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An efficient approach employing 4-dimethylaminopyridine and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride as the coupling reagent is presented, which enables the functionalization of cotton linter paper substrates with the 19F spin label N-boc-cis-4-fluoro-l-proline. This spin label can be easily quantified by 19F magic angle spinning (MAS) NMR experiments to determine its loading on paper substrates. During the functionalization, the spin label stays intact, as confirmed by the 1H–19F heterocorrelation (1H → 19F CP MAS FSLG HETCOR) experiments. In combination with dynamic nuclear polarization (19F MAS DNP), the N-boc-cis-4-fluoro-l-proline spin label allows us to inspect 1 μmol/g and even lower molecule loadings on paper substrates, providing a highly sensitive local probe to analyze the structure of biofunctionalizations at the nanoscale on paper substrates in the future.

We report a paper-based photodetector made from mixed cation organic perovskite halide MA1–xFAxPbI3(MA = methylammonium (CH3NH3); FA = formamidium CH(NH2)2). The detector shows a substantial photogain and photoresponse at low illumination intensity (<10 μW/cm2) and a broad band response that extends from 300 to 800 nm at the optimum substitutional level with x= 0.4. A peak responsivity of 0.27 A/W in the paper photodetector was observed at a wavelength of ∼775 nm at a bias of 5 V. The responsivity stayed above 0.1 A/W for a broad optical wavelength range of 550 to 825 nm that covers a good range of the visible spectra. The detector has a low dark current (<10–9A) at highest bias of operation and an rms current noise of ≤10 pA. The mixed halide detector was grown on conventional paper using a one-pot chemical process. The detector reported here is stable at a room ambience and does not deteriorate under prolonged exposure to illumination. It combines the high response of MAPbI3and the stability of FAPbI3. The paper photodetector is useful in a number of applications needing flexible and disposable detectors, and the power requirement even at full operation is <0.5 μW at a low bias (<5 V) making it compatible with battery-powered operation.

Photoelectrochemical water splitting is a promising strategy to harvest energy from the sun; it utilizes a photoactive material, coupled with a slight electrical input, to convert water into hydrogen and oxygen. These generated gases are stored as chemical energy and can later be used as fuels. Among many reported photoactive materials, tin disulfide (SnS2) offers unique advantages due to the earth abundance of tin and its appropriate bandgap. Here, we report the fabrication of high-density two-dimensional vertically aligned SnS2nanoflakes anchored on a conductive substrate for photoelectrochemical water splitting application. The as-fabricated nanoflakes were carefully studied, where crystalline, hexagonal SnS2flakes can clearly be observed; their crystal structure has been indexed with the assistance of high-resolution transmission electron microscopy. For photoelectrochemical testing, a Solartron potentiostat was used to perform the indicative electrochemistry tests, including linear polarization, electrochemical impedance spectroscopy, and potential static with a light on–off current. A Horiba Hal-320 solar simulator was used as a light source to illuminate the active samples placed in a 0.5 M Na3PO4aqueous electrolyte. The incident photon to converted electron figure was also calculated and was found to have 2.66% efficiency at zero bias (i.e., spontaneous evolution reaction) and 20.53% efficiency at 1 V bias. This high efficiency is probably due to both the high optical gap of ∼2.4 eV obtained from these 2D nanostructures and their physical structure that maximizes light trapping of the incident source.

Electrochemical measurement of pH on paper artifacts is a very important tool to assess the state of paper conservation. Different methods using different types of electrodes have been standardized to provide reproducible pH values of paper. One of these methodologies is not very invasive since it is made on the paper surface by means of a surface electrode in contact with the paper through a small layer of water previously added at the measurement point. This method is very convenient but suffers from the fact that the pH value given by the instrument is continuously changing during the measurement with a very fast rate in the first seconds and tending to reach a plateau value after very long time. Usually, the measure is taken at a time after which the rate of pH change is below a given value, i.e., when the value can be considered constant. This condition is usually signaled by an automatic instrumental alert provided to the operator. This pH value, however, is not the asymptotic one, which can be reached only at infinite time. Here we have investigated this behavior showing that it is simply due to the gradual diffusion of water away from the measurement region under the electrode. A theoretical model, which reproduces very well the time dependence discussed above, has been developed. The validity of the model has been completely proven by taking in consideration experiments where water diffusion is prevented in a simple confining apparatus. This work shows that it is possible to eliminate any factor affecting accuracy and reproducibility of the pH data for paper measured by the surface electrode method.

A low-cost foldable asymmetric supercapacitor (ASC) with remarkable capacitive performances is fabricated by using conventional filter papers as substrate via a simple and cost-effective method. A hybrid nanonetwork consisting of MnO2/polyaniline (PANI) as positive electrode and a highly compact 2D configuration of chemically reduced graphene oxide (rGO) as negative electrode are prepared. MnO2/PANI nanocomposite (MPNC) is directly synthesized on a macroporous cellulose fiber network of paper through a one-step in situ polymerization technique. A highly flexible negative electrode based on 2D rGO sheets is prepared by using a simple two-step approach including vacuum filtration followed by a freeze-drying step. High specific capacitance over a broad operational voltage window in combination with reasonable cycling stability makes this simple and cost-effective paper-based supercapacitor a promising candidate for play a pivotal role in addressing earth-friendly energy-storage systems. The fabricated ASC keeps its remarkable capacitive performance when it is bent and folded, which provides the potential for wearable energy-storage devices.

Herein, the manufacturing of a free-standing N-doped mesoporous carbon (CPPY) paper by straightforward carbonization of polypyrrole-coated nanocellulose paper is described. The deposition of Na and Li on these CPPY electrodes, which also serve as current collectors, is studied using a combination of experiments and theoretical calculations. The porous CPPY electrodes gave rise to decreased current densities, which helped to prolong the life-time of the Na electrodes. While the density functional theory calculations suggest that both Na and Li should be deposited uniformly on the CPPY electrodes, the experimental results clearly show that the sodium deposition was more well-defined on the surface of the CPPY electrodes. In contrast to Li, dendrite-free Na depositions could be carried out using deposition capacities up to 12 mAh cm–2and a stable Na electrode cycling performance was found during 1000 h at 1 mA cm–2. The results suggest that it was difficult to predict the Na or Li deposition behavior merely based on calculations of the metal adsorption energies, as kinetic effects should also be taken into account. Nevertheless, the experimental results clearly show that the use of the present type of porous electrodes provides new possibilities for the development of durable Na electrodes for high-performance sodium metal batteries.

