,
Seung-Min Oh - , and
Arumugam Manthiram *
As nickel-rich layered oxide cathodes start to attract worldwide interest for the next-generation lithium-ion batteries, their long-term cyclability in full cells remains a challenge for electric vehicles. Here we report a long-life Ni-rich layered oxide cathode (LiNi0.7Co0.15Mn0.15O2) with a uniform surface coating of the cathode particles with Li2ZrO3. A pouch-type full cell fabricated with the Li2ZrO3-coated cathode and a graphite anode displays 73.3% capacity retention after 1500 cycles at a C/3 rate. The Li2ZrO3 coating has been optimized by a systematic study with different synthesis approaches, annealing temperatures, and coating amounts. The complex relationship among the coating conditions, uniformity, and morphology of the coating layer and their impacts on the electrochemical properties are discussed in detail.

The Role of Air–Electrode Structure on the Incorporation of Immiscible PFCs in Nonaqueous Li–O2 Battery
Moran Balaish *- and
Yair Ein-Eli *
Perfluorocarbons (PFCs) are considered advantageous additives to nonaqueous Li–O2 battery due to their superior oxygen solubility and diffusivity compared to common battery electrolytes. Up to now, the main focus was concentrated on PFCs–electrolyte investigation; however, no special attention was granted to the role of carbon structure in the PFCs–Li–O2 system. In our current research, immiscible PFCs, rather than miscible fluorinated ethers, were added to activated carbon class air electrode due to their higher susceptibility toward O2•– attack and to their ability to shift the reaction from two-phase to an artificial three-phase reaction zone. The results showed superior battery performance upon PFCs addition at lower current density (0.05 mA cm–2) but unexpectedly failed to do so at higher current density (0.1 and 0.2 mA cm–2), where oxygen transport limitation is best illustrated. The last was a direct result of liquid–liquid displacement phenomenon occurring when the two immiscible liquids were introduced into the porous carbon medium. The investigation and role of carbon structure on the mechanism upon PFCs addition to Li–O2 system are suggested based on electrochemical characterization, wettability behavior studies, and the physical adsorption technique. Finally, we suggest an optimum air–electrode structure enabling the incorporation of immiscible PFCs in a nonaqueous Li–O2 battery.

Graphene Oxide Involved Air-Controlled Electrospray for Uniform, Fast, Instantly Dry, and Binder-Free Electrode Fabrication
Ling Fei - ,
Sang Ha Yoo - ,
Rachel Ann R. Villamayor - ,
Brian P. Williams - ,
Seon Young Gong - ,
Sunchan Park - ,
Kyusoon Shin - , and
Yong Lak Joo *
We report a facile air-controlled electrospray method to directly deposit binder-free active materials/graphene oxide (GO) onto current collectors. This method is inspired from an electrospinning process, and possesses all the advantages that electrospinning has such as low cost, easy scaling up, and simultaneous solvent evaporation during the spraying process. Moreover, the spray slurry is only a simple mixture of active materials and GO suspension in water, no binder polymer, organic solvent, and conductive carbon required. In our research, high-capacity Si nanoparticles (Si NP, 70–100 nm) and SiO microparticles (SiO MP, 3–10 μm) were selected to demonstrate the capability of this method to accommodate particles with different sizes. Their mixture with GO was sprayed onto a collector and then thermally annealed in an inert gas to obtain Si NP or SiO MP/reduced graphene oxide (RGO) binder-free electrodes. We are also able to directly deposit fairly large electrode sheets (e.g., 12 × 21 in.) upon the application requirement. To the best of our knowledge, this is the simplest approach to produce Si-related materials/RGO layered structures directly on current collector with controllable area and loading. Si and SiO MP/RGO are evaluated in both half and full lithium cells, showing good electrochemical performance. Prelithiation is also studied and gives a high first cycle Coulombic efficiency. In addition to Si-related materials, other materials with different shapes and sizes (e.g., MoO3 nanobelts, Sn/carbon nanofibers, and commercial sulfur particles) can also be sprayed. Beyond the preparation of battery electrodes, this approach can also be applied for other types of electrode preparation such as that of a supercapacitor, fuel cell, and solar cell.

Enhanced Structural and Electrochemical Stability of Self-Similar Rice-Shaped SnO2 Nanoparticles
Du Pan - ,
Ning Wan - ,
Yong Ren - ,
Weifeng Zhang - ,
Xia Lu - ,
Yuesheng Wang - ,
Yong-Sheng Hu - , and
Ying Bai *
A facile one-pot hydrothermal strategy is applied to prepare Co and F codoped SnO2 (Co–F/SnO2) nanoparticles, which exhibit a unique rice-shaped self-similar structure. Compared with the pristine and Co-doped counterparts (SnO2 and Co/SnO2), the Co–F/SnO2 electrode demonstrates higher capacity, better cyclability, and rate capability as anode material for lithium ion batteries (LIBs). A high charge capacity of 800 mAh g–1 can be successfully delivered after 50 cycles at 0.1 C, and a high reversible capacity of 700 mAh g–1 could be retained after 100 cycles at 5 C. The excellent lithium storage performances of the Co–F/SnO2 nanoparticles could be attributed to the synergetic effects of the doped Co and F, as well as the unique hierarchical self-similar structure with moderate oxygen defect and inactive pillars, which not only facilitates the fast diffusion of Li ions, but also stabilizes the structure during the electrochemical cycling.

A Novel Magnetically Recoverable Ni-CeO2–x/Pd Nanocatalyst with Superior Catalytic Performance for Hydrogenation of Styrene and 4-Nitrophenol
Yi-Fan Jiang - ,
Cheng-Zong Yuan - ,
Xiao Xie - ,
Xiao Zhou - ,
Nan Jiang - ,
Xin Wang - ,
Muhammad Imran - , and
An-Wu Xu *
Metal/support nanocatalysts consisting of various metals and metal oxides not only retain the basic properties of each component but also exhibit higher catalytic activity due to their synergistic effects. Herein, we report the creation of a highly efficient, long-lasting, and magnetic recyclable catalyst, composed of magnetic nickel (Ni) nanoparticles (NPs), active Pd NPs, and oxygen-deficient CeO2–x support. These hybrid nanostructures composed of oxygen deficient CeO2–x and active metal nanoparticles could effectively facilitate diffusion of reactant molecules and active site exposure that can dramatically accelerate the reaction rate. Impressively, the rate constant k and k/m of 4-nitrophenol reduction over 61 wt % Ni-CeO2–x/0.1 wt % Pd catalyst are 0.0479 s–1 and 2.1 × 104 min–1 g–1, respectively, and the reaction conversion shows negligible decline even after 20 cycles. Meanwhile, the optimal 61 wt % Ni-CeO2–x/3 wt % Pd catalyst manifests remarkable catalytic activity toward styrene hydrogenation with a high TOF of 6827 molstyrene molPd–1 h–1 and a selective conversion of 100% to ethylbenzene even after eight cycles. The strong metal–support interaction (SMSI) between Ni NPs, Pd NPs, and oxygen-deficient CeO2–x support is beneficial for superior catalytic efficiency and stability toward hydrogenation of styrene and 4-nitrophenol. Moreover, Ni species could boost the catalytic activity of Pd due to their synergistic effect and strengthen the interaction between reactant and catalyst, which seems responsible for the great enhancement of catalytic activity. Our findings provide a new perspective to develop other high-performance and magnetically recoverable nanocatalysts, which would be widely applied to a variety of catalytic reactions.

Transparent and Self-Supporting Graphene Films with Wrinkled- Graphene-Wall-Assembled Opening Polyhedron Building Blocks for High Performance Flexible/Transparent Supercapacitors
Na Li *- ,
Xuankai Huang - ,
Haiyan Zhang - ,
Yunyong Li - , and
Chengxin Wang *
Improving mass loading while maintaining high transparency and large surface area in one self-supporting graphene film is still a challenge. Unfortunately, all of these factors are absolutely essential for enhancing the energy storage performance of transparent supercapacitors for practical applications. To solve the above bottleneck problem, we produce a novel self-supporting flexible and transparent graphene film (STF-GF) with wrinkled-wall-assembled opened-hollow polyhedron building units. Taking advantage of the microscopic morphology, the STF-GF exhibits improved mass loading with high transmittance (70.2% at 550 nm), a large surface area (1105.6 m2/g), and good electrochemical performance: high energy (552.3 μWh/cm3), power densities (561.9 mW/cm3), a superlong cycle life, and good cycling stability (the capacitance retention is ∼94.8% after 20,000 cycles).

Functionalized Metal–Organic Framework as a Biomimetic Heterogeneous Catalyst for Transfer Hydrogenation of Imines
Jingwen Chen - ,
Zhiguo Zhang *- ,
Zongbi Bao - ,
Ye Su - ,
Huabin Xing - ,
Qiwei Yang - , and
Qilong Ren
Mimicking a biocatalytic system has been one of the prevalent strategies for the design of novel and efficient chemical transformations. Among the enzyme-catalyzed reactions, the cooperative interplay of Lewis- and Brønsted-acidic functionalities at active sites represents a common feature in activating reactants. Employing MIL-101(Cr) as a biomimetic platform, we customize a sulfonic group (SO3H) into its hierarchical pores to generate a heterogeneous catalyst for transfer hydrogenation of imines by using Hantzsch ester as the reductant. Both aldimines and ketimines were efficiently converted to their hydrogenated counterparts in a manner similar to metal enzymes. The Cr3+ node and sulfonic acid functionality encapsulated in MOF cages worked cooperatively in promoting this transformation, resulting in an enhanced reactivity as compared to its homogeneous analogue. Furthermore, MIL-101(Cr)-SO3H could be recycled for many times without considerable loss in reactivity.

Hierarchical Structural Evolution of Zn2GeO4 in Binary Solvent and Its Effect on Li-ion Storage Performance
Wei Liu - ,
Tengfei Zhou - ,
Yang Zheng - ,
Jianwen Liu - ,
Chuanqi Feng - ,
Yue Shen - ,
Yunhui Huang - , and
Zaiping Guo *
Zinc germinate (Zn2GeO4) with a hierarchical structure was successfully synthesized in a binary ethylenediamine/water (En/H2O) solvent system by wet chemistry methods. The morphological evolution process of the Zn2GeO4 was investigated in detail by tuning the ratio of En to H2O in different solvent systems, and a series of compounds with awl-shaped, fascicular, and cross-linked hierarchical structures was obtained and employed as anode materials in lithium-ion batteries. The materials with fascicular structure exhibited excellent electrochemical performance, and a specific reversible capacity of 1034 mA h g–1 was retained at a current density of 0.5 A g–1 after 160 cycles. In addition, the as-prepared nanostructured electrode also delivered impressive rate capability of 315 mA h g–1 at the current density of 10 A g–1. The remarkable electrochemical performances could be ascribed to the following aspects. First, each unit in the three-dimensional fascicular structure can effectively buffer the volume expansions during the Li+ extraction/insertion process, accommodate the strain induced by the volume variation, and stabilize its whole configuration. Meanwhile, the small fascicular units can enlarge the electrode/electrolyte contact area and form an integrated interlaced conductive network which provides continuous electron/ion pathways.

