The giant delocalized π-electron system in pristine graphene is a double-edged sword; i.e., it gives rise to high electrical conductivity but results in chemical inertness. Therefore, graphene cannot be directly used as an anode for alkali metal-ion batteries due to its poor ion adsorption capacity. We propose a two-dimensional carbon allotrope (named TOD-graphene) with a combined kagome–honeycomb lattice. The robust energetic, dynamic, thermodynamic, and mechanical stabilities of TOD-graphene indicate the feasibility of the synthesis. The introduction of the kagome topology can disrupt the π-bonding network, thereby enhancing the surface reactivity. Its inherent metallicity and remarkable surface activity render TOD-graphene a promising anode material for high-performance potassium-ion batteries (PIBs). The TOD-graphene monolayer is characterized by high energy density (theoretical specific capacity of 1115.8 mA h g^–1), good rate performance (diffusion barrier of 0.36 eV), and low output voltage (average open-circuit voltage of 0.52 V). In the presence of electrolytes, there is an apparent enhancement of K adsorption and diffusion capabilities. Moreover, bilayer TOD-graphene significantly affects both the adsorption strength and the mobility of K. These findings demonstrate that TOD-graphene is an excellent anode material for PIBs.

Reasonably designing nanostructures with high electrochemical activity is the key to improving the redox chemical properties of battery-type materials. In this work, three-dimensional layered Cu(OH)@NiCo double hydroxide nanotube arrays have been synthesized by in situ etching and solvothermal methods successively. The core–shell array of Cu(OH)₂ nanotubes was encapsulated by NiCo-binary hydroxide (NiCo-BH) nanosheets, with a mass load of 10.7 mg cm^–2, reaching a commercial level. The electrode material of the nanotube array structure exposes abundant active sites that are conducive to redox reactions and abundant microspaces for accelerating the electron and ion transport. Moreover, without adding conductive agents and binders but directly depositing on the current collector results in their homogeneous contact on the current collector and endows a binder-free electrode, further accelerates electron transport, and provides robust support. After optimization, the nickel cobalt content ratio in the Cu(OH)₂@NiCo-BH electrode material is 2:1, and the mass load is 10.7 mg cm^–2. As verified by electrochemical testing, the material exhibits an ultrahigh area capacitance of 13.5 F cm^–2 (1262 F g^–1) at 1 mA cm^–2, and its 85% capacitance maintenance is still achieved at 20 mA cm^–2. Meanwhile, it has remarkable stability in cycling, with a 94% of cap retention after 5000 cycles. In the asymmetric ultracapacitor constructed with Cu(OH)₂@NiCo-BH//activated carbon (AC) as the positive electrode, it exhibits a high energy density of 0.762 mWh cm^–2 at 4 mW cm^–2, and the retention of capacitance is still maintained at 89% after 5000 cycles. Thus, the material shows significant potential for high-energy and high-power storage applications.

Covalent organic framework (COF) materials are characterized by periodic π arrays and orderly open channels, but poor electrical conductivity limits their applications in opt-electric fields. In this paper, 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (TFPT) and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) were used to synthesize TPT-COF with a redox unit of triazine by Schiff base reaction. In order to improve the electrical conductivity of TPT-COF, we prepared Nickel Nanowires (NiNWs) by a chemical reduction method and then prepared TPT-COF/NiNWs composites with different loading amounts of NiNWs. With the addition of NiNWs, the two materials are assembled to obtain a nanorod structure by using the π–π packing effect of the COF and the bridging of function conductive NiNWs. The electrochemical properties of composite electrode materials with different contents of NiNWs were tested, and TPT-COF/NiNWs-15% exhibited better electrochemical performance in sulfuric acid electrolytes. The specific capacitance of TPT-COF/NiNWs-15% is 343 F/g, and the high power density is 10945 W/kg. The addition of NiNWs provides a good strategy to improve the electrical performance of the COF-based electrode materials.

Perovskite-inspired materials (PIMs) provide low-toxicity and air-stable photo-absorbers for several possible optoelectronic devices. In this context, the pnictogen-based halides Cu₂AgBiI₆ (CABI) are receiving increasing attention in photovoltaics. Despite extensive studies on power conversion efficiency and shelf-life stability, nearly no attention has been given to the physicochemical properties of the interface between CABI and the hole transport layer (HTL), which can strongly impact overall cell operations. Here, we address this specific interface with three polymeric HTLs: poly(N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine) (poly-TPD), thiophene-(poly(3-hexylthiophene)) (P3HT), and poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA). Our findings reveal that devices fabricated with poly-TPD and P3HT outperform the commonly used Spiro-OMeTAD in terms of device operational stability, while PTAA exhibits worse performances. Density functional theory calculations unveil the electronic and chemical interactions at the CABI–HTL interfaces, providing new insights into observed experimental behaviors. Our study highlights the importance of addressing the buried interfaces in PIM-based devices to enhance their overall performance and stability.

Single-atom (SA) Fe–N–C catalysts are considered as promising electrocatalysts for the oxygen reduction reaction (ORR). However, due to the drawbacks of the microporous structure and very strong binding with O intermediates, Fe–N_x active sites may not always display satisfactory catalytic performance. Therefore, simultaneously engineering hierarchical pores and introducing the second metal atom are promising strategies to break the bottleneck of SA Fe performance. Herein, an economical and environmentally friendly method is used to prepare an Fe–Co dual-atom catalyst (DAC) with a microporous/mesoporous coupled structure (HP/FeCo-NC-2). HP/FeCo-NC-2 effectively enhances the mass transfer process and the ORR activity of Fe–N–C. The atomic dispersion of the as-synthesized catalyst was confirmed by synchrotron X-ray absorption spectroscopy. The Brunauer–Emmett–Teller test was used to assess the number of catalyst-mesoporous structures, and HP/FeCo-NC-2 has a more mesoporous structure than HP/FeCo-NC-1. More mesopores allow faster electrolyte access to the active sites inside the catalyst, facilitating the rate of mass transfer during the reaction. Consequently, the structural advantages and interactions between Fe and Co endow HP/FeCo-NC-2 with ORR performance superior to those of HP/FeCo-NC-1 and HP/Fe-NC-2 in 0.1 M KOH.