Lithium–sulfur batteries (LSBs) are of great interest as a promising energy storage device because of their high theoretical capacity and energy density. However, they exhibit poor discharge capacity and capacity retention during long-term cycling because of their inherent drawbacks including the poor conductivity of sulfur and lithium sulfide, the shuttle effect of lithium polysulfides (LiPSs), and the large volume expansion of sulfur to lithium sulfide. An effective approach that can solve these problems is to use an interlayer inserted between the separator and the cathode. Nevertheless, the underlying adsorption mechanism of LiPSs on the interlayer has not yet been widely investigated. Herein, the effect of lithium bond chemistry on the adsorption of LiPSs on the functionalized carbon fiber paper (CFP) interlayer containing hydroxyl, carboxyl, or amide functional groups is investigated by a density functional theory approach. It is found that the functionalized CFP exhibits a strong lithium bond interaction between the Li electron acceptor of LiPSs and the N or O electron donor of the functionalized CFP interlayer. In addition, the correlation between the adsorption energy of LiPSs on the interlayer and the electrochemical performance of LSBs is investigated. The results provide the fundamental understanding of the structure–property relationship for the adsorption of LiPSs on the functional groups of the interlayer, which will be beneficial for the further development of advanced LSBs.

Due to the expeditious expansion of wearable electronics, all-solid-state flexible supercapacitors are being contemplated as promising energy-storage devices. Through the successful preparation of large quantities of high-quality semiconducting-type thin molybdenum disulfide (MoS2) sheets suspended in water, the authors have developed an environmentally friendly and simple method to fabricate ternary flexible electrodes with MoS2, polyaniline (PANI), and carbon nanotubes (CNTs). The resulting MoS2/PANI/CNT all-solid-state supercapacitor can be easily integrated in series to power commercial light-emitting diodes without an external bias voltage. In addition, such a supercapacitor exhibits remarkable energy density (0.013 Wh cm–3) and power density (1.000 W cm–3), thus making it superior to commercially available lithium thin-film batteries (4 V/500 μA h) and 2.75 V/44 mF activated carbon electrochemical capacitors. These results demonstrate that the exfoliated MoS2-based composite is a promising material for the development of high-performance and low-cost energy-storage devices.

Self-powered photodetectors (SPPDs) are promising candidates for high-sensitivity and high-speed applications because they do not require batteries as an external power source. It is a challenge to fabricate visible-light photodetectors. Herein, vertically aligned two-dimensional (2D) Sn3O4nanoflakes on carbon fiber paper were prepared by a modified hydrothermal approach and used as a self-powered photoelectrochemical cell-type visible-light detector. The detector exhibits reproducible and flexible properties as well as an enhanced photosensitive performance. The improved photoresponse was attributed to the synergistic effects of the vertically grown Sn3O4nanoflakes and carbon fiber paper substrate; the former provided efficient active sites, as it exposed more catalytic sites to the electrolyte and absorbed more light scattered among the nanoflakes, and the latter benefited charge transport. The photocatalytic activity of the three-dimensional (3D) Sn3O4hierarchal structure on rhodamine B under visible-light irradiation was investigated and shown to have a degradation rate constant of 3.2 × 10–2min–1. The advantage over ordinal materials for use in an SPPD device is that this material is flexible and easily recoverable as a photocatalyst.

In this work, it is shown how solid-state NMR combined with dynamic nuclear polarization (DNP) can be employed as a powerful tool to selectively enhance the spectral intensity of functional groups on the surface of cellulose fibers in paper materials. As a model system, a poly(benzyl methacrylate) (PBEMA)-functionalized paper material is chosen that contains hydrophobic and hydrophilic domains. Detailed analysis of the DNP NMR data and of T1ρdata suggests that inhomogeneous 1H–1H spin diffusion is responsible for the observed differences in signal enhancement. These findings are fundamental for structural understanding of complex paper substrates for fluid transport or sensor materials.

Functionalized graphene oxide papers are assembled materials with a wide range of potential applications; however, scientific studies about how the physical properties of functionalized graphene oxide papers are affected by the presence of new functional groups have not been addressed. Here, electrical resistance, optical band gap, and mechanical properties of flexible and free-standing functionalized graphene oxide papers with nitroxide moieties (NGOP’s) have been studied, and two of them (mechanicals and electricals) were correlated with the interlayer dspacing for the first time; herein, a new insight about the key role that an optimum amount of functionalization agent plays over the physical properties of NGOP’s is presented. In all cases, (functionalized or pristine) graphene oxide papers were prepared using anhydrous DMF instead water in order to study and highlight the pure effect of the functionalized groups over their physical properties. The functionalized nanomaterials exhibited significantly improved physical properties, which can be tuned by varying the interlayer dspacing, and this interlayer distance was systematically modified controlling the amount of functionalizing agent used. Thus, controlling the amount of functionalizing agent in the functionalization process is possible to obtain new assembled materials with modulated properties.

In this study, a chemical stabilization method, that preserves the tensile strength of artificially aged paper pretreated with an aqueous solution of ionic liquid, is presented. Pure cotton cellulose paper samples were soaked with cholinium glycinate ionic-liquid solution either before or after the artificial aging process, which was based on thermal degradation in dry air. The tensile strength of artificially aged paper was measured by using the double-folding technique. The role of ionic liquids was investigated by mid-infrared and terahertz time-domain absorption spectroscopy. It was found that the tensile strength of pretreatedsamples is higher than that of other aged samples. A model for changes in the cellulose structure caused by oxidation and by the binding of ionic liquid molecules is proposed, based on the analysis of the mid-infrared absorption bands in the carbonyl/carboxyl region at 1590–1750 cm–1. Terahertz spectroscopy data indicate that the ionic liquid molecules penetrate in the larger size porosity, acting as binders among cellulose fibers to maintain the tensile strength of paper.

The hopping charge transfer between polarons and bipolarons and metal-like band structure in polaron lattice of polyaniline makes it of high scientific worth. With above views polyaniline has been deposited on paper by a low cost chemical method to make the paper electrically conductive and functional. The prepared conductive papers were characterized using X-ray diffraction measurement, FTIR, UV–vis–NIR spectrophotometric measurement, and electrical conductivity measurement. Impressive electrical properties with good optical transparency were obtained with a highest light transmittance of 94.0% at 550 nm and electrical sheet resistance of 8.92 × 105Ω/□. In addition, repeated cycles of deformation of the electrically conductive polyaniline incorporated flexible paper do not produce any noticeable change in its electrical conductivity and optical absorbance. The electrically conductive papers are of significant interest in preparing flexible and foldable circuits. The polyaniline-deposited conductive papers are of low cost, and these are environmentally stable.

