Sodium borohydride (NaBH₄) has been found to display superionic Na⁺ conductivity upon partial oxidation. Herein, by controlling the hydrolysis of NaBH₄ and by thermally stabilizing the oxide phase formed, i.e., NaB(OH)₄, Na⁺ ionic conductivity increased from ∼10^–10 S cm^–1 for unmodified NaBH₄ to 2.2 × 10^–5 S cm^–1 at room temperature and 2.6 × 10^–3 S cm^–1 at 75 °C for hydrolyzed NaBH₄. More remarkably, this approach allowed for a comprehensive multidimensional ²³Na–¹H and ¹¹B–¹H solid-state NMR analysis and determination of the interplay between pristine α-NaBH₄ and NaB(OH)₄ in leading to high Na⁺ ionic conductivity. Not only NMR analysis confirmed that the superionic behavior observed in partially hydrolyzed NaBH₄ was the result of Na⁺ hopping, but 2D NMR also revealed that the hopping mechanism was the result of the formation of a highly defective structure at the α-NaBH₄/NaB(OH)₄ interface, leading to high Na⁺ conductivity. Given the simplicity of the oxidation process reported here, this finding opens novel and facile methodologies for the development of promising solid-state electrolytes for sodium-based batteries.

The Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) and Li_1.6Al_0.5Ge_1.5P_2.9Si_0.1O₁₂ (LAGPS) compounds with the NASICON structure have been studied both theoretically and experimentally. The theoretical approach involved analyzing free space in crystal structures (geometrical-topological analysis, GT), calculating ion migration energies using the bond valence site energy (BVSE) method, and determining ionic conductivity at various temperatures through kinetic Monte Carlo simulations. Density functional theory (DFT) calculations were also applied to obtain precise results. While the GT and BVSE analyses revealed similar three-dimensional lithium-ion migration maps for both LAGP and LAGPS structures, DFT calculations indicated a difference in the migration energies: LAGP exhibited a 3D migration energy of 0.84 eV, whereas LAGPS showed a lower energy of 0.57 eV. At the same time, 1D and 2D Li ion diffusions have a lower migration energy. LAGP and LAGPS glass-ceramics were obtained successfully, and their samples were characterized by differential scanning calorimetry. This confirmed the absence of residual glass phases in the samples, as expected. Atomic force microscopy data showed the formation of a continuous texture in both samples. Impedance spectroscopy was used to measure conductivity in the range of −45 to 140 °C. This revealed the absence of any phase transitions in the structures. At various temperatures, the contributions of the bulk and grain-boundary components to the total conductivity were determined. The LAGPS sample showed a higher grain-boundary conductivity and total conductivity compared to those of the LAGP sample, which coincides well with the theoretical results.

The development of lithium–sulfur (Li–S) batteries is highly dependent on overcoming the technical issues such as the shuttling behavior of lithium polysulfides (LiPSs). In this work, we report a multifunctional layer composed of MXene/ZIF-8 (MXZ) nanohybrids to enhance the electrochemical performance of Li–S batteries. During the preparation of MXZ, ZIF-8 is hybridized with Ti₃C₂T_x MXene, where the ZIF-8 is decorated on the surface of Ti₃C₂T_x MXene by in situ growth. During thermal treatment, MXZ developed a hybrid phase of TiO₂ (brookite and rutile) as well as N-doped carbon microstructures. Spectroscopic analysis confirms that the complementary contribution by the hybrid phase of TiO₂, N-doped carbon microstructures, plays a critical role as electrocatalysts via efficient adsorption and conversion of LiPSs to fulfill high-performance Li–S batteries.

We use the nuclear ensemble approach to study the mechanism of thermally activated delayed fluorescence (TADF) in a carbene-copper-amide (CMA1) emitter. The results obtained for the emitter in the gas phase are consistent with previously published surface hopping nonadiabatic dynamics simulations for the same system. CMA1 has two excited state conformations with distinct excited state dynamics. For both conformations, the intersystem crossing (ISC) from the S₁ state occurs via higher-lying triplets, but the reverse ISC (rISC) can occur exclusively in the perpendicular orientation of the ligands, directly between the T₁ and S₁ states. Nonadiabatic mixing with higher triplet states is not required for efficient rISC, but T₁ changes diabatic character significantly along the vibrational modes. Furthermore, we find that the inclusion of the solvent effects has a significant impact on the TADF mechanism, enabling rISC in both conformations. The calculated rate constants and lifetimes are within an order of magnitude of the experimental values.

Oxygen vacancy (O_V)-enriched black TiO₂ (BTO) is a promising material for supporting well-studied noble metals in the hydrogen evolution reaction (HER). Blackening TiO₂ by incorporating O_Vs substantially changes the electronic state of BTO and enhances HER catalytic performance compared to pristine TiO₂. Furthermore, the incorporation of vacancies leads to deviation from a single anatase phase on a localized scale and creates a heterojunction by promoting the occurrence of localized rutile segments. Hence, synthesizing biphasic (rutile and anatase) BTO with abundant O_Vs and optimized Pt-metallic clusters substantially improves the electrochemical HER kinetics, though it demands a complicated multistep synthesis. Conversely, herein, a solvent-free, single-pot green synthesis route is corroborated using a pulse laser irradiation technique to achieve the desired O_v-enriched BTO structure. Controlled irradiation of anatase TiO₂ with a Pt precursor under optimized parameters in an air environment creates O_Vs and decorates the metal oxide with Pt nanoclusters. This defect formation decreases the activation energy of BTO, favoring the anatase phase and forming a localized rutile phase, which enhances HER activity through localized heterojunctions. The combined impacts of Pt nanoclusters and O_Vs revealed an outstanding specimen achieving a HER overpotential of 169 mV at 10 mA/cm² and a Tafel slope of 73.3 mV/dec Importantly, long-term stability during overall water splitting was further achieved. This approach offers valuable perceptions into designing highly competent catalysts and their supporting structures for various energy-associated solicitations.