Electrocatalytic reduction of organic halides and subsequent carboxylation are promising methods for the valorization of CO₂ as a C1 source in synthetic organic chemistry. The reaction mechanism underlying the selectivity and reduction mechanism of benzyl halides is highly dependent on the nature of the electrode material as well as the processes, composition, and structure of the liquid phase at the electrode–solution interface. Herein, we present a computational study on the influence of the electric double layer (EDL) on the activation of benzyl halides at different applied potentials over the Au (111) cathode. Using a multiscale modeling approach, we demonstrate that, under realistic electrocatalytic conditions, the formation of a dense EDL over the cathode hampers the diffusion of benzyl halides toward the electrode surface. A combination of classical molecular dynamics simulations and density functional theory calculations reveals the most favorable benzyl halide electro-carboxylation pathway over the EDL that does not require direct substrate adsorption to the cathode surface. The dense EDL promotes the dissociative reduction of the benzyl halides via the outer-sphere electron transfer from the cathode surface to the electrolyte. Such a reduction mechanism results in a benzyl radical intermediate, which is then converted to benzyl anions in the EDL via an additional electron transfer step.

The composite support strategy is of great significance in regulating the reaction performance of catalysts. In this paper, the water–gas shift reaction catalyzed by copper clusters supported on the TiO₂ and CeO_x–TiO₂ mixed support was studied comparatively. The introduction of a Ce₂O_x overlayer increases the adsorption energy of oxygen-containing species due to the conversion of adsorption sites from metals to the Cu₈–CeO_x interface. It is more advantageous to react on copper clusters on the Cu/TiO₂ surface, mainly through the redox mechanism. The reaction on the Cu/CeO_x–TiO₂ surface is more advantageous at the Cu₈–CeO_x interface, also through the redox mechanism. Microkinetic analysis shows that the addition of the CeO_x support significantly enhances the performance of the water–gas shift reaction. The reason for the high activity of the Cu/CeO_x–TiO₂ catalyst is that the rate-determining step changes from H₂O dissociation to OH dissociation. Fundamentally, the Ce site on the Cu₈/CeO_x interface activates H₂O and promotes the decomposition of H₂O. As CeO_x can promote H₂O dissociation largely, the excessive OH* results in surface poisoning and reduced C–O (or H₂) formation, and the appropriate concentration of OH* is better for WGSR due to the balance of O–H bond activation and C–O (or H–H) bond formation, so the Cu–Ce–Ti model with the OH* ligand maybe the candidate of the active site for Cu/CeO_x/TiO₂. OH self-promoting reaction mechanism offers new insights into the fundamental role of surface adsorbed OH intermediate in WGSR. This article reveals the essence of the composite oxide support strategy in improving reaction performance, pointing out a new direction for regulating reaction performance.

In order to understand the recent experimentally measured initial sticking probability CO₂ on Cu(110), a globally accurate high-dimensional potential energy surface (PES) is constructed based on machine learning of density functional theory data. The reaction path revealed two saddle points flanking chemisorbed CO₂ with a bent configuration, which serves as a precursor for dissociation. Quasi-classical trajectory studies on this PES found a small and monotonically increasing initial sticking probability, consistent with the recent experiment. The dissociation is enhanced by both incidence energy and internal excitation of impinging CO₂. Mechanistic analysis revealed that the reaction is indirect and involves two very different reaction coordinates for the two barriers. The multidimensionality of the reaction path suggests that the one-dimensional model commonly used to describe direct dissociation is inadequate for this indirect process.

Ternary Cu/Zn/ZrO₂ catalysts prepared recently using atomic layer deposition (ALD) have shown increased performance toward methanol synthesis. In the present computational study, we have investigated the structure, composition, and stability of various zinc- and copper-containing subnano size species on a zirconia support. Density functional theory calculations with minima hopping were used to sample the positioning and geometry of supported Zn_xCu_yO_z structures up to 8 metal atoms in total. ZnO monomeric species were found to be energetically more favorable than small clusters, which could suggest a resistance to initial stage agglomeration. Ab-initio thermodynamics revealed that under typical methanol synthesis conditions, the complete reduction of ZnO and mixed ZnO/Cu clusters is unfavorable. The investigated ZnO monomers and clusters are able to provide CO₂ activation sites, with the Cu/ZnO/ZrO₂ triple interface offering the best stabilization for the adsorbed CO₂. All in all, the findings suggest that small ZnO species generated by ALD could be stabilized by the zirconia component, while contact with copper species at the interface benefits CO₂ activation.

Fe-based catalysts are highly selective for the hydrodeoxygenation of biomass-derived oxygenates but are prone to oxidative deactivation. Promotion with a noble metal has been shown to improve oxidative resistance. The chemical properties of such bimetallic systems depend critically on the surface geometry and spatial configuration of surface atoms in addition to their coverage (i.e., noble metal loading), so these aspects must be taken into account in order to develop reliable models for such complex systems. This requires sampling a vast configurational space, which is rather impractical using density functional theory (DFT) calculations alone. Moreover, “DFT-based” models are limited to length scales that are often too small for experimental relevance. Here, we circumvent this challenge by constructing DFT-parametrized lattice gas cluster expansions (LG CEs), which can describe these types of systems at significantly larger length scales. Here, we apply this strategy to Fe(100) promoted with four technologically relevant precious metals: Pd, Pt, Rh, and Ru. The resultant LG CEs have remarkable predictive accuracy, with predictive errors below 10 meV/site over a coverage range of 0 to 2 monolayers. The ground state configurations for each noble metal were identified, and the analysis of the cluster energies reveals a significant disparity in their dispersion tendency.