Surface-enhanced Raman spectroscopy (SERS) is a powerful tool for the specific, rapid, and nondestructive detection of small molecules. For detection applications, it is desirable to develop means for synthesizing SERS substrates that provide large and consistent Raman enhancement, are inexpensive and simple to synthesize, and are active for a wide variety of molecules. Here we demonstrate that nanoparticle colloids (ranging in size from 5 to 100 nm) that are purposely aggregated using electrolytes can be stabilized in the solid state using common filter paper. The SERS substrate enhancement factor (EF) is characterized using trans-1,2-bis(4-pyridyl)ethylene, and it is observed that an intermediate aggregation state provides the largest substrate EF of ∼3 × 104. Generalized Mie theory is used to investigate the relationship between nanoparticle aggregation extent, cluster geometry, and plasmonic enhancement. Overall, the electrodynamics simulations are in good agreement with experimental EF values and provide a framework for understanding which aggregate structures provide the best enhancement (linear aggregates). The approach outlined here for stabilizing and characterizing deliberately aggregated plasmonic nanoparticles is general and provides a consistent means for testing the SERS substrate properties of nanoparticle colloids that are stabilized in the solid state.

A simple and effective method to prepare an active and stable nanostructured working electrode for electrochemical water splitting is described. Specifically, mixed Fe–Ni diphosphide was prepared by sputtering a 200-nm-thick layer of Permalloy onto carbon paper gas diffusion layer followed by gas transport phosphorization reaction. The mass density of the resultant diphosphide phase was established to be ≈1.1 mg/cm2. Energy-dispersive X-ray microanalysis shows that the actual elemental composition of the resultant ternary electrocatalyst is approximately Fe0.2Ni0.8P2, while the powder X-ray diffraction analysis confirms that the electrocatalyst crystallizes in NiP2cubic pyrite-like structure. As a cathode for hydrogen evolution reaction (HER) in acidic and alkaline electrolytes, this earth-abundant electrode has exchange current densities of 6.84 × 10–3and 3.16 × 10–3mA/cm2and Tafel slopes of 55.3 and 72.2 mV/dec, respectively. As an anode for oxygen evolution reaction (OER) in alkaline electrolyte, the electrode shows an exchange current density of 2.88 × 10–4mA/cm2and Tafel slope of 49.3 mV/dec. The observed high activity of the electrode correlates well with its electronic structure, which was assessed by density functional theory (DFT) calculations. The stability of Fe0.2Ni0.8P2electrocatalyst in HER and OER was evaluated by means of accelerated degradation test and chronopotentiometry. The results of these experiments elucidate partial dissolution and entire chemical transformation of Fe0.2Ni0.8P2as the main mechanisms of the electrode degradation during HER and OER, respectively. Overall, our findings could facilitate the composition-based design of active, stable, and durable phosphide electrodes for electrochemical water splitting.

A promising NiFe(OH)xcatalyst for oxygen evolution reaction (OER) has been successfully fabricated and studied in detail using in situX-ray absorption near-edge structure (XANES) spectroscopy. The chemical nature of elements (Ni, Fe) in electrocatalysts has been elucidated from Fe and Ni K- and L-edge XANES. The increase of oxidation states of Ni from Ni(III) to Ni(3.6) together with a highly covalent Fe(IV)–O bond under OER process is observed. Charge transfer between Ni and Fe through a “Ni–O–Fe” bond is proposed, accounting for the high catalytic activities of NiFe(OH)x.

The gas diffusion layer (GDL) is one of the core components of the proton exchange membrane fuel cell. The complex internal structure of the GDL makes it challenging to accurately predict the mechanical response during clamping compression. In this study, the mechanical properties of the carbon paper-based GDL were investigated using a combination of experimental and numerical simulation. The explicit finite element method (FEM) was used to perform quasi-static compression simulations on the reconstructed GDL. The simulation accounted for the fiber dynamic contact, predicting the true deformation of the GDL. Validation between simulation and experiments was conducted, identifying the initiation point of fiber fracture failure during the compression. The effective range of the elastic constitutive model was determined. The changes in tortuosity, effective diffusivity, absolute permeability, and conductivity in different directions were examined. Reliable experimental results were obtained when the sample quantity was five. Initially, the stress–strain curve exhibited distinct nonlinear characteristics. The equivalent elastic modulus of the GDL continuously increased, stabilizing after a certain compression ratio. With a compression ratio of 27%, the elastic model could accurately reflect the mechanical properties of GDL. Beyond this range, the fiber began to fracture, at which point the stress was 0.064 MPa. Bending and frictional sliding were the main deformation modes of the carbon fibers. The gas diffusion capacity increased first and then decreased; for in-plane direction and through-plane direction, the maximum value appeared at 10 and 5% compression ratio, respectively. The permeability was reduced monotonously. The mass transfer capacity in the in-plane direction of the carbon paper was superior to that in the through-plane direction. The effective conductivity increases in through-plane and in-plane directions were 1354.8 and 57.9%, respectively, at a compression ratio of 35%. Combined with the macroscopic and microscopic levels, it provides a reference for an in-depth understanding of the compressive mechanical properties of fiber porous media and improving the performance of fuel cells.

An electrostatic self-assembly method is used to synthesize FeSiCr/MXene, and the effect of MXene on the wave-absorbing properties is studied in this paper. The electromagnetic parameters of the composites are adjusted by optimizing the amount of MXene to improve the dielectric polarization and achieving impedance matching in order to enhance the microwave-absorbing properties. The lowest reflection loss (RLmin) of FeSiCr/MXene composites is −50.34 dB at 13.75 GHz. When the quantity of MXene composite is 15 wt % and the matching thickness is only 1.32 mm, the effective absorption bandwidth (EAB) at 2.00 mm approaches 11.05 GHz. The improved FeSiCr impedance matching, together with synergistic effects such as dielectric loss and interfacial polarization, results in outstanding microwave absorption performance for the FeSiCr/MXene composites. This paper proposes a new approach to developing and synthesizing materials with lightweight and efficient electromagnetic wave absorption.