Current synthesis and transfer methods of 2D materials (2DMs) have fallen short of realizing their promised high-end applications on an industrial scale. In addressing this gap, the method of chemical vapor deposition (CVD) on a liquid substrate envisions cost-effective continuous synthesis and transfer of single-crystal 2DMs. For practical and economical reasons, unlocking effective low-temperature 2DM growth on a liquid catalyst would be a major milestone. Here, we explore the potential of heterogeneous liquid-phase single-atom catalysts (LSACs) for low-temperature 2DM synthesis, specifically the CVD of graphene on liquid Sn–M alloys (M representing a solute metal, acting as LSACs). Through systematic screening over the periodic table based on physical properties and quantum chemical calculations, we identified liquid Sn–Ni (92:8 atom %) as a promising candidate. Experimental studies in the 1000–1200 K temperature range have revealed clear evidence of catalytic activity by the solute Ni single atoms in the liquid alloy for graphene synthesis. These results indicate the scientific richness and technological opportunities that LSACs can provide for efficient mass production of 2DMs.

We used isothermal titration calorimetry to measure the bulk heats for the deprotonation of the carboxylic functional group ([≡COOH]) on graphene oxide (GO) and those of Eu(III) and U(VI) sorption to GO at 25 °C. The enthalpies for the specific sorption reactions were calculated by fitting these bulk heat data sets. The GO speciation used for enthalpy calculation was simulated based on an electrostatic double-layer model for GO surface protonation/deprotonation and Eu(III)/U(VI) sorption to GO. The enthalpy for the deprotonation of [≡COOH] on GO is calculated to be 14.7 kJ/mol, by fitting the heat release data sets of NaOH titration to GO at variable concentrations (0.1, 0.5, and 1 g/L). This endothermic enthalpy for the deprotonation of the carboxylic site is consistent with that for bicarbonate. The enthalpy for Eu(III) and U(VI) complexation to GO was calculated to be 16.86 ± 1.83 and 33.8 ± 3.36 kJ/mol, by fitting multiple bulk heat data sets of EuCl₃ or UO₂(NO₃)₂ titration to GO. The enthalpies for Eu(III) and U(VI) sorption to GO were extrapolated from batch sorption data sets at variable temperatures based on the van’t Hoff relationship in a previous study, but these values are not reaction or site-specific, while this work presents an alternative method to quantify the enthalpy of reactions for GO associated with the specific functional group.

Understanding the intricate relationship between structure and surface energy is essential for a thorough comprehension of the external surface structure and crystal morphology of zeolites. In this study, we evaluated the surface energies of various zeolite surfaces across multiple representative frameworks with DFT calculations. Our analysis reveals a linear relationship between the calculated surface energy and the surface hydroxyl density, which is slightly disrupted due to the formation of hydrogen bonds. Using a symbolic regression approach, we establish a mathematical formula that correlates the surface energy with the density of surface hydroxyl groups and hydrogen bonds. We show that using the surface hydroxyl density alone can rapidly predict zeolite crystal morphologies with a high degree of accuracy, demonstrated by a promising Wulff similarity of 98%. The applicability and potential of our findings are demonstrated in estimating the Wulff shapes of 237 zeolite framework types in the database and predicting the crystal morphology evolution of a representative zeolite with pH, confirming the general validity of our approach based on straightforward structural analysis and thermodynamic principles. This work establishes a solid foundation for advancing the structural design of silica-based materials, particularly in applications requiring precise control of the surface structure and crystal habit.

Surface formation markedly influences the stability and properties of nanoalloys. The surface states of nanoalloys are sensitive to the constituent elements and to the surrounding environment. In this study, Fourier transform-infrared (FT-IR) spectroscopy and an evolution strategy (ES) combined with density functional theory calculations and multivariate analysis were used to explore the stable configuration of NO-adsorbed PdRu nanoalloys. FT-IR analysis indicated that the NO molecules were adsorbed on the Ru-related sites, which was inconsistent with the stable surface state of the isolated PdRu nanoalloy models. The ES revealed that the stable surface state consisted mainly of Ru atoms owing to molecular adsorption. In addition, the Pd–Ru mixing was facilitated by the adsorption. According to the multivariate analysis, the adsorption energies on the Ru-related sites were more negative than those on the Pd-related sites and became more negative as the number of neighboring Pd atoms increased. These adsorption characteristics are opposite to those of the stability of the isolated PdRu nanoalloys. The energy gain owing to NO adsorption overcomes the energy loss due to the Pd–Ru bonds and placement of Ru atoms at the surface. This study highlights the importance of understanding stable surface states in a reactive atmosphere for the application of nanoalloys.

With the development of nuclear energy, a large number of radionuclides are inevitably released into the natural environment. An important strategy for the management of radioactive nuclides in complex environments is the development of efficient nanomaterials. In this work, heterojunctions assembled with monolayers of Mg(OH)₂ and two-dimensional (2D) sheets (graphene, 1T–MoS₂, WSe₂, Ti₂CF₂, Ti₂CO₂) were designed for the removal of uranyl(VI). Our results indicate that uranyl(VI) prefers to be adsorbed on the Mg(OH)₂ side of the heterojunctions in the inner-sphere binding mode. Various chemical bond analyses were employed to reveal the bonding natures of uranyl(VI) with the heterojunctions. The adsorption of uranyl(VI) is enhanced in the explicit solvation environment due to the interactions of uranyl(VI) and surrounding H₂O molecules. The diffusion energy barriers of uranyl(VI) on the heterojunctions were assessed. AIMD simulations at ambient temperature indicate that uranyl(VI) can efficiently anchor on the heterojunction surface in an aqueous environment. This study may provide theoretical support for the development of novel nanomaterials for the removal of radionuclides.