Reducing carbon monoxide (CO) plays an essential role in the goal of C1 chemistry. This study aims to design and develop B-doped fullerenes as the electrocatalyst for the CO reduction reaction using first-principles calculations based on density functional theory. The computational hydrogen electrode model has been employed to evaluate the catalytic properties of B-doped fullerene. It has been confirmed that the CO molecule adsorbs stably on C₅₉B with an adsorption energy of −0.35 eV. When an external voltage of 0.39 V, the overvoltage, is applied, all reactions proceed downhill, selectively producing methane in an acidic environment. This value is sufficiently lower than previously reported values on metal surfaces. The reaction process to determine the overvoltage is the initial hydrogenation process, *CO → *CHO. On the other hand, the CO molecule does not adsorb on a flat B-doped graphene nanocluster, implying that the curvature of the carbon network plays an important role in CO adsorption. Thus, we have investigated the dependence of the radius of the curvature on the adsorption energy and the overvoltage using a different size of fullerene, C₆₉B. The reaction site with a radius of curvature of 4.86 Å for C₆₉B has a minimum overvoltage of 0.26 V. However, the adsorption energy of CO molecules is −0.12 eV, higher than that of C₅₉B. This suggests the existence of an optimal radius of curvature for various applications. The curvature of the fullerene surface plays an important role as a catalyst for the CO reduction. This research will pave the way for developing catalytic properties of surfaces with curvature.

The solvent tetrahydrofuran (THF) stabilizes Na/Br carbenoids in the liquid phase. We investigate the importance of the THF solvent upon Na/Br carbenoid adsorption on Ag(111) using density functional theory and scanning tunneling microscopy. The three-dimensional structure of the Na/Br carbenoid is maintained upon surface adsorption. A second solvation shell of molecules surrounds it. Whether or not additional THF molecules, calculated to stabilize the Na of the Na/Br carbenoid in the gas phase, are liberated upon adsorption cannot be determined solely experimentally due to the negligible contribution of the THF molecules to the STM tunneling current. Our study highlights the importance of large-scale STM image calculation for interpreting nonplanar and solvated molecules.

Searching for new energy sources and improving the already existing ones are among the most important tasks in physics, material sciences, and chemistry. These three disciplines especially come together in the development of new catalytic materials for fuel cell applications. Herein, a novel nanoframe-based PtNiRu/SnO₂ catalyst for ethanol oxidation reaction (EOR) is proposed. Owing to properties resulting from chemical composition, shape, and structure, the catalyst shows enhanced electrocatalytic performance. The presented nanocatalyst is obtained from solid rhombic dodecahedral nanoparticles during galvanic replacement reaction with the following SnO₂ nanoparticles deposition on its surface. PtNiRu/SnO₂, as well as PtNiRu catalyst, were characterized by transmission electron microscopy and X-ray diffraction and tested electrochemically. PtNiRu/SnO₂ nanocatalysts exhibit the highest activity toward EOR and have the lowest onset potential among all of the tested catalysts. The achieved results suggest that the presented nanocatalysts could find application as an anode in a direct ethanol fuel cell for ethanol oxidation.

Copper and palladium exhibit excellent catalytic performance for the electrochemical reduction of CO₂ (CO₂RR). Here, a Pd_xCu_4–x (x = 2, 3) cluster was supported on CeO₂ with different sites to form three kinds of novel nanocatalysts, namely, Pd₂Cu₂/CeO₂, Pd₃Cu/CeO₂ (Pd–Pd), and Pd₃Cu/CeO₂ (Pd–Cu). Based on density functional theory, the catalytic performance and selective mechanisms were studied systematically. During the process of CO₂RR, *CO was hydrogenated to produce deeply reduced products such as CH₄ or CH₃OH due to its strong adsorption energies on all three catalysts (Pd₃Cu/CeO₂(Pd–Pd) for 0.95 eV, Pd₃Cu/CeO₂(Pd–Cu) for 0.89 eV, and Pd₂Cu₂/CeO₂ for 1.22 eV). The overpotential to form the CH₄ or CH₃OH product can be changed by varying the atomic ratio or anchoring sites of Pd_xCu_4–x clusters on CeO₂. In particular, the CO₂RR on Pd₂Cu₂/CeO₂ showed the lowest overpotentiontial (−0.60 eV) compared to the other two Pd₃Cu/CeO₂ catalysts. This study extends the family of CO₂RR catalysts and the application scenarios of bimetallic catalysts, which provides new insights into the design and preparation of composite nanocatalysts.

Although facets play an important role in catalysis, the relationship between facets and the active site has rarely been reported. Herein, Pd-loaded C₃N₄ photocatalysts with different exposed metal Pd facets were synthesized by controlling the flow-rate of the precursor. The influence of facets on active site in photocatalytic methanol reforming was monitored through an nuclear magnetic resonance molecular probe. The catalyst prepared at a low flow rate (Pd–C₃N₄-7.5) exhibited both Pd(111) and (100) facets, whereas that prepared at a high flow rate (Pd–C₃N₄-150) predominantly had Pd(100) facets. Furthermore, different crystal facets exhibited different active-site locations. The oxidation sites were dispersed over the entire surface (Pd, C₃N₄ surface, and Pd/C₃N₄ interface) of the catalysts with only Pd(100) facets. In contrast, they were mainly located on the metal Pd(111) surface and the Pd/C₃N₄ interface for catalysts with both Pd(111) and (100) facets. We believe this study would improve our understanding of the relationship between facet and active site.