Continuous Size Tuning of Monodispersed ZnO Nanoparticles and Its Size Effect on the Performance of Perovskite Solar Cells
Rong Zhang - ,
Chengbin Fei - ,
Bo Li - ,
Haoyu Fu - ,
Jianjun Tian *- , and
Guozhong Cao *
ZnO has been demonstrated to be a promising candidate to fabricate high efficiency perovskite solar cells (PSCs) in terms of its better electron extraction and transport properties. However, the inability of synthesis of ZnO nanoparticles (NPs) with minimal surface defects and agglomeration remains a great challenge hindering the fabrication of highly efficient PSCs. In this work, highly crystalline and agglomeration-free ZnO NPs with controlled size were synthesized through a facile solvothermal method. Such ZnO NPs were applied in the fabrication of meso-structured PSCs. The solar cells with ∼40 nm ZnO NPs exhibit the highest power conversion efficiency (PCE) of 15.92%. Steady-state and time-resolved photoluminescence measurements revealed the faster injection and lower charge recombination at the interface of ∼40 nm ZnO NPs and perovskite, resulting in significantly enhanced JSC and VOC.

Microfibrous-Structured Pd/AlOOH/Al-Fiber for CO Coupling to Dimethyl Oxalate: Effect of Morphology of AlOOH Nanosheet Endogenously Grown on Al-Fiber
Chunzheng Wang - ,
Jia Ding - ,
Guofeng Zhao - ,
Tao Deng - ,
Ye Liu - , and
Yong Lu *
We report a green, template-free, and general one-pot method of endogenous growth of free-standing boehmite (AlOOH) nanosheets on a 3D-network 60 μm-Al-fiber felt through water-only hydrothermal oxidation reaction between Al metal and H2O (2Al + 4H2O → 2AlOOH + 3H2). Content and morphology of AlOOH nanosheets can be finely tuned by adjusting the hydrothermal oxidation time length and temperature. Palladium is highly dispersed on such AlOOH endogenously formed on Al-fiber felt via incipient wetness impregnation method and as-obtained Pd/AlOOH/Al-fiber catalysts are checked in the CO coupling to dimethyl oxalate (DMO) reaction. Interestingly, Pd dispersion is very sensitive to the thickness (26–68 nm) of AlOOH nanosheet, and therefore the conversion shows strong AlOOH-nanosheet-thickness dependence whereas the intrinsic activity (TOF) is AlOOH-nanosheet-thickness independence. The most promising structured catalyst is the one using a microfibrous-structured composite with the thinnest AlOOH nanosheet (26 nm) to support a small amount of Pd of only 0.26 wt %. This catalyst, with high thermal-conductivity and satisfying structural robustness, delivers 67% CO conversion and 96% DMO selectivity at 150 °C using a feed of CH3ONO/CO/N2 (1/1.4/7.6, vol) and a gas hourly space velocity of 3000 L kg–1 h–1, and particularly, is very stable for at least 150 h without deactivation sign.

Synthesis and Properties of Poly(ether sulfone)s with Clustered Sulfonic Groups for PEMFC Applications under Various Relative Humidity
Shih-Wei Lee - ,
Jyh-Chien Chen *- ,
Jin-An Wu - , and
Kuei-Hsien Chen
Novel sulfonated poly(ether sulfone) copolymers (S4PH-x-PSs) based on a new aromatic diol containing four phenyl substituents at the 2, 2′, 6, and 6′ positions of 4,4′-diphenyl ether were synthesized. Sulfonation was found to occur exclusively on the 4 position of phenyl substituents by NMR spectroscopy. The ion exchange capacity (IEC) values can be controlled by adjusting the mole percent (x in S4PH-x-PS) of the new diol. The fully hydrated sulfonated poly(ether sulfone) copolymers had good proton conductivity in the range 0.004–0.110 S/cm at room temperature. The surface morphology of S4PH-x-PSs and Nafion 212 was investigated by atomic force microscopy (tapping-mode) and related to the percolation limit and proton conductivity. Single H2/O2 fuel cell based on S4PH-40-PS loaded with 0.25 mg/cm2 catalyst (Pt/C) exhibited a peak power density of 462.6 mW/cm2, which was close to that of Nafion 212 (533.5 mW/cm2) at 80 °C with 80% RH. Furthermore, fuel cell performance of S4PH-35-PS with various relative humidity was investigated. It was confirmed from polarization curves that the fuel cell performance of S4PH-35-PS was not as high as that of Nafion 212 under fully hydrated state due to higher interfacial resistance between S4PH-35-PS and electrodes. While under low relative humidity (53% RH) at 80 °C, fuel cells based on S4PH-35-PS showed higher peak power density (234.9 mW/cm2) than that (214.0 mW/cm2) of Nafion 212.

Active Site and Electronic Structure Elucidation of Pt Nanoparticles Supported on Phase-Pure Molybdenum Carbide Nanotubes
Shuai Tan - ,
Lucun Wang - ,
Shibely Saha - ,
Rebecca R Fushimi - , and
Dongmei Li *
We recently showed that phase-pure molybdenum carbide nanotubes can be durable supports for platinum (Pt) nanoparticles in hydrogen evolution reaction (HER). In this paper we further characterize surface properties of the same Pt/β-Mo2C catalyst platform using carbon monoxide (CO)-Pt and CO-Mo2C bond strength of different Pt particle sizes in the <3 nm range. Results from diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temporal analysis of products (TAP) revealed the existence of different active sites as Pt particle size increases. Correlation between the resultant catalyst activity and deposited Pt particle size was further investigated using water–gas-shift (WGS) as a probe reaction, suggesting that precise control of particle diameter and thickness is needed for optimized catalytic activity.

Preparation of Partially Poisoned Alkanethiolate-Capped Platinum Nanoparticles for Hydrogenation of Activated Terminal Alkynes
Khin Aye San - ,
Vivian Chen - , and
Young-Seok Shon *
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Stable and isolable alkanethiolate-stabilized Pt nanoparticles (PtNP) were synthesized using the two-phase thiosulfate method with sodium S-alkylthiosulfate as ligand precursor. The mechanistic formation of octanethiolate-capped PtNP (Pt-SC8) from both sodium S-octylthiosulfate and 1-octanethiol ligands was investigated by using 1H NMR and UV–vis spectroscopies, which revealed the formation of different Pt complexes as the reaction intermediates. The synthesis using S-octylthiosulfate ligand precursor produced Pt-SC8 in higher yields than that using 1-octanethiol ligand. The obtained nanoparticles were characterized by 1H NMR, UV–vis spectroscopy, infrared spectroscopy (IR), thermogravimetric analysis, and transmission electron microscopy (TEM). The results obtained from 1H NMR, IR, and UV–vis spectroscopy were consistent with the formation of stable and pure alkanethiolate-capped PtNP. TEM images of PtNP confirmed their small average core size (∼1.5 nm) and high monodispersity. The partially poisoned PtNP with thiolate monolayer ligands were further investigated for the hydrogenation of various alkynes to understand the organic ligands-induced geometric and electronic surface properties of colloidal Pt nanoparticle catalysts. The high catalytic activity of activated terminal alkynes, but the significantly low activity of internal alkynes and unactivated terminal alkynes, were observed under the mild reaction conditions (room temperature and atmospheric pressure). These results indicated that the presence of alkanethiolate ligands could decrease the coordination activity of PtNP surface especially for the bulkier and unactivated substrates.
Functional Inorganic Materials and Devices

Controllable Synthesis and Optical Properties of ZnS:Mn2+/ZnS/ZnS:Cu2+/ZnS Core/Multishell Quantum Dots toward Efficient White Light Emission
Fei Li - ,
Zhiguo Xia *- , and
Quanlin Liu
The ability to control dopants and defects, as well as the core/shell structures, of quantum dots (QDs) is an essential nanotechnology to modify and optimize their photoluminescence properties. Herein, the optimized ZnS:Mn2+/ZnS/ZnS:Cu2+/ZnS core/multishell QDs have been prepared, and their luminescence properties depending on the ratios of the starting materials and the injection temperature of an extra sulfur source were discussed; finally the white light can be possibly obtained by mixing the blue light (emission peak at 450 nm originating from Cu2+ dopants or emission peaks at 405 and 430 nm corresponding to a defect emission center) and orange light (emission peak at 585 nm from Mn2+ dopants). As a controlled synthesis comparison, the optimum core/shell structures and key synthesis parameters have been determined, and the quantum yield (QY) of the as-obtained ZnS:Mn2+/ZnS/ZnS:Cu2+/ZnS core/multishell white light emitting QDs without defect emission was determined to be 38%. The practical white light device prototype has been also fabricated and the CIE color coordinate of (0.32, 0.34) with a warm white light has been realized upon the excitation of the commercial 370 nm UV LED chip, which demonstrated potential application for micro/nano optical functional devices.

Phosphine-Free Synthesis of Metal Chalcogenide Quantum Dots by Directly Dissolving Chalcogen Dioxides in Alkylthiol as the Precursor
Dong Yao - ,
Wei Xin - ,
Zhaoyu Liu - ,
Ze Wang - ,
Jianyou Feng - ,
Chunwei Dong - ,
Yi Liu *- ,
Bai Yang - , and
Hao Zhang
Semiconductor quantum dots (QDs) are competitive emitting materials in developing new-generation light-emitting diodes (LEDs) with high color rendering and broad color gamut. However, the use of highly toxic alkylphosphines cannot be fully avoided in the synthesis of metal selenide and telluride QDs because they are requisite reducing agents and solvents for preparing chalcogen precursors. In this work, we demonstrate the phosphine-free preparation of selenium (Se) and tellurium (Te) precursors by directly dissolving chalcogen dioxides in the alkylthiol under the mild condition. The chalcogen dioxides are reduced to elemental chalcogen clusters, while the alkylthiol is oxidized to disulfides. The chalcogen clusters further combine with the disulfides, generating dispersible chalcogen precursors. The resulting chalcogen precursors are suitable for synthesizing various metal chalcogenide QDs, including CdSe, CdTe, Cu2Te, Ag2Te, PbTe, HgTe, and so forth. In addition, the precursors are of high reactivity, which permits a shorter QD synthesis process at lower temperature. Owing to the high quantum yield (QYs) and easy tunability of the photoluminescence (PL), the as-synthesized QDs are further employed as down-conversion materials to fabricate monochrome and white LEDs.

Strongly Enhanced Piezoelectric Response in Lead Zirconate Titanate Films with Vertically Aligned Columnar Grains
Minh D. Nguyen *- ,
Evert P. Houwman - ,
Matthijn Dekkers - , and
Guus Rijnders
This publication is Open Access under the license indicated. Learn More
Pb(Zr0.52Ti0.48)O3 (PZT) films with (001) orientation were deposited on Pt(111)/Ti/SiO2/Si(100) substrates using pulsed laser deposition. Variation of the laser pulse rate during the deposition of the PZT films was found to play a key role in the control of the microstructure and to change strongly the piezoelectric response of the thin film. The film deposited at low pulse rate has a denser columnar microstructure, which improves the transverse piezoelectric coefficient (d31f) and ferroelectric remanent polarization (Pr), whereas the less densely packed columnar grains in the film deposited at high pulse rates give rise to a significantly higher longitudinal piezoelectric coefficient (d33f) value. The effect of film thickness on the ferroelectric and piezoelectric properties of the PZT films was also investigated. With increasing film thickness, the grain column diameter gradually increases, and also the average Pr and d33f values become larger. The largest piezoelectric coefficient of d33f = 408 pm V–1 was found for a 4-μm film thickness. From a series of films in the thickness range 0.5–5 μm, the z-position dependence of the piezoelectric coefficient could be deduced. A local maximum value of 600 pm V–1 was deduced in the 3.5–4.5 μm section of the thickest films. The dependence of the film properties on film thickness is attributed to the decreasing effect of the clamping constraint imposed by the substrate and the increasing spatial separation between the grains with increasing film thickness.