Nature’s enzymes exhibit remarkable substrate specificity and catalytic efficiency by transforming substrates within confined active sites. To emulate this, various molecular containers, including zeolites, cyclodextrins, calix[n]arenes, cavitands, cucurbit[n]urils, metal–organic frameworks, covalent organic frameworks, and carbon nanotubes (CNTs), have been explored. Among these, CNTs are notable for their unique physical and chemical properties, enabling them to control reactions through spatial confinement. This study investigates the effect of CNT encapsulation on metal-free 1,3-dipolar Huisgen cycloaddition reactions between benzyl azide and substituted alkynes. Experimental results showed that CNTs significantly enhance the selectivity for the 1,4-triazole product. Computational studies using density functional theory further elucidate the impact of CNT confinement on reaction mechanisms and regioselectivity. The findings reveal that confinement within CNTs alters potential energy surfaces, favoring 1,4-triazole formation over 1,5-triazole, driven by steric and electronic factors. Additionally, comparative analyses highlight the influence of CNT diameter on activation energies and product stability, particularly with energy decomposition analysis and noncovalent interaction plots. This research underscores the potential of CNTs as nanoscale reactors for controlled synthesis, providing insights into the design of new catalytic systems and advancing the field of molecular encapsulation for selective organic transformations.

In this study, we investigated the atomic-level interaction between CO molecules and a well-ordered Mn₃O₄(001) thin film. The oxide film, initially grown on a single-crystal Au(111) substrate, was characterized using X-ray photoelectron spectroscopy (XPS) to determine its oxidation state. Further examination of the film structure through scanning transmission electron microscopy (STEM) and low-energy electron diffraction (LEED) revealed its growth orientation along the [001] direction, with three domains rotated by 60° and aligned with the ⟨110⟩_Au directions. Notably, the termination of the film features a layer of Mn³⁺ cations covered with oxygen atoms. The study then focused on the interaction of the film with CO, employing infrared reflection absorption spectroscopy (IRAS) and temperature-programmed IRAS (TP-IRAS). The results unveiled two distinct IR peaks related to CO adsorption: one at 2140 cm^–1, signifying that CO molecules weakly adsorbed on the oxygen-terminated surface of Mn³⁺ cations, and another at 2105 cm^–1, indicative of CO molecules bound to Mn²⁺ cations at oxygen vacancies.

To elucidate the role of low-coordinated sites in the partial methanol oxidation to methyl formate (MeFo), the isothermal reactivity of flat Au(111) and stepped Au(332) in pulsed molecular beam experiments was compared for a broad range of reaction conditions. Low-coordinated step sites were found to enhance MeFo selectivity, especially at low coverage conditions, as found at higher temperatures. The analysis of the transient kinetics provides evidence for the essential role of Au_xO_y phases for MeFo formation and the complex interplay of different oxygen species for the observed selectivity. Ab initio molecular dynamic simulations yielded microscopic insights in the formation of Au_xO_y phases on flat and stepped gold surfaces emphasizing the role of low-coordinated sites in their formation. Moreover, associated surface restructuring provides atomic-scale insights which align with the experimentally observed transient kinetics in MeFo formation.

The intermediate toxic species CO_ads produced by electrocatalytic oxidation of methanol have a high adsorption energy on the surface of Pt active sites and are difficult to convert, which is the main reason for the poisoning and deactivation of Pt electrocatalysts in direct methanol fuel cells. In this study, a series of PtSn/CeO₂-CNTs alloy catalysts were prepared by an ethylene glycol hydrothermal reduction method using CeO₂-modified carbon nanotubes (CNTs) as the support. The electrochemical properties of a series of PtSn alloy catalysts were measured by using a methanol oxidation reaction (MOR) as a probe reaction. The results show that the excellent electrochemical performance is mainly attributed to the introduction of CeO₂ and the synergistic effect among the Sn and Pt intermetallic nanoparticles. An in situ transient analysis platform investigated the electrocatalytic oxidation path of methanol molecules at the surface and interface of Pt₁₀₀-CNTs and Pt₄₂Sn₅₈/CeO₂-CNTs catalysts. It was clear that methanol was converted by the CO path, and the introduction of Sn and CeO₂ synergistically promoted the rapid conversion of intermediate toxic species CO_ads, which effectively improved the activity and stability of Pt catalysts and accelerated the MOR rate. It provides a new idea and basis for the rational design and optimization of Pt electrocatalysts.

Semiconductor heterojunctions could accelerate carrier separation and transfer for improving light-to-hydrogen (LTH) conversion efficiency. However, the lack of tight and efficient interfacial charge cross in three-dimensional semiconductor-based heterojunctions limits their practical application and the relevant profound understanding of the interfacial charge delivery. In this work, porphyrin (Cu)-based COF with a highly conjugated structure was deposited onto three-dimensional (3D) ZnIn₂S₄ by a facile solvothermal method to prepare a 3D/2D ZnIn₂S₄@CuP–Ph COF heterojunction. The content-optimized ZnIn₂S₄@CuP–Ph COF composite showed an excellent LTH conversion rate of up to 2667.94 μmol g^–1 h^–1, about 13.5 times higher than that of pristine ZnIn₂S₄. The significantly meliorated photocatalytic performance is attributed to the synergistically functioning contributors, that is, the fast interfacial charge transfer and the augmented light capturing capability after integration. Also, the work function results by DFT calculation reveals that the electrons of CuP–Ph COF (Φ = 4.41 eV) transfer from the interface electron delivery channels of the two components to ZIS (Φ = 7.03 eV) until the Fermi level of the two components reaches equilibrium. This moment, the work function of ZnIn₂S₄@CuP–Ph COF (Φ = 6.50 eV) lies between the two components, and an electron accumulation region is formed on the side of ZIS. Additionally, the free-energy barriers of hydrogen evolution dominated by ZnIn₂S₄@CuP–Ph COF (0.0955 eV) is much lower than that of ZnIn₂S₄ (0.1256 eV). This study possesses certain guiding significance for the design of organic–inorganic heterojunction photocatalysts for efficient LTH conversion.