Redox-active metal oxides are prevalent in the fields of thermal, photo-, and electrocatalysis. Thermodynamics of proton-coupled electron transfer (PCET) reactions at their surfaces are critical, as they scale with their activity as a catalyst. The free energy of H atom binding on the catalyst surface is employed as a catalytic descriptor for reactions of H₂, O₂, and many others. The structural heterogeneity and ambiguity of surface sites have largely precluded structural understanding of the exact redox-active sites, challenging chemists to design the catalyst structure down to the atomic level. Here, we report electrochemically determined stoichiometry and thermodynamics of PCET reactions of the cerium-based metal–organic framework (MOF), Ce-MOF-808. Cyclic voltammograms (CVs) of the MOF-deposited electrodes in aqueous buffers at various pHs revealed a Faradaic couple that can be ascribed to Ce^4+/3+ redox. Plotting the half-wave potential (E_1/2) against the electrolyte pH resulted in a Pourbaix diagram with a slope of 65 ± 9 mV/pH, suggesting a 1H⁺/1e^– stoichiometry. Using the thermochemical analogy between 1H⁺/1e^– and one H atom (H•), the H atom binding energy on the hexanuclear Ce₆ node, the Ce³⁺O–H bond dissociation free energy (BDFE), was calculated to be 78 ± 2 kcal mol^–1. In-silico calculations quantitatively corroborated our BDFE measurements. Furthermore, multiple proton topologies were computationally elucidated to exhibit BDFEs similar to the experimental values, agreeing with the wide Faradaic features of all CVs, implicating that the system has a substantial BDFE distribution. To the best of our understanding, this is the first thermochemical measurement of H atom binding at the MOF-liquid interface. Implications of the presented thermochemical measurements for catalysis using metal oxides and MOFs are discussed.

The combined route of stoichiometric combustion + three-way catalysis (TWC) is an era choice for natural gas vehicles (NGVs) to actively respond to the environmental protection requirements of gradual pressurization. However, synergistic and efficient purification of exhaust gas in a humid atmosphere is still one of the key challenges. The catalytic performance of phosphorus-doped and phosphorus-free CeO₂–ZrO₂–Al₂O₃ (CZA)-supported Pd-based model catalysts for CH₄, NO, and CO was evaluated in a practical operating environment close to stoichiometric combustion. Phosphorus doping induces the formation of abundant surface lattice oxygen, promotes the active migration of interface charges, and improves the catalytic activity of the Pd/CeO₂–ZrO₂–P₂O₅–Al₂O₃ (Pd/CZPA) catalyst for CH₄ and NO conversion. However, the catalytic oxidation of CO strongly depends on the dispersion of Pd nanoparticles, regardless of whether phosphorus is added or not. This research provides a useful guidance for the development of new pure palladium TWC for NGVs, regional environmental governance, as well as re-examining the value of phosphorus.

Herein, ultrathin CoO_x/BiO_2–x nanosheets (∼4 nm) have been in situ synthesized by using a microwave-assisted hydrothermal method. The amount-optimized CoO_x/BiO_2–x nanosheets display 4.7-fold higher photocatalytic activity than classical P25 TiO₂ for 2-chlorophenol (2-CP) degradation under full-spectrum irradiation with exceptional mineralization. The high photoactivity is attributed to the excitation-wavelength-dependent O₂ activation involved with the mainly produced ^•O₂^– via charge separation and ¹O₂ through energy transfer with ultraviolet–visible (UV–vis, <450 nm) and visible-near-infrared (vis-NIR, >550 nm) light irradiation, respectively. Moreover, the modified CoO_x with high dispersion could effectively trap photogenerated holes, thereby promoting charge separation and also facilitating the formation of ¹O₂ from ^•O₂^– by holes. By means of liquid chromatography tandem mass spectra and theoretical simulation, the generated nucleophilic ^•O₂^– and electrophilic ¹O₂ radicals exhibit distinct preferences in attacking different sites of 2-CP, resulting in direct ring-opening processes and ultimately enabling rapid mineralization.

The role that fluoroethylene carbonate (FEC) plays in the construction of the solid electrolyte interphase (SEI) on graphite anodes of lithium-ion batteries is understood by theoretical calculations combined with electrochemical measurements and spectral characterizations. It is found that FEC is different from ethylene carbonate (EC), although they have a similar structure. FEC presents a stronger ability than EC to combine with PF₆^–, which is helpful for the reduction of LiPF₆ to construct a LiF-rich inner layer of SEI. Additionally, FEC has a more negative electron affinity than EC, which makes it much easier to reduce, resulting in F-containing polymers that contribute to the outer layer of SEI. Consequently, the FEC-constructed SEI endows the graphite anode with excellent cycling stability.

The development of Pt on Ni nanoparticles is critical for the improvement of water splitting reactions. Here, the growth of small, below 2 nm Pt islands on crystalline branched Ni nanoparticles was investigated by tuning the size of the islands using a slow seeded-growth synthesis. Smaller island size results in a greater shift in the hydrogen binding energy on the Pt sites, as characterized by the hydrogen underpotential peak position in the voltammogram. This shift indicates the weakening of the binding to hydrogen, which leads to enhanced alkaline hydrogen evolution reaction activity with smaller Pt island size.

We have found that lysozyme crystallization is promoted by gap-mode surface plasmon resonance of gold nanoparticles (AuNPs). Crystallization experiments were performed by dropping a metastable lysozyme solution in a supersaturated state in which spontaneous nucleation does not occur onto substrates prepared by dropping a 40 nm diameter AuNP colloidal solution onto a glass substrate and subsequent drying. These substrates were capable of inducing gap-mode surface plasmon resonance. Crystals were deposited on the prepared substrates in numbers that increased with light irradiation, whereas none were deposited on control substrates. A crystallization mechanism involving lysozyme adsorption on AuNPs was proposed. The results showed that the number of lysozyme molecules adsorbed on the AuNPs corresponded well to the number of deposited crystals. We demonstrated that when gap-mode surface plasmon resonance is induced, the enhanced electric field in the gap between the AuNPs traps and concentrates the adsorbed lysozymes, leading to crystallization.