Lightweight Open-Cell Scaffolds from Sea Urchin Spines with Superior Material Properties for Bone Defect Repair
Lei Cao - ,
Xiaokang Li - ,
Xiaoshu Zhou - ,
Yong Li - ,
Kenneth S. Vecchio - ,
Lina Yang - ,
Wei Cui - ,
Rui Yang - ,
Yue Zhu *- ,
Zheng Guo *- , and
Xing Zhang *
Sea urchin spines (Heterocentrotus mammillatus), with a hierarchical open-cell structure similar to that of human trabecular bone and superior mechanical property (compressive strength ∼43.4 MPa) suitable for machining to shape, were explored for potential applications of bone defect repair. Finite element analyses reveal that the compressive stress concentrates along the dense growth rings and dissipates through strut structures of the stereoms, indicating that the exquisite mesostructures play an important role in high strength-to-weight ratios. The fracture strength of magnesium-substituted tricalcium phosphate (β-TCMP) scaffolds produced by hydrothermal conversion of urchin spines is about 9.3 MPa, comparable to that of human trabecular bone. New bone forms along outer surfaces of β-TCMP scaffolds after implantation in rabbit femoral defects for one month and grows into the majority of the inner open-cell spaces postoperation in three months, showing tight interface between the scaffold and regenerative bone tissue. Fusion of beagle lumbar facet joints using a Ti-6Al-4V cage and β-TCMP scaffold can be completed within seven months with obvious biodegradation of the β-TCMP scaffold, which is nearly completely degraded and replaced by newly formed bone ten months after implantation. Thus, sea urchin spines suitable for machining to shape have advantages for production of biodegradable artificial grafts for bone defect repair.
Organic Electronic Devices

Surface-Mediated Solidification of a Semiconducting Polymer during Time-Controlled Spin-Coating
Jin Yeong Na - ,
Boseok Kang - ,
Seung Goo Lee - ,
Kilwon Cho *- , and
Yeong Don Park *
Spin-casting a polymer semiconductor solution over a short period of only a few seconds dramatically improved the molecular ordering and charge transport properties of the resulting semiconductor thin films. In this process, it was quite important to halt spinning before the drying line propagation had begun. Here, we elucidated the effects of the substrate surface characteristics on the drying kinetics during spin-coating, systematically investigated the microstructural evolution during semiconducting polymer solidification, and evaluated the performances of the resulting polymer field-effect transistors. We demonstrated that the spin time required to enhance the molecular ordering and electrical properties of the polythiophene thin films was strongly correlated with the solidification onset time, which was altered by surface treatments introduced onto the substrate surfaces.

Enhanced Internal Quantum Efficiency in Dye-Sensitized Solar Cells: Effect of Long-Lived Charge-Separated State of Sensitizers
Haiya Sun - ,
Dongzhi Liu - ,
Tianyang Wang - ,
Ting Lu - ,
Wei Li - ,
Siyao Ren - ,
Wenping Hu - ,
Lichang Wang - , and
Xueqin Zhou *
Effective charge separation is one of the key determinants for the photovoltaic performance of the dye-sensitized solar cells (DSSCs). Herein, two charge-separated (CS) sensitizers, MTPA-Pyc and YD-Pyc, have been synthesized and applied in DSSCs to investigate the effect of the CS states of the sensitizers on the device’s efficiency. The CS states with lifetimes of 64 and 177 ns for MTPA-Pyc and YD-Pyc, respectively, are formed via the photoinduced electron transfer (PET) from the 4-styryltriphenylamine (MTPA) or 4-styrylindoline (YD) donor to the pyrimidine cyanoacrylic acid (Pyc) acceptor. DSSCs based on MTPA-Pyc and YD-Pyc exhibit high internal quantum efficiency (IQE) values of over 80% from 400 to 600 nm. In comparison, the IQEs of the charge transfer (CT) sensitizer cells are 10–30% lower in the same wavelength range. The enhanced IQE values in the devices based on the CS sensitizers are ascribed to the higher electron injection efficiencies and slower charge recombination. The results demonstrate that taking advantage of the CS states in the sensitizers can be a promising strategy to improve the IQEs and further enhance the overall efficiencies of the DSSCs.

Highly Efficient Long-Wavelength Thermally Activated Delayed Fluorescence OLEDs Based on Dicyanopyrazino Phenanthrene Derivatives
Shipan Wang - ,
Zong Cheng - ,
Xiaoxian Song - ,
Xianju Yan - ,
Kaiqi Ye - ,
Yu Liu *- ,
Guochun Yang *- , and
Yue Wang *
Highly efficient long-wavelength thermally activated delayed fluorescence (TADF) materials are developed using 2,3-dicyanopyrazino phenanthrene (DCPP) as the electron acceptor (A), and carbazole (Cz), diphenylamine (DPA), or 9,9-dimethyl-9,10-dihydroacridine (DMAC) as the electron donor (D). Because of the large, rigid π-conjugated structure and strong electron-withdrawing capability of DCPP, TADF molecules with emitting colors ranging from yellow to deep-red are realized with different electron-donating groups and π-conjugation length. The connecting modes between donor and acceptor, that is, with or without the phenyl ring as π-bridge, are also investigated to study the π-bridge effect on the thermal, photophysical, electrochemical, and electroluminescent properties. Yellow, orange, red, and deep-red organic light-emitting diodes (OLEDs) based on DCPP derivatives exhibit high efficiencies of 47.6 cd A–1 (14.8%), 34.5 cd A–1 (16.9%), 12.8 cd A–1 (10.1%), and 13.2 cd A–1 (15.1%), with Commission Internationale de L’Eclairage (CIE) coordinates of (0.44, 0.54), (0.53, 0.46), (0.60, 0.40), and (0.64, 0.36), respectively, which are among the best values for long-wavelength TADF OLEDs.

Asymmetric Alkylthienyl Thienoacenes Derived from Anthra[2,3-b]thieno[2,3-d]thiophene for Solution-Processable Organic Semiconductors
Yuta Ogawa - ,
Kazuhiro Yamamoto - ,
Chiyo Miura - ,
Shigeki Tamura - ,
Mitsuki Saito - ,
Masashi Mamada - ,
Daisuke Kumaki - ,
Shizuo Tokito - , and
Hiroshi Katagiri *
Anthra[2,3-b]thieno[2,3-d]thiophene (ATT), which is readily accessed from thieno[3,2-b]thiophene and 2,3-naphthalenedicarboxylic anhydride, allows for selective substitution at the terminal thiophene ring, thereby providing asymmetric monoalkyl and monoalkylthienyl thienoacenes. Alkyl-substituted ATT (CnATT, n = 6, 8, 10, 12) has characteristics of a p-type field-effect transistor (FET), with mobility on the order of 0.01 cm2 V–1 s–1, which is the same as ATT. Conversely, alkylthienyl-substituted ATT (CnTATT, n = 6, 8, 10, 12) exhibits FET mobility of 0.15–1.9 cm2 V–1 s–1, which is up to 2 orders of magnitude greater than that of ATT and CnATT. Moreover, CnTATT forms crystalline thin films both by spin coating and drop casting, and C8TATT in particular exhibits a mobility of up to 1.6 cm2 V–1 s–1 in the drop-cast film. X-ray diffraction patterns of CnTATT thin films indicate that the molecules become oriented edge-on at the substrate surface with a highly ordered structure in the in-plane direction. Accordingly, CnTATT serves as a solution-processable p-type organic field-effect transistor, where the additional thiophene ring contributes significantly to the highly ordered thin-film structure and the high carrier mobility.

Thermal Gradient During Vacuum-Deposition Dramatically Enhances Charge Transport in Organic Semiconductors: Toward High-Performance N-Type Organic Field-Effect Transistors
Joo-Hyun Kim - ,
Singu Han - ,
Heejeong Jeong - ,
Hayeong Jang - ,
Seolhee Baek - ,
Junbeom Hu - ,
Myungkyun Lee - ,
Byungwoo Choi - , and
Hwa Sung Lee *
A thermal gradient distribution was applied to a substrate during the growth of a vacuum-deposited n-type organic semiconductor (OSC) film prepared from N,N′-bis(2-ethylhexyl)-1,7-dicyanoperylene-3,4:9,10-bis(dicarboxyimide) (PDI-CN2), and the electrical performances of the films deployed in organic field-effect transistors (OFETs) were characterized. The temperature gradient at the surface was controlled by tilting the substrate, which varied the temperature one-dimensionally between the heated bottom substrate and the cooled upper substrate. The vacuum-deposited OSC molecules diffused and rearranged on the surface according to the substrate temperature gradient, producing directional crystalline and grain structures in the PDI-CN2 film. The morphological and crystalline structures of the PDI-CN2 thin films grown under a vertical temperature gradient were dramatically enhanced, comparing with the structures obtained from either uniformly heated films or films prepared under a horizontally applied temperature gradient. The field effect mobilities of the PDI-CN2-FETs prepared using the vertically applied temperature gradient were as high as 0.59 cm2 V–1 s–1, more than a factor of 2 higher than the mobility of 0.25 cm2 V–1 s–1 submitted to conventional thermal annealing and the mobility of 0.29 cm2 V–1 s–1 from the horizontally applied temperature gradient.

Butanedithiol Solvent Additive Extracting Fullerenes from Donor Phase To Improve Performance and Photostability in Polymer Solar Cells
Yuanpeng Xie - ,
Xiaotian Hu - ,
Jingping Yin - ,
Lin Zhang - ,
Xiangchuan Meng - ,
Guodong Xu - ,
Qingyun Ai - ,
Weihua Zhou *- , and
Yiwang Chen *
In this work, we demonstrated that the excited poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2,6-diyl)] (PTB7-Th) will be degraded by [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) or photolysis fragment of 1,8-diiodooctane (DIO) in the presence of oxygen and under irradiation of red light. From the previous reports, the fragment of DIO may be involved in the reaction directly. Our work indicates the PC71BM is not directly involved in the reaction, but is acting as a catalyst to promote the reaction of excited donors with oxygen. Thus, PTB7-Th urgently needs a kind of nonresidual iodine-free additive to replace DIO and remove the fullerene from the donor phase at the same time. Taking into consideration PC71BM solubility and boiling point difference between solvent additives and host solvents, 1,4-butanedithiol solvent was selected to fabricate PTB7-Th:PC71BM-based solar cells achieving a best power conversion efficiency (PCE) of 10.2% (8.5% for PTB7:PC71BM). Iodine-free butanedithiol can not only avoid excited polymer reacting with the photolysis fragment of DIO but also suppress the degradation of the excited PTB7-Th caused by synergistic effect between the fullerene and oxygen via extracting the free/trapped PC71BM from the donor phase. Eventually, the film prepared with 1,4-butanedithiol shows higher stability than the film prepared without any additives and much better than the film with DIO in macro-/micromorphology, light absorption, and device performance.