Co₂C nanoprisms were developed for the Fischer–Tropsch to olefins (FTO) reaction a few years ago, while to the best of our knowledge, the study of the electronic promoters were hardly reported due to the instability of the Co₂C nanostructures with promoters. The absence of the promoters limited the performance modulation and industrial application of the Co₂C-based FTO catalysts. The work reported here was aimed at developing a new strategy to synthesize the Zn-promoted Co₂C nanoprisms and understanding the electronic effects of the Zn promoters on the Co₂C facets without confusion over the geometric effects. Detailed characterizations of the carbonized and spent samples suggested that the Zn promoters lowered the stability of the Co₂C nanostructures and led to the formation of the surface Co⁰ species in the spent samples with high Zn contents, which was responsible for the decrease of the O/P ratios and the increase of the CH₄ selectivity. The XPS results showed that the electrons transferring from the Zn promoters to the Co₂C facets enriched the density of the electron clouds of the Co species on the Co₂C facets. Further evidence for the enhanced CO adsorption and dissociation routes were obtained from the measurements of the CO temperature-programmed desorption. The Zn promoters increased the strong adsorption sites, which were not active for the Boudouard reaction and the increase of the CO₂ selectivity originated from the Water–Gas Shift reaction. The activation route of the adsorbed CO species on the strong adsorption sites was H-assisted dissociation rather than direct dissociation, resulting in the inhibition of the carbene-mediated routes and the shifting of product selectivity toward light hydrocarbons.

Hydrogen adsorption on platinum (Pt) single-crystal electrodes has been studied intensively in both experiments and computations. Yet, the precise origin and nature of the repulsive interactions observed between hydrogen adsorbates (H_ads) have remained elusive. Here, we use first-principles density functional theory calculations to investigate in detail the interactions between H_ads on Pt(111), Pt(100), and Pt(110) surfaces. The repulsive interaction between H_ads on Pt(111) is deconvoluted into three different physical contributions, namely, (i) electrostatic interactions, (ii) surface distortion effect, and (iii) surface coordination effect. The long-range electrostatic interaction, which is generally considered the most important source of repulsive interactions in surface adsorption, was found to contribute less than 30% of the overall repulsive interaction. The remaining >70% arises from the other two contributions, underscoring the critical influence of surface-mediated interactions on the adsorption process. Surface distortion and coordination effects are found to strongly depend on the coverage and adsorption geometry: the effect of surface distortion dominates when adsorbates reside two or more Pt atoms apart; the effect of surface coordination dominates if hydrogen is adsorbed on neighboring adsorption sites. The above effects are considerably less pronounced on Pt(100) and Pt(110), therefore resulting in weaker interactions between H_ads on these two surfaces. Overall, the study highlights the relevance of surface-mediated effects on adsorbate–adsorbate interactions, such as the often-overlooked surface distortion. The effect of these interactions on the hotly debated adsorption site for the adsorbed hydrogen intermediate in the hydrogen evolution reaction is also discussed.

Biomedical applications of plasmonic nanoparticle (NP) conjugates need control over their optical properties modulated by surface coating with stabilizing or targeting molecules often attached to or embedded in the secondary functionalization shell, such as silica. Although current numerical techniques can simulate the plasmonic response of such structures, it is desirable in practice to have analytical models based on simple physical ideas that can be implemented without considerable computer resources. Here, we present two efficient analytical methods based on improved electrostatic approximation (IEA) and modal expansion method (MEM) combined with the dipole equivalence method. The last approach avoids additional electromagnetic simulations and provides a direct bridge between analytical IEA and MEM models for bare particles and those with multilayer shells. As simple as the original IEA and MEM, the developed analytical extensions provide accurate extinction and scattering spectra for coated particles compared to exact calculations by separation of variable method and COMSOL. The possibility and accuracy of analytical models are illustrated by extensive simulations for prolate and oblate gold and silver NPs with a maximal size of up to 200 nm, aspect ratio from 2 to 6, and 3–30 nm dielectric coating.

This study explores the optical properties of porous porphyrin cages through the use of spectroscopic techniques. The findings reveal that cages featuring electron-donating nitrogen functional groups display distinct alterations in their absorption spectra, including a red-shift and broadening of Soret bands, and a decrease in the Soret:Q-band ratio. The extent of conjugation within the cages significantly impacts their molar absorptivity, demonstrating a linear correlation with the number of saturated cage linkages and a superlinear increase for highly conjugated cages. The emission spectra of the cages largely mirror that of the monomer, barring fully conjugated cages. The relative fluorescence quantum yields differ among the cages, with some showing enhancements and others reductions, likely due to variations in cage rigidity. Time-resolved emission measurements indicate that the number of porphyrins in the cages affects the emission lifetime, with increased conjugation resulting in a shorter lifetime due to exciton delocalization. These insights underscore the potential of highly conjugated cages in optoelectronic devices, photosensitizers, and photocatalysts, given their effective light absorption and energy distribution capabilities.

Raman spectroscopy allows for material characterization of nanoparticles; however, probing individual nanoparticles requires an efficient way of isolating and enhancing the signal. Past works have used optical trapping with nanoapertures in metal films to measure the Raman spectra of individual nanoparticles; however, those works required custom laser tweezer systems that provided a transmission signal to verify trapping events as well as costly top-down nanofabrication. Here, we trapped Titania nanoparticles in a commercial Raman system using double nanoholes (DNH) and measured their spectra while trapped. The microscope camera allowed for measuring the trapping event in reflection mode, and a simultaneous Raman spectrum was recorded to allow for material characterization. The Raman signal was comparable to a past work that used particles a million times larger in volume without utilizing double nanoholes, and all other features were similar. The DNHs were created with a colloidal lithography technique and identified in the microscope, as confirmed by electron microscopy registration. Therefore, this approach allows a simple way of characterizing the Raman signal of individual nanoparticles while in solution by using existing commercial Raman systems.

