Bimetallic nanoparticles (NPs) are complex systems with properties that far exceed those of the individual constituents. In particular, association of a noble metal and a first-row transition metal are attracting increasing interest for applications in catalysis, electrocatalysis, and magnetism, among others. Such objects display a rich structural chemistry thanks to their ability to form intermetallic phases, random alloys, or core–shell species. However, under reaction conditions, the surface of these nanostructures may be modified due to migration, segregation, or isolation of single atoms, leading to the formation of original structures with enhanced catalytic activity. In this respect, Zakhtser et al. report in this issue of ACS Nano the synthesis and study of the chemical evolution of the surface of a series of PtZn nanostructured alloys. In this Perspective, we report some selected examples of bimetallic nanocatalysts and their increased activity compared to that of the corresponding pure noble metal, with a special focus on Pt-based systems. We also discuss the mobility of the species present on the catalyst surface and the electronic influence of one metal to the other.

Due to the limited ability of conventional methods and the limited perspective of human diagnostics, patients are often diagnosed incorrectly or at a late stage as their disease condition progresses. They may then undergo unnecessary treatments due to inaccurate diagnoses. In this Perspective, we offer a brief overview on the integration of nanotechnology-based medical sensors and artificial intelligence (AI) for advanced clinical decision support systems to help decision-makers and healthcare systems improve how they approach information, insights, and the surrounding contexts, as well as to promote the uptake of personalized medicine on an individualized basis. Relying on these milestones, wearable sensing devices could enable interactive and evolving clinical decisions that could be used for evidence-based analysis and recommendations as well as for personalized monitoring of disease progress and treatment. We present and discuss the ongoing challenges and future opportunities associated with AI-enabled medical sensors in clinical decisions.

The emergence of precise and scalable synthetic methods for producing anisotropic semiconductor nanostructures provides opportunities to tune the photophysical properties of these particles beyond their band gaps, and to incorporate them into higher-order structures with macroscopic anisotropic responses to electric and optical fields. This perspective article discusses some of these opportunities in the context of colloidal semiconductor nanoplatelets, with a focus on the influence of confinement anisotropy on processes that dictate the emission.

On-surface synthesis via covalent coupling of adsorbed precursor molecules on metal surfaces has emerged as a promising strategy for the design and fabrication of novel organic nanoarchitectures with unique properties and potential applications in nanoelectronics, optoelectronics, spintronics, catalysis, etc. Surface-chemistry-driven molecular engineering (i.e., bond cleavage, linkage, and rearrangement) by means of thermal activation, light irradiation, and tip manipulation plays critical roles in various on-surface synthetic processes, as exemplified by the work from the Ernst group in a prior issue of ACS Nano. In this Perspective, we highlight recent advances in and discuss the outlook for on-surface syntheses and molecular engineering of carbon-based nanoarchitectures.

Conventional materials are reaching their limits in computation, sensing, and data storage capabilities, ushered in by the end of Moore’s law, myriad sensing applications, and the continuing exponential rise in worldwide data storage demand. Conventional materials are also limited by the controlled environments in which they must operate, their high energy consumption, and their limited capacity to perform simultaneous, integrated sensing, computation, and data storage and retrieval. In contrast, the human brain is capable of multimodal sensing, complex computation, and both short- and long-term data storage simultaneously, with near instantaneous rate of recall, seamless integration, and minimal energy consumption. Motivated by the brain and the need for revolutionary new computing materials, we recently proposed the data-driven materials discovery framework, autonomous computing materials. This framework aims to mimic the brain’s capabilities for integrated sensing, computation, and data storage by programming excitonic, phononic, photonic, and dynamic structural nanoscale materials, without attempting to mimic the unknown implementational details of the brain. If realized, such materials would offer transformative opportunities for distributed, multimodal sensing, computation, and data storage in an integrated manner in biological and other nonconventional environments, including interfacing with biological sensors and computers such as the brain itself.

Lateral flow assays (LFAs) are paper-based point-of-care (POC) diagnostic tools that are widely used because of their low cost, ease of use, and rapid format. Unfortunately, traditional commercial LFAs have significantly poorer sensitivities (μM) and specificities than standard laboratory tests (enzyme-linked immunosorbent assay, ELISA: pM–fM; polymerase chain reaction, PCR: aM), thus limiting their impact in disease control. In this Perspective, we review the evolving efforts to increase the sensitivity and specificity of LFAs. Recent work to improve the sensitivity through assay improvement includes optimization of the assay kinetics and signal amplification by either reader systems or additional reagents. Together, these efforts have produced LFAs with ELISA-level sensitivities (pM–fM). In addition, sample preamplification can be applied to both nucleic acids (direct amplification) and other analytes (indirect amplification) prior to LFA testing, which can lead to PCR-level (aM) sensitivity. However, these amplification strategies also increase the detection time and assay complexity, which inhibits the large-scale POC use of LFAs. Perspectives to achieve future rapid (<30 min), ultrasensitive (PCR-level), and “sample-to-answer” POC diagnostics are also provided. In the case of LFA specificity, recent research efforts have focused on high-affinity molecules and assay optimization to reduce nonspecific binding. Furthermore, novel highly specific molecules, such as CRISPR/Cas systems, can be integrated into diagnosis with LFAs to produce not only ultrasensitive but also highly specific POC diagnostics. In summary, with continuing improvements, LFAs may soon offer performance at the POC that is competitive with laboratory techniques while retaining a rapid format.

Extracellular vesicles (EVs) and microbubbles are nanoparticles in drug-delivery systems that are both considered important for clinical translation. Current research has found that both microbubbles and EVs have the potential to be utilized as drug-delivery agents for therapeutic targets in various diseases. In combination with EVs, microbubbles are capable of delivering chemotherapeutic drugs to tumor sites and neighboring sites of damaged tissues. However, there are no standards to evaluate or to compare the benefits of EVs (natural carrier) versus microbubbles (synthetic carrier) as drug carriers. Both drug carriers are being investigated for release patterns and for pharmacokinetics; however, few researchers have focused on their targeted delivery or efficacy. In this Perspective, we compare EVs and microbubbles for a better understanding of their utility in terms of delivering drugs to their site of action and future clinical translation.

Two-dimensional (2D) nanostructures are a frontier in materials chemistry as a result of their extraordinary properties. Metal-free 2D nanomaterials possess extra appeal due to their improved cost-effectiveness and lower toxicity with respect to many inorganic structures. The outstanding electronic characteristics of some metal-free 2D semiconductors have projected them into the world of organic synthesis, where they can function as high-performance photocatalysts to drive the sustainable synthesis of high-value organic molecules. Recent reports on this topic have inspired a stream of research and opened up a theme that we believe will become one of the most dominant trends in the forthcoming years.

DNA nanotechnology has produced a wide range of self-assembled structures, offering unmatched possibilities in terms of structural design. Because of their programmable assembly and precise control of size, shape, and function, DNA particles can be used for numerous biological applications, including imaging, sensing, and drug delivery. While the biocompatibility, programmability, and ease of synthesis of nucleic acids have rapidly made them attractive building blocks, many challenges remain to be addressed before using them in biological conditions. Enzymatic hydrolysis, low cellular uptake, immune cell recognition and degradation, and unclear biodistribution profiles are yet to be solved. Rigorous methodologies are needed to study, understand, and control the fate of self-assembled DNA structures in physiological conditions. In this review, we describe the current challenges faced by the field as well as recent successes, highlighting the potential to solve biology problems or develop smart drug delivery tools. We then propose an outlook to drive the translation of DNA constructs toward preclinical design. We particularly believe that a detailed understanding of the fate of DNA nanostructures within living organisms, achieved through thorough characterization, is the next required step to reach clinical maturity.

In nature, cellulose nanofibers form hierarchical structures across multiple length scales to achieve high-performance properties and different functionalities. Cellulose nanofibers, which are separated from plants or synthesized biologically, are being extensively investigated and processed into different materials owing to their good properties. The alignment of cellulose nanofibers is reported to significantly influence the performance of cellulose nanofiber-based materials. The alignment of cellulose nanofibers can bridge the nanoscale and macroscale, bringing enhanced nanoscale properties to high-performance macroscale materials. However, compared with extensive reviews on the alignment of cellulose nanocrystals, reviews focusing on cellulose nanofibers are seldom reported, possibly because of the challenge of aligning cellulose nanofibers. In this review, the alignment of cellulose nanofibers, including cellulose nanofibrils and bacterial cellulose, is extensively discussed from different aspects of the driving force, evaluation, strategies, properties, and applications. Future perspectives on challenges and opportunities in cellulose nanofiber alignment are also briefly highlighted.

Graphene nanoribbons (GNRs) have recently emerged as promising candidates for channel materials in future nanoelectronic devices due to their exceptional electronic, thermal, and mechanical properties and chemical inertness. However, the adoption of GNRs in commercial technologies is currently hampered by materials science and integration challenges pertaining to synthesis and devices. In this Review, we present an overview of the current status of challenges, recent breakthroughs toward overcoming these challenges, and possible future directions for the field of GNR electronics. We motivate the need for exploration of scalable synthetic techniques that yield atomically precise, placed, registered, and oriented GNRs on CMOS-compatible substrates and stimulate ideas for contact and dielectric engineering to realize experimental performance close to theoretically predicted metrics. We also briefly discuss unconventional device architectures that could be experimentally investigated to harness the maximum potential of GNRs in future spintronic and quantum information technologies.