This paper reports the synthesis of different crystalline phase-pure Co-vanadates (CVOs), CoV2O6, Co2V2O7, and Co3V2O8, in the same structure. Electrochemical performance experiments were conducted, and density functional theory calculation was used to study their crystalline properties. This paper finds that the supercapacitor performance of CVOs largely depends on the crystalline structure property and charge storage mechanism. Co2V2O7has the biggest tunnel size and thus exhibits the best electrochemical performance at a low rate. In the aspect of Co3V2O8, superior crystalline structure properties are attributed to excellent performance at a high rate. We anticipate that this study will make a contribution toward offering theoretical guidance for CVO supercapacitor electrode materials.

Porous magnetic nanomaterials are attracting increasing attention due to their potential applications in environmental remediation, catalysis, biomedical fields, and magnetic storage media. This paper presents a leaching-based pore engineering approach for the synthesis of porous γ-Fe2O3. This environmentally benign approach uses a citrate buffer for the leaching process. The citrate ligands play a role by binding to surface/interface ions and leaching them into the solution, affecting micropore widths. Concurrently, the citrate ligands also lixiviate smaller-sized particles in the size distribution, resulting in a 6% increase in the average mesopore size. A two-level hierarchical pore size regime is created. The smaller size regime results in a 33% increase in adsorption capacity, and the bigger size regime leads to a 36% enhancement in the mass transport rate of methylene blue (MB) in γ-Fe2O3nanoparticles leached for 6 days. During ultrasonication for MB adsorption studies, a dynamic pore evolution is observed, leading to a remarkable 183% increase in the MB adsorption capacity for sixth-day leached samples after 60 min. Changes in the pore width influence interparticle magnetic interactions. The blocking temperature decreases from 126 K in the as-prepared sample to 116 K in the sixth-day sample. This study highlights the potential of the citrate leaching process for pore engineering.

The synthesis, characterization, and computational modeling of AuCuNiPd nanoparticle alloys are reported in this paper. It was demonstrated that the AuCuNiPd alloys present dispersed atoms along the nanoparticles without any chemical order. The chemical analysis showed the alloys present a stoichiometry consistent with the Au35Cu35Ni15Pd15phase, at times showing segregation related to the Pd and Ni atoms. Molecular dynamics calculations were carried out to describe the stable phase of the nanoparticles, showing remarkable agreement with the experimental results. These findings are consistent with the high-entropy alloy predictions. Therefore, multimetallic nanoparticles with large enough sizes are an excellent model to study multimetallic alloys.

This paper presents a comprehensive mechanistic investigation into the partial oxidation of methane to methanol on bare and ZSM-5-supported Pd4clusters utilizing N2O as an oxidant. The study employs density functional theory (DFT) with ONIOM2 (QM: MM) (B3PW91/LANL2DZ/6-31G(d,p):UFF) with dispersion correction calculations to explore potential energy surfaces (PESs) associated with the methane-to-methanol conversion process in a ZSM-5-supported Pd4cluster. Two spin multiplicities (SM = 1, 3) were considered for the overall reaction pathway. The investigation reveals that C–H activation of methane takes place subsequent to the formation of Pd4O from the N2O decomposition step, which ultimately leads to methanol formation. The study indicates that in terms of activation barrier, the N–O and C–H activation steps exhibit a lower energy barrier in the singlet state, while the recombination step of CH3and OH moieties is preferable in the triplet spin state. However, the reaction process does not involve any spin crossover, as the triplet spin state consistently maintains the lowest energy pathway throughout the reaction. From the overall analysis of the reaction mechanisms for methane to methanol, it is evident that zeolite support and spin multiplicity play a significant role in lowering the activation barriers.

This study looks at energy-dispersive X-ray spectroscopy (EDX) maps of fluorine in NMC 622 cathodes and the efforts made to improve the spatial resolution of fluorine mapping. The transition to electric vehicles demands faster and efficient production of next-generation lithium-ion batteries. To achieve this goal, the industry needs to take advantage of state-of-the-art battery characterization techniques in the pursuit of gaining a greater understanding of electrode structure and production. The binder location within an electrode is critical to electrochemical performance and contains fluorine, yielding an opportunity to use it as a marker and a way to visualize binder distribution and therefore, better understand process-structure relations. However, fluorine is difficult to differentiate from cobalt and manganese in an EDX spectrum due to similar Kα energy. Fluorine also interacts with the electron beam, potentially leading to poor spatial resolution. This paper examines different EDX parameters and compares the spatial resolution of fluorine in the maps of lithium-ion cathode cross sections. Analysis of the EDX maps showed that reducing the accelerating voltage from 20 to 5 kV improved the spatial resolution of fluorine 10-fold, from 2553 to 238 nm, supported by CASINO simulations. The EDX maps also indicated that imaging for one long scan at a 2500 μs dwell time produced a higher spatial resolution than imaging for 10 scans at 250 μs. Repeated line scans of the sample showed the extent of fluorine mobility; fluorine-rich zones emit less, while fluorine-free zones begin to emit more fluorine X-rays. This work shows that the spatial resolution of fluorine maps can be increased by imaging at 5 kV and scanning for one pass at 2500 μs. This methodology can be used to create more representative EDX maps of the binder in the cathodes. Visual analysis or further processing with an image analysis can reveal binder distributions and potential binder gradients. This technique is useful in understanding how changes to electrode manufacturing can change the electrode structure and binder distribution.

Ammonia synthesis by nitrogen and water reaction is essentially a process of nitrogen and hydrogen ion coupling, with electrons forming an N–H bond. In this paper, friction can continuously provide electrons and hydrogen ions in the catalytic reaction of Si3N4to realize the nitrogen fixation process, so as to achieve high efficiency of friction catalytic nitrogen fixation at room temperature. For the direct nitrogen fixation of air and water to produce ammonia, the ammonia yield can reach 1273.4 μmol/g at 5 h, while the ammonia yield can reach 1865.2 μmol/g at 5 h under pure nitrogen and water nitrogen fixation. The rapid contact and separation between a PTFE rod, Si3N4particles, and a glass reactor causes continuous positive and negative charge formation on the surface of Si3N4. The positive charges react with the sacrificial agent methanol and water to generate hydrogen ions, which not only consumes the positive charges, inhibits the recombination of positive and negative charges, and improves the utilization rate of electrons but also provides a large number of hydrogen ion sources for the reaction. Based on the results of density functional theory (DFT) calculations, which indicate that silicon atoms on the surface of silicon nitride have no catalytic activity, while nitrogen atoms can effectively activate nitrogen molecules and catalyze the nitrogen fixation reaction, we designed a tribocatalysis process to continuously break the catalyst particles to expose more surface nitrogen atoms as active sites in situ to promote the nitrogen fixation reaction. In addition, the friction force can provide energy for the reaction in the instantaneous process, which is conducive to the activation of nitrogen molecules to promote the reaction, and together with the continuous charge provided by the friction process, it finally enables Si3N4to catalyze nitrogen fixation efficiently at room temperature.