Two-dimensional (2D) perovskites have received a lot of attention due to their more stable properties than three-dimensional perovskites. Here, temperature-dependent UV–vis absorption and transient absorption (TA) measurements were performed for the 2D Dion–Jacobson phase organic–inorganic hybrid perovskite (4AMP)PbI₄ (4AMP = 4-(aminomethyl)piperidinium). At 80–295 K, the exciton absorption peak red-shifts with increasing temperature, indicating that the electron–phonon interaction dominates in (4AMP)PbI₄. The TA spectra show that with the decrease of temperature, the lattice shrinks and the transient Stark effect is enhanced. By comparing the dynamics, we find that the carrier relaxation lifetime becomes longer with the increase of temperature. On the one hand, the free carriers increase in proportion due to the generation of exciton-polarons. On the other hand, on account of the thermally assisted Rashba effect, the carrier recombination is slowed down by the shift of band extrema in k-space. This study reveals the effect of temperature on carrier behavior in (4AMP)PbI₄, which is of great significance for its applications in optoelectronic devices.

The construction of afterglow materials with full-color tunable emissions is attractive but still a challenging task. Herein, a host–guest doping strategy was proposed to produce afterglow materials with an emission-color span of almost 210 nm (from blue to deep red) by heat treating the aqueous mixture of arylboronic acids and boric acid (BA). In-depth structural, photophysical, and theoretical studies revealed that the heat treatment process resulted in the dehydration of BA and the formation of a glassy state host, and arylboronic acids were loaded as guest molecules through H-bonds and covalent bonds with BA. The afterglow originated from arylboronic acids, and the afterglow color of products was related to their degree of conjugation of aromatic groups. The host–guest doping strategy significantly improved the photophysical performances of arylboronic acids, achieving a photoluminescence quantum yield as high as 81.7% and an emission lifetime of 2.90 s (afterglow >22 s). Triple information encryption based on emission lifetime and color-encoding was also achieved, demonstrating their commercial potential for use in anticounterfeiting and information storage.

The stability of drum-shaped boron clusters and their feasible modification for metal doping render these nanomaterials potential candidates for nonlinear optics. In the present study, systematic theoretical calculations are performed to study the possible formation of finite-size nanowire assemblies by stacking B₁₄ or B₁₄M (M = Fe, Co) building blocks. The size evolution of structure, electronic, static, and dynamic nonlinear optical (NLO) properties of (B₁₄)_n, (B₁₄Fe)_n, and (B₁₄Co)_n with n = 1–6 are investigated. Although the drum-shaped structure of the building blocks is retained in most cases, however, in larger sizes of assemblies, the small expansion of building blocks in the middle and the compression at the terminals are observed. Our results highlight that the energy gap of boron nanowire assemblies can be finely tuned by altering their length. This is also inspiring for the modulation of the first hyperpolarizability by varying the number of stacked units. Among all of the examined systems, the highest hyperpolarizability (β_tot = 1.35 × 10⁵ a.u.) is observed for (B₁₄Fe)₆ owing to the reduced energy gap and increased charge transfer. To study the dynamic NLO response, the frequency-dependent properties in terms of electro-optical Pockels effects (EOPE), second harmonic generation (SHG), hyper-Rayleigh scattering (HRS), dc-Kerr coefficients, electric field-induced second harmonic generation (ESHG), and nonlinear refractive index (n₂) are evaluated. In most cases, the SHG process has a stronger NLO response than EOPE and HRS at the incident wavelength of Nd:YAG laser. In the case of third-order properties, high-frequency-induced ESHG up to 3.4 × 10⁷ a.u. is computed for the designed nanowires. The present research inspires experimental exploration for the synthesis of boron-based nanowires and highlights the potential application of these materials for second harmonic generators.

Interpretation of the spectroscopic properties of Cr³⁺ ions in garnets is sufficiently complicated by the variation of the crystal-field strength. Occupation by Cr³⁺ ions of octahedral sites with different local crystal-field strengths alters their emission spectra. In the present work, we report the changes in the emission spectra of Cr³⁺:GGG nanoceramics synthesized by the high isostatic pressure (HIP) method. The influence of the energy transfer process between Cr³⁺ ions on their emission spectra is shown. The room temperature excitation and emission spectra are similar for the samples doped with different concentrations of Cr³⁺ ions. At the same time, in the low-temperature emission spectra, the impact of ⁴T_2g(⁴F) → ⁴A_2g(⁴F) broadband emission on the overall Cr³⁺ emission increases with Cr³⁺ concentration. Since Racah parameters are within the measurement error for Cr³⁺:GGG nanoceramics, the difference in low-temperature emission spectra was explained by the increase in energy transfer between Cr³⁺ ions, thus increasing the ratio of emission intensity of Cr³⁺ ions in the low crystal field to the total luminescence.

Most materials in Nature expand when heated, and very limited materials show the opposite behavior, i.e., negative thermal expansion (NTE). Here, we observed that NTE is associated with the rarely occurring Fano antiresonance in Raman spectroscopy and investigated the role of electron–phonon coupling on the negative thermal expansion observed in the multiferroic ErFeO₃ perovskite; for this purpose, the temperature-dependent synchrotron-based X-ray diffraction and Raman scattering experiments were carried out in the temperature range 80–300 K. The occurrence of NTE was also confirmed via the strain gauge measurement technique. A one-to-one correlation between strong electron–phonon coupling, as reflected in the Fano antiresonance in Raman spectra, with q ≈ 0, and the geometrical rotation of the Fe–O–Fe bond angle that has been observed. It has been demonstrated that the NTE is controlled by the strong temperature dependence of electron–phonon coupling in the prepared ErFeO₃ sample. The present report may provide a new strategy for manipulating NTE behaviors by tuning the electron–phonon coupling.