Recently, the research of organic room temperature phosphorescence (RTP) materials has become a research hotspot in the field of materials science and chemistry, especially the use of a small molecule doping system to achieve long life and efficient RTP. Herein, an efficient stimulus responsive room temperature phosphorescent material is prepared by a simple host/guest eutectic method. Due to the high crystallinity of the host matrix, it provides a rigid environment for the guest emitter, and the appropriate triplet energy level provides a bridge for the energy transfer of the guest emitter. The prepared crystal material has a long lifetime of RTP with a lifetime of 0.82 s and a phosphorescence quantum yield of 12.3%. In addition, the introduction of fluorescent dyes in the eutectic system can adjust the afterglow color through energy transfer from triplet to singlet. Interestingly, the RTP properties of this material are sensitive to alkaline environments because it can destroy the crystalline structure of the host molecule, thereby reducing the rigidity of the entire system. Finally, the multicolor display and anticounterfeiting encryption of printed patterns are successfully applied by using the characteristics of afterglow color change and alkali response of doped materials.

In this study, we conduct a comprehensive investigation into the temperature and pressure dependencies of photoluminescence (PL) in a bulk GaSe_0.5Te_0.5 alloy. By using density functional theory (DFT) calculations and experimental measurements, we identify and distinguish the contributions of free excitons and indirect transitions to the PL spectrum. Our analysis reveals a nonlinear redshift for these transitions over the temperature range of 90–667 K, evolving in accord with the modified Varshni equation. We observe a pronounced influence of electron–phonon coupling in the GaSe_0.5Te_0.5 alloy compared to that of GaTe and GaSe crystal structures. Below 180 K, we detect the emergence of new broad bands associated with bound excitons and radiative recombination of trap states. Furthermore, by employing the Arrhenius plots, we determine activation energies for nonradiative recombination of the indirect and free exciton transitions. Concerning the pressure dependence of the PL spectra, the free exciton and indirect transitions undergo a linear redshift within the specific pressure range of 0.3 to 4.3 GPa, accompanied by a continuous reduction in PL intensity, leading to complete quenching at 4.8 GPa. This phenomenon is attributed to a direct-to-indirect band gap crossover. Pressure-dependent band structure calculation via DFT supports this assumption and shows a further metallization of the GaSe_0.5Te_0.5 alloy at ∼8.0 GPa. This study sheds new light on understanding the optical properties of the GaSe_0.5Te_0.5 alloy under extreme pressure and temperature conditions, thereby opening avenues for tailored applications and guiding future research efforts in this field.

Aggregation-induced emission (AIE) materials are in high demand for various practical applications in organic optoelectronics, sensorics, and bioimaging applications. Typically, these materials were designed to have nonplanar molecular structures with at least one-rotor moiety and intramolecular motion/rotation. Here, we designed, synthesized, and comprehensively studied 1,4-bis((9H-(1,8-diazafluoren)-9-ylidene)methyl)phenylene (1,8-BDFMP), demonstrating a unique and counterintuitive behavior. Despite the rigid and planar molecular structure caused by the effective conjugation and intramolecular N···H interactions coupled with strong H-aggregation, it clearly demonstrated AIE activity. The photoluminescence quantum yield of the luminophore in solution was only 0.04%, whereas its single crystals, despite strong π-stacking intermolecular interactions, were emissive with a photoluminescence quantum yield of 10%. The charge transport in 1,8-BDFMP single crystals and drop-cast films was evaluated. The detailed photophysics of 1,8-BDFMP was studied both experimentally and computationally. The conical intersection of the S₁–S₀ states was demonstrated to be the main nonradiative deactivation pathway in the monomeric state.

Fluorescence of molecules on metal substrates has attracted much attention because of its relevance to various optical devices, such as light-emitting diodes, sensors, and solar cells. However, the fluorescence measurement near the metal substrates is challenging due to the rapid quenching of the excited state of the molecules. In this study, fluorescence of tetraphenylporphyrin (TPP) on Au(111) substrates was successfully measured by fabricating a mixed self-assembled monolayer (SAM) of the tripodal molecules with and without TPP dye. The rigid tripodal molecules suppressed quenching, prevented structural changes, and reduced interactions between TPP moieties. These features made it possible to measure the fluorescence of TPP molecules isolated and dispersed on Au(111) in a uniform and well-defined structure. Through excitation spectra acquired by sweeping the excitation wavelength, information about TPP absorption was also obtained. In addition, these measurements were possible under potential control in an electrochemical environment due to the stability of the SAMs. Thus, we demonstrated that the system based on tripodal molecules can serve as a platform for measuring the fluorescence and absorption of molecules on metal substrates in the atmospheric and electrochemical environments in which various optical devices operate.

