Search

Starting with a short biography, Schatz then reviews Van Duyne's leading contributions to the discovery and development of SERS as well as pioneering work on localized surface plasmon resonance (LSPR), tip-enhanced Raman scattering (TERS), electrochemical surface-enhanced Raman scattering (SERS)/TERS, and ultrafast nonlinear techniques. SP [ sp 1 SP ] sp The second paper by Moskovits and Piorek is also important, giving a brief history of SERS and its connection with localized surface plasmon excitation. The resulting particle-tipped needles allow dual enhancement of the Raman signals from microdroplets of low concentration analytes by combining analyte enrichment through solvent evaporation and plasmonic SERS enhancement. They discuss the challenges and perspectives in designing and synthesizing nanogap structures that deliver strong, reproducible, and reliable SERS signals for quantitative SERS analysis. SP [ sp 11 SP ] sp In the work presented by Xu, Bell, et al., a SERS-active superhydrophobic (SHP) tip is constructed by an adsorbing a layer of densely packed and uniform plasmonic nanoparticles onto a hydrophilic tip. Also, by utilizing the LRSP mode, electrochemical reactions on the Pt surface could be protected from any nanoscale effects, which is advantageous over conventional SERS. SP [ sp 16 SP ] sp Murakoshi et al. carry out electrochemical SERS measurements to clarify the detailed molecular behavior in the strong coupling regime. [Extracted from the article]

Due to the superior catalytic activity and efficient utilization of noble metals, nanocatalysts are extensively used in the modern industrial production of chemicals. The surface structures of these materials are significantly influenced by reactive adsorbates, leading to dynamic behavior under experimental conditions. The dynamic nature poses significant challenges in studying the structure–activity relations of catalysts. Herein, we unveil an anomalous entropic effect on catalysis via surface pre‐melting of nanoclusters through machine learning accelerated molecular dynamics and free energy calculation. We find that due to the pre‐melting of shell atoms, there exists a non‐linear variation in the catalytic activity of the nanoclusters with temperature. Consequently, two notable changes in catalyst activity occur at the respective temperatures of melting for the shell and core atoms. We further study the nanoclusters with surface point defects, i.e. vacancy and ad‐atom, and observe significant decrease in the surface melting temperatures of the nanoclusters, enabling the reaction to take place under more favorable and milder conditions. These findings not only provide novel insights into dynamic catalysis of nanoclusters but also offer new understanding of the role of point defects in catalytic processes. [ABSTRACT FROM AUTHOR]

Due to the superior catalytic activity and efficient utilization of noble metals, nanocatalysts are extensively used in the modern industrial production of chemicals. The surface structures of these materials are significantly influenced by reactive adsorbates, leading to dynamic behavior under experimental conditions. The dynamic nature poses significant challenges in studying the structure–activity relations of catalysts. Herein, we unveil an anomalous entropic effect on catalysis via surface pre‐melting of nanoclusters through machine learning accelerated molecular dynamics and free energy calculation. We find that due to the pre‐melting of shell atoms, there exists a non‐linear variation in the catalytic activity of the nanoclusters with temperature. Consequently, two notable changes in catalyst activity occur at the respective temperatures of melting for the shell and core atoms. We further study the nanoclusters with surface point defects, i.e. vacancy and ad‐atom, and observe significant decrease in the surface melting temperatures of the nanoclusters, enabling the reaction to take place under more favorable and milder conditions. These findings not only provide novel insights into dynamic catalysis of nanoclusters but also offer new understanding of the role of point defects in catalytic processes. [ABSTRACT FROM AUTHOR]