Electron microscopy, while reliable, is an expensive, slow, and inefficient technique for thorough size distribution characterization of both monodisperse and polydisperse colloidal nanoparticles. If rapid in situ characterization of colloid samples is to be achieved, a different approach, based on fast, widely accessible, and inexpensive optical measurements such as UV–vis spectroscopy in combination with spectral interpretation related to Mie scattering theory, is needed. In this article, we present a tandem deep neural network (DNN) for the size distribution and concentration prediction of close to spherical silver colloidal nanoparticle batches synthesized via the seeded-growth method. The first DNN identified the dipole component of the localized surface plasmon resonance, and the second one determined the size distribution from the isolated spectral component. The training data was engineered to be bias-free and generated numerically. High prediction accuracy with root-mean-square percentage error of mean size down to 1.2% was achieved, spanning the entire prediction range from 1 up to 150 nm in radius, suggesting the possible extension limits of the effective medium theory used for simulating the spectra. The DNN-predicted nanoparticle concentrations also were very close to the ones expected based on synthesis precursor contents as well as those measured by atomic absorption spectroscopy.

The PbS colloidal quantum dots (CQDs), with the advantages of a strong quantum confinement effect and broad range adjustable in photoluminescence, have been paid much attention because of their great potential applications in the field of infrared optoelectronics. Therefore, it is of great significance to investigate their photoluminescence properties. In this study, three PbS CQDs are fabricated by the thermal injection method, and their sizes are adjusted from 3.8 to 5.1 nm by controlling the growth duration. Their room-temperature PL spectra are centered at 1323, 1341, and 1440 nm. The temperature- and power-dependent PL spectra are further investigated to reveal the emission mechanism. The peak positions have a distinct blue shift with an increasing temperature. Meanwhile, a thermal activation phenomenon is observed in the PbS CQDs with sizes of 3.8 and 4.4 nm, which is attributed to the size-dependent quantum confinement effect and electron–phonon interaction. This work has a great influence on the adjustment of the optical properties of PbS CQDs.

The characteristics of oxide surfaces such as their hydroxyl density, the associated acid–base chemistry, and the resulting surface charge play a crucial role in modulating the solvent organization and electrostatics at interfaces found in chemical and environmental processes. Here, the nitrile mode of acetonitrile, a neutral Stark-active molecule, is used to probe the local electric fields and solvent organization that result from surface charge at the α-Al₂O₃(0001)/aqueous and SiO₂/aqueous interfaces using vibrational sum frequency generation (vSFG). The vSFG response in the C≡N stretch region for H₂O–acetonitrile mixtures displays an asymmetric line shape and unique pH-dependent behavior, which we attributed to interference with the H₂O combination (bend + libration). Stark spectroscopy results at both interfaces reveal that the density of surface hydroxyl groups influences the magnitude of the local electric field experienced by acetonitrile. While the nitrile group of acetonitrile probes single-point charges at the SiO₂ surface at pH 6–11, the local electric field sampled by the nitrile group at the Al₂O₃ interface is impacted by multiple charged hydroxyl sites at elevated pH. These findings highlight the influence of inhomogeneous surface-charging behavior on interfacial solvent structure and local electric fields.

Copper oxides play a crucial role in a wide range of research areas, such as catalysis, photocatalysis, sensing, energy storage, biomedicine, and spintronics. However, further insights into the surface structure and the related magnetic properties of copper oxides are required to improve their performance. Here, we present a computational study on the structural and magnetic properties of low-index Cu₂O and CuO surfaces including their bulk oxides based on spin-polarized density functional theory (DFT) via DFT + U and the ab initio atomistic thermodynamics approach. We found that Cu₂O surfaces with an excess of oxygen atoms show surface ferromagnetism, while CuO surfaces with an excess of copper atoms exhibit surface atoms without a magnetic moment. By analyzing the density of states and the Bader charges of the surface atoms, we discuss the electronic properties of the copper oxide surfaces and the origin of the observed magnetism. Finally, we derive a correlation between the structure and the magnetic properties of copper oxide surfaces and suggest a possible explanation for the observed magnetism within a simplified model.

Two-dimensional (2D) polar materials can exhibit a pronounced bulk photovoltaic effect (BPVE). Here, we report single-element polarity and BPVE in the bilayer blue phosphorus (blue-P) homojunction and blue/black phosphorus (blue-P/black-P) heterojunction, where the individual layers are nonpolar due to the centrosymmetric structures. For the homojunction, bilayer blue-P exhibits sliding ferroelectricity with switchable out-of-plane polarization and a small shift current susceptibility. For the heterojunction, we obtain an in-plane polarization and a stronger shift current response by vertical stacking blue-P and black-P with the overlapped mirror plane, where the strong BPVE is due to the enhanced charge transfer. Combining a k·p model with first-principles calculations, we further show that the photovoltaic performance of the heterojunction depends on the interlayer coupling, which has a significant effect on the shift vector. These findings indicate that 2D phosphorus sheets can be used as unique building units for designing configurable layered nonlinear optical materials.

Since the introduction of hybrid van der Waals heterostructures (h-vdWHs) for device architecture development, many vertically staked organic two-dimensional materials have been investigated in order to control transport properties. This article introduces a novel h-vdWH that achieves periodic interaction by the development of a superlattice. We describe a complete investigation of the diphenyl-functionalized p-benzoquinonemonoimine zwitterion on highly oriented pyrolytic graphite and monolayer graphene using high-resolution scanning tunneling microscopy images and numerical simulations. The molecular phase on both substrates exhibits a structurally identical antiparallel dipole alignment in a head-to-tail dimer configuration. Density functional theory calculations reveal that this molecular adsorption induces a local dipole at the graphene interface due to the rearrangement of the electron density distribution.