Upconversion nanoparticles (UCNPs) represent a class of optical nanomaterials that can convert low-energy excitation photons to high-energy fluorescence emissions. On the basis of UCNPs, heterostructured UCNPs, consisting of UCNPs and other functional counterparts (metals, semiconductors, polymers, etc.), present an intriguing system in which the physicochemical properties are largely influenced by the entire assembled particle and also by the morphology, dimension, and composition of each individual component. As multicomponent nanomaterials, heterostructured UCNPs can overcome challenges associated with a single component and exhibit bifunctional or multifunctional properties, which can further expand their applications in bioimaging, biodetection, and phototherapy. In this review, we provide a summary of recent achievements in the field of heterostructured UCNPs in the aspects of construction strategies, synthetic approaches, and types of heterostructured UCNPs. This review also summarizes the trends in biomedical applications of heterostructured UCNPs and discusses the challenges and potential solutions in this field.

T cells play an important role in immunity and repair and are implicated in diseases, including blood cancers, viral infections, and inflammation, making them attractive targets for the treatment and prevention of diseases. Over recent years, the advent of nanomedicine has shown an increase in studies that use nanoparticles as carriers to deliver therapeutic cargo to T cells for ex vivo and in vivo applications. Nanoparticle-based delivery has several advantages, including the ability to load and protect a variety of drugs, control drug release, improve drug pharmacokinetics and biodistribution, and site- or cell-specific targeting. However, the delivery of nanoparticles to T cells remains a major technological challenge, which is primarily due to the nonphagocytic nature of T cells. In this review, we discuss the physiological barriers to effective T cell targeting and describe the different approaches used to deliver cargo-loaded nanoparticles to T cells for the treatment of disease such as T cell lymphoma and human immunodeficiency virus (HIV). In particular, engineering strategies that aim to improve nanoparticle internalization by T cells, including ligand-based targeting, will be highlighted. These nanoparticle engineering approaches are expected to inspire the development of effective nanomaterials that can target or manipulate the function of T cells for the treatment of T cell-related diseases.

X-ray-based analytics are routinely applied in many fields, including physics, chemistry, materials science, and engineering. The full potential of such techniques in the life sciences and medicine, however, has not yet been fully exploited. We highlight current and upcoming advances in this direction. We describe different X-ray-based methodologies (including those performed at synchrotron light sources and X-ray free-electron lasers) and their potentials for application to investigate the nano–bio interface. The discussion is predominantly guided by asking how such methods could better help to understand and to improve nanoparticle-based drug delivery, though the concepts also apply to nano–bio interactions in general. We discuss current limitations and how they might be overcome, particularly for future use in vivo.

To address the serious threat of bacterial infection to public health, great efforts have been devoted to the development of antimicrobial agents for inhibiting bacterial growth, preventing biofilm formation, and sterilization. Very recently, metal–organic frameworks (MOFs) have emerged as promising materials for various antimicrobial applications owing to their different functions including the controlled/stimulated decomposition of components with bactericidal activity, strong interactions with bacterial membranes, and formation of photogenerated reactive oxygen species (ROS) as well as high loading and sustained releasing capacities for other antimicrobial materials. This review focuses on recent advances in the design, synthesis, and antimicrobial applications of MOF-based materials, which are classified by their roles as component-releasing (metal ions, ligands, or both), photocatalytic, and chelation antimicrobial agents as well as carriers or/and synergistic antimicrobial agents of other functional materials (antibiotics, enzymes, metals/metal oxides, carbon materials, etc.). The constituents, fundamental antimicrobial mechanisms, and evaluation of antimicrobial activities of these materials are highlighted to present the design principles of efficient MOF-based antimicrobial materials. The prospects and challenges in this research field are proposed.

Naturally derived nanocellulose (NC) is a renewable, biodegradable nanomaterial with high strength, low density, high surface area, and tunable surface chemistry, which allows its interaction with other polymers and nanomaterials in a controlled manner. In recent years, NC aerogel has gathered a lot of attention due to environmental concerns. This review presents recent developments of NC-based aerogels and their controlled interactions with other polymers and nanomaterials for thermal applications that include electronic devices, the apparel industry, superinsulating materials, and flame-retardant smart building materials. After going through the distinctive properties of NC aerogels, they are orderly categorized and discussed as thermally insulated, thermally conductive, and flame-retardant materials.

Emerging flexible artificial sensory systems using neuromorphic electronics have been considered as a promising solution for processing massive data with low power consumption. The construction of artificial sensory systems with synaptic devices and sensing elements to mimic complicated sensing and processing in biological systems is a prerequisite for the realization. To realize high-efficiency neuromorphic sensory systems, the development of artificial flexible synapses with low power consumption and high-density integration is essential. Furthermore, the realization of efficient coupling between the sensing element and the synaptic device is crucial. This Review presents recent progress in the area of neuromorphic electronics for flexible artificial sensory systems. We focus on both the recent advances of artificial synapses, including device structures, mechanisms, and functions, and the design of intelligent, flexible perception systems based on synaptic devices. Additionally, key challenges and opportunities related to flexible artificial perception systems are examined, and potential solutions and suggestions are provided.

The synergistic union of nanomaterials with biomaterials has revolutionized synthetic chemistry, enabling the creation of nanomaterial-based biohybrids with distinct properties for biomedical applications. This class of materials has drawn significant scientific interest from the perspective of functional extension via controllable coupling of synthetic and biomaterial components, resulting in enhancement of the chemical, physical, and biological properties of the obtained biohybrids. In this review, we highlight the forefront materials for the combination with biomacromolecules and living organisms and their advantageous properties as well as recent advances in the rational design and synthesis of artificial biohybrids. We further illustrate the incredible diversity of biomedical applications stemming from artificially bioaugmented characteristics of the nanomaterial-based biohybrids. Eventually, we aim to inspire scientists with the application horizons of the exciting field of synthetic augmented biohybrids.

Development of carbon neutral and sustainable energy sources should be considered as a top priority solution for the growing worldwide energy demand. Photovoltaics are a strong candidate, more specifically, organic photovoltaics (OPV), enabling the design of flexible, lightweight, semitransparent, and low-cost solar cells. However, the active layer of OPV is, for now, mainly deposited from chlorinated solvents, harmful for the environment and for human health. Active layers processed from health and environmentally friendly solvents have over recent years formed a key focus topic of research, with the creation of aqueous dispersions of conjugated polymer nanoparticles arising. These nanoparticles are formed from organic semiconductors (molecules and macromolecules) initially designed for organic solvents. The topic of nanoparticle OPV has gradually garnered more attention, up to a point where in 2018 it was identified as a “trendsetting strategy” by leaders in the international OPV research community. Hence, this review has been prepared to provide a timely roadmap of the formation and application of aqueous nanoparticle dispersions of active layer components for OPV. We provide a thorough synopsis of recent developments in both nanoprecipitation and miniemulsion for preparing photovoltaic inks, facilitating readers in acquiring a deep understanding of the crucial synthesis parameters affecting particle size, colloidal concentration, ink stability, and more. This review also showcases the experimental levers for identifying and optimizing the internal donor–acceptor morphology of the nanoparticles, featuring cutting-edge X-ray spectromicroscopy measurements reported over the past decade. The different strategies to improve the incorporation of these inks into OPV devices and to increase their efficiency (to the current record of 7.5%) are reported, in addition to critical design choices of surfactant type and the advantages of single-component vs binary nanoparticle populations. The review naturally culminates by presenting the upscaling strategies in practice for this environmentally friendly and safer production of solar cells.

Nanoarchitected materials are considered as a promising research field, deriving distinctive mechanical properties by combining nanomechanical size effects with conventional structural engineering. Despite the successful demonstration of the superiority and feasibility of nanoarchitected materials, scalable and facile fabrication techniques capable of macroscopically producing such materials at a low cost are required to take advantage of the nanoarchitected materials for specific applications. Unlike conventional techniques, proximity-field nanopatterning (PnP) is capable of simultaneously obtaining high spatial resolution and mass producibility in synthesizing such nanoarchitected materials in the form of an inch-scale film. Herein, we focus on the feasibility of using PnP as a scalable fabrication technique for three-dimensional nanostructures and the superiority of the resultant thin-shell oxide nanoarchitected materials for specific applications, such as lightweight structural materials, mechanically robust nanocomposites, and high-performance piezoelectric materials. This review will discuss and summarize the relevant results obtained for nanoarchitected materials synthesized by PnP and provide suggestions for future research directions for scalable manufacturing and application.