The conversion of methane under ambient conditions has attracted significant attention. Although advancements have been made using active oxygen species from photo‐ and electro‐ chemical processes, challenges such as complex catalyst design, costly oxidants, and unwanted byproducts remain. This study exploits the concept of contact‐electro‐catalysis, initiating chemical reactions through charge exchange at a solid–liquid interface, to report a novel process for directly converting methane under ambient conditions. Utilizing the electrification of commercially available Fluorinated Ethylene Propylene (FEP) with water under ultrasound, we demonstrate how this interaction promote the activation of methane and oxygen molecules. Our results show that the yield of HCHO and CH3OH can reach 467.5 and 151.2 μmol ⋅ gcat−1, respectively. We utilized electron paramagnetic resonance (EPR) to confirm the evolution of hydroxyl radicals (⋅OH) and superoxide radicals (⋅OOH). Isotope mass spectrometry (MS) was employed to analyze the elemental origin of CH3OH, which can be further oxidized to HCHO. Additionally, we conducted density functional theory (DFT) simulations to assess the reaction energies of FEP with H2O, O2, and CH4 under these conditions. The implications of this methodology, with its potential applicability to a wider array of gas‐phase catalytic reactions, underscore a significant advance in catalysis. [ABSTRACT FROM AUTHOR]

The conversion of methane under ambient conditions has attracted significant attention. Although advancements have been made using active oxygen species from photo‐ and electro‐ chemical processes, challenges such as complex catalyst design, costly oxidants, and unwanted byproducts remain. This study exploits the concept of contact‐electro‐catalysis, initiating chemical reactions through charge exchange at a solid–liquid interface, to report a novel process for directly converting methane under ambient conditions. Utilizing the electrification of commercially available Fluorinated Ethylene Propylene (FEP) with water under ultrasound, we demonstrate how this interaction promote the activation of methane and oxygen molecules. Our results show that the yield of HCHO and CH3OH can reach 467.5 and 151.2 μmol ⋅ gcat−1, respectively. We utilized electron paramagnetic resonance (EPR) to confirm the evolution of hydroxyl radicals (⋅OH) and superoxide radicals (⋅OOH). Isotope mass spectrometry (MS) was employed to analyze the elemental origin of CH3OH, which can be further oxidized to HCHO. Additionally, we conducted density functional theory (DFT) simulations to assess the reaction energies of FEP with H2O, O2, and CH4 under these conditions. The implications of this methodology, with its potential applicability to a wider array of gas‐phase catalytic reactions, underscore a significant advance in catalysis. [ABSTRACT FROM AUTHOR]

In order to investigate the adsorption process of malachite green (MG) on gold nanoparticles, a simple gold nanoparticles‐assembled film was prepared as a substrate of surface‐enhanced Raman spectroscopy (SERS), and it was soaked in MG solutions of different concentrations. The kinetic adsorption process was investigated by SERS method and density functional theoretical calculations. When saturated adsorption was achieved, the relationship between the characteristic SERS band signal intensity and the logarithm of solution concentration of MG was consistent with Temkin adsorption isotherm model, where the R2 value was greater than 0.995, and the linear range was 1 × 10−3–1 × 10−7 M. Finally, a SERS quantitative analysis model of the relationship between the adsorption properties of surface species and the bulk concentration was established. According to the electrostatic interaction and co‐adsorption, we proposed the surface adsorption configurations and adsorption process of MG on the nanostructured gold films. [ABSTRACT FROM AUTHOR]

Molecular assembly is the process of organizing individual molecules into larger structures and complex systems. The self-assembly approach is predominantly utilized in creating artificial molecular assemblies, and was believed to be the primary mode of molecular assembly in living organisms as well. However, it has been shown that the assembly of many biological complexes is "catalysed" by other molecules, rather than relying solely on self-assembly. In this review, we summarize these catalysed-assembly (catassembly) phenomena in living organisms and systematically analyse their mechanisms. We then expand on these phenomena and discuss related concepts, including catalysed-disassembly and catalysed-reassembly. Catassembly proves to be an efficient and highly selective strategy for synergistically controlling and manipulating various noncovalent interactions, especially in hierarchical molecular assemblies. Overreliance on self-assembly may, to some extent, hinder the advancement of artificial molecular assembly with powerful features. Furthermore, inspired by the biological catassembly phenomena, we propose guidelines for designing artificial catassembly systems and developing characterization and theoretical methods, and review pioneering works along this new direction. Overall, this approach may broaden and deepen our understanding of molecular assembly, enabling the construction and control of intelligent assembly systems with advanced functionality. [ABSTRACT FROM AUTHOR]