Fluorine-Induced Highly Reproducible Resistive Switching Performance: Facile Morphology Control through the Transition between J- and H-Aggregation
Yang Li - ,
Zhaojun Liu - ,
Hua Li *- ,
Qingfeng Xu - ,
Jinghui He - , and
Jianmei Lu *
Improving the reproducibility and air-endurance of organic resistance switching (RS) devices, in particular multilevel-cell RS devices, is critical for the confirmation of its competency to realize big data storage capability. However, such enhancement still remains challenging. In this report, we demonstrated that fluorine (F)-embedding should be an effective way to enhance the overall performance of RS devices. Four new azo-cored analogues (IDAZO, FIDAZO, F2IDAZO, and F4IDAZO) have been designed and synthesized. These four compounds have similar structures with different numbers of F substituents. Interestingly, UV–vis measurements reveal that upon F-embedding, an exceptional transition from molecular J-aggregation to H-aggregation is achieved. As a result, the morphology of RS films becomes more and more uniform, as determined by AFM and XRD. Meanwhile, the hydrophobicity of RS film is promoted, which further improves the device atmospheric stability. The total RS reproducibility increases to 96% (the uppermost value), and the tristage RS reproducibility rises to 64%, accompanied by a more stable OFF state and lower logic SET voltages. Our study suggests F-embedding would be a promising strategy to achieve highly reproducible and air-endurable organic multilevel-cell RS devices.
Functional Nanostructured Materials (including low-D carbon)

Petal-Inspired Diffractive Grating on a Wavy Surface: Deterministic Fabrications and Applications to Colorizations and LED Devices
Kyung Jin Park - ,
Jae Hoon Park - ,
Ji-Hyeok Huh - ,
Chan Ho Kim - ,
Dong Hae Ho - ,
Gwan H. Choi - ,
Pil J. Yoo - ,
Sung Min Cho - ,
Jeong Ho Cho *- , and
Seungwoo Lee *
Interestingly, the petals of flowering plants display unique hierarchical structures, in which surface relief gratings (SRGs) are conformably coated on a curved surface with a large radius of curvature (hereafter referred to as wavy surface). However, systematic studies on the interplay between the diffractive modes and the wavy surface have not yet been reported, due to the absence of deterministic nanofabrication methods capable of generating combinatorially diverse SRGs on a wavy surface. Here, by taking advantage of the recently developed nanofabrication composed of evaporative assembly and photofluidic holography inscription, we were able to achieve (i) combinatorially diverse petal-inspired SRGs with controlled curvatures, periodicities, and dimensionalities, and (ii) systematic optical studies of the relevant diffraction modes. Furthermore, the unique diffraction modes of the petal-inspired SRGs were found to be useful for the enhancement of the outcoupling efficiency of an organic light emitting diode (OLED). Thus, our systematic analysis of the interplay between the diffractive modes and the petal-inspired SRGs provides a basis for making more informed decisions in the design of petal-inspired diffractive grating and its applications to optoelectronics.

Highly Networked Capsular Silica–Porphyrin Hybrid Nanostructures as Efficient Materials for Acetone Vapor Sensing
Izabela Osica - ,
Gaku Imamura - ,
Kota Shiba - ,
Qingmin Ji - ,
Lok Kumar Shrestha - ,
Jonathan P. Hill *- ,
Krzysztof J. Kurzydłowski - ,
Genki Yoshikawa - , and
Katsuhiko Ariga *
The development of novel functional nanomaterials is critically important for the further evolution of advanced chemical sensor technology. For this purpose, metalloporphyrins offer unique binding properties as host molecules that can be tailored at the synthetic level and potentially improved by incorporation into inorganic materials. In this work, we present a novel hybrid nanosystem based on a highly networked silica nanoarchitecture conjugated through covalent bonding to an organic functional molecule, a tetraphenylporphyrin derivative, and its metal complexes. The sensing properties of the new hybrid materials were studied using a nanomechanical membrane-type surface stress sensor (MSS) with acetone and nitric oxide as model analytes. This hybrid inorganic–organic MSS-based system exhibited excellent performance for acetone sensing at low operating temperatures (37 °C), making it available for diagnostic monitoring. The hybridization of an inorganic substrate of large surface area with organic molecules of various functionalities results in sub-ppm detection of acetone vapors. Acetone is an important metabolite in lipid metabolism and can also be present in industrial environments at deleterious levels. Therefore, we believe that the analysis system presented by our work represents an excellent opportunity for the development of a portable, easy-to-use device for monitoring local acetone levels.

Iron Nanoclusters as Template/Activator for the Synthesis of Nitrogen Doped Porous Carbon and Its CO2 Adsorption Application
Ning Fu - ,
Huan-Ming Wei - ,
Hua-Lin Lin - ,
Le Li - ,
Cui-Hong Ji - ,
Ning-Bo Yu - ,
Hai-Jun Chen - ,
Sheng Han *- , and
Gu-Yu Xiao *
We propose a facile synthesis approach for nitrogen doped porous carbon and demonstrate a novel pore-forming method that iron nanoclusters act as a template or activator at different carbonization temperatures based on Fe3+-poly(4-vinyipyridine) (P4VP) coordination. P4VP will completely decompose even in an inert atmosphere, but under the coordination and catalysis of Fe3+, it can be converted to carbon at a very low temperature (400 °C). The aggregation of iron nanoclusters in the carbonization process showed different pore-forming methods at different temperatures. The as-prepared materials possess high specific surface area (up to 1211 m2 g–1), large pore volume (up to 0.96 cm3 g–1), narrow microporosity, and high N content (up to 9.9 wt %). Due to these unique features, the materials show high CO2 uptake capacity and excellent selectivity for CO2/N2 separation. The CO2 uptake capacity of NDPC-2-600 is up to 6.8 and 4.3 mmol g–1 at 0 and 25 °C; the CO2/N2 (0.15/0.85) selectivity at 0 and 25 °C also reaches 18.4 and 15.2, respectively.

Strong Electromagnetic Wave Response Derived from the Construction of Dielectric/Magnetic Media Heterostructure and Multiple Interfaces
Bin Quan - ,
Xiaohui Liang - ,
Guangbin Ji *- ,
Jianna Ma - ,
Peiyi Ouyang - ,
He Gong - ,
Guoyue Xu - , and
Youwei Du
A novel yolk–shell structure of cobalt nanoparticle embedded nanoporous carbon@carbonyl iron (Co/NPC@Void@CI) was synthesized via metal organic chemical vapor deposition (MOCVD) and subsequent calcination treatment. The in situ generation of void layer, which originated from the shrink of a Co-based zeolitic imidazolate framework (ZIF-67) during carbonization, embodies distinct advantage compared to the conventional template method. Thanks to the introduction of custom-designed dielectric/magnetic media heterostructure and multiple interfaces, the composites filled with 40 wt % of Co/NPC@Void@CI samples in paraffin exhibit a maximum reflection loss of −49.2 dB at 2.2 mm; importantly, a broad absorption bandwidth (RL < −10 dB) of 6.72 GHz can be obtained, which covers more than one-third of the whole frequency region from 10.56 to 17.28 GHz. This study not only develops the application of carbonyl iron as a high-efficiency light absorber but also initiates a fire-new avenue for artificially designed heterostructures with target functionalities.

Selective Oxidizing Gas Sensing and Dominant Sensing Mechanism of n-CaO-Decorated n-ZnO Nanorod Sensors
Gun-Joo Sun - ,
Jae Kyung Lee - ,
Seungbok Choi - ,
Wan In Lee *- ,
Hyoun Woo Kim - , and
Chongmu Lee *
In this work, we investigated the NO2 and CO sensing properties of n-CaO-decorated n-ZnO nanorods and the dominant sensing mechanism in n–n heterostructured one-dimensional (1D) nanostructured multinetworked chemiresistive gas sensors utilizing the nanorods. The CaO-decorated n-ZnO nanorods showed stronger response to NO2 than most other ZnO-based nanostructures, including the pristine ZnO nanorods. Many researchers have attributed the enhanced sensing performance of heterostructured sensors to the modulation of the conduction channel width or surface depletion layer width. However, the modulation of the conduction channel width is not the true cause of the enhanced sensing performance of n–n heterostructured 1D gas sensors, because the radial modulation of the conduction channel width is not intensified in these sensors. In this work, we demonstrate that the enhanced performance of the n-CaO-decorated n-ZnO nanorod sensor is mainly due to a combination of the enhanced modulation of the potential barrier height at the n–n heterojunctions, the larger surface-area-to-volume ratio and the increased surface defect density of the decorated ZnO nanorods, not the enhanced modulation of the conduction channel width.

Dual-Targeted Multifunctional Nanoparticles for Magnetic Resonance Imaging Guided Cancer Diagnosis and Therapy
Xueyan Nan - ,
Xiujuan Zhang *- ,
Yanqiu Liu - ,
Mengjiao Zhou - ,
Xianfeng Chen *- , and
Xiaohong Zhang *
Hybrid nanostructures with combined functionalities can be rationally designed to achieve synergistic effects for efficient cancer treatment. Herein, a multifunctional nanoplatform is constructed, containing an inner core of an anticancer drug MTX surrounding by a nanometer-thin layer of gold as the shell with Fe3O4 magnetic nanoparticles (NPs) evenly distributed in the gold layer, and the outermost hybrid LA-PEG-MTX molecules as surface coating agent (denoted as MFG-LPM NPs). This nanocomposite possesses very high drug loading capacity as the entire core is MTX and integrates magnetic- and active- targeting drug delivery, light-controlled drug release, magnetic resonance imaging (MRI), as well as photothermal and chemotherapy. With a strong near-infrared (NIR) absorbance at 808 nm, the nanocomposite enables temperature elevation and light-triggered MTX release. In vitro cytotoxicity studies indicate that the strategy of combining therapy leads to a synergistic effect with high cancer cell killing efficacy. In consistency with this, due to the high accumulation of MFG-LPM NPs at tumor site and their combinatorial chemo-photothermal effects, 100% in vivo tumor elimination can be achieved. Additionally, in vivo MRI of tumor-bearing mice demonstrates an impressive performance of MFG-LPM NPs as a T2 contrast agent. Therefore, such multifunctional nanocomposite has the potential to serve as an excellent theranostic agent that collectively integrates multiple functions for efficient MRI guided cancer diagnosis and treatment.

Peptide Cross-linkers: Immobilization of Platinum Nanoparticles Highly Dispersed on Graphene Oxide Nanosheets with Enhanced Photocatalytic Activities
Tsukasa Mizutaru - ,
Galina Marzun - ,
Sebastian Kohsakowski - ,
Stephan Barcikowski - ,
Dachao Hong - ,
Hiroaki Kotani - ,
Takahiko Kojima - ,
Takahiro Kondo - ,
Junji Nakamura - , and
Yohei Yamamoto *
For exerting potential catalytic and photocatalytic activities of metal nanoparticles (MNPs), immobilization of MNPs on a support medium in highly dispersed state is desired. In this Research Article, we demonstrated that surfactant-free platinum nanoparticles (PtNPs) were efficiently immobilized on graphene oxide (GO) nanosheets in a highly dispersed state by utilizing oligopeptide β-sheets as a cross-linker. The fluorenyl-substituted peptides were designed to form β-sheets, where metal-binding thiol groups and protonated and positively charged amino groups are integrated on the opposite sides of the surface of a β-sheet, which efficiently bridge PtNPs and GO nanosheet. In comparison to PtNP/GO composite without the peptide linker, the PtNP/peptide/GO ternary complex exhibited excellent photocatalytic dye degradation activity via electron transfer from GO to PtNP and simultaneous hole transfer from oxidized GO to the dye. Furthermore, the ternary complex showed photoinduced hydrogen evolution upon visible light irradiation using a hole scavenger. This research provides a new methodology for the development of photocatalytic materials by a bottom-up strategy on the basis of self-assembling features of biomolecules.

Efficient Nitrogen Doping of Single-Layer Graphene Accompanied by Negligible Defect Generation for Integration into Hybrid Semiconductor Heterostructures
George Sarau - ,
Martin Heilmann - ,
Muhammad Bashouti - ,
Michael Latzel - ,
Christian Tessarek - , and
Silke Christiansen *
While doping enables application-specific tailoring of graphene properties, it can also produce high defect densities that degrade the beneficial features. In this work, we report efficient nitrogen doping of ∼11 atom % without virtually inducing new structural defects in the initial, large-area, low defect, and transferred single-layer graphene. To shed light on this remarkable high-doping–low-disorder relationship, a unique experimental strategy consisting of analyzing the changes in doping, strain, and defect density after each important step during the doping procedure was employed. Complementary micro-Raman mapping, X-ray photoelectron spectroscopy, and optical microscopy revealed that effective cleaning of the graphene surface assists efficient nitrogen incorporation accompanied by mild compressive strain resulting in negligible defect formation in the doped graphene lattice. These original results are achieved by separating the growth of graphene from its doping. Moreover, the high doping level occurred simultaneously with the epitaxial growth of n-GaN micro- and nanorods on top of graphene, leading to the flow of higher currents through the graphene/n-GaN rod interface. Our approach can be extended toward integrating graphene into other technologically relevant hybrid semiconductor heterostructures and obtaining an ohmic contact at their interfaces by adjusting the doping level in graphene.