Multiscale and multimodal imaging of material structures and properties provides solid ground on which materials theory and design can flourish. Recently, KAIST announced 10 flagship research fields, which include KAIST Materials Revolution: Materials and Molecular Modeling, Imaging, Informatics and Integration (M3I3). The M3I3 initiative aims to reduce the time for the discovery, design and development of materials based on elucidating multiscale processing–structure–property relationship and materials hierarchy, which are to be quantified and understood through a combination of machine learning and scientific insights. In this review, we begin by introducing recent progress on related initiatives around the globe, such as the Materials Genome Initiative (U.S.), Materials Informatics (U.S.), the Materials Project (U.S.), the Open Quantum Materials Database (U.S.), Materials Research by Information Integration Initiative (Japan), Novel Materials Discovery (E.U.), the NOMAD repository (E.U.), Materials Scientific Data Sharing Network (China), Vom Materials Zur Innovation (Germany), and Creative Materials Discovery (Korea), and discuss the role of multiscale materials and molecular imaging combined with machine learning in realizing the vision of M3I3. Specifically, microscopies using photons, electrons, and physical probes will be revisited with a focus on the multiscale structural hierarchy, as well as structure–property relationships. Additionally, data mining from the literature combined with machine learning will be shown to be more efficient in finding the future direction of materials structures with improved properties than the classical approach. Examples of materials for applications in energy and information will be reviewed and discussed. A case study on the development of a Ni–Co–Mn cathode materials illustrates M3I3’s approach to creating libraries of multiscale structure–property–processing relationships. We end with a future outlook toward recent developments in the field of M3I3.

Sensors are becoming increasingly significant in our daily life because of the rapid development in electronic and information technologies, including Internet of Things, wearable electronics, home automation, intelligent industry, etc. There is no doubt that their performances are primarily determined by the sensing materials. Among all potential candidates, layered nanomaterials with two-dimensional (2D) planar structure have numerous superior properties to their bulk counterparts which are suitable for building various high-performance sensors. As an emerging 2D material, MXenes possess several advantageous features of adjustable surface properties, tunable bandgap, and excellent mechanical strength, making them attractive in various applications. Herein, we particularly focus on the recent research progress in MXene-based sensors, discuss the merits of MXenes and their derivatives as sensing materials for collecting various signals, and try to elucidate the design principles and working mechanisms of the corresponding MXene-based sensors, including strain/stress sensors, gas sensors, electrochemical sensors, optical sensors, and humidity sensors. In the end, we analyze the main challenges and future outlook of MXene-based materials in sensor applications.

We report on the shape, composition (from Pt₉₅Zn₅ to Pt₇₇Zn₂₃), and surface chemistry of Pt–Zn nanoparticles obtained by reduction of precursors M²⁺(acac)₂^– (M²⁺: Pt²⁺ and Zn²⁺) in oleylamine, which serves as both solvent and ligand. We show first that the addition of phenyl ether or benzyl ether determines the composition and shape of the nanoparticles, which point to an adsorbate-controlled synthesis. The organic (ligand)/inorganic (nanoparticles) interface is characterized on the structural and chemical level. We observe that the particles, after washing with ethanol, are coated with oleylamine and the oxidation products of the latter, namely, an aldimine and a nitrile. After exposure to air, the particles oxidize, covering themselves with a few monolayer thick ZnO film, which is certainly discontinuous when the particles are low in zinc. Pt–Zn particles are unstable and prone to losing Zn. We have strong indications that the driving force is the preferential oxidation of the less noble metal. Finally, we show that adsorption of CO on the surface of nanoparticles modifies the oxidation state of amine ligands and attribute it to the displacement of hydrogen adsorbed on Pt. All the structural and chemical information provided by the combination of electron microscopy and X-ray photoelectron spectroscopy allows us to give a fairly accurate picture of the surface of nanoparticles and to better understand why Pt–Zn alloys are efficient in certain electrocatalytic reactions such as the oxidation of methanol.

The evolution of life on earth eventually leads to the emergence of species with increased complexity and diversity. Similarly, evolutionary chemical space exploration in the laboratory is a key step to pursue the structural and functional diversity of supramolecular systems. Here, we present a powerful tool that enables rapid peptide diversification and employ it to expand the chemical space for supramolecular functions. Central to this strategy is the exploitation of palladium-catalyzed Suzuki–Miyaura cross-coupling reactions to direct combinatorial synthesis of peptide arrays in microtiter plates under an open atmosphere. Taking advantage of this in situ library design, our results unambiguously deliver a fertile platform for creating a set of intriguing peptide functions including green fluorescent protein-like peptide emitters with chemically encoded emission colors, hierarchical self-assembly into nano-objects, and macroscopic hydrogels. This work also offers opportunities for quickly surveying the diversified peptide arrays and thereby identifying the structural factors that modulate peptide properties.

Ultrathin transparent conductive oxides (TCOs) are emerging candidates for next-generation transparent electronics. Indium oxide (In₂O₃) incorporated with post-transition-metal ions (e.g., Sn) has been widely studied due to their excellent optical transparency and electrical conductivity. However, their electron transport properties are deteriorated at the ultrathin two-dimensional (2D) morphology compared to that of intrinsic In₂O₃. Here, we explore the domain of transition-metal dopants in ultrathin In₂O₃ with the thicknesses down to the single-unit-cell limit, which is realized in a large area using a low-temperature liquid metal printing technique. Zn dopant is selected as a representative to incorporate into the In₂O₃ rhombohedral crystal framework, which results in the gradual transition of the host to quasimetallic. While the optical transmittance is maintained above 98%, an electron field-effect mobility of up to 87 cm² V^–1 s^–1 and a considerable sub-kΩ^–1 cm^–1 ranged electrical conductivity are achieved when the Zn doping level is optimized, which are in a combination significantly improved compared to those of reported ultrathin TCOs. This work presents various opportunities for developing high-performance flexible transparent electronics based on emerging ultrathin TCO candidates.

Screening for prostate cancer relies on the serum prostate-specific antigen test, which provides a high rate of false positives (80%). This results in a large number of unnecessary biopsies and subsequent overtreatment. Considering the frequency of the test, there is a critical unmet need of precision screening for prostate cancer. Here, we introduced a urinary multimarker biosensor with a capacity to learn to achieve this goal. The correlation of clinical state with the sensing signals from urinary multimarkers was analyzed by two common machine learning algorithms. As the number of biomarkers was increased, both algorithms provided a monotonic increase in screening performance. Under the best combination of biomarkers, the machine learning algorithms screened prostate cancer patients with more than 99% accuracy using 76 urine specimens. Urinary multimarker biosensor leveraged by machine learning analysis can be an important strategy of precision screening for cancers using a drop of bodily fluid.

The structures as building blocks for designing functional nanomaterials have fueled the development of versatile nanoprobes to understand local structures of noncrystalline specimens. Progress in analyzing structures of individual specimens with atomic scale accuracy has been notable recently. In most cases, however, only a limited number of specimens are inspected lacking statistics to represent the systems with structural inhomogeneity. Here, by employing single-particle imaging with X-ray free electron lasers and algorithms for multiple-model 3D imaging, we succeeded in investigating several thousand specimens in a couple of hours and identified intrinsic heterogeneities with 3D structures. Quantitative analysis has unveiled 3D morphology, facet indices, and elastic strain. The 3D elastic energy distribution is further corroborated by molecular dynamics simulations to gain mechanical insight at the atomic level. This work establishes a route to high-throughput characterization of individual specimens in large ensembles, hence overcoming statistical deficiency while providing quantitative information at the nanoscale.

X-ray photon detection is important for a wide range of applications. The highest demand, however, comes from medical imaging, which requires cost-effective, high-resolution detectors operating at low-photon flux, therefore stimulating the search for novel materials and new approaches. Recently, hybrid halide perovskite CH₃NH₃PbI₃ (MAPbI₃) has attracted considerable attention due to its advantageous optoelectronic properties and low fabrication costs. The presence of heavy atoms, providing a high scattering cross-section for photons, makes this material a perfect candidate for X-ray detection. Despite the already-successful demonstrations of efficiency in detection, its integration into standard microelectronics fabrication processes is still pending. Here, we demonstrate a promising method for building X-ray detector units by 3D aerosol jet printing with a record sensitivity of 2.2 × 10⁸ μC Gy_air^–1 cm^–2 when detecting 8 keV photons at dose rates below 1 μGy/s (detection limit 0.12 μGy/s), a 4-fold improvement on the best-in-class devices. An introduction of MAPbI₃-based detection into medical imaging would significantly reduce health hazards related to the strongly ionizing X-rays’ photons.

Light matter interactions are greatly enhanced in two-dimensional (2D) semiconductors because of strong excitonic effects. Many optoelectronic applications would benefit from creating stacks of atomically thin 2D semiconductors separated by insulating barrier layers, forming multiquantum-well structures. However, most 2D transition metal chalcogenide systems require serial stacking to create van der Waals multilayers. Hybrid metal organic chalcogenolates (MOChas) are self-assembling hybrid materials that combine multiquantum-well properties with scalable chemical synthesis and air stability. In this work, we use spatially resolved linear and nonlinear optical spectroscopies over a range of temperatures to study the strongly excitonic optical properties of mithrene, that is, silver benzeneselenolate, and its synthetic isostructures. We experimentally probe s-type bright excitons and p-type excitonic dark states formed in the quantum confined 2D inorganic monolayers of silver selenide with exciton binding energy up to ∼0.4 eV, matching recent theoretical predictions of the material class. We further show that mithrene’s highly efficient blue photoluminescence, ultrafast exciton radiative dynamics, as well as flexible tunability of molecular structure and optical properties demonstrate great potential of MOChas for constructing optoelectronic and quantum excitonic devices.