Fast charging of lithium-ion batteries (LIBs) is now a critical challenge for the development of electric vehicles (EVs). The difficulty of achieving fast-charging LIBs arises from the sluggish Li-ion transport in both electrolytes and electrode materials and the sluggish charge transfer processes across the electrode–electrolyte interphases (EEIs). To overcome these obstacles, it is important to fully understand the transport mechanism of Li+in electrode materials, electrolytes, and EEIs. Spectroscopic techniques are useful tools to detect the structural changes and reveal the mass transport mechanism during the cycling of the batteries, which are helpful to guide the design of novel electrode materials and electrolytes as well as optimal interphases for fast-charging batteries. In this paper, recent advancements in the application of spectroscopic techniques for the development of fast-charging LIBs are reviewed. We focus on the key roles of spectroscopic techniques in revealing the reasons for improved fast-charging capabilities of LIBs, including their application in the fields of electrolyte engineering, interphase modification, Li-plating detection, and composition/structure optimization. Moreover, the application of electrospectroscopic techniques in exploring the interfacial reactions of the electrodes is also discussed. Finally, some perspectives and research directions for improving spectroscopic techniques to advance the development of fast-charging LIBs are provided.

Organic solar cells (OSCs) are lightweight, flexible, and highly transparent; however, their power conversion efficiency is currently subpar. This has motivated researchers to intensify their efforts to augment the performance of these devices. In non-fullerene-acceptor (NFA) OSCs, the impact of spin-triplet states has proved to be significant. In addition, it has been shown that the low exciton binding energies in NFAs, such as Y6, can lead to self-dissociation. These findings call for a deeper exploration. In this paper, we introduce an extended hot kinetic model that accounts for all spin states and the direct dissociation of local exciton states to evaluate their effects on OSC performance. The machine learning technique, specifically a regression neural network algorithm, is employed to handle the complex calculations related to the model. This algorithm generates the current density–voltage (J–V) curves for OSCs, from which three crucialfactors are identified out of 28 examined factors, and their influence on the OSC performance parameters is thoroughly investigated. The analysis indicates that improving charge carrier mobility enhances the fill factor (FF), raising the energy of singlet charge transfer states increases the open-circuit voltage (VOC), and thicker film generally boosts short-circuit current density (JSC) but reduces the FF. Additionally, we explore how these three parameters affect device performance collectively. This research offers fresh insights into designing more efficient OSC devices.

This paper reports the construction of a series of two-dimensional (2D) transition metal coordinated porphyrin-analogue catalytic materials and employs a combined strategy of the first-principles calculations and high-throughput screening to systematically investigate their catalytic activity and reaction mechanisms of electrocatalytic nitrogen reduction reaction (NRR). Ninety metal porphyrin-analogue catalysts are obtained by embedding 30 transition metals (3–5d series) into three classes of two-dimensional porphyrin-analogue substrates. High-throughput screening and full reaction pathway search reveal that MoPp-β-H-meso-Diyne, MoPp-meso-H-β-Ph and MoPp-meso-H-β-Py are the optimal catalysts via the distal pathway with onset potentials of −0.21, −0.26 and −0.28 V, respectively. WPp-meso-H-β-Py and RePp-β-H-meso-Diyne also exhibit good catalytic performance with onset potentials of −0.46 and −0.46 V, respectively. All five catalytic materials demonstrate good electronic conductivity and high stability. A volcano-shaped relationship is unveiled between the free energy change of the first protonation step (ΔG*N2→ *N2H) and the onset potential (Uonset), which can be utilized to describe the catalytic activity of NRR and guide the design and selection of efficient catalysts.

In this paper, we propose a strategy for screening multicomponent alloys using evidence theory and high-throughput density functional theory calculations. We demonstrate an electrochemical C2-selective CO2reduction reaction (eCO2RR) on multicomponent alloys as a practical study. The proposed strategy can screen potential C2-selective alloys from enormous element combinations without complicated structural descriptors or a complete data set. Therefore, this strategy is expected to effectively design multicomponent alloys with vast element combinations.

In this paper, we report on one of the first applications of fluorophore-induced plasmonic current (FIPC) developed, namely, the direct detection of analytes using turn-onfluorescent sensing probes. Recent work by our group has demonstrated the utility of various types of metal nanoparticle films and how these different films can provide the suitable spectral overlap for a wide range of fluorophores and chromophores to be directly detected “electrically”. In this article, we subsequently share our findings pertaining to the sensing of aqueous Fe3+ions via a turn-on fluorescent probe. The probe’s responses are compared between their typical fluorescence solution-based responses as well as their ability to sense Fe3+via the new FIPC transduction mechanism. Our results suggest a pathway for the development of FIPC-based detection of analytes vs using traditional fluorescence sensing techniques, albeit, with nearly identical sensing instrumentation.

In the present paper, we have investigated the evolution of structure followed by local structure-driven magnetic properties in CoxMn3-xO4nanoparticles synthesized through a facile coprecipitation technique. Rietveld refinement of the X-ray diffraction pattern reveals a structural phase transition from the coexistence of tetragonal and cubic to a pure cubic phase with increasing xfrom 1.00 to 2.00. Such transition is validated with local structure analysis where it is observed that while Mn3+and Co2+ions are distributed among B and A sites, respectively, in x= 1.00, with increase in x,Mn3+in the B site is replaced by Co3+ions. When x≥ 1.75, the additional presence of Mn4+is observed from extended X-ray absorption fine structure spectroscopy and confirmed by X-ray photoelectron spectroscopy. In accordance with two structural phases, for x= 1.00, two magnetic transitions Tc1and Tc2at 165 and 93 K, respectively, are observed. With an increase in x, Tc1grows at the expense of Tc2and finally, at x= 2.0, only Tc1is detected. Unusual temperature-dependent Hc is observed for the coexistence of the cubic and tetragonal phase. Such magnetic behavior is discussed based on the competition between magnetic ions occupying the tetrahedral and octahedral sites.