Spatiotemporal Control of Supramolecular Self-Assembly and Function
Jie Zhan - ,
Yanbin Cai - ,
Shenglu Ji - ,
Shuangshuang He - ,
Yi Cao *- ,
Dan Ding - ,
Ling Wang - , and
Zhimou Yang *
The enzyme-triggered self-assembly of peptides has flourished in controlling the self-assembly kinetics and producing nanostructures that are typically inaccessible by conventional self-assembly pathways. However, the diffusion and nanoscale chemical gradient of self-assembling peptides generated by the enzyme also significantly affect the outcome of self-assembly, which has not been reported yet. In this work, we demonstrated for the first time a spatiotemporal control of enzyme-triggered peptide self-assembly. By simply adjusting the temperature, we could change both the catalytic activity of the enzyme of phosphatase and their aggregation states. The strategy kinetically controls the production rate of self-assembling peptides and spatially controls their distribution in the system, leading to the formation of nanoparticles at 37 °C and nanofibers at 4 °C. The nanofibers showed ∼10 times higher cellular uptake by 3T3 cells than the nanoparticles, thanks to their higher stability and more ordered structures. Using such spatiotemporal control, we could prepare optimized nanoprobes with low background fluorescence, rapid and high cellular uptake, and high sensitivity. We postulate that this strategy would be very useful in general for preparing self-assembled nanomaterials with controllable morphology and function.

Air-Stable Humidity Sensor Using Few-Layer Black Phosphorus
Jinshui Miao - ,
Le Cai - ,
Suoming Zhang - ,
Junghyo Nah - ,
Junghoon Yeom - , and
Chuan Wang *
As a new family member of two-dimensional layered materials, black phosphorus (BP) has attracted significant attention for chemical sensing applications due to its exceptional electrical, mechanical, and surface properties. However, producing air-stable BP sensors is extremely challenging because BP atomic layers degrade rapidly in ambient conditions. In this study, we explored the humidity sensing properties of BP field-effect transistors fully encapsulated by a 6 nm-thick Al2O3 encapsulation layer deposited by atomic layer deposition. The encapsulated BP sensors exhibited superior ambient stability with no noticeable degradation in sensing response after being stored in air for more than a week. Compared with the bare BP devices, the encapsulated ones offered long-term stability with a trade-off in slightly reduced sensitivity. Capacitance–voltage measurement results further reveal that instead of direct charge transfer, the electrostatic gating effect on BP flakes arising from the dipole moment of adsorbed water molecules is the basic mechanism governing the humidity sensing behavior of both bare and encapsulated BP sensors. This work demonstrates a viable approach for achieving air-stable BP-based humidity or chemical sensors for practical applications.

Ultrasmall Pt Nanoclusters as Robust Peroxidase Mimics for Colorimetric Detection of Glucose in Human Serum
Lihua Jin *- ,
Zheng Meng - ,
Yongqing Zhang - ,
Shijie Cai - ,
Zaihua Zhang - ,
Cong Li - ,
Li Shang *- , and
Yehua Shen
In this work, a new type of ultrasmall Pt nanoclusters (Pt NCs) was prepared via a facile one-pot approach by using yeast extract as the reductant and stabilizer. Besides their excellent water solubility, these yeast extract-stabilized Pt NCs also possess attractive peroxidase mimicking property. They can efficiently catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the coexistence of hydrogen peroxide (H2O2). Catalytic mechanism analysis suggested that the peroxidase mimicking activity of these Pt NCs might originate from their characteristic of accelerating electron transfer between TMB and H2O2, and their enzymatic kinetics followed typical Michaelis–Menten theory. On the basis of these findings, we developed a new highly sensitive colorimetric method for glucose detection, and the limit of detection was calculated as low as 0.28 μM (S/N = 3). Further application of the present system for glucose detection in human serum has been successfully demonstrated, suggesting its promising utilization as robust peroxidase mimics in the clinical diagnosis, pharmaceutical, and environmental chemistry fields.

Receptor-Mediated Surface Charge Inversion Platform Based on Porous Silicon Nanoparticles for Efficient Cancer Cell Recognition and Combination Therapy
Feng Zhang - ,
Alexandra Correia - ,
Ermei Mäkilä - ,
Wei Li - ,
Jarno Salonen - ,
Jouni J. Hirvonen - ,
Hongbo Zhang *- , and
Hélder A. Santos *
Negatively charged surface-modified drug delivery systems are promising for in vivo applications as they have more tendency to accumulate in tumor tissues. However, the inefficient cell uptake of these systems restricts their final therapeutic performance. Here, we have fabricated a receptor-mediated surface charge inversion nanoparticle made of undecylenic acid modified, thermally hydrocarbonized porous silicon (UnTHCPSi) nanoparticles core and sequentially modified with polyethylenimine (PEI), methotrexate (MTX), and DNA aptamer AS1411 (herein termed as UnTHCPSi-PEI-MTX@AS1411) for enhancing the cell uptake of nucleolin-positive cells. The efficient interaction of AS1411 and the relevant receptor nucleolin caused the disintegration of the negative-charged AS1411 surface. The subsequent surface charge inversion and exposure of the active targeting ligand, MTX, enhanced the cell uptake of the nanoparticles. On the basis of this synergistic effect, the UnTHCPSi-PEI-MTX@AS1411 (hydrodynamic diameter is 242 nm) were efficiently internalized by nucleolin-positive MDA-MB-231 breast cancer cells, with an efficiency around 5.8 times higher than that of nucleolin-negative cells (NIH 3T3 fibroblasts). The receptor competition assay demonstrated that the major mechanism (more than one-half) of the internalized nanoparticles in MDA-MB-231 cells was due to the receptor-mediated surface charge inversion process. Finally, after loading of sorafenib, the nanosystem showed efficient performance for combination therapy with an inhibition ratio of 35.6%.

Transcriptome Analysis Reveals Silver Nanoparticle-Decorated Quercetin Antibacterial Molecular Mechanism
Dongdong Sun - ,
Weiwei Zhang - ,
Zhipeng Mou - ,
Ying Chen - ,
Feng Guo - ,
Endong Yang - , and
Weiyun Wang *
Facile and simple method is developed to synthesize silver-nanoparticle-decorated quercetin nanoparticles (QA NPs). Modification suggests that synergistic quercetin (Qe) improves the antibacterial effect of silver nanoparticles (Ag NPs). Characterization experiment indicates that QA NPs have a diameter of approximately 10 nm. QA NPs show highly effective antibacterial activities against drug-resistant Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). We explore antibacterial mechanisms using S. aureus and E. coli treated with QA NPs. Through morphological changes in E. coli and S. aureus, mechanisms are examined for bacterial damage caused by particulate matter from local dissociation of silver ion and Qe from QA NPs trapped inside membranes. Moreover, we note that gene expression profiling methods, such as RNA sequencing, can be used to predict discover mechanisms of toxicity of QA NPs. Gene ontology (GO) assay analyses demonstrate the molecular mechanism of the antibacterial effect of QA NPs. Regarding cellular component ontology, “cell wall organization or biogenesis” (GO: 0071554) and “cell wall macromolecule metabolic process” (GO: 0044036) are the most represented categories. The present study reports that transcriptome analysis of the mechanism offers novel insights into the molecular mechanism of antibacterial assays.
Applications of Polymer, Composite, and Coating Materials

UV Fluorescent Epoxy Adhesives from Noncovalent and Covalent Incorporation of Coumarin Dyes
Peter D. McFadden - ,
Kevin Frederick - ,
Liliana A. Argüello - ,
Yizheng Zhang - ,
Pamela Vandiver - ,
Nancy Odegaard - , and
Douglas A. Loy *
Epoxies are commonly used in art conservation as adhesives for artifact reconstruction and repair. However, with the development of colorless epoxies, it has become more difficult to detect repair work. Fluorescent epoxies would allow for easy detection of the epoxy joints by simple visual inspection under UV light while remaining unnoticeable under normal display lighting. Coumarins are natural dyes that can be added in very small amounts to make thermosets fluoresce. Depending on the functionality of the coumarin used, the dye may be physically encapsulated in the cross-linked polymer or it may be bound to the polymer through covalent bonds. In this paper, we examine the efficacy of coumarin (1) and coumarin 480 (2) as physically encapsulated dyes and 7-hydroxycoumarin (3) and 7-glycidyloxycoumarin (4) as covalently bound dyes in a commercial epoxy thermoset, Epo-Tek 301. All four dyes could be used to make the epoxy fluorescent, but coumarins 1 and 2 slightly reduced the lap shear strength of the thermoset and could be extracted with solvent. In contrast, coumarins 3 and 4 had little effect on the mechanical properties of the epoxy and only minute amounts could be extracted.

Amplified Peroxidase-Like Activity in Iron Oxide Nanoparticles Using Adenosine Monophosphate: Application to Urinary Protein Sensing
Ya-Chun Yang - ,
Yen-Ting Wang - , and
Wei-Lung Tseng *
Numerous compounds such as protein and double-stranded DNA have been shown to efficiently inhibit intrinsic peroxidase-mimic activity in Fe3O4 nanoparticles (NP) and other related nanomaterials. However, only a few studies have focused on finding new compounds for enhancing the catalytic activity of Fe3O4 NP-related nanomaterials. Herein, phosphate containing adenosine analogs are reported to enhance the oxidation reaction of hydrogen peroxide (H2O2) and amplex ultrared (AU) for improving the peroxidase-like activity in Fe3O4 NPs. This enhancement is suggested to be a result of the binding of adenosine analogs to Fe2+/Fe3+ sites on the NP surface and from adenosine 5′-monophosphate (AMP) acting as the distal histidine residue of horseradish peroxidase for activating H2O2. Phosphate containing adenosine analogs revealed the following trend for the enhanced activity of Fe3O4 NPs: AMP > adenosine 5′-diphosphate > adenosine 5′-triphosphate. The peroxidase-like activity in the Fe3O4 NPs progressively increased with increasing AMP concentration and polyadenosine length. The Michaelis constant for AMP attached Fe3O4 NPs is 5.3-fold lower and the maximum velocity is 2.7-fold higher than those of the bare Fe3O4 NPs. Furthermore, on the basis of AMP promoted peroxidase mimicking activity in the Fe3O4 NPs and the adsorption of protein on the NP surface, a selective fluorescent turn-off system for the detection of urinary protein is developed.

Highly Flexible and Self-Healable Thermal Interface Material Based on Boron Nitride Nanosheets and a Dual Cross-Linked Hydrogel
Hongbo Jiang - ,
Zifeng Wang - ,
Huiyuan Geng - ,
Xiufeng Song - ,
Haibo Zeng *- , and
Chunyi Zhi *
The booming growth of flexible and stretchable electronic devices with increasing power and multifunctionalities calls for novel highly efficient thermal interface materials (TIMs) with versatile functions, such as high deformability and self-healing ability, whereas traditional metallic-based or grease-based ones could hardly provide. Herein, we report a highly flexible and self-healable dual-cross-linked hydrogel-based nanocomposite filled with hexagonal boron nitride (h-BN) nanosheets fabricated by in situ polymerization of acrylic acid (AA). The thermal conductivity of the composites can be tuned by adjusting both fraction of BNNSs and water content. Although a solid, the highly flexible characteristic of the developed TIMs enables a perfect ability to replicate the texture of a rough surface, which may greatly enhance thermal transfer between adjacent surfaces. By increasing the water content to soften the material, it can be recycled and reused for different kinds of rough surface. In addition, benefiting from the dual-cross-linked structure, the composites are capable of recovering both mechanical strength and thermal conductivity even from severe structural breakdowns, for example, three consecutive cutting and healing cycles. This study may pave the way to fabrication of multifunctional highly flexible TIMs, which may promote the development of heat dissipation materials.