In recent years, the development of nanopore-based membranes has revitalized the prospect of harvesting salinity gradient (blue) energy. In this study, we systematically analyze the energetic performance of nanopore-based power generation (NPG) at various process scales, beginning with a single nanopore, followed by a multipore membrane coupon, and ending with a full-scale system. We confirm the high power densities attainable by a single nanopore and demonstrate that, at the coupon scale and above, concentration polarization severely hinders the power density of NPG, revealing the common, yet significant, error in linearly extrapolating single-pore performance to multipore membranes. Through our consideration of concentration polarization, we also importantly show that the development of materials with exceptional nanopore properties provides limited enhancement of practical process performance. For a full-scale NPG membrane module, we find an inherent tradeoff between power density and thermodynamic energy efficiency, whereby achieving a high power density sacrifices the energy efficiency. Furthermore, we derive a simple expression for the theoretical maximum energy efficiency of NPG, showing it is solely related to the membrane selectivity (i.e., S²/2). Through this relation, it is apparent that the energy efficiency of NPG is limited to only 50% (for a completely selective membrane, i.e., S = 1), reinforcing our optimistic full-scale simulations which result in a (practical) maximum energy efficiency of 42%. Finally, we assess the net extractable energy of a full-scale NPG system which mixes river water and seawater by including the energy losses from pretreatment and pumping, revealing that the NPG process—both in its current state of development and in the case of highly optimistic performance with minimized external energy losses—is not viable for power generation.

In systems with reduced dimensions, quantum fluctuations have a strong influence on the electronic conduction, even at very low temperatures. In superconductors, this is especially interesting, since the coherent state of the superconducting electrons strongly interacts with these fluctuations and therefore is a sensitive tool to study them. In this paper, we report on comprehensive measurements of superconducting nanowires in the quantum phase slip regime. Using an intrinsic electromigration process, we have developed a method to lower the nanowire’s resistance in situ and therefore eliminate quantum phase slips in small consecutive steps. We observe critical (Coulomb) blockade voltages and superconducting critical currents, in good agreement with theoretical models. Between these two regimes, we find a continuous transition displaying a nonlinear metallic-like behavior. The reported intrinsic electromigration technique is not limited to low temperatures, as we find a similar change in resistance that spans over 3 orders of magnitude also at room temperature. Aside from superconducting quantum circuits, such a technique to reduce the resistance may also have applications in modern electronic circuits.

Mechanoluminescent materials, which emit light in response to elastic deformation, are demanded for use as in situ stress sensors. ZnS doped with Mn is known to exhibit one of the lowest reported thresholds for appearance of mechanoluminescence, with repeatable light emission under contact pressure <10 MPa. The physical basis for such behavior remains as yet unclear. Here, reliable microscopic detection of mechanoluminescence of single ZnS:Mn microparticles, in combination with nanoscale structural characterization, provides evidence that the mechanoluminescent properties of these particles result from interplay between a non-centrosymmetric crystal lattice and its defects, viz., dislocations and stacking faults. Statistical analysis of the distributions of mechanoluminescence energy release trajectories reveals two distinct mechanisms of excitation: one attributable to a piezo-phototronic effect and the other due to dislocation motion. At pressures below 8.1 MPa, both mechanisms contribute to mechanoluminescent output, with a dominant contribution from the piezo-phototronic mechanism. In contrast, above 8.1 MPa, dislocation motion is the primary excitation source. For the piezo-phototronic mechanism, we propose a specific model that accounts for elastic ZnS:Mn mechanoluminescence under very low pressure. The charged interfaces in stacking faults lead to the presence of filled traps, which otherwise would be empty in the absence of the built-in electric field. Upon application of external stress, local enhancement of the piezoelectric field at the stacking faults’ interfaces facilitates release of the trapped carriers and subsequent luminescence. This field enhancement explains how <10 MPa pressure produces thousands of photons.

Carbon nanothreads, which are one-dimensional sp³-rich polymers, combine high tensile strength with flexibility owing to subnanometer widths and diamond-like cores. These extended carbon solids are constructed through pressure-induced polymerization of sp² molecules such as benzene. Whereas a few examples of carbon nanothreads have been reported, the need for high onset pressures (≥17 GPa) to synthesize them precludes scalability and limits scope. Herein, we report the scalable synthesis of carbon nanothreads based on molecular furan, which can be achieved through ambient temperature pressure-induced polymerization with an onset reaction pressure of only 10 GPa due to its lessened aromaticity relative to other molecular precursors. When slowly compressed to 15 GPa and gradually decompressed to 1.5 GPa, a sharp 6-fold diffraction pattern is observed in situ, indicating a well-ordered crystalline material formed from liquid furan. Single-crystal X-ray diffraction (XRD) of the reaction product exhibits three distinct d-spacings from 4.75 to 4.9 Å, whose size, angular spacing, and degree of anisotropy are consistent with our atomistic simulations for crystals of furan nanothreads. Further evidence for polymerization was obtained by powder XRD, Raman/IR spectroscopy, and mass spectrometry. Comparison of the IR spectra with computed vibrational modes provides provisional identification of spectral features characteristic of specific nanothread structures, namely syn, anti, and syn/anti configurations. Mass spectrometry suggests that molecular weights of at least 6 kDa are possible. Furan therefore presents a strategic entry toward scalable carbon nanothreads.

Optical imaging probes have played a major role in detecting and monitoring a variety of diseases. In particular, nonlinear optical imaging probes, such as second harmonic generating (SHG) nanoprobes, hold great promise as clinical contrast agents, as they can be imaged with little background signal and unmatched long-term photostability. As their chemical composition often includes transition metals, the use of inorganic SHG nanoprobes can raise long-term health concerns. Ideally, contrast agents for biomedical applications should be degraded in vivo without any long-term toxicological consequences to the organism. Here, we developed biodegradable harmonophores (bioharmonophores) that consist of polymer-encapsulated, self-assembling peptides that generate a strong SHG signal. When functionalized with tumor cell surface markers, these reporters can target single cancer cells with high detection sensitivity in zebrafish embryos in vivo. Thus, bioharmonophores will enable an innovative approach to cancer treatment using targeted high-resolution optical imaging for diagnostics and therapy.

Resistance switching in metal–insulator–metal structures has been extensively studied in recent years for use as synaptic elements for neuromorphic computing and as nonvolatile memory elements. However, high switching power requirements, device variabilities, and considerable trade-offs between low operating voltages, high on/off ratios, and low leakage have limited their utility. In this work, we have addressed these issues by demonstrating the use of ultraporous dielectrics as a pathway for high-performance resistive memory devices. Using a modified atomic layer deposition based technique known as sequential infiltration synthesis, which was developed originally for improving polymer properties such as enhanced etch resistance of electron-beam resists and for the creation of films for filtration and oleophilic applications, we are able to create ∼15 nm thick ultraporous (pore size ∼5 nm) oxide dielectrics with up to 73% porosity as the medium for filament formation. We show, using the Ag/Al₂O₃ system, that the ultraporous films result in ultrahigh on/off ratio (>10⁹) at ultralow switching voltages (∼±600 mV) that are 10× smaller than those for the bulk case. In addition, the devices demonstrate fast switching, pulsed endurance up to 1 million cycles. and high temperature (125 °C) retention up to 10⁴ s, making this approach highly promising for large-scale neuromorphic and memory applications. Additionally, this synthesis methodology provides a compatible, inexpensive route that is scalable and compatible with existing semiconductor nanofabrication methods and materials.

An emerging class of methylammonium lead iodide (MAPbI₃)-based Ruddlesden–Popper (RP) phase perovskites, BA₂MA_n–1Pb_nI_3n+1 (n = 1–7), exhibit enhanced stability to environmental conditions relative to MAPbI₃, yet still degrade at elevated temperatures. We experimentally determine the thermal conductivities of these layered RP phases for n = 1–6, where n defines the number of repeated perovskite octahedra per layer. We measure thermal conductivities of 0.37 ± 0.13/0.12, 0.17 ± 0.08/0.07, 0.21 ± 0.05/0.04, and 0.19 ± 0.04/0.03 W/m·K in thin films of n = 1–4 and 0.08 ± 0.06/0.04, 0.06 ± 0.04/0.03, 0.06 ± 0.03/0.03, and 0.08 ± 0.07/0.04 W/m·K in single crystals of n = 3–6. With the exception of n = 1, these thermal conductivities are lower than the range of 0.34–0.50 W/m·K reported for single-crystal MAPbI₃. Reduced-order lattice dynamics modeling suggests that the initially decreasing trend of thermal conductivity in similarly oriented perovskites with increasing n may result from the transport properties of coherent phonons, emergent from the superstructure, that do not scatter at the interfaces of organic butylammonium chains and perovskite octahedra. Reduced group velocity of coherent phonons in n = 3–6, a consequence of band flattening in the phonon dispersion, is primarily responsible for their ultralow thermal conductivities. Similar effects on thermal conductivity have been experimentally demonstrated in deposited superlattices, but never in naturally defined materials such as RP phases. GIWAXS measurements reveal that higher n RP phase thin films are less orientationally controlled and therefore possess apparently elevated thermal conductivities relative to single crystals of the same n.