This paper reports X-ray chromophorebehavior: the substituents of an X-ray-absorbing atom (here phosphorus) were found to contribute consistent absorptions, in intensity and in relative peak position (transition energy). Linear relations for absolute peak position, as a function of the sum of the phosphorus neighbor-atom electronegativities (Σχ), have been found for ten chromophore peaks: P–F, P–O, P–Cl, P–N, P–CI, P–WI, P–CII(Ph), P–CII(pyr) P–CII(Fc), P–WII. The discovery was made by finding (i) surprisingly rich phosphorus K-edge X-ray absorption spectra [P X-ray absorption spectroscopy (XAS)] for several four-coordinate-phosphorus compounds, including four new ones involving the W(CO)5substituent, (ii) a vastly improved time-dependent (linear-response-based) density-functional-theory prediction method for P XAS which provides unprecedented XAS peak-assignment ability, and (iii) a fresh antibonding-orbital-based interpretive framework. The discovery, that selective X-ray excitation of substituents is possible, opens the door for studies of chemical reactivity implications (X-ray photochemistry), and improved studies of X-ray radiation exposure effects and damage.

Electrochemical water splitting is a promising strategy for reducing hydrogen production costs. However, the conventional phosphate buffer (PBS) electrolyte incurs a huge energy penalty in high overpotential ranges. This study investigates the hydrogen evolution reaction (HER) performance using two buffer electrolytes with different charge properties: H2PO4–/HPO42–(PBS pKa= 6.90) and IMZH+/IMZ (IMZS pKa= 7.03). On Pt microelectrodes, results reveal that the plateau current density of PBS correlates closely with the electrode potential, a trend not observed with IMZS. In addition, when using commercial Pt/C nanocatalysts loaded on carbon paper, the plateau current density phenomenon disappears in the IMZS electrolyte, which is attributed to the preconcentration effect of the positively charged hydrogen source. In situ Raman characterization indicates that the configuration of H2PO4–at the electrochemical interface changes as the electrode potential becomes progressively negative. In comparison, the adsorption configuration of IMZH+remains considerably stable across the tested potential range. The grand canonical density functional theory method with both implicit and explicit solvation models was further used to investigate the influence of electrode potential on the dissociation of a differently charged hydrogen source. Results indicate that when the electrode potential becomes progressively negative, H2PO4–is repelled from the electrode surface owing to electrostatic forces, increasing Gibbs free energy of dissociation accordingly. This phenomenon contributes to the inevitable energy penalty observed in the PBS electrolyte for the HER. In comparison, the Gibbs free energy of dissociation of IMZH+decreases monotonically with the progressive negative cathode potential. To explain this discrepancy, this study briefly examined the influence of electrode potential in two aspects: theoretical thermodynamics energy and the state of the hydrogen source near the electrode surface.

In our recent paper [Phys. Rev. B2023, 107, 184314], we introduced a Floquet electronic friction model to describe nonadiabatic molecular dynamics near metal surfaces in the presence of periodic driving. In this work, we combine the quantum transport study with Langevin dynamics and demonstrate that the nonvanishing antisymmetric friction tensor associated with Floquet driving results in a closed trajectory for the nuclei in the long-time limit. We show that Floquet driving strongly affects nuclear motion, resembling the Lorentz force. Our results indicate that Floquet driving can increase the temperature of the nuclei at low bias voltages, whereas Floquet driving can cool down the nuclei at high bias voltages. In addition, we show that Floquet driving can affect electron transport strenuously. Finally, we find out that there is an optimal frequency that maximizes electron current. We expect that the Floquet electronic friction model will provide a powerful tool for further research in nonadiabatic molecular dynamics near metal surfaces under Floquet driving.

Efficiently separating sulfur hexafluoride/nitrogen (SF6/N2) poses an urgent challenge. Four covalent organic frameworks (COFs) (Re % > 80%) with greater performance in SF6/N2separation experiment were selected from the CURATED database by high-throughput screening in this paper. XGB was selected among four machine learning models (SVM, RF, GBRT, and XGB) and this model had good fitting effects in terms of both regeneration (Re %, R2= 0.809) and ln(Sads). Relative importance analyses of XGB described that porosity and infinite dilution heat are the most key features for Re % and ln(Sads). The binding energy, charge density difference, Bader charge, and independent gradient model based on Hirshfeld partition (IGMH) analysis were all calculated to investigate the adsorption mechanisms. GCMC simulations combined with density functional theory calculations revealed that COF-638 exhibited an excellent SF6/N2separation performance. The probability distribution diagram of the center of mass illustrates the adsorption sites of SF6in coadsorption.

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 TiO2and CeOx–TiO2mixed support was studied comparatively. The introduction of a Ce2Oxoverlayer increases the adsorption energy of oxygen-containing species due to the conversion of adsorption sites from metals to the Cu8–CeOxinterface. It is more advantageous to react on copper clusters on the Cu/TiO2surface, mainly through the redox mechanism. The reaction on the Cu/CeOx–TiO2surface is more advantageous at the Cu8–CeOxinterface, also through the redox mechanism. Microkinetic analysis shows that the addition of the CeOxsupport significantly enhances the performance of the water–gas shift reaction. The reason for the high activity of the Cu/CeOx–TiO2catalyst is that the rate-determining step changes from H2O dissociation to OH dissociation. Fundamentally, the Ce site on the Cu8/CeOxinterface activates H2O and promotes the decomposition of H2O. As CeOxcan 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/CeOx/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.

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.

Proton exchange membrane water electrolysis (PEMWE) is one of the potential strategies to generate green hydrogen energy, and anticorrosive coatings are mandatory to protect the bipolar plates, an important component of PEMWE. However, it is still challenging to explore the high-corrosion-resistance coatings by trial and error. In this paper, the corrosion properties of Ta and its alloys as examples are studied theoretically; in particular, the influences of crystal planes and alloying elements on the corrosion resistance have been studied systematically. Four descriptors, surface energy density ξ, work function τ, electronic descriptor ψ, and d band center ς, are proposed to screen the high-corrosion-resistance coatings. It is found that the electronic descriptor ψ can well predict the atomic escape energy and thus the corrosion resistance of Ta-based binary alloys with the coefficient of determination R2of 0.804 and 0.949, respectively. Among them, TaW and TaCr alloys exhibit the most excellent corrosion resistance with the lowest Icorr(<1.59 × 10–7A cm–2) and the highest Ucorr(> −0.011 V vs SHE) because of the largest −IpCOHP values and thus the strongest binding strength. The screening method is also applicable to the other alloys.