High-Strength Stereolithographic 3D Printed Nanocomposites: Graphene Oxide Metastability
Jill Z. Manapat - ,
Joey Dacula Mangadlao - ,
Brylee David Buada Tiu - ,
Grace C. Tritchler - , and
Rigoberto C. Advincula *
The weak thermomechanical properties of commercial 3D printing plastics have limited the technology’s application mainly to rapid prototyping. In this report, we demonstrate a simple approach that takes advantage of the metastable, temperature-dependent structure of graphene oxide (GO) to enhance the mechanical properties of conventional 3D-printed resins produced by stereolithography (SLA). A commercially available SLA resin was reinforced with minimal amounts of GO nanofillers and thermally annealed at 50 and 100 °C for 12 h. Tensile tests revealed increasing strength and modulus at an annealing temperature of 100 °C, with the highest tensile strength increase recorded at 673.6% (for 1 wt % GO). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) also showed increasing thermal stability with increasing annealing temperature. The drastic enhancement in mechanical properties, which is seen to this degree in 3D-printed samples reported in literature, is attributed to the metastable structure of GO, polymer–nanofiller cross-linking via acid-catalyzed esterification, and removal of intercalated water, thus improving filler–matrix interaction as evidenced by spectroscopy and microscopy analyses.

Interfacial Design of Ternary Mixed Matrix Membranes Containing Pebax 1657/Silver-Nanopowder/[BMIM][BF4] for Improved CO2 Separation Performance
Ehsan Ghasemi Estahbanati - ,
Mohammadreza Omidkhah *- , and
Abtin Ebadi Amooghin *
In this research, Pebax1657 as an organic phase and silver nanoparticles as an inorganic phase were used for preparation of binary mixed matrix membranes (MMMs). Silver nanoparticles as a filler could enter the polymer chains and enhance the gas permeability by increasing the fractional free volume of membranes. Afterward, ternary MMMs were fabricated by addition of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) ionic liquid, in order to have better polymer/filler adhesion and eliminate interfacial defects and nonselective voids. In addition, positively polarized silver nanoparticles in the presence of the IL could interact with PEO segment of the polymer and increase the CO2 affinity of membranes, which results in increasing the CO2/light gases permselectivity of MMMs. Gas permeation properties of MMMs were studied at a temperature of 35 °C and operating pressures from 2 to 10 bar. Moreover, fabricated membranes were characterized by fourier transform infrared-attenuated total reflectance (FTIR-ATR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimeter (DSC). The analysis revealed that there is a proper adhesion between positively charged surface of nanoparticles and the polymer, and both filler and IL decrease the crystallinity of the membranes, which could enhance the polar gas transport properties. Gas permeation results showed significant enhancement in CO2 permeability (325 Barrer) for binary membrane (Pebax 1657/1%Ag) at 35 °C and 10 bar. Moreover, ternary MMM (Pebax 1657/0.5%Ag/50%IL) encountered significant increase in both permeability and selectivity in comparison with neat membrane. Indeed, the CO2 permeability increased from 110 Barrer to 180 (about 64%). Moreover, the related CO2/CH4 and CO2/N2 selectivities were increased from 20.8 to 61.0 (more than 193%) and from 78.6 to 187.5 (about 139%), respectively.

The Role of Field Electron Emission in Polypropylene/Aluminum Nanodielectrics Under High Electric Fields
Guoqiang Zhang - ,
Yue Li - ,
Saide Tang - ,
Rhett D. Thompson - , and
Lei Zhu *
Polymer/metallic particle nanocomposites or nanodielectrics can exhibit colossal dielectric constants with a relatively low dissipation factor under low electric fields and thus seem to be promising for high-energy density dielectric capacitors. To study this possibility, this work focused on the dielectric performance and loss mechanisms in polypropylene (PP)/aluminum nanoparticle (nAl NP) composites under high electric fields. Phosphonic acid-terminated poly(ethylene-co-1-butene) was grafted to the Al2O3 surface layer on the nAl NPs in order to achieve reasonable dispersion in the PP matrix. The dielectric breakdown study showed that the breakdown strength decreased to nearly 1/20 that of the neat PP film as the nAl content increased to 25.0 vol %. The leakage current study revealed three electronic conduction mechanisms in the PP/100 nm nAl nanocomposites, namely, ohmic conduction at low fields, hopping conduction at intermediate fields, and Fowler–Nordheim (FN) field electron emission above a critical field, depending on the filler content. Compared to the 100 nm nAl NPs, smaller (e.g., 18 nm) nAl NPs needed a much higher electric field to exhibit FN field electron emission. It was the FN electron tunneling that induced a substantial reduction in breakdown strength for the PP/nAl nanocomposites. Meanwhile, electron-tunneling injected space charges (electrons) from nAl NPs into the PP matrix, and internal electronic conduction led to significant dielectric nonlinearity at high poling fields. Although polymer/metallic NP composites are not suitable for high-field electric applications, they can be good candidates for electrical switches and quantum tunneling composites operated at relatively low electric fields.

Metal–Organic–Inorganic Nanocomposite Thermal Interface Materials with Ultralow Thermal Resistances
Cengiz Yegin - ,
Nirup Nagabandi - ,
Xuhui Feng - ,
Charles King - ,
Massimo Catalano - ,
Jun Kyun Oh - ,
Ansam J. Talib - ,
Ethan A. Scholar - ,
Stanislav V. Verkhoturov - ,
Tahir Cagin - ,
Alexei V. Sokolov - ,
Moon J. Kim - ,
Kaiser Matin - ,
Sreekant Narumanchi - , and
Mustafa Akbulut *
As electronic devices get smaller and more powerful, energy density of energy storage devices increases continuously, and moving components of machinery operate at higher speeds, the need for better thermal management strategies is becoming increasingly important. The removal of heat dissipated during the operation of electronic, electrochemical, and mechanical devices is facilitated by high-performance thermal interface materials (TIMs) which are utilized to couple devices to heat sinks. Herein, we report a new class of TIMs involving the chemical integration of boron nitride nanosheets (BNNS), soft organic linkers, and a copper matrix—which are prepared by the chemisorption-coupled electrodeposition approach. These hybrid nanocomposites demonstrate bulk thermal conductivities ranging from 211 to 277 W/(m K), which are very high considering their relatively low elastic modulus values on the order of 21.2–28.5 GPa. The synergistic combination of these properties led to the ultralow total thermal resistivity values in the range of 0.38–0.56 mm2 K/W for a typical bond-line thickness of 30–50 μm, advancing the current state-of-art transformatively. Moreover, its coefficient of thermal expansion (CTE) is 11 ppm/K, forming a mediation zone with a low thermally induced axial stress due to its close proximity to the CTE of most coupling surfaces needing thermal management.

Micropatterned Pyramidal Ionic Gels for Sensing Broad-Range Pressures with High Sensitivity
Sung Hwan Cho - ,
Seung Won Lee - ,
Seunggun Yu - ,
Hyeohn Kim - ,
Sooho Chang - ,
Donyoung Kang - ,
Ihn Hwang - ,
Han Sol Kang - ,
Beomjin Jeong - ,
Eui Hyuk Kim - ,
Suk Man Cho - ,
Kang Lib Kim - ,
Hyungsuk Lee - ,
Wooyoung Shim *- , and
Cheolmin Park *
The development of pressure sensors that are effective over a broad range of pressures is crucial for the future development of electronic skin applicable to the detection of a wide pressure range from acoustic wave to dynamic human motion. Here, we present flexible capacitive pressure sensors that incorporate micropatterned pyramidal ionic gels to enable ultrasensitive pressure detection. Our devices show superior pressure-sensing performance, with a broad sensing range from a few pascals up to 50 kPa, with fast response times of <20 ms and a low operating voltage of 0.25 V. Since high-dielectric-constant ionic gels were employed as constituent sensing materials, an unprecedented sensitivity of 41 kPa–1 in the low-pressure regime of <400 Pa could be realized in the context of a metal–insulator–metal platform. This broad-range capacitive pressure sensor allows for the efficient detection of pressure from a variety of sources, including sound waves, a lightweight object, jugular venous pulses, radial artery pulses, and human finger touch. This platform offers a simple, robust approach to low-cost, scalable device design, enabling practical applications of electronic skin.

Controlling Agglomeration of Protein Aggregates for Structure Formation in Liquid Oil: A Sticky Business
Auke de Vries - ,
Yuly Lopez Gomez - ,
Bas Jansen - ,
Erik van der Linden - , and
Elke Scholten *
This publication is Open Access under the license indicated. Learn More
Proteins are known to be effective building blocks when it comes to structure formation in aqueous environments. Recently, we have shown that submicron colloidal protein particles can also be used to provide structure to liquid oil and form so-called oleogels (de Vries, A. J. Colloid Interface Sci. 2017, 486, 75−83). To prevent particle agglomeration, a solvent exchange procedure was used to transfer the aggregates from water to the oil phase. The aim of the current paper was to elucidate on the enhanced stability against agglomeration of heat-set whey protein isolate (WPI) aggregates to develop an alternative for the solvent exchange procedure. Protein aggregates were transferred from water to several solvents differing in polarity to investigate the effect on agglomeration and changes in protein composition. We show that after drying protein aggregates by evaporation from solvents with a low polarity (e.g., hexane), the protein powder shows good dispersibility in liquid oil compared to powders dried from solvents with a high polarity. This difference in dispersibility could not be related to changes in protein composition or conformation but was instead related to the reduction of attractive capillary forces between the protein aggregates during drying. Following another route, agglomeration was also prevented by applying high freezing rates prior to freeze-drying. The rheological properties of the oleogels prepared with such freeze-dried protein aggregates were shown to be similar to that of oleogels prepared using a solvent exchange procedure. This Research Article provides valuable insights in how to tune the drying process to control protein agglomeration to allow for subsequent structure formation of proteins in liquid oil.

Interfacial Shish-Kebabs Lengthened by Coupling Effect of In Situ Flexible Nanofibrils and Intense Shear Flow: Achieving Hierarchy To Conquer the Conflicts between Strength and Toughness of Polylactide
Sheng-Yang Zhou - ,
Ben Niu - ,
Xu-Long Xie - ,
Xu Ji - ,
Gan-Ji Zhong *- ,
Benjamin S. Hsiao - , and
Zhong-Ming Li *
The challenge of hitherto elaborating a feasible pathway to overcome the conflicts between strength and toughness of polylactide (PLA) still remains among academia and industry. In the current work, a unique hierarchal structure of flexible poly(butylene adipate-co-terephthalate) (PBAT) in situ nanofibrils integrating with abundant PLA shish-kebabs as a strong building block was disclosed and expresses its capability to conquer this dilemma. Substantially simultaneous enhancement on tensile strength, impact strength, and elongation at break could be achieved up to 91.2 MPa, 14.9 KJ/m2, and 15.7%, respectively, compared with pure PLA (61.5 MPa, 4.3 KJ/m2, and 6.2%). Through investigating the phase (and crystalline) morphology and molecular chain behavior in the PLA/PBAT system, the formation mechanism of this structure facilitated by a coupling effect of PBAT flexible phase and shear flow was definitely elucidated. The dispersed phase of PBAT would be more inclined to existing as a fibrillar form within the PLA matrix benefiting from low interfacial tension. Interestingly, this phase morphology with large specific surface area changes the crystallization behavior of PLA significantly, once introducing an intense shear flow (∼103 s–1), in situ shear-formed nanofibrils of PBAT would show strong coupling effect with shear flow on PLA crystallization: they can not only induce abundant shish-kebabs of PLA at its interfaces, which possesses lengthened shish and more densely arranged kebabs, but also further retard the relaxation of PLA chains through hysteretic relaxation of its PBAT phase, which can effectively prevent the collapse of established shish. Of immense significance is this particular hierarchical-architecture composed by flexible nanofibers (PBAT) and rigid shish-kebabs (PLA), which provides significant guidance for the simultaneous reinforcement and toughness of polymer materials.