Antivirulence therapy by cell membrane coated nanoparticles has shown promise against bacterial infections. However, current approaches remain unsatisfactory when facing Escherichia coli (E. coli) infections, since the E. coli secretes multiple bacterial toxins including endotoxins and exotoxins that are challenging to eliminate simultaneously. What is worse, the absorptive scavengers normally rely on random contact of the diffuse toxins, which is not efficient. For the current cell membrane coated platform, the single type of cell membrane cannot fully meet the detoxing requirement facing multiple toxins. To address these problems, a polymyxin B (PMB)-modified, red blood cell (RBC)-mimetic hybrid liposome (P-RL) was developed. The P-RL was fabricated succinctly through fusion of PMB-modified lipids and the RBC membranes. By the strong interaction between PMB and the E. coli membrane, P-RL could attach and anchor to the E. coli; attributed to the fused RBC membrane and modified PMB, the P-RL could then efficiently neutralize both endotoxins and exotoxins from the toxin fountainhead. In vitro and in vivo results demonstrated the P-RL had a significant anchoring effect to E. coli. Moreover, compared with the existing RBC vesicles or PMB-modified liposomes, P-RL exhibited a superior therapeutic effect against RBC hemolysis, macrophage activation, and a mixed-toxin infection in mice. Potently, P-RL could inhibit E. coli O157:H7-induced skin damage, intestinal infection, and mouse death. Overall, the P-RL could potentially improve the detoxing efficiency and markedly expand the detoxification spectrum of current antivirulence systems, which provides different insights into drug-resistant E. coli treatment.

Technological breakthroughs in electron microscopy (EM) have made it possible to solve structures of biological macromolecular complexes and to raise novel challenges, specifically related to sample preparation and heterogeneous macromolecular assemblies such as DNA–protein, protein–protein, and membrane protein assemblies. Here, we built a V-shaped DNA origami as a scaffolding molecular system to template proteins at user-defined positions in space. This template positions macromolecular assemblies of various sizes, juxtaposes combinations of biomolecules into complex arrangements, isolates biomolecules in their active state, and stabilizes membrane proteins in solution. In addition, the design can be engineered to tune DNA mechanical properties by exerting a controlled piconewton (pN) force on the molecular system and thus adapted to characterize mechanosensitive proteins. The binding site can also be specifically customized to accommodate the protein of interest, either interacting spontaneously with DNA or through directed chemical conjugation, increasing the range of potential targets for single-particle EM investigation. We assessed the applicability for five different proteins. Finally, as a proof of principle, we used RNAP protein to validate the approach and to explore the compatibility of the template with cryo-EM sample preparation.

This article describes a theoretical and computational study of the dynamical assembly of a protein shell around a complex consisting of many cargo molecules and long, flexible scaffold molecules. Our study is motivated by bacterial microcompartments, which are proteinaceous organelles that assemble around a condensed droplet of enzymes and reactants. As in many examples of cytoplasmic liquid–liquid phase separation, condensation of the microcompartment interior cargo is driven by flexible scaffold proteins that have weak multivalent interactions with the cargo. Our results predict that the shell size, amount of encapsulated cargo, and assembly pathways depend sensitively on properties of the scaffold, including its length and valency of scaffold–cargo interactions. Moreover, the ability of self-assembling protein shells to change their size to accommodate scaffold molecules of different lengths depends crucially on whether the spontaneous curvature radius of the protein shell is smaller or larger than a characteristic elastic length scale of the shell. Beyond natural microcompartments, these results have important implications for synthetic biology efforts to target alternative molecules for encapsulation by microcompartments or viral shells. More broadly, the results elucidate how cells exploit coupling between self-assembly and liquid–liquid phase separation to organize their interiors.

Out of the different structural phases of molybdenum ditelluride (MoTe₂), the distorted octahedral 1T′ possesses great interest for fundamental physics and is a promising candidate for the implementation of innovative devices such as topological transistors. Indeed, 1T′-MoTe₂ is a semimetal with superconductivity, which has been predicted to be a Weyl semimetal and a quantum spin Hall insulator in bulk and monolayer form, respectively. Large instability of monolayer 1T′-MoTe₂ in environmental conditions, however, has made its investigation extremely challenging so far. In this work, we demonstrate homogeneous growth of large single-crystal (up to 500 μm) monolayer 1T′-MoTe₂ via chemical vapor deposition (CVD) and its stabilization in air with a scalable encapsulation approach. The encapsulant is obtained by electrochemically delaminating CVD hexagonal boron nitride (hBN) from copper foil, and it is applied on the freshly grown 1T′-MoTe₂ via a top-down dry lamination step. The structural and electrical properties of encapsulated 1T′-MoTe₂ have been monitored over several months to assess the degree of degradation of the material. We find that when encapsulated with hBN, the lifetime of monolayer 1T′-MoTe₂ successfully increases from a few minutes to more than a month. Furthermore, the encapsulated monolayer can be subjected to transfer, device processing, and heating and cooling cycles without degradation of its properties. The potential of this scalable heterostack is confirmed by the observation of signatures of low-temperature phase transition in monolayer 1T′-MoTe₂ by both Raman spectroscopy and electrical measurements. The growth and encapsulation methods reported in this work can be employed for further fundamental studies of this enticing material as well as facilitate the technological development of monolayer 1T′-MoTe₂.

High ionic strength environments can profoundly influence catalytic reactions involving charged species. However, control of selectivity and yield of heterogeneous catalytic reactions involving nano- and microscale colloids remains hypothetical because high ionic strength leads to aggregation of particle dispersions. Here we show that microscale hedgehog particles (HPs) with semiconductor nanoscale spikes display enhanced stability in solutions of monovalent/divalent salts in both aqueous and hydrophobic media. HPs enable tuning of photocatalytic reactions toward high-value products by adding concentrated inert salts to amplify local electrical fields in agreement with Derjaguin, Landau, Verwey, and Overbeek theory. After optimization of HP geometry for a model photocatalytic reaction, we show that high salt conditions increase the yield of HP-facilitated photooxidation of 2-phenoxy-1-phenylethanol to benzaldehyde and 2-phenoxyacetophenone by 6 and 35 times, respectively. Depending on salinity, electrical fields at the HP–media interface increase from 1.7 × 10⁴ V/m to 8.5 × 10⁷ V/m, with high fields favoring products generated via intermediate cation radicals rather than neutral species. Electron transfer rates were modulated by varying the ionic strength, which affords a convenient and hardly used reaction pathway for engineering a multitude of redox reactions including those involved in the environmental remediation of briny and salty water.

The development of highly efficient catalysts in the cathodes of rechargeable Li–O₂ batteries is a considerable challenge. Polyelemental catalysts consisting of two or more kinds of hybridized catalysts are particularly interesting because the combination of the electrochemical properties of each catalyst component can significantly facilitate oxygen evolution and oxygen reduction reactions. Despite the recent advances that have been made in this field, the number of elements in the catalysts has been largely limited to two metals. In this study, we demonstrate the electrochemical behavior of Li–O₂ batteries containing a wide range of catalytic element combinations. Fourteen different combinations with single, binary, ternary, and quaternary combinations of Pt, Pd, Au, and Ru were prepared on carbon nanofibers (CNFs) via a joule heating route. Importantly, the Li–O₂ battery performance could be significantly improved when using a polyelemental catalyst with four elements. The cathode containing quaternary nanoparticles (Pt–Pd–Au–Ru) exhibited a reduced overpotential (0.45 V) and a high discharge capacity based on total cathode weight at 9130 mAh g^–1, which was ∼3 times higher than that of the pristine CNF electrode. This superior electrochemical performance is be attributed to an increased catalytic activity associated with an enhanced O₂ adsorbability by the quaternary nanoparticles.

MXenes are a young family of two-dimensional transition metal carbides, nitrides, and carbonitrides with highly controllable structure, composition, and surface chemistry to adjust for target applications. Here, we demonstrate the modifications of two-dimensional MXenes by low-energy ion implantation, leading to the incorporation of Mn ions in Ti₃C₂T_x (where T_x is a surface termination) thin films. Damage and structural defects caused by the implantation process are characterized at different depths by XPS on Ti 2p core-level spectra, by ToF-SIMS, and with electron energy loss spectroscopy analyses. Results show that the ion-induced alteration of the damage tolerant Ti₃C₂T_x layer is due to defect formation at both Ti and C sites, thereby promoting the functionalization of these sites with oxygen groups. This work contributes to the inspiring approach of tailoring 2D MXene structure and properties through doping and defect formation by low-energy ion implantation to expand their practical applications.

Supraparticles are large clusters of much smaller colloidal particles. Controlling the shape and anisotropy of supraparticles can enhance their functionality, enabling applications in fields such as optics, magnetics, and medicine. The evaporation of self-lubricating colloidal ouzo droplets is an easy and efficient strategy to create supraparticles, overcoming the problem of the “coffee-stain effect” during drop evaporation. Yet, the parameters that control the shape of the supraparticles formed in such evaporating droplets are not fully understood. Here, we show that the size of the colloidal particles determines the shape of the supraparticle. We compared the shape of the supraparticles made of seven different sizes of spherical silica particles, namely from 20 to 1000 nm, and of the mixtures of small and large colloidal particles at different mixing ratios. Specifically, our in situ measurements revealed that the supraparticle formation proceeds via the formation of a flexible shell of colloidal particles at the rapidly moving interfaces of the evaporating droplet. The time t_c0 when the shell ceases to shrink and loses its flexibility is closely related to the size of particles. A lower t_c0, as observed for smaller colloidal particles, leads to a flat pancake-like supraparticle, in contrast to a more curved American football-like supraparticle from larger colloidal particles. Furthermore, using a mixture of large and small colloidal particles, we obtained supraparticles that display a spatial variation in particle distribution, with small colloids forming the outer surface of the supraparticle. Our findings provide a guideline for controlling the supraparticle shape and the spatial distribution of the colloidal particles in supraparticles by simply self-lubricating ternary drops filled with colloidal particles.