In this paper, we adopt a novel approach to investigate the ionic conduction near the percolation transition in a porous nanomaterial. We make use of a recently discovered humidity sensing property of aerosol-printed MoS2ink films, where the conductance, originated from ionic transport through water nanochannels within the films, is dependent on the ambient humidity. The experiments, performed for a set of four devices inside a chamber with controlled humidity, allow the experimental fine-tuning of the ionic conduction percolation within each nanoporous device by changing the ambient relative humidity, without the need of different samples for different stoichiometries as in usual percolation experiments. Our results indicate the existence, in our devices, of a common phenomenology consisting of two sequential modifications of the conductance as a function of humidity near percolation. The first is the true percolation transition with a universal critical exponent very close to unity. This is followed by an apparent increase in the critical exponent above the true transition. We also perform molecular dynamics simulations that allow the identification of a possible mechanism for dimensionality changes in the water nanochannels inside the material as a function of either humidity or material geometry as a possible scenario for the observed conductance modification in the conductive phase.

In this paper, the thermal transport characteristics of penta-CN2and -BCN, which can be seen as the analogues of penta-graphene, are systematically studied by first-principles calculation and solving the phonon Boltzmann transport equation. The results reveal that, in contrast to the traditional two-dimensional materials, the three-phonon scattering process is insufficient to adequately characterize the thermal transport mechanisms of the above two materials, and the four-phonon scattering process has an enormous impact on their thermal transport processes. The thermal conductivity of penta-CN2at room temperature is reduced by 44.1% after considering four-phonon scattering, and that of penta-BCN is dropped by 60.0% in the same case. Combining with phonon analysis, it can be found that four-phonon scattering mainly affects the phonons in the ZA branch, which is mainly due to the extremely isolated distribution of the ZA branch. Further, it can also be noticed that the number of the phonon scattering channel involved in the redistribution process is significantly higher than those of the other two four-phonon scattering processes, i.e., splitting and recombination processes, and even reaches the level of the three-phonon scattering processes. Under the influence of the above factors, the four-phonon scattering process plays an extremely important role in the thermal transport properties of penta-CN2and -BCN. Considering that the dispersion curves of the two structures do not have an obvious phonon bandgap, we can notice that the impact mechanism of four-phonon scattering in penta-CN2and -BCN is significantly different from those of other structures, which are also greatly affected by four-phonon scattering, e.g., BAs. The results in this work provide strong theoretical support for expanding the application of penta-structures and four-phonon scattering processes in the field of nanoscale heat transfer.

Hydrogen is a potential alternative reducing agent, which can greatly reduce CO2emission in the ironmaking process of vanadium titanomagnetite. This paper investigated the reaction process and kinetic characteristics of the hydrogen reduction of both untreated and preoxidized vanadium titanomagnetite using a thermogravimetric analyzer (TG). The effects of different preoxidation temperatures (Toxi= 500 °C, Toxi= 700 °C, and Toxi= 900 °C) on the reduction characteristics of vanadium titanomagnetite were compared at a reduction temperature of 1000 °C. It was found that the reduction degree and reduction rate of low-temperature (Toxi= 500 °C and Toxi= 700 °C) preoxidized vanadium titanomagnetite are higher than those of high-temperature (Toxi= 900 °C) preoxidized vanadium titanomagnetite. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses show that the low-temperature preoxidation process separates the Fe/Ti in vanadium titanomagnetite and forms micropores on the surface of the vanadium titanomagnetite, while the high-temperature preoxidation process allows the separated hematite and ilmenite to recombine and form pseudobrookite. The isothermal reduction experiments on untreated and preoxidized vanadium titanomagnetite were carried out, with reduction temperatures ranging from 600 to 1000 °C. The obtained results were subjected to kinetic analysis using conventional model-fitting and iso-conversional methods. The fitting results of different kinetic models show that the activation energies of the preoxidized vanadium titanomagnetite reduction reaction are lower than those of untreated vanadium titanomagnetite. In the entire range of the reduction reaction, the contracting area model (R2) can best describe the reaction between hydrogen and untreated and preoxidized vanadium titanomagnetite. After the preoxidized treatment, the reduction energy barrier of vanadium titanomagnetite decreases by about 38.0%.

Structure-sensitive chiroptical properties favor applications such as polarization detection and nonlinearity; however, large-scale tuning of circular dichroism (CD), for instance, flipped signal, is typically realized in two enantiomers with distinct handedness and rarely in a single planar chiral nanostructure. This paper numerically studies a trident-shaped nanostructure array that allows magnetic-field enhancement by forming semiclosed loop currents in quadrupolar localized plasmon (QL) to generate substantial chiroptical responses with a maximum CD magnitude of 33.1%. Locally changing the rotation of the building block at a small angle of 15° can efficiently modify the structural chirality of the unit cells and thus dramatically inverse the chiroptical responses from negative to positive. We arranged two trident-shaped nanostructures with slightly different configurations but opposite optical chirality into a unit to achieve a high-contrast CD signal with a narrowed line width. Calculations show that the new metamaterial with large electromagnetic-field enhancement in sharp corners enables the detection of low-concentration bovine serum albumin protein with the largest sensitivity of SCD= 795 RIU–1.

Optical matter (OM) arrays are self-organizing, ordered arrangements of nanometer- to micrometer-size particles, where interparticle forces are mediated by incident and scattered coherent light. The structures that form and their dynamics depend on the properties (e.g., material, size) of the constituent particles, as well as the incident and scattered light. While significant progress has been made toward understanding how the OM arrays are affected by the phase, polarization, and intensity profile of the incident light, the polarization induced in the particles and the light scattered by OM arrays have received less attention. In this paper, we establish the roles of electrodynamic interference, many-body coupling, and induced-polarization concomitant with the coherent light scattered by OM arrays. Experiments and simulations together demonstrate that the spatial profile and directionality of coherent light scattered by OM arrays in the far field are primarily influenced by interference, while electrodynamic coupling (interactions) and the associated polarization induced in the nanoparticle constituents have a quantitative wavelength-dependent effect on the total amount of light scattered by the arrays. Furthermore, the electrodynamic coupling in silver nanoparticle OM arrays is significantly enhanced by constructive interference and increases superextensively with the number of particles in the array. Particle size, and hence polarizability, also has a significant effect on the strength of the coupling. Finally, we simulate larger hexagonal OM arrays of Ag nanoparticles to demonstrate that the electrodynamic coupling and scattering enhancement observed in small OM arrays develop into surface lattice resonances observed in the infinite array limit. Our work provides insights for designing OM arrays to tune many-body forces and the coherent light that they scatter.