We investigate ion–electron Coulomb drag in 2D nanofluidic slits using a generic physical model based on the Boltzmann transport formalism. The emphasis is placed on the fluid, oxide, and semiconductor dielectric constants as well as on the geometry and oxide thickness to maximize the electronic drag current and power output. Our model confirms electronic drag current amplification predicted in silicon nanochannels and shows that optimum amplification is achieved for an oxide dielectric constant equal to the geometric mean of the fluid and semiconductor constants, as well as with thin oxide layers while maintaining high surface carrier concentrations in semiconducting layers surrounding the 2D nanoslit. Our analysis, which provides guidelines for 2D slit design optimization, also shows that nanoslits made of 2D materials like graphene combined with thin oxide and optimized dielectric constants enhance drag current amplification over conventional Si/SiO₂ nanochannels.

The refractive index is one of the main optical parameters of any semiconductor medium, including halide perovskites. To model devices, such as laser cavities, it is important to know not only the absolute value of the refractive index but also its spectral behavior, the dispersion. In this work, the refractive index dispersion n(E) in the MAPbI₃ (MA⁺ = CH₃NH₃⁺) halide perovskite single crystal is determined in the temperature range from 4 to 88 K by studying the interference of light in a microcavity. It has been shown that in the most practically important transparency region of the material, the dispersion of the refractive index is determined not only by the excitonic transition located nearby but also by higher-lying interband transitions.

Zeolites contain extraframework cations that are exchangeable under favorable aqueous conditions; this is the fundamental feature for their application in water purification and necessary to produce cation forms for other applications such as catalysis. Optimization of the process is common, but there is little fundamental understanding based on real-time experiments of the mechanism of exchange for most zeolites. The sodium and potassium forms of zeolite chabazite selectively uptake Cs⁺ by ion exchange, leading to its application in removing radioactive ¹³⁷Cs⁺ from industrial nuclear waste streams, as well as from contaminated environments in the aftermath of the Fukushima and Three Mile Island accidents. In this study, in situ synchrotron powder X-ray diffraction patterns have been collected on chabazite as it undergoes Cs-ion exchange. Applying Rietveld refinement to these patterns has revealed the time-resolved structural changes that occur in the zeolite as exchange progresses, charting the changes in the spatial distribution of the extraframework cations and water molecules in the structure during the reaction. Ultimately, a detailed mechanistic understanding of how this dynamic ion-exchange reaction occurs has been obtained.

Incorporation of nanostructured photochromic WO_3–x (NP-WO) in polymer optical fibers (POFs) made of polyethersulfone using a postdrawing coating method is reported. Upon ultraviolet (UV) irradiation, a higher coloring intensity of the cladding of nanostructured fibers is linked with a remarkably clear amplification (negative photochromism) of the transmission signal through the fiber. The postcoating method was thoroughly optimized by using poly(vinylpyrrolidone) (PVP) both as a dispersant agent and a cladding matrix for NP-WO. Modeling shows that the decrease of the real refractive index n in the transparency range of the POF (600–1200 nm) associated with the increase of the absorption coefficient k versus coloring under UV light allows the controllable “opening” of the fiber transmission. The fiber core negative photochromism implying the coloration under UV irradiation of the NP-WO-based fiber cladding represents a brand new optical effect, which could be used in various applications such as sensing, camouflage, or smart envelops.

Strongly coupled light–matter systems are becoming a ubiquitous platform for investigating an increasing number of physical phenomena from modifying charge transport, altered emission, and relaxation pathways to selective or enhanced chemical reactivity. Such systems are investigated across a large length scale from few-nanometer-sized particles to macroscopic cavities encompassing many interacting moieties. Describing these numerous and varied physical systems is attempted in various ways from classical coupled harmonic oscillator models through quantum Hamiltonians to ab initio modeling. Here, by combining time-dependent density functional theory modeling and analysis with macroscopic models, we elucidate the origin of modifications of effective interaction parameters in terms of microscopic changes to the electronic density and Kohn–Sham transitions of the plasmonic particle and its coupled molecular counterpart. Specifically, we demonstrate how the emergence of mixed metal-molecular states and transitions modifies the effective resonances of the underlying plasmon and molecule in the regime of strong coupling and how these changes subsequently lead to the formation of mixed light–matter polaritons.

It is known that fluorine-containing carbon materials are highly insulating and exhibit low dielectric permittivity due to the presence of covalent C–F bonds and F atoms with small polarizability. These electrical properties can be improved by defluorination (F loss) and by partial restoration of the aromatic character of the carbon networks. Contrary to this knowledge, we show herein that γ-irradiation of graphite fluoride (CF)_n improves its conductivity and charge transport/storage properties while preserving the F content. It is found that the crystallinity and specific surface area decrease by γ-irradiation, but the platy morphology, composition, surface functional, thermal stability, and optical band gap are maintained. Comparing to the nonirradiated one, the sample irradiated at 400 kGy shows increased conductivity (10^–9 vs 10^–10 S·cm^–1) and shorter relaxation time (0.3 vs 0.9 ms), consistent with the decreased apparent activation energy (76.3 vs 82.4 kJ·mol^–1). Meanwhile at 200 kGy, the dielectric permittivity increases to ∼6 (from 4.2) with the loss tangent close to the nonirradiated sample. These findings are attributed to the variation of effective dimension of charge carriers which is optimized (depending on the properties considered) at 200/400 kGy and at 50 °C but not at elevated temperatures. The chemical-free, ambient-temperature tuning of electrical properties by γ-irradiation is also demonstrated by the calculated refractive index (up to 2.4, temperature-independent from RT to 200 °C) and the dielectric heating coefficient, which varies by a factor of 2 at the same temperature range.