We present a simple yet versatile method for sculpting ultra-thick, enzyme-generated hyaluronan polymer brushes with light. The patterning mechanism is indirect, driven by reactive oxygen species created by photochemical interactions with the underlying substrate. The reactive oxygen species disrupt the enzyme hyaluronan synthase, which acts as the growth engine and anchor of the end-grafted polymers. Spatial control over the grafting density is achieved through inactivation of the enzyme in an energy density dose-dependent manner, before or after polymerization of the brush. Quantitative variation of the brush height is possible using visible wavelengths and illustrated by the creation of a brush gradient ranging from 0 to 6 μm in height over a length of 56 μm (approximately a 90 nm height increase per micron). Building upon the fundamental insights presented in this study, this work lays the foundation for the flexible and quantitative sculpting of complex three-dimensional landscapes in enzyme-generated hyaluronan brushes.

Protein molecules bring a rich functionality to the field of designed nanoscale architectures. High-symmetry protein cages are rapidly finding diverse applications in biomedicine, nanotechnology, and imaging, but methods for their reliable and predictable construction remain challenging. In this study we introduce an approach for designing protein assemblies that combines ideas and favorable elements adapted from recent work. Cubically symmetric cages can be created by combining two simpler symmetries, following recently established principles. Here, two different oligomeric protein components are brought together in a geometrically specific arrangement by their separate genetic fusion to individual components of a heterodimeric coiled-coil polypeptide motif of known structure. Fusions between components are made by continuous α-helices to limit flexibility. After a computational design, we tested 10 different protein cage constructions experimentally, two of which formed larger assemblies. One produced the intended octahedral cage, ∼26 nm in diameter, while the other appeared to produce the intended tetrahedral cage as a minor component, crystallizing instead in an alternate form representing a collapsed structure of lower stoichiometry and symmetry. Geometric distinctions between the two characterized designs help explain the different degrees of success, leading to clearer principles and improved prospects for the routine creation of nanoscale protein architectures using diverse methods.

The current quest for two-dimensional transition metal carbides and nitrides (MXenes) has been to circumvent the slow, hazardous, and laborious multistep synthesis procedures associated with conventional chemical MAX phase exfoliation. Here, we demonstrate a one-step synthesis method with local Ti₃AlC₂ MAX to Ti₃C₂T_z MXene conversion on the order of milliseconds, facilitated by proton production through solution dissociation under megahertz frequency acoustic excitation. These protons combined with fluorine ions from LiF to selectively etch the MAX phase into MXene, whose delamination is aided by the acoustic forcing. These results have important implications for the future applicability of MXenes, which crucially depend on the development of more efficient synthesis procedures. For proof-of-concept, we show that flexible electrodes fabricated by this method exhibit comparable electrochemical performance to that previously reported.

Insulin therapy is the central component of treatment for type 1 and advanced type 2 diabetes; however, its narrow therapeutic window is associated with a risk of severe hypoglycemia. A glucose-responsive carrier that demonstrates consistent and slow basal insulin release under a normoglycemic condition and accelerated insulin release in response to hyperglycemia in real-time could offer effective blood glucose regulation with reduced risk of hypoglycemia. Here, we describe a poly(l-lysine)-derived biodegradable glucose-responsive cationic polymer for constructing polymer–insulin complexes for glucose-stimulated insulin delivery. The effects of the modification degree of arylboronic acid in the synthesized cationic polymer and polymer-to-insulin ratio on the glucose-dependent equilibrated free insulin level and the associated insulin release kinetics have been studied. In addition, the blood glucose regulation ability of these complexes and the associated glucose challenge-triggered insulin release are evaluated in type 1 diabetic mice.

Autoimmune diseases like multiple sclerosis (MS), type 1 diabetes, and lupus occur when the immune system attacks host tissue. Immunotherapies that promote selective tolerance without suppressing normal immune function are of tremendous interest. Here, nanotechnology was used for rational assembly of peptides and modulatory immune cues into immune complexes. Complexes containing self-peptides and regulatory nucleic acids reverse established paralysis in a preclinical MS model. Importantly, mice responding to immunotherapy maintain healthy, antigen-specific B and T cell responses during a foreign antigen challenge. A therapeutic library isolating specific components reveals that regulatory nucleic acids suppress inflammatory genes in innate immune cells, while disease-matched peptide sequences control specificity of tolerance. Distinct gene expression profiles in cells and animals are associated with the immune signals administered in particulate and soluble forms, highlighting the impact of biophysical presentation of signals. This work provides insight into the rational manipulation of immune signaling to drive tolerance.

Bone is a hierarchical material primarily composed of collagen, water, and mineral that is organized into discrete molecular, nano-, micro-, and macroscale structural components. In contrast to the structural knowledge of the collagen and mineral domains, the nanoscale porosity of bone is poorly understood. In this study, we introduce a well-established pore characterization technique, positron annihilation lifetime spectroscopy (PALS), to probe the nanoscale size and distribution of each component domain by analyzing pore sizes inherent to hydrated bone together with pores generated by successive removal of water and then organic matrix (including collagen and noncollagenous proteins) from samples of cortical bovine femur. Combining the PALS results with simulated pore size distribution (PSD) results from collagen molecule and microfibril structure, we identify pores with diameter of 0.6 nm that suggest porosity within the collagen molecule regardless of the presence of mineral and water. We find that water occupies three larger domain size regions with nominal mean diameters of 1.1, 1.9, and 4.0 nm—spaces that are hypothesized to associate with intercollagen molecular spaces, terminal segments (d-spacing) within collagen microfibrils, and interface spacing between collagen and mineral structure, respectively. Subsequent removal of the organic matrix determines a structural pore size of 5–6 nm for deproteinized bone—suggesting the average spacing between mineral lamella. An independent method to deduce the average mineral spacing from specific surface area (SSA) measurements of the deproteinized sample is presented and compared with the PALS results. Together, the combined PALS and SSA results set a range on the mean mineral lamella thickness of 4–8 nm.

Colloidal suspensions of two species have the ability to form binary crystals under certain conditions. The hunt for these functional materials and the countless investigations on their formation process are justified by the plethora of synergetic and collective properties these binary superlattices show. Among the many crystal structures observed over the past decades, the highly exotic colloidal icosahedral AB₁₃ crystal was predicted to be stable in binary hard-sphere mixtures nearly 30 years ago, yet the kinetic pathway of how homogeneous nucleation occurs in this system is still unknown. Here we investigate binary nucleation of the AB₁₃ crystal from a binary fluid phase of nearly hard spheres. We calculate the nucleation barrier and nucleation rate as a function of supersaturation and draw a comparison with nucleation of single-component and other binary crystals. To follow the nucleation process, we employ a neural network to identify the AB₁₃ phase from the binary fluid phase and the competing fcc crystal with single-particle resolution and significant accuracy in the case of bulk phases. We show that AB₁₃ crystal nucleation proceeds via a coassembly process where large spheres and icosahedral small-sphere clusters simultaneously attach to the nucleus. Our results lend strong support for a classical pathway that is well-described by classical nucleation theory, even though the binary fluid phase is highly structured and exhibits local regions of high bond orientational order.

The rich functionalities of transition-metal oxides and their interfaces bear an enormous technological potential. Its realization in practical devices requires, however, a significant improvement of yet relatively low electron mobility in oxide materials. Recently, a mobility boost of about 2 orders of magnitude has been demonstrated at the spinel–perovskite γ-Al₂O₃/SrTiO₃ interface compared to the paradigm perovskite–perovskite LaAlO₃/SrTiO₃ interface. We explore the fundamental physics behind this phenomenon from direct measurements of the momentum-resolved electronic structure of this interface using resonant soft-X-ray angle-resolved photoemission. We find an anomaly in orbital ordering of the mobile electrons in γ-Al₂O₃/SrTiO₃ which depopulates electron states in the top SrTiO₃ layer. This rearrangement of the mobile electron system pushes the electron density away from the interface, which reduces its overlap with the interfacial defects and weakens the electron–phonon interaction, both effects contributing to the mobility boost. A crystal-field analysis shows that the band order alters owing to the symmetry breaking between the spinel γ-Al₂O₃ and perovskite SrTiO₃. Band-order engineering, exploiting the fundamental symmetry properties, emerges as another route to boost the performance of oxide devices.

Short major histocompatibility complex (MHC) class I (MHC-I)-restricted peptides contain the minimal biochemical information to induce antigen (Ag)-specific CD8⁺ cytotoxic T cell responses but are generally ineffective in doing so. To address this, we developed a cobalt–porphyrin (CoPoP) liposome vaccine adjuvant system that induces rapid particleization of conventional, short synthetic MHC-I epitopes, leading to strong cellular immune responses at nanogram dosing. Along with CoPoP (to induce particle formation of peptides), synthetic monophosphoryl lipid A (PHAD) and QS-21 immunostimulatory molecules were included in the liposome bilayer to generate the “CPQ” adjuvant system. In mice, immunization with a short MHC-I-restricted peptide, derived from glycoprotein 70 (gp70), admixed with CPQ safely generated functional, Ag-specific CD8⁺ T cells, resulting in the rejection of multiple tumor cell lines, with durable immunity. When cobalt was omitted, the otherwise identical peptide and adjuvant components did not result in peptide binding and were incapable of inducing immune responses, demonstrating the importance of stable particle formation. Immunization with the liposomal vaccine was well-tolerated and could control local and metastatic disease in a therapeutic setting. Mechanistic studies showed that particle-based peptides were better taken up by antigen-presenting cells, where they were putatively released within endosomes and phagosomes for display on MHC-I surfaces. On the basis of the potency of the approach, the platform was demonstrated as a tool for in vivo epitope screening of peptide microlibraries comprising a hundred peptides.