Vibrational circular dichroism (VCD) is an important method used to assign absolute configuration to chiral molecules, but inherently weak signals necessitate high concentrations and long acquisition times for analysis. Plasmonic nanostructures are of interest for enhancement of VCD signals. However, understanding the influence of plasmonic structures on molecular VCD spectral features is important for assessing the information content of the spectra. Here, we present a study of plasmonic gold nanobowl hole (NBH) structures and the influence on the VCD spectra of achiral molecules. VCD bands for the symmetric and antisymmetric methylene stretching modes of 1-octadecanethiol (ODT) on NBHs were observed. Measurements of ODT on CaF₂ substrates without plasmonic structures confirmed that the bands were not an artifact of tilting the substrate. The handedness of the VCD bands showed an inverse dependence on the handedness of the extrinsic CD response of the NBHs, producing a relative handedness of the opposite sign. By controlling the size of the NBHs, the localized surface plasmon resonance (LSPR) and CD bands were tuned relative to the spectral position of the ODT VCD bands. The amplitude and line shape of the methylene stretch VCD bands showed a strong dependence on overlap with the plasmonic CD band in the same spectral region. To further investigate the origin of the molecular VCD bands, nanobowls without holes (NBs) and nanodisks (NDs) were fabricated. The LSPR behavior of NBs and NDs was similar to NBHs, but the structures did not exhibit the extrinsic CD responses of NBHs, evidenced by the lack of defined CD bands and handedness conversion. Although the NBs and NDs exhibited small CD signals, VCD bands were not observed for ODT on the NBs and NDs. Stearic acid (SA) on NBHs also produced VCD bands, demonstrating the influence of the plasmonic nanostructures on molecules with different surface interactions and organization. Asymmetric line shapes of the VCD bands of ODT appeared similar to Fano resonance line shapes observed in surface-enhanced infrared absorption (SEIRA) spectroscopy; however, the NBH CD response was shown to be a key factor in producing the VCD bands, rather than the primary LSPR that influences the line shapes and enhancements in SEIRA. The studies of VCD spectra of achiral molecules on plasmonic structures highlight the importance of understanding how the plasmonic and chiroptical behaviors of the substrates impact the spectral features used to identify enantiomers in VCD spectroscopy, especially for configuration analysis and comparison with quantum calculations.

Electrokinetic surface-enhanced Raman spectroscopy (EK-SERS) is an emerging high-order analytical technique that combines the plasmonic sensitivity of SERS with the electrode interfacial molecular control of electrokinetics. However, previous EK-SERS works primarily focused on non-Faradaic direct current (DC) operation, limiting the understanding of the underlying mechanisms. Additionally, developing reliable EK-SERS devices with electrically connected plasmonic hotspots remains challenging for achieving high sensitivity and reproducibility in EK-SERS measurements. In this study, we investigated the use of two-tier nanolaminate nano-optoelectrode arrays (NL-NOEAs) for DC and alternating current (AC) EK-SERS measurements of charged analyte molecules in ionic solutions. The NL-NOEAs consist of Au/Ag/Au multilayered plasmonic nanostructures on conductive nanocomposite nanopillar arrays (NC-NPAs). We demonstrate that the NL-NOEAs exhibit high SERS enhancement factors (EFs) of ∼10⁶ and can be used to modulate the concentration and orientation of Rhodamine 6G (R6G) molecules at the electrode surface by applying DC and AC voltages. We also performed numerical simulations to investigate the ion and R6G dynamics near the electrode surface under DC and AC voltage modulation. Our results show that AC EK-SERS can provide additional insights into the dynamics of molecular transport and adsorption processes compared to DC EK-SERS. This study demonstrates the potential of NL-NOEAs for developing high-performance EK-SERS sensors for a wide range of applications.

We present a novel and straightforward design for a photonic crystal fiber (PCF)-based surface plasmon resonance sensor suitable for a wide range of sensing applications. The sensor’s performance is numerically analyzed using the finite element method implemented in COMSOL Multiphysics software. Our numerical results demonstrate a wavelength sensitivity(WS) of 88,000 nm/RIU and an amplitude sensitivity(AS) of 3136 RIU^–1, with a resolution of 1.136 × 10^–6 RIU. The proposed sensor is capable of detecting analytes within the refractive index (RI) range of 1.29–1.44. Additionally, we investigate the sensor’s fabrication tolerance concerning variations in pitch, air-hole diameter, and channel size, and it exhibits good tolerance to these variations. The sensor also demonstrates a high figure of merit of 1517. With its high sensitivity, broad sensing capability, and excellent fabrication tolerance, this sensor is highly versatile for detecting a wide range of analytes, including glucose, cholesterol, and hemoglobin, making it suitable for various biological and biochemical applications.

Herein, we explored the charge transfer (CT) effect on the excited-state structural and electronic evolution of N,N′-diphenyl-dihydrodibenzo[a,c]phenazine (DPAC) featuring various electron-donating groups (EDGs). Upon photoexcitation, DPAC molecules undergo a sequential multistep structural transformation along the Franck–Condon (FC) state, CT-controlled bent state (responsible for E1─420 nm), and twisted state (responsible for E2─600 nm). By introducing different EDGs to the DPAC core, we can fine-tune the balance between the inherent decay of the CT-controlled bent state and its progression into the twisted state by adjusting the CT effect. As the electron-donating ability of the EDG increases, the strong CT effect can produce a “deep” (stable) CT-controlled bent state, in which the transformation of the excited molecular skeleton from bent into twisted was partly suppressed. This research provides valuable insights into organic chromophores’ excited-state structural and electronic evolution, revealing how competitive decay pathways are contingent upon the CT effect.

Cu₂ZnSnS₄ has attracted significant attention as a promising material for solar cells. However, to the best of our knowledge, the research on utilizing indium reagent for modification remains largely unexplored to date. In this study, first-principles calculations were utilized to systematically investigate the structural and electronic properties of Cu₂Zn_1–xIn_xSnS₄ (x = 0, 1/8, 1/2, and 1). Our calculations, based on the formation enthalpies, indicate that the crystal structures of Cu₂Zn_1–xIn_xSnS₄ remain stable upon indium varying concentrations. Furthermore, phonon dispersion analysis shows that increasing indium content shifts the phonon dispersion curves of Cu₂Zn_1–xIn_xSnS₄ toward imaginary frequencies. In addition, the calculations reveal that the band gap can be effectively tuned. With increasing indium concentrations, the band gap of Cu₂ZnSnS₄ becomes narrow. Notably, for Cu₂Zn_1–xIn_xSnS₄ (x = 0, 1/8, and 1/2), all exhibit direct band gaps. The density of states analysis indicates that indium mainly occupies the d-orbitals. These results demonstrate that indium has a substantial impact on the electronic properties. Our findings could be very useful for synthetics of these materials.