Graphene-Borate as an Efficient Fire Retardant for Cellulosic Materials with Multiple and Synergetic Modes of Action
Md J. Nine - ,
Diana N. H. Tran - ,
Tran Thanh Tung - ,
Shervin Kabiri - , and
Dusan Losic *
To address high fire risks of flamable cellulosic materials, that can trigger easy combustion, flame propagation, and release of toxic gases, we report a new fire-retardant approach using synergetic actions combining unique properties of reduced graphene oxide (rGO) and hydrated-sodium metaborates (SMB). The single-step treatment of cellulosic materials by a composite suspension of rGO/SMB was developed to create a barrier layer on sawdust surface providing highly effective fire retardant protection with multiple modes of action. These performances are designed considering synergy between properties of hydrated-SMB crystals working as chemical heat-sink to slow down the thermal degradation of the cellulosic particles and gas impermeable rGO layers that prevents access of oxygen and the release of toxic volatiles. The rGO outer layer also creates a thermal and physical barrier by donating carbon between the flame and unburnt wood particles. The fire-retardant performance of developed graphene-borate composite and mechanism of fire protection are demonstrated by testing of different forms of cellulosic materials such as pine sawdust, particle-board, and fiber-based structures. Results revealed their outstanding self-extinguishing behavior with significant resistance to release of toxic and flammable volatiles suggesting rGO/SMB to be suitable alternative to the conventional toxic halogenated flame-retardant materials.

Investigating the Photocatalytic Degradation of Oil Paint using ATR-IR and AFM-IR
Suzanne Morsch *- ,
Birgit A. van Driel - ,
Klaas Jan van den Berg - , and
Joris Dik
As linseed oil has a longstanding and continuing history of use as a binder in artistic paints, developing an understanding of its degradation mechanism is critical to conservation efforts. At present, little can be done to detect the early stages of oil paint deterioration due to the complex chemical composition of degrading paints. In this work, we use advanced infrared analysis techniques to investigate the UV-induced deterioration of model linseed oil paints in detail. Subdiffraction limit infrared analysis (AFM-IR) is applied to identify and map accelerated degradation in the presence of two different grades of titanium white pigment particles (rutile or anatase TiO2). Differentiation between the degradation of these two formulations demonstrates the sensitivity of this approach. The identification of characteristic peaks and transient species residing at the paint surface allows infrared absorbance peaks related to degradation deeper in the film to be extricated from conventional ATR-FTIR spectra, potentially opening up a new approach to degradation monitoring.

Construction of Supramolecular Nanoassembly for Responsive Bacterial Elimination and Effective Bacterial Detection
Qiaoying Li - ,
Yuanhao Wu - ,
Hongguang Lu - ,
Xinshi Wu - ,
Shuai Chen - ,
Nan Song - ,
Ying-Wei Yang *- , and
Hui Gao *
There is an urgent need for developing novel strategies for bacterial detection and inhibition. Herein, a multifunctional nanomaterial based on mesoporous silica nanoparticles (MSNs) is designed, loaded with amoxicillin (AMO), and surface-coated with 1,2-ethanediamine (EDA)-modified polyglycerol methacrylate (PGEDA), cucurbit[7]uril (CB[7]), and tetraphenylethylene carboxylate derivatives (TPE-(COOH)4) by the layer-by-layer (LbL) self-assembly technique. When bacteria contacts with this nanoassembly, the binding of anionic bacterial surface toward the cationic PGEDA layer of this material can reduce or break the interactions between PGEDA layer and TPE-(COOH)4 layer, leading to attenuated TPE-(COOH)4 emission due to the weakening of aggregation-induced emission (AIE) effect. Furthermore, upon adding adamantaneamine (AD), the more stable AD⊂CB[7] complex forms and PGEDA is liberated through competitive replacement, thus leading to the release of AMO and resulting in much higher antibacterial ability of this nanomaterial. This newly designed nanomaterial possesses dual functions of controllable antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, and bacterial detection ability in aqueous media, suggesting that the design of this multifunctional antibacterial material will provide a simple, effective, and rapid way to control the activity of antimicrobial and open up an alternative new avenue for bacterial detection and elimination.

Highly Sensitive Textile Strain Sensors and Wireless User-Interface Devices Using All-Polymeric Conducting Fibers
Jimi Eom - ,
Rawat Jaisutti - ,
Hyungseok Lee - ,
Woobin Lee - ,
Jae-Sang Heo - ,
Jun-Young Lee - ,
Sung Kyu Park *- , and
Yong-Hoon Kim *
Emulation of diverse electronic devices on textile platform is considered as a promising approach for implementing wearable smart electronics. Of particular, the development of multifunctional polymeric fibers and their integration in common fabrics have been extensively researched for human friendly wearable platforms. Here we report a successful emulation of multifunctional body-motion sensors and user-interface (UI) devices in textile platform by using in situ polymerized poly(3,4-ethylenedioxythiophene) (PEDOT)-coated fibers. With the integration of PEDOT fibers in a fabric, via an optimization of the fiber pattern design, multifunctional textile sensors such as highly sensitive and reliable strain sensors (with maximum gauge factor of ∼1), body-motion monitoring sensors, touch sensors, and multilevel strain recognition UI devices were successfully emulated. We demonstrate the facile utilization of the textile-based multifunctional sensors and UI devices by implementing in a wireless system that is capable of expressing American Sign Language through predefined hand gestures.
Surfaces, Interfaces, and Applications

Photodiode Response in a CH3NH3PbI3/CH3NH3SnI3 Heterojunction
Massimo Spina - ,
László Mihály - ,
Károly Holczer - ,
Bálint Náfrádi *- ,
Andrea Pisoni - ,
László Forró - , and
Endre Horváth
Here we report another surprising feature of the methylammonium metal halide material family, the phototunability of the diode response of a heterojunction made of CH3NH3PbI3 and its close relative, CH3NH3SnI3. In the dark state the device behaves as a diode, with the Sn homologue acting as the “p” side. The junction is extremely sensitive to illumination. A complete reversal of the diode polarity, the first observation of its kind, is seen when the junction is exposed to red laser light of 25 mW/cm2 or larger power density. This finding opens up the possibility for a novel class of optoelectronic devices.

Interfacial Mechanical Properties of Graphene on Self-Assembled Monolayers: Experiments and Simulations
Qing Tu - ,
Ho Shin Kim - ,
Thomas J. Oweida - ,
Zehra Parlak - ,
Yaroslava G. Yingling - , and
Stefan Zauscher *
Self-assembled monolayers (SAMs) have been widely used to engineer the electronic properties of substrate-supported graphene devices. However, little is known about how the surface chemistry of SAMs affects the interfacial mechanical properties of graphene supported on SAMs. Fluctuations and changes in these properties affect the stress transfer between substrate and the supported graphene and thus the performance of graphene-based devices. The changes in interfacial mechanical properties can be characterized by measuring the out-of-plane elastic properties. Combining contact resonance atomic force microcopy experiments with molecular dynamics simulations, we show that the head group chemistry of a SAM, which affects the interfacial interactions, can have a significant effect on the out-of-plane elastic modulus of the graphene–SAM heterostructure. Graphene supported on hydrophobic SAMs leads to heterostructures stiffer than those of graphene supported on hydrophilic SAMs, which is largely due to fewer water molecules present at the graphene–SAM interface. Our results provide an important, and often overlooked, insight into the mechanical properties of substrate-supported graphene electronics.

Chlorine-Resistant Polyamide Reverse Osmosis Membrane with Monitorable and Regenerative Sacrificial Layers
Hai Huang - ,
Saisai Lin - ,
Lin Zhang *- , and
Li’an Hou
Improving chlorine stability is a high priority for aromatic polyamide (PA) reverse osmosis (RO) membranes especially in long-term desalination. In this Research Article, PA RO membranes of sustainable chlorine resistance was synthesized. Glycylglycine (Gly) was grafted onto the membrane surface as a regenerative chlorine sacrificial layer, and the zeta-potential was used to monitor the membrane performance and to conduct timely regeneration operations for chlorinated Gly. The Gly-grafted PA membrane exhibited ameliorative chlorine resistance in which the N–H moiety of glycylglycine served as sacrificial pendants against chlorine attacks. Cyclic chlorination experiments, combined with FT-IR and XPS analysis, were carried out to characterize the membrane. Results indicated that the resulting N-halamines could be fast regenerated by a simple alkaline reduction step (pH 10). A synchronous relationship between the zeta-potential and the chlorination extent of the sacrificial layer was observed. This indicated that the zeta-potential can be used as an on-site sensor to conduct a timely regeneration operation. The intrinsic mechanism of the surface sacrificial process was also studied.

Ultra Water Repellent Polypropylene Surfaces with Tunable Water Adhesion
Tang Zhu - ,
Chao Cai - ,
Jing Guo - ,
Rong Wang - ,
Ning Zhao *- , and
Jian Xu *
Polypropylene (PP), including isotactic PP (i-PP) and atactic PP (a-PP) with distinct tacticity, is one of the most widely used general plastics. Herein, ultra water repellent PP coatings with tunable adhesion to water were prepared via a simple casting method. The pure i-PP coating shows a hierarchical morphology with micro/nanobinary structures, exhibiting a water contact angle (CA) larger than 150° and a sliding angle less than 5° (for 5 μL water droplet). In contrast, the pure a-PP coating has a less rough morphology with a water contact angle of about 130°, and the water droplets stick on the coating at any tilted angles. For the composite i-PP/a-PP coatings, however, ultra water repellency with CA > 150° but water adhesion tailorable from slippery to sticky can be realized, depending on the contents of a-PP and i-PP. The different wetting behaviors are due to the various microstructures of the composite coatings resulting from the distinct crystallization ability of a-PP and i-PP. Furthermore, the existence of a-PP in the composite coatings enhances the mechanical properties compared to the i-PP coating. The proposed method is feasible to modify various substrates and potential applications in no-loss liquid transportation, slippery surfaces, and patterned superhydrophobic surfaces are demonstrated.

Exceptional Anti-Icing Performance of Self-Impregnating Slippery Surfaces
Christos Stamatopoulos - ,
Jaroslav Hemrle - ,
Danhong Wang - , and
Dimos Poulikakos *
A heat exchange interface at subzero temperature in a water vapor environment exhibits high probability of frost formation due to freezing condensation, a factor that markedly decreases the heat transfer efficacy due to the considerable thermal resistance of ice. Here we report a novel strategy to delay ice nucleation on these types of solid–water vapor interfaces. With a process-driven mechanism, a self-generated liquid intervening layer immiscible to water is deposited on a textured superhydrophobic surface and acts as a barrier between the water vapor and the solid substrate. This liquid layer imparts remarkable slippery conditions resulting in high mobility of condensing water droplets. A large increase of the ensuing ice coverage time is shown compared to the cases of standard smooth hydrophilic or textured superhydrophobic surfaces. During deicing of these self-impregnating surfaces we show an impressive tendency of ice fragments to skate expediting defrosting. Robustness of such surfaces is also demonstrated by operating them under subcooling for at least 490 h without a marked degradation. This is attributed to the presence of the liquid intervening layer, which protects the substrate from hydrolyzation, enhancing longevity and sustaining heat transfer efficiency.