Spin waves or their quanta magnons raise the prospect to act as information carriers in the absence of Joule heating. The challenge to excite spin waves with nanoscale wavelengths free of nanolithography becomes a critical bottleneck for the application of nanomagnonics. Magnetic skyrmions are chiral magnetic textures at the nanoscale. In this work, short-wavelength exchange spin waves are demonstrated to be chirally emitted in a low damping magnetic insulating thin film by magnetic skyrmions. The spin-wave chirality originates from the chiral spin pumping effect and is determined by the cross product of the magnetization orientation and the film normal direction. The Halbach effect explains the enhancement or attenuation of the spin-wave amplitude with a reversed sign of the Dyzaloshinskii–Moriya interaction. Controllable spin-wave propagation is demonstrated by rotating a moderate applied field. Our findings are key for building compact low-power nanomagnonic devices based on intrinsic nanoscale magnetic textures.

Recently, flexible capacitive pressure sensors have received significant attention in the field of wearable electronics. The high sensitivity over a wide linear range combined with long-term durability is a critical requirement for the fabrication of reliable pressure sensors for versatile applications. Herein, we propose a special approach to enhance the sensitivity and linearity range of a capacitive pressure sensor by fabricating a hybrid ionic nanofibrous membrane as a sensing layer composed of Ti₃C₂T_x MXene and an ionic salt of lithium sulfonamides in a poly(vinyl alcohol) elastomer matrix. The reversible ion pumping triggered by a hydrogen bond in the hybrid sensing layer leads to high sensitivities of 5.5 and 1.5 kPa^–1 in the wide linear ranges of 0–30 and 30–250 kPa, respectively, and a fast response time of 70.4 ms. In addition, the fabricated sensor exhibits a minimum detection limit of 2 Pa and high durability over 20 000 continuous cycles even under a high pressure of 45 kPa. These results indicate that the proposed sensor can be potentially used in mobile medical monitoring devices and next-generation artificial e-skin.

DNA nanotechnology produces precision nanostructures of defined chemistry. Expanding their use in biomedicine requires designed biomolecular interaction and function. Of topical interest are DNA nanostructures that function as vaccines with potential advantages over nonstructured nucleic acids in terms of serum stability and selective interaction with human immune cells. Here, we describe how compact DNA nanobarrels bind with a 400-fold selectivity via membrane anchors to white blood immune cells over erythrocytes, without affecting cell viability. The selectivity is based on the preference of the cholesterol lipid anchor for the more fluid immune cell membranes compared to the lower membrane fluidity of erythrocytes. Compacting DNA into the nanostructures gives rise to increased serum stability. The DNA barrels furthermore functionally modulate white blood cells by suppressing the immune response to pro-inflammatory endotoxin lipopolysaccharide. This is likely due to electrostatic or steric blocking of toll-like receptors on white blood cells. Our findings on immune cell-specific DNA nanostructures may be applied for vaccine development, immunomodulatory therapy to suppress septic shock, or the targeting of bioactive substances to immune cells.

High-quality homogeneous junctions are of great significance for developing transition metal dichalcogenides (TMDs) based electronic and optoelectronic devices. Here, we demonstrate a lateral p-type/intrinsic/n-type (p-i-n) homojunction based multilayer WSe₂ diode. The photodiode is formed through selective doping, more specifically by utilizing self-aligning surface plasma treatment at the contact regions, while keeping the WSe₂ channel intrinsic. Electrical measurements of such a diode reveal an ideal rectifying behavior with a current on/off ratio as high as 1.2 × 10⁶ and an ideality factor of 1.14. While operating in the photovoltaic mode, the diode presents an excellent photodetecting performance under 450 nm light illumination, including an open-circuit voltage of 340 mV, a responsivity of 0.1 A W^–1, and a specific detectivity of 2.2 × 10¹³ Jones. Furthermore, benefiting from the lateral p-i-n configuration, the slow photoresponse dynamics including the photocarrier diffusion in undepleted regions and photocarrier trapping/detrapping due to dopants or doping process induced defect states are significantly suppressed. Consequently, a record-breaking response time of 264 ns and a 3 dB bandwidth of 1.9 MHz are realized, compared with the previously reported TMDs based photodetectors. The above-mentioned desirable properties, together with CMOS compatible processes, make this WSe₂ p-i-n junction diode promising for future applications in self-powered high-frequency weak signal photodetection.

The design of atomically dispersed single atom catalysts (SACs) must consider high metal-atom loading amount, effective confinement, and strong interactions with matrix, which can maximize their catalytic performance. Here reported is a promising method to synthesize SACs on highly conductive multiwall carbon nanotube (MWCNT) supports using pulsed laser confinement (PLC) process in liquid. Atomic cobalt (Co) and phosphorus (P) with a high loading density are homogeneously incorporated on the outer wall of the MWCNT (Co–P SAC MWCNT). Density functional theory (DFT) calculations in combination with systematic control experiments found that the incorporated Co and P adatoms act as an adsorption energy optimizer and a charge transfer promoter, respectively. Hence, favorable kinetics and thermodynamics in Co–P SAC MWCNT can be simultaneously achieved for water oxidation resulting in a superior catalytic performance than the benchmark RuO₂ catalyst. Crucially, total processing time for assembling Co–P SAC MWCNT via PLC process is less than 60 min, shedding light on the promising practical applications of our SAC design strategy.

Natural swarms can be formed by various creatures. The swarms can conduct demanded behaviors to adapt to their living environments, such as passing through harsh terrains and protecting each other from predators. At micrometer and nanometer scales, formation of a swarm pattern relies on the physical or chemical interactions between the agents owing to the absence of an on-board device. Independent pattern formation of different swarms, especially under the same input, is a more challenging task. In this work, a swarm of nickel nanorods is proposed and by exploiting its different behavior with the nanoparticle swarm, independent pattern formation of diverse microrobotic swarms under the same environment can be conducted. A mathematical model for the nanorod swarm is constructed, and the mechanism is illustrated. Two-region pattern changing of the nanorod swarm is discovered and compared with the one-region property of the nanoparticle swarm. Experimental characterization of the nanorod swarm pattern is conducted to prove the concept and validate the effectiveness of the theoretical analysis. Furthermore, independent pattern formation of different microrobotic swarms was demonstrated. The pattern of the nanorod swarm could be adjusted while the other swarm was kept unchanged. Simultaneous pattern changing of two swarms was achieved as well. As a fundamental research on the microrobotic swarm, this work presents how the nanoscale magnetic anisotropy of building agents affects their macroscopic swarm behaviors and promotes further development on the independent control of microrobotic swarms under a global field input.

Assembling two-dimensional (2D) materials by polyelectrolyte often suffers from inhomogeneous microstructures due to the conventional mixing-and-simultaneous-complexation procedure (“mix-and-complex”) in aqueous solution. Herein a “mix-then-on-demand-complex” concept via on-demand in situ cascade anionization and ionic complexation of 2D materials is raised that drastically improves structural order in 2D assemblies, as exemplified by classical graphene oxide (GO)-based ultrathin membranes. Specifically, in dimethyl sulfoxide, the carboxylic acid-functionalized GO sheets (COOH–GOs) were mixed evenly with a cationic poly(ionic liquid) (PIL) and upon filtration formed a well-ordered layered composite membrane with homogeneous distribution of PIL chains in it; next, whenever needed, it was alkali-treated to convert COOH–GO in situ into its anionized state COO^––GO that immediately complexed ionically with the surrounding cationic PIL chains. This “mix-then-on-demand-complex” concept separates the ionic complexation of GO and polyelectrolytes from their mixing step. By synergistically combining the PIL-induced hydrophobic confinement effect and supramolecular interactions, the as-fabricated nanofiltration membranes carry interface transport nanochannels between GO and PIL, reaching a high water permeability of 96.38 L m^–2 h^–1 bar^–1 at a maintained excellent dye rejection 99.79% for 150 h, exceeding the state-of-the-art GO-based hybrid membranes. The molecular dynamics simulations support the experimental data, confirming the interface spacing between GO and PIL as the water transport channels.