A one-step metal-catalyzed process for transforming carbon films into high-quality graphene layers for potential use in various cutting-edge technologies was developed in this study. Carbon ultrathin films grown on CoFe alloy ultrathin sublayers by filtered cathodic vacuum arc using different ion kinetic energies were subjected to thermal annealing at 650 °C for 150 s. X-ray photoelectron spectroscopy, Raman spectroscopy, and molecular dynamics simulations provided insight into phase changes and graphenization at the molecular level. Atomic force microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy were used to characterize the surface morphology and elemental composition of the C films and the CoFe sublayer before and after thermal annealing. It was found that increasing the C⁺ ion kinetic energy during C film deposition enhanced graphenization; however, a very high ion kinetic energy had the opposite effect. The sp³/sp² ratio in the as-deposited C films played a critical role in graphene formation during thermal annealing. Contrary to amorphization, graphenization involved a three-step process encompassing the sequential transformation of high sp³ C to low sp³ C, low sp³ C to graphite, and, last, graphite to nanocrystalline graphite. Variations in the C⁺ ion kinetic energy indirectly affected the dependence of graphene growth on the hybridization state of the as-deposited C films, the carbon concentration in the CoFe sublayer, and the stability and uniformity of the catalyst CoFe sublayer during thermal annealing, in this manner influencing the overall metal-catalyzed C graphenization process.

The present work examines reaction and oxygen exchange processes in magnetron-sputtered Mg–CuO nanolaminates as a function of bilayer spacing. Energy production in stoichiometric Mg–CuO films with bilayer thicknesses between 170 and 1020 nm is examined via differential scanning calorimetry (DSC), and classical Kissinger analysis methods are implemented to determine effective activation energies (E_a). To elucidate structural evolution in the Mg–CuO system, select samples are analyzed via in situ high-temperature X-ray diffraction (HTXRD). DSC curves show exothermic maxima near critical temperatures reported in the Mg–Cu phase diagram, along with decreases in exothermic peak temperatures and effective E_a values as bilayer spacing increases. Thermal trends indicate three distinct reaction regions that emerge as a function of bilayer thickness: (i) 1020 nm thick Mg–CuO samples react near the Mg melting point (∼650 °C) and have an effective E_a of ∼600 kJ/mol. (ii) Mg–CuO films with 510–255 nm thick bilayers exhibit reactions between 511 and 548 °C, with effective E_a values significantly decreasing to 128–162 kJ/mol. At these thicknesses, Mg–CuO reaction temperatures occur near the Mg₂Cu/Mg and Mg₂Cu/Cu₂Mg eutectic points of 483 and 551 °C, respectively, suggesting the presence of a liquid phase enhancing mass transport. (iii) Mg–CuO samples with 204–170 nm thick bilayers appear to react via a solid-state reaction process as they exhibit exothermic behavior between 388 and 421 °C and have the lowest effective E_a values of 102–106 kJ/mol. DSC results are corroborated by in situ HTXRD results on Mg–CuO films with bilayer thicknesses of 1 μm and 340 and 204 nm that show transient intermetallic peaks coinciding with Cu/Mg phase diagram predictions and the appearance of Cu peaks at 640, 530, and 415 °C, respectively. These findings indicate that factors such as reactant properties and bilayer thickness significantly influence observed reaction pathways and that material concepts such as phase diagrams may act as heuristic guides to developing new reactive materials.

A borondipyrromethene (BODIPY)–ferrocene dyad where both units are connected by an ethynylstyryl linker was synthesized, and its fluorescence and electrochemical and electrofluorochromic features were analyzed first in solution and then as a surface-confined species. Immobilization was achieved by a siloxane derivatization at the meso position of the BODIPY, which enabled covalent grafting onto the ITO surface. The resulting monolayer showed high stability in the redox response and positive electrofluorochromism. Fluorescent emission was indeed switched on upon oxidation and monitored electrochemically, with good reversibility across cycles. This demonstrated that electrofluorochromic properties could be transposed from solution to the surface in the case of dyads whose emission is initially quenched.

Understanding the interaction between hydrogen cyanide (HCN) and silicate surfaces is crucial for elucidating the prebiotic processes occurring on interstellar grain cores as well as in cometary and meteoritic matrices. In this study, we characterized the adsorption features of HCN on crystalline forsterite (Mg₂SiO₄) surfaces, one of the most abundant cosmic silicates, by combining experimental infrared spectra at low temperatures (100–150 K) with periodic DFT simulations. Results showed the coexistence of both molecular and dissociative HCN adsorption complexes as a function of the considered forsterite crystalline face. Molecular adsorptions dominate on the most stable surfaces, while dissociative adsorptions occur predominantly on surfaces of lower stability, catalyzed by the enhanced Lewis acid–base behavior of surface-exposed Mg²⁺–O^2– ion pairs. On the whole set of adsorption cases, harmonic frequency calculations were carried out and compared with the experimental infrared bands. To disentangle each vibrational mode contributing to the experimental broad bands, we run the best nonlinear fit between the predicted set of frequencies and the experimental bands. The outcome of this procedure allowed us to (i) deconvolute the experimental IR spectrum by assigning computed normal modes of vibrations to the main features of each band and (ii) reveal which crystal faces are responsible for the largest contribution to the adsorbate vibrational bands, giving information about the morphology of the samples. The present straightforward procedure is quite general and of broad interest in the fine characterization of the infrared spectra of adsorbates on complex inorganic material surfaces.