Amine-Reactive Azlactone-Containing Nanofibers for the Immobilization and Patterning of New Functionality on Nanofiber-Based Scaffolds
Michael J. Kratochvil - ,
Matthew C. D. Carter - , and
David M. Lynn *
We report the design of amine-reactive polymer nanofibers and nonwoven reactive nanofiber mats fabricated by the electrospinning of azlactone-functionalized polymers. We demonstrate that randomly oriented nanofibers fabricated using a random copolymer of methyl methacrylate and 2-vinyl-4,4-dimethylazlactone contain intact and reactive azlactone groups that can be used to introduce new chemical functionality and modulate important interfacial properties of these materials (e.g., wetting behaviors) by postfabrication treatment with primary amine-based nucleophiles. The facile and “click-like” nature of these reactions permits functionalization under mild conditions without substantial changes to nanofiber or mat morphologies. This approach also enables the patterning of new functionality on mat-coated surfaces by treatment with bulk solutions of primary amines or by using methods such as microcontact printing. Further, these reactive mats can also, themselves, be contact-transferred or “printed” onto secondary surfaces by pressing them into contact with other amine-functionalized objects. Finally, we demonstrate that functionalization with hydrophobic amines can increase the stability of these materials in aqueous environments and yield hydrophobic nanofiber scaffolds useful for the design of “slippery” liquid-infused materials. The approaches reported here enable the introduction of new properties to reactive polymer mats after fabrication and, thus, reduce the need to synthesize individual functional polymers prior to electrospinning to achieve new properties. The azlactone chemistry used here broadens the scope of reactions that can be used to functionalize polymer nanofibers and is likely to prove general. We anticipate that this approach can be used with a range of amines or other nucleophiles (e.g., alcohols or thiols) to design nanofibers and reactive nanofiber-based materials with new physical properties, surface features, and behaviors that may be difficult to achieve by the direct electrospinning of conventional materials or other functional polymers.

Impacts of Cross-Linkers on Biological Effects of Mesoporous Silica Nanoparticles
Yi-Ping Chen - ,
Si-Han Wu - ,
I-Chih Chen - , and
Chien-Tsu Chen *
Chemically synthesized cross-linkers play decisive roles in variable cargos attached to nanoparticles (NPs). Previous studies reported that surface properties, such as the size, charge, and surface chemistry, are particularly important determinants influencing the biological fate and actions of NPs and cells. Recent studies also focused on the relationship of serum proteins with the surface properties of NPs (also called the protein corona), which is recognized as a key factor in determining the cytotoxicity and biodistribution. However, there is concern that cross-linkers conjugated onto NPs might induce undesirable biological effects. Cell responses induced by cross-linkers have not yet been precisely elucidated. Herein, using mesoporous silica nanoparticles (MSNs) the surfaces of which were separately conjugated with four popular heterobifunctional cross-linkers, i.e., N-[α-maleimidoacetoxy]succinimide ester (AMAS), m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC), and maleimide poly(ethylene glycol) succinimidyl carboxymethyl ester (MAL-PEG-SCM), we investigated cross-linker-conjugated MSNs to determine whether they can cause cytotoxicity, or enhance reactive oxygen species (ROS) generation, nuclear factor (NF)-κB activation, and p-p38 or p21 protein expressions in RAW264.7 macrophage cells. Furthermore, we also separately conjugated two biomolecules containing TAT peptides and bovine serum albumin (BSA) as model systems to study their cell responses in detail. Finally, in vivo mice studies evaluated the biodistribution and blood assays (biochemistry and complete blood count) of PEG-derivative NPs, and results suggested that TAT peptides caused significant white blood cell (WBC)-related cell and platelet abnormalities, as well as liver and kidney dysfunction compared to BSA when conjugated onto MSNs. The results showed that attention to cross-linkers should be considered an issue in the surface modification of NPs. We anticipate that our results could be helpful in developing biosafety nanomaterials.

Separation and Sequential Recovery of Tetracycline and Cu(II) from Water Using Reusable Thermoresponsive Chitosan-Based Flocculant
Kexin Ren - ,
Hongwei Du - ,
Zhen Yang *- ,
Ziqi Tian - ,
Xuntong Zhang - ,
Weiben Yang *- , and
Jianqiang Chen
Coexistence of antibiotics and heavy metals is typically detected in water containing both organic and inorganic contaminants. In this work, a flocculation method using a reusable thermoresponsive chitosan-based flocculant (CS-g-PNNPAM) was applied for separation and sequential recovery of tetracycline (TC) and Cu(II) from water. High synergistic removal rates of both TC and Cu(II) from water (>90%) were reached. Interactive effects among targeted water temperature (T1), stock solution temperature (T2), and flocculant dosage on flocculation performance were assessed using response surface methodology. To optimize flocculation, operation strategies of adjusting T2 and dosage according to T1 based on the interactive effects were given through mathematical analyses. The flocculation mechanism as well as interfacial interactions among CS-g-PNNPAM, TC, and Cu(II) were studied through experimental investigations (floc size monitoring, X-ray photoelectron spectroscopy, and UV spectra) and theoretical calculations (density functional theory and molecular dynamics simulations). Coordination of Cu(II) with TC and the flocculant promoted flocculation; switchable interactions (H bonds and hydrophobic association) of the TC–flocculant at different temperatures were key factors affecting operation strategies. When these interactions were weakened step by step, TC and Cu(II) were sequentially recovered from flocs using certain solutions. Meanwhile, the flocculant in flocs was regenerated and found reusable with high flocculation efficiency.

Nitrogen-Doped Porous Carbons from Ionic Liquids@MOF: Remarkable Adsorbents for Both Aqueous and Nonaqueous Media
Imteaz Ahmed - ,
Tandra Panja - ,
Nazmul Abedin Khan - ,
Mithun Sarker - ,
Jong-Sung Yu *- , and
Sung Hwa Jhung *
Porous carbons were prepared from a metal–organic framework (MOF, named ZIF-8), with or without modification, via high-temperature pyrolysis. Porous carbons with high nitrogen content were obtained from the calcination of MOF after introducing an ionic liquid (IL) (IL@MOF) via the ship-in-bottle method. The MOF-derived carbons (MDCs) and IL@MOF-derived carbons (IMDCs) were characterized using various techniques and used for liquid-phase adsorptions in both water and hydrocarbon to understand the possible applications in purification of water and fuel, respectively. Adsorptive performances for the removal of organic contaminants, atrazine (ATZ), diuron, and diclofenac, were remarkably enhanced with the modification/conversion of MOFs to MDC and IMDC. For example, in the case of ATZ adsorption, the maximum adsorption capacity of IMDC (Q0 = 208 m2/g) was much higher than that of activated carbon (AC, Q0 = 60 m2/g) and MDC (Q0 = 168 m2/g) and was found to be the highest among the reported results so far. The results of adsorptive denitrogenation and desulfurization of fuel were similar to that of water purification. The IMDCs are very useful in the adsorptions since these new carbons showed remarkable performances in both the aqueous and nonaqueous phases. These results are very meaningful because hydrophobic and hydrophilic adsorbents are usually required for the adsorptions in the water and fuel phases, respectively. Moreover, a plausible mechanism, H-bonding, was also suggested to explain the remarkable performance of the IMDCs in the adsorptions. Therefore, the IMDCs derived from IL@MOF might have various applications, especially in adsorptions, based on high porosity, mesoporosity, doped nitrogen, and functional groups.

Stable Zr(IV)-Based Metal–Organic Frameworks with Predesigned Functionalized Ligands for Highly Selective Detection of Fe(III) Ions in Water
Bin Wang - ,
Qi Yang - ,
Chao Guo - ,
Yuxiu Sun - ,
Lin-Hua Xie *- , and
Jian-Rong Li
Metal–organic frameworks are a class of attractive materials for fluorescent sensing. Improvement of hydrolytic stability, sensitivity, and selectivity of function is the key to advance application of fluorescent MOFs in aqueous media. In this work, two stable MOFs, [Zr6O4(OH)8(H2O)4(L1)2] (BUT-14) and [Zr6O4(OH)8(H2O)4(L2)2] (BUT-15), were designed and synthesized for the detection of metal ions in water. Two new ligands utilized for construction of the MOFs, namely, 5′,5‴-bis(4-carboxyphenyl)-[1,1′:3′,1″:4″,1‴:3‴,1′′′′-quinquephenyl]-4,4′′′′-dicarboxylate (L1) and 4,4′,4″,4‴-(4,4′-(1,4-phenylene)bis(pyridine-6,4,2-triyl))tetrabenzoate (L2), are structurally similar with the only difference being that the latter is functionalized by pyridine N atoms. The two MOFs are isostructural with a sqc-a topological framework structure, and highly porous with the Brunauer–Emmett–Teller (BET) surface areas of 3595 and 3590 m2 g–1, respectively. Interestingly, they show intense fluorescence in water, which can be solely quenched by trace amounts of Fe3+ ions. The detection limits toward the Fe3+ ions were calculated to be 212 and 16 ppb, respectively. The efficient fluorescent quenching effect is attributed to the photoinduced electron transfer between Fe3+ ions and the ligands in these MOFs. Moreover, the introduced pyridine N donors in the ligand of BUT-15 additionally donate their lone-pair electrons to the Fe3+ ions, leading to significantly enhanced detection ability. It is also demonstrated that BUT-15 exhibits an uncompromised performance for the detection of Fe3+ ions in a simulated biological system.

Thermal Atomic Layer Etching of SiO2 by a “Conversion-Etch” Mechanism Using Sequential Reactions of Trimethylaluminum and Hydrogen Fluoride
Jaime W. DuMont - ,
Amy E. Marquardt - ,
Austin M. Cano - , and
Steven M. George *
The thermal atomic layer etching (ALE) of SiO2 was performed using sequential reactions of trimethylaluminum (TMA) and hydrogen fluoride (HF) at 300 °C. Ex situ X-ray reflectivity (XRR) measurements revealed that the etch rate during SiO2 ALE was dependent on reactant pressure. SiO2 etch rates of 0.027, 0.15, 0.20, and 0.31 Å/cycle were observed at static reactant pressures of 0.1, 0.5, 1.0, and 4.0 Torr, respectively. Ex situ spectroscopic ellipsometry (SE) measurements were in agreement with these etch rates versus reactant pressure. In situ Fourier transform infrared (FTIR) spectroscopy investigations also observed SiO2 etching that was dependent on the static reactant pressures. The FTIR studies showed that the TMA and HF reactions displayed self-limiting behavior at the various reactant pressures. In addition, the FTIR spectra revealed that an Al2O3/aluminosilicate intermediate was present after the TMA exposures. The Al2O3/aluminosilicate intermediate is consistent with a “conversion-etch” mechanism where SiO2 is converted by TMA to Al2O3, aluminosilicates, and reduced silicon species following a family of reactions represented by 3SiO2 + 4Al(CH3)3 → 2Al2O3 + 3Si(CH3)4. Ex situ X-ray photoelectron spectroscopy (XPS) studies confirmed the reduction of silicon species after TMA exposures. Following the conversion reactions, HF can fluorinate the Al2O3 and aluminosilicates to species such as AlF3 and SiOxFy. Subsequently, TMA can remove the AlF3 and SiOxFy species by ligand-exchange transmetalation reactions and then convert additional SiO2 to Al2O3. The pressure-dependent conversion reaction of SiO2 to Al2O3 and aluminosilicates by TMA is critical for thermal SiO2 ALE. The “conversion-etch” mechanism may also provide pathways for additional materials to be etched using thermal ALE.
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