In this paper, the effects of crystallization advance on the material structure and electrical properties of lithium-ion Na+super ionic conductor (NASICON) glass ceramics were investigated. Glasses with Li1.5Al0.5Ge1.5(PO4)3and Li1.5Sc0.17Al0.33Ge1.5(PO4)3compositions were crystallized in controlled conditions to obtain gradual increment of the volume crystallized fraction. The glass-to-crystal transformation was then monitored by differential scanning calorimetry analysis (DSC), X-ray diffractometry (XRD), Raman spectroscopy, solid-state nuclear magnetic resonance spectroscopy (MAS NMR), and electron microscopy, along with chemical analyses. Finally, the electrical properties of the specimens were evaluated by impedance spectroscopy to observe the changes in electrical properties according to the crystallization advance. Results revealed that glasses containing scandium are more stable against crystallization than their neat counterparts. Crystallization led to the formation of single-phase NASICON glass ceramics. Scandium induced a lattice expansion of the NASICON structure. Furthermore, crystallization induces remarkable structural changes in the materials as a whole, either in local order or in medium to long order. No important increase in conductivity was observed in earlier stages of crystallization. After the percolation of crystals, conductivity increases sharply and the remaining glassy phase has little impact on the total conductivity of the material. Scandium expands the rhombohedral structure but increases the glass stability and reduces the sizes of crystals for the fully crystallized glass ceramics. Glass ceramics with larger grains are more propitious for conductivity than the more refined ones. Therefore, this paper offers key information about the understanding of NASICON crystallization and its structural evolution, providing important insights into the crystallization of these electrolytes.

Many different types of nanoparticles have been developed for photothermal therapy (PTT), but directly comparing their efficacy as heaters and determining how they will perform when localized at depth in tissue remains complex. To choose the optimal nanoparticle for a desired hyperthermic therapy, it is vital to understand how efficiently different nanoparticles extinguish laser light and convert that energy to heat. In this paper, we apply photothermal mass conversion efficiency (ηm) as a metric to compare nanoparticles of different shapes, sizes, and conversion efficiencies. We selected silica-gold nanoshells (AuNShells), gold nanorods (AuNRs), and gold nanostars (AuNStars) as three archetypal nanoparticles for PTT and measured the ηmof each to demonstrate the importance of considering both photothermal efficiency and extinction cross section when comparing nanoparticles. By utilizing a Monte Carlo model, we further applied ηmto model how AuNRs performed when located at tissue depths of 0–30 mm by simulating the depth penetration of near-infrared (NIR) laser light. These results show how nanoparticle concentration, laser power, and tissue depth influence the ramp time to a hyperthermic temperature of 43 °C. The methodology outlined in this paper creates a framework to benchmark the heating efficacy of different nanoparticle types and a means of estimating the feasibility of nanoparticle-mediated PTT at depth in the NIR window. These are key considerations when predicting the potential clinical impact in the early stages of nanoparticle design.

The formation of 1:1 and 2:1 inclusion complexes between the hosts cyclodextrins (α-, β-, and γ-CD) and the guest 1-(4-carboxybenzyl)-4-[2-(4-pyridyl)vinyl]pyridinium chloride (guest CPP+·Cl–) was demonstrated by NMR spectroscopy. The inclusion complexes CPP+@α-CD, CPP+@β-CD and CPP+@γ-CD2display photochromic properties from pale yellow to red in the solid state. The electron-spin resonance (ESR) spectroscopic data of the CPP+@γ-CD2suggest that the photochromic behavior arises from the generation of the free radicals. The CPP+@γ-CD2can be easily coated on the filter paper and used in erasable inkless printing and anticounterfeiting. Most importantly, the mixture of CPP+@γ-CD2and 1+@β-CD (an inclusion complex previously reported, whose color after irradiation was blue) also can be coated on the filter paper, and the color of printing on the filter paper is tunable by controlling the mass proportions of CPP+@γ-CD2and 1+@β-CD.

This paper examines the reactive surface dynamics of energy- and angle-selected N2dissociation on a clean Ru(0001) surface. Presented herein are the first STM images of highly energetic N2dissociation on terrace sites utilizing a novel UHV instrument that combines a supersonic molecular beam with an in situSTM that is in-line with the molecular beam. Atomically resolved visualization of individual N2dissociation events elucidates the fundamental reactive dynamics of the N2/Ru(0001) system by providing a detailed understanding of the on-surface dissociation dynamics: the distance and angle between nitrogen atoms from the same dissociated N2molecule, site specificity and coordination of binding on terrace sites, and the local evolution of surrounding nanoscopic areas. These properties are precisely measured over a range of impinging N2kinetic energies and angles, revealing previously unattainable information about the energy dissipation channels that govern the reactivity of the system. The experimental results presented in this paper provide insight into the fundamental N2dissociation mechanism that, in conjunction with ongoing theoretical modeling, will help determine the role of dynamical processes such as energy transfer to surface phonons and nonadiabatic excitation of electron–hole pairs (ehps). These results will not only help uncover the underlying chemistry and physics that give rise to the unique behavior of this activated dissociative chemisorption system but also represent an exciting approach to studying reaction dynamics by pairing the angstrom-level spatiotemporal resolution of an in situSTM with nonequilibrium fluxes of reactive gases generated in a supersonic molecular beam to access highly activated chemical dynamics and observe the results of individual reaction events.

Pyrite FeS2has been investigated for a wide range of applications, including thermoelectrics, due to previous observations of large thermopower at room temperature. However, the values of thermopower reported in the literature are extremely sensitive to the nature of the sample─whether they are natural or lab-grown, bulk crystals or thin films─and an ambiguity in the magnitude and sign of the thermopower of pure FeS2exists. Variation in the magnitude of room-temperature thermopower has also been observed in Co-doped samples. Therefore, it is of interest to clarify the intrinsic thermopower of this system that could be measured in more pure samples. In this paper, we investigate the thermoelectric properties of Co-doped FeS2using first-principles calculations. We apply three different doping schemes to understand the effect of electron doping in FeS2, namely, explicit Co substitution, jellium doping, and electron addition within a rigid band approximation (RBA) picture. The calculated thermopower is less than −50 μV/K for all values of Co doping that we studied, suggesting that this system may not be useful in thermoelectric applications. Interestingly, we find that RBA substantially overestimates the magnitude of calculated thermopower compared to the explicit Co substitution and jellium doping schemes. The overestimation occurs because the changes in the electronic structure due to doping-induced structural modification and charge screening are not taken into account by the rigid shift of the Fermi level within RBA. RBA is frequently used in first-principles investigations of the thermopower of doped semiconductors, and Co-substituted FeS2illustrates a case where it fails.