This study utilizes the Kane-Mele (KM) and Hubbard models to investigate the thermodynamic and magnetic properties of the α-T₃ system, a two-dimensional (2D) material with unique electronic characteristics. The α-T₃ system features a distinct flat band in its electronic structure, influencing its behavior under various external conditions such as spin–orbit coupling (SOC), on-site Coulomb repulsion (OSCR), temperature, and doping. The research demonstrates how SOC and OSCR significantly change the electronic density of states, electronic heat capacity, and Pauli magnetic susceptibility. Notably, SOC induces band splitting, while increased OSCR shifts and splits the flat band, enhancing thermodynamic properties. The results display that the α-T₃ system exhibits paramagnetic behavior for a SOC strength (λ) of 0.5 eV and an α value of 0.5. An intriguing observation is that OSCR induces a transition from a paramagnetic phase to an antiferromagnetic phase. These findings highlight the potential of the α-T₃ system for applications in spintronics, thermal management, and nanoelectronics, offering new avenues for technological advancements in energy storage and sensing.

The presence of Fano resonance in a system often proves to be very useful in understanding various electronic and quantum properties of materials, especially in semiconductors. Although identifiable using Raman spectroscopy through the presence of Fano-type characteristics such as asymmetry and antiresonance in spectral line shape, it is difficult to unambiguously identify its presence and nature due to other factors/processes also affecting them. A wavelength- and power-dependent Raman scattering experiment, along with appropriate theoretical analysis, reveals the resonant nature of electron–phonon interaction in the A_g Raman mode (994 cm^–1) in orthorhombic V₂O₅. The asymmetric Raman line shape with an antiresonance dip and an electronic Raman background support the presence of a Fano interaction. The theoretical fitting of experimental data quantifies the electron–phonon coupling strength by the Fano coupling parameter (q). The excitation wavelength-dependent Raman spectra appear to contradict the Fano-type behavior, which has been used to identify the resonant nature of the Fano interaction. The Fano interaction weakens on increasing the excitation power due to the involvement of anharmonic effects.

Supramolecular assemblies composed of nanomaterials and mediated by DNAs are a special class of superstructures that serve various functions, such as drug and gene delivery, providing a platform for bioreactions and as photodynamic and photothermal therapeutic agents depending upon the nanomaterial/s used. This work has demonstrated the formation of carbon dots (CD) and gold nanoparticle (AuNP)-based fluorescent supramolecular assemblies mediated by DNAs (helix, i-motif, and G-quadruplex). The CDs and the AuNPs have paired up as energy donors and acceptors, helping to understand the network formation spectroscopically. Partial complementary G-quadruplexes and i-motif DNAs were attached to the surface of the synthesized CDs and AuNPs, respectively, which were allowed to interact, resulting in the formation of fluorescent sheet-like structures. These sheets tear from all directions at acidic pH (=5) and show 3D compaction at pH 8.5. It is also observed that photosensitization of the CDs gets slightly enhanced upon DNA grafting and further on incorporation of the DNA-functionalized AuNPs in the network.

Molecular self-assembly is considered a promising tool for creating functional molecular structures on surfaces, e.g., for future molecular electronic devices and sensor applications. In molecular self-assembly, the target structure is encoded in the molecular building blocks, which are driven toward their thermodynamically favored arrangement on the surface. This approach is, however, intrinsically limited to a single molecular pattern on the surface. Structures beyond this thermodynamic ground state minimizing the free energy might become accessible through competing pathways. Here, we make use of different sample preparation pathways for arriving at distinctly different molecular structures of C₆₀ on the (111) cleavage plane of the calcium fluoride. Using dynamic atomic force microscopy operated in an ultrahigh vacuum, we investigate the resulting island geometries as a function of the preparation pathway. When deposited onto the surface at low temperatures (about 120 K), C₆₀ forms single-layer hexagonal islands. Upon heating to about 320 K, these islands transform into double-layer islands with irregular edges (two-step experiment). Interestingly, distinctly different, truncated triangular double-layer islands are obtained from a direct preparation pathway (one-step experiment), i.e., when the molecules are deposited onto the sample kept at 320 K. This pathway dependence demonstrates that nonequilibrium structures are involved. Our results are corroborated by kinetic Monte Carlo simulations, which reveal the same pathway-dependent structures as those in the experiments. Based on the simulations, we identify the barrier for freely diffusing molecules to jump from the first into the second layer (ascension barrier) as key for the formation of the different island morphologies. The second ingredient to arrive at different islands is that edge diffusion rates for single-layer and double-layer islands differ. While edge diffusion is enabled for single-layer islands, it is greatly suppressed in the case of double-layer islands (essentially due to additional bonds formed with molecules in the second layer). Thus, a given island shape is effectively stabilized when molecules can jump into the second layer. In essence, allowing the molecules to ascend into the second layer provides a means to stabilize the prepared molecular islands. Our work illustrates how different preparation protocols can be used to enhance the structural variability of molecular structure formation on surfaces.

To improve the interfacial charge transfer over a tungsten oxide (WO₃) photoanode for an efficient photoelectrocatalytic (PEC) process, WO₃ was fluorinated in a solvothermal process in the presence of NH₄F. It was shown that, after the fluorination with the molar ratio of NH₄F to WO₃ at 0.4, the charge separation and charge injection efficiencies increased from 22.02 to 61.15% at 0.5 V vs Ag/AgCl and from 44.71 to 72.69% at 0.5 V vs Ag/AgCl, respectively, significantly enhancing the PEC performances for synergetic tetracycline degradation and H₂ evolution. Various characterization and density functional theory calculation results revealed that the incorporation of fluorine into the WO₃ lattice by fluorination substantially raises the Fermi level of WO₃, which bends the energy bands of WO₃ more upward at the semiconductor/electrolyte interface. The intensified upward bending bands effectively promote charge transfer at the fluorinated WO₃ photoanode/electrolyte interface, achieving the observed efficient PEC performances.