Surface phenomena such as proton transfer occurring near solid–liquid or solid–solid interfaces represent key events in catalysis as well as electrochemical processes. In the case of TiO₂, this event is related to water splitting processes, which are often utilized in hydrogen generation or photocatalysis in wastewater management. Recent investigations of R-TiO₂(001) showed that this facet has the potential to increase the photocatalytic activity. However, due to its highly reactive character, this surface is known to undergo rapid reconstruction. This makes the measurement and characterization of the respective surface structures challenging, not only in experimental, but also in theoretical investigations. In previous work, a novel 2d-periodic QM/MM protocol was applied to investigate proton transfer reactions occurring at the R-TiO₂(001) facet in contact with a H₂O monolayer. It was concluded that to evaluate the established protonation, long MD simulations are required, which are impossible to perform via conventional DFT. However, the application of SCC DFTB provides an efficient alternative to reduce the computational cost. Nonetheless, the implementation of a solvent monolayer seemingly represents a solid–gas environment. In the current work, an enhanced QM/MM framework is present, enabling the inclusion of additional solvent molecules to study surface protonation events in more detail. For comparison, an alternative setup including all solvent molecules in the QM zone is conducted. The result showed that the structure and dynamics of the solvent close to the interfaces of both the QM/MM and all-QM models are almost identical, which verifies the applicability of the suggested 2d-periodic QM/MM protocol as a general framework for theoretical investigations of surface structures.

Electrochemical impedance spectroscopy (EIS) has played a crucial role in understanding electronic and ionic responses in MHPs through frequency and time domain analyses. This study introduces a novel approach by integrating supervised machine learning to develop in-line automation for classifying and fitting the EIS spectra for metal halide perovskite single crystals (MHPSCs). By employing widely used EIS circuits for MHPSCs, we establish a chronological link and offer a comprehensive physical interpretation. Our model utilizes simulated data to accurately classify experimental EIS spectra and provides precise fitting values of electronic components, enhancing the spectroscopic analysis of MHPSCs. The Decision Tree classifier demonstrates superior accuracy in classifying EIS spectra compared to Random Forest and XGBoost models. Incorporating 3-fold cross-validation confirms its reliability with notable versatility in capturing spectral changes under varying bias conditions. Our study establishes a chronological link between the widely used EIS circuits for MHPSCs and offers comprehensive physical interpretations.

In situ structural analysis under loads of amorphous adhesives buried between metal substrates was conducted by using synchrotron X-ray nanobeam diffraction and an embedded local strain probe. Thermoplastic resins composed of polyrotaxanes, featuring bulky cyclic molecules threaded with a linear polymer, were sandwiched between stainless-steel substrates with diffraction data attributed to the correlation distance between their cyclic components being collected. The nanobeam was irradiated parallel to the substrates and scanned, while distances from the substrate were changed to obtain depth profiles of correlation distance. Then, tensile loads were applied stepwise to the sandwiched sample to reveal local strain distributions of the resins under different loads. Different strain distributions and their changes with loads were observed in resins with different adhesive strengths. The sample with strong adhesion showed pronounced strain localization near the interface between resin and substrate, whereas the weak sample displayed moderate strain further from the interface, with negligible strain near the interface. When the load increased, localized strain saturation occurred, followed by strain propagation into adjacent areas, indicative of a typical strain delocalization process associated with strain hardening near a highly constrained interface by substrates. This analysis elucidated the deformation and fracture processes of buried polymers, offering insight into those adhesive strength differences phenomenologically. This in situ analysis of local strain distribution contributes to comprehending adhesion mechanisms required for advancing multimaterialization technology and holds applicability to materials with buried interfaces such as nanocomposites.

Charge carrier conversion in alkali oxide-incorporated transition metal oxide-containing glasses has been investigated extensively; however, the influences of protons on this phenomenon have not been systematically probed. In this study, we employed electrochemical alkali (Na⁺)–proton substitution (APS) in an attempt to fabricate a mixed protonic–electronic conductor and thus prepared 30HO_1/2–6VO_5/2–14VO₂–50PO_5/2 glass from 30NaO_1/2–10VO_5/2–10VO₂–50PO_5/2 precursor glass. The precursor glass was a mixed ionic–electronic conductor; however, the product APS-treated glass was a pure proton conductor, contrary to expectations. The suppression of electronic conduction in the APS-treated glass was investigated using Mott’s theoretical expression of small polaron hopping conduction in semiconducting glasses. Our findings indicated that the V ions in the APS-treated and precursor glass specimens existed mainly as VO₆ and VO₄ with large and small electron wave function decay constants, respectively. Therefore, in the APS-treated glass, the electron wave functions between adjacent V ions did not overlap, resulting in miniscule electronic conductivity. The proton conductivity of the APS-treated glass (1 × 10^–5 S·cm^–1 at 300 °C) was lower than that of conventional APS-derived proton-conducting phosphate glasses, owing to the low proton mobility stemming from the strong proton-trapping feature of the nonbridging oxygen in VO₆.

Due to the low dimensionality in the quantization of the electronic states and degree of freedom for device modulation, two-dimensional ferromagnetism plays a critical role in lots of fields. In this study, we perform first-principles calculation to investigate the Ising ferromagnetism and half-metallicity of the kagome V₂O₃ monolayer (ML). Based on the calculations using different functionals, it is found that generalized gradient approximation (GGA)–Perdew–Burke–Ernzerhof (PBE) gives a half-metallic band gap, while the GGA + U gives a semiconductor narrow band gap (∼1.1 meV), which shows quasi-half metallic nature. By studying the magnetic properties with LDA, GGA-PBE, and GGA + U, we get a robust ferromagnetic ground state, where the giant perpendicular magnetic anisotropy energy of ∼0.544 meV is achieved by applying the spin–orbit coupling with GGA + U. Furthermore, by exploring the orbital contribution to the electronic bands and the magnetic crystalline anisotropy, it is uncovered that the 3d (V) orbitals contribute to the out-of-plane. The electronic band structure shows two flat bands (F₁ and F₂) and two Dirac points (D₁ and D₂), which further confirm that the kagome V₂O₃ ML can also be used for topological properties. Besides, the Curie temperature of the V₂O₃ ML is calculated to be 640 K by Metropolis Monte Carlo simulations.