Nanoparticle-based delivery systems for cancer immunotherapies aim to improve the safety and efficacy of these treatments through local delivery to specialized antigen-presenting cells (APCs). Multifunctional mesoporous silica nanoparticles (MSNs), with their large surface areas, their tunable particle and pore sizes, and their spatially controlled functionalization, represent a safe and versatile carrier system. In this study, we demonstrate the potential of MSNs as a pH-responsive drug carrier system for the anticancer immune-stimulant R848 (resiquimod), a synthetic Toll-like receptor 7 and 8 agonist. Equipped with a biotin–avidin cap, the tailor-made nanoparticles showed efficient stimuli-responsive release of their R848 cargo in an environmental pH of 5.5 or below. We showed that the MSNs loaded with R848 were rapidly taken up by APCs into the acidic environment of the lysosome and that they potently activated the immune cells. Upon subcutaneous injection into mice, the particles accumulated in migratory dendritic cells (DCs) in the draining lymph nodes, where they strongly enhanced the activation of the DCs. Furthermore, simultaneous delivery of the model antigen OVA and the adjuvant R848 by MSNs resulted in an augmented antigen-specific T-cell response. The MSNs significantly improved the pharmacokinetic profile of R848 in mice, as the half-life of the drug was increased 6-fold, and at the same time, the systemic exposure was reduced. In summary, we demonstrate that MSNs represent a promising tool for targeted delivery of the immune modulator R848 to APCs and hold considerable potential as a carrier for cancer vaccines.

Development of bioinspired nanomachines with an efficient propulsion and cargo-towing has attracted much attention in the last years due to their potential biosensing, diagnostics, and therapeutics applications. In this context, self-propelled synthetic nanomotors are promising carriers for intelligent and controlled release of therapeutic payloads. However, the implementation of this technology in real biomedical applications is still facing several challenges. Herein, we report the design, synthesis, and characterization of innovative multifunctional gated platinum–mesoporous silica nanomotors constituted of a propelling element (platinum nanodendrite face), a drug-loaded nanocontainer (mesoporous silica nanoparticle face), and a disulfide-containing oligo(ethylene glycol) chain (S–S–PEG) as a gating system. These Janus-type nanomotors present an ultrafast self-propelled motion due to the catalytic decomposition of low concentrations of hydrogen peroxide. Likewise, nanomotors exhibit a directional movement, which drives the engines toward biological targets, THP-1 cancer cells, as demonstrated using a microchip device that mimics penetration from capillary to postcapillary vessels. This fast and directional displacement facilitates the rapid cellular internalization and the on-demand specific release of a cytotoxic drug into the cytosol, due to the reduction of the disulfide bonds of the capping ensemble by intracellular glutathione levels. In the microchip device and in the absence of fuel, nanomotors are neither able to move directionally nor reach cancer cells and deliver their cargo, revealing that the fuel is required to get into inaccessible areas and to enhance nanoparticle internalization and drug release. Our proposed nanosystem shows many of the suitable characteristics for ideal biomedical destined nanomotors, such as rapid autonomous motion, versatility, and stimuli-responsive controlled drug release.

As a two-dimensional semiconductor with many physical properties, including, notably, layer-controlled electronic bandgap and coupled spin-valley degree of freedom, monolayer MoSe₂ is a strong candidate material for next-generation opto- and valley-electronic devices. However, due to substrate effects such as lattice mismatch and dielectric screening, preserving the monolayer’s intrinsic properties remains challenging. This issue is generally significant for metallic substrates whose active surfaces are commonly utilized to achieve direct chemical or physical vapor growth of the monolayer films. Here, we demonstrate high-temperature-annealed Au foil with well-defined (100) facets as a weakly interacting substrate for atmospheric pressure chemical vapor deposition of highly crystalline monolayer MoSe₂. Low-temperature scanning tunneling microscopy/spectroscopy measurements reveal a honeycomb structure of MoSe₂ with a quasi-particle bandgap of 1.96 eV, a value comparable with other weakly interacting systems such as MoSe₂/graphite. Density functional theory calculations indicate that the Au(100) surface exhibits the preferred energetics to electronically decouple from MoSe₂, compared with the (110) and (111) crystal planes. This weak coupling is critical for the easy transfer of monolayers to another host substrate. Our study demonstrates a practical means to produce high-quality monolayers of transition-metal dichalcogenides, viable for both fundamental and application studies.

Using electron spin resonance spectroscopy, we demonstrate that the morphological asymmetries present in small spheroidal metallic nanoparticles give rise to asymmetries in the behavior of electrons held in states near the metal’s Fermi energy. We find that the effects of morphological asymmetries for these spheroidal systems are more important than the effects of size distributions when explaining the asymmetry in electronic behavior. This is found to be true for all the particles examined, which were made from Cu, Ag, Pd, Ir, Pt, and Au, bearing dodecanethiolate ligands. In the case of the Ag particles, we also demonstrate that the same model used to account for morphological effects in the electron spin resonance spectra can be used to account for small asymmetries present in the plasmon spectrum. This result demonstrates that the electronic properties of even small particles are tunable via morphological changes.

Tailoring the grain boundaries (GBs) and twist angles between two-dimensional (2D) crystals are two crucial synthetic challenges to deterministically enable envisioned applications such as moiré excitons, emerging magnetism, or single-photon emission. Here, we reveal how twisted 2D bilayers can be synthesized from the collision and coalescence of two growing monolayer MoS₂ crystals during chemical vapor deposition. The twisted bilayer (TB) moiré angles are found to preserve the misorientation angle (θ) of the colliding crystals. The shapes of the TB regions are rationalized by a kink propagation model that predicts the GB formed by the coalescing crystals. Optical spectroscopy measurements reveal a θ-dependent long-range strain in crystals with stitched grain boundaries and a sharp (θ > 20°) threshold for the appearance of TBs, which relieves this strain. Reactive molecular dynamics simulations explain this strain from the continued growth of the crystals during coalescence due to the insertion of atoms at unsaturated defects along the GB, a process that self-terminates when the defects become saturated. The simulations also reproduce atomic-resolution electron microscopy observations of faceting along the GB, which is shown to arise from the growth-induced long-range strain. These facets align with the axes of the colliding crystals to provide favorable nucleation sites for second-layer growth of a TB with twist angles that preserve the misorientation angle θ. This interplay between strain generation and aligned nucleation provides a synthetic pathway for the growth of TBs with deterministic angles.

Herein, a functional class of microenvironment-associated nanomaterials is reported for improving the second near-infrared (NIR-II) imaging and photothermal therapeutic effect on intracranial tumors via a spontaneous membrane-adsorption approach. Specific peptides, photothermal agents, and biological alkylating agents were designed to endow the nanogels with high targeting specificity, photothermal properties, and pharmacological effects. Importantly, the frozen scanning electron microscopy technology (cryo-SEM) was utilized to observe the self-association of nanomaterials on tumor cells. Interestingly, the spontaneous membrane-adsorption behavior of nanomaterials was captured through direct imaging evidence. Histological analysis showed that the cross-linking adhesion in intracranial tumor and monodispersity in normal tissues of the nanogels not only enhanced the retention time but also ensured excellent biocompatibility. Impressively, in vivo data confirmed that the microenvironment-associated nanogels could significantly enhance brain tumor clearance rate within a short treatment timeframe (only two weeks). In short, utilizing the spontaneous membrane-adsorption strategy can significantly improve NIR-II diagnosis and phototherapy in brain diseases while avoiding high-risk complications.

The hydrophobicity of monolayer-protected gold nanoparticles is a crucial design parameter that influences self-assembly, preferential binding to proteins and membranes, and other nano–bio interactions. Predicting the effects of monolayer components on nanoparticle hydrophobicity is challenging due to the nonadditive, cooperative perturbations to interfacial water structure that dictate hydrophobicity at the nanoscale. In this work, we quantify nanoparticle hydrophobicity by using atomistic molecular dynamics simulations to calculate local hydration free energies at the nanoparticle–water interface. The simulations reveal that the hydrophobicity of large gold nanoparticles is determined primarily by ligand end group chemistry, as expected. However, for small gold nanoparticles, long alkanethiol ligands interact to form anisotropic bundles that lead to substantial spatial variations in hydrophobicity even for homogeneous monolayer compositions. We further show that nanoparticle hydrophobicity is modulated by changing the ligand structure, ligand chemistry, and gold core size, emphasizing that single-ligand properties alone are insufficient to characterize hydrophobicity. Finally, we illustrate that hydration free energy measurements correlate with the preferential binding of propane as a representative hydrophobic probe molecule. Together, these results show that both physical and chemical properties influence the hydrophobicity of small nanoparticles and must be considered together when predicting gold nanoparticle interactions with biomolecules.

Exsolution phenomena are highly debated as efficient synthesis routes for nanostructured composite electrode materials for the application in solid oxide cells (SOCs) and the development of next-generation electrochemical devices for energy conversion. Utilizing the instability of perovskite oxides, doped with electrocatalytically active elements, highly dispersed nanoparticles can be prepared at the perovskite surface under the influence of a reducing heat treatment. For the systematic study of the mechanistic processes governing metal exsolution, epitaxial SrTi_0.9Nb_0.05Ni_0.05O_3-δ thin films of well-defined stoichiometry are synthesized and employed as model systems to investigate the interplay of defect structures and exsolution behavior. Spontaneous phase separation and the formation of dopant-rich features in the as-synthesized thin film material is revealed by high-resolution transmission electron microscopy (HR-TEM) investigations. The resulting nanostructures are enriched by nickel and serve as preformed nuclei for the subsequent exsolution process under reducing conditions, which reflects a so far unconsidered process drastically affecting the understanding of nanoparticle exsolution phenomena. Using an approach of combined morphological, chemical, and structural analysis of the exsolution response, a limitation of the exsolution dynamics for nonstoichiometric thin films is found to be correlated to a distortion of the perovskite host lattice. Consequently, the incorporation of defect structures results in a reduced particle density at the perovskite surface, presumably by trapping of nanoparticles in the oxide bulk.