Charged microdroplets are favored in microfluidic control, biomedicine, chemistry and materials processing due to their unique physicochemical environment, including interface double layers, high electric fields, surface concentration enrichment, and more. Herein, we investigated the crystallization of charged sodium chloride microdroplets and achieved the formation of hollow single crystals in a single-step process lasting only a few seconds, without the use of templates. Additionally, we discussed the plausible crystal growth mechanism, which appears to be an unconventional outward-inward growth process. [ABSTRACT FROM AUTHOR]

The direct epitaxial growth of graphene on semi‐insulating SiC presents significant potential for a variety of technologically important applications, including next‐generation electronics, photonics, and quantum metrology. However, this approach also poses a competitive disadvantage in terms of quality and cost, primarily due to the uncontrollable and time‐consuming nature of the annealing process. Herein, a thermal shock annealing (TSA) method is reported that enables kinetics‐controlled epitaxial growth of graphene on SiC within 10 s, which efficiently fulfills the requirements for producing high‐quality, few‐layer, and low‐cost graphene on SiC. The epitaxial graphene (EG) grown on both β‐SiC nanoparticles (SiC@EG NPs) and centimeter‐scale α‐SiC wafer (EG/SiC) exhibits mono‐ or bi‐layer features with negligible structural defects. Moreover, the findings indicate that the TSA method can efficiently mitigate the persistent issue of step bunching conundrum and improve the flatness of EG/SiC. As an application demonstration, the significant enhancement of surface‐enhanced infrared absorption (SEIRA) by SiC@EG NPs is exhibited. The graphene plasmon arising on SiC@EG NPs enables SEIRA detection sensitivity of up to a monolayer of p‐nitrobenzenethiol (p‐NTP). Consequently, the precise regulation and comprehensive comprehension of TSA afford an exceedingly desirable approach to produce cost‐effective, high‐quality EG growth on SiC for diverse emerging application scenarios. [ABSTRACT FROM AUTHOR]

Synthesis of formate from hydrogenation of carbon dioxide (CO2) is an atom‐economic reaction but is confronted with challenges in developing high‐performance non‐precious metal catalysts for application of the process. Herein, we report a highly durable edge‐rich molybdenum disulfide (MoS2) catalyst for CO2 hydrogenation to formate at 200 °C, which delivers a high selectivity of over 99 % with a superior turnover frequency of 780.7 h−1 surpassing those of previously reported non‐precious metal catalysts. Multiple experimental characterization techniques combined with theoretical calculations reveal that sulfur vacancies at MoS2 edges are the active sites and the selective production of formate is enabled via a completely new water‐mediated hydrogenation mechanism, in which surface OH* and H* species in dynamic equilibrium with water serve as moderate hydrogenating agents for CO2 with residual O* reduced by hydrogen. This study provides a new route for developing low‐cost high‐performance catalysts for CO2 hydrogenation to formate. [ABSTRACT FROM AUTHOR]

Synthesis of formate from hydrogenation of carbon dioxide (CO2) is an atom‐economic reaction but is confronted with challenges in developing high‐performance non‐precious metal catalysts for application of the process. Herein, we report a highly durable edge‐rich molybdenum disulfide (MoS2) catalyst for CO2 hydrogenation to formate at 200 °C, which delivers a high selectivity of over 99 % with a superior turnover frequency of 780.7 h−1 surpassing those of previously reported non‐precious metal catalysts. Multiple experimental characterization techniques combined with theoretical calculations reveal that sulfur vacancies at MoS2 edges are the active sites and the selective production of formate is enabled via a completely new water‐mediated hydrogenation mechanism, in which surface OH* and H* species in dynamic equilibrium with water serve as moderate hydrogenating agents for CO2 with residual O* reduced by hydrogen. This study provides a new route for developing low‐cost high‐performance catalysts for CO2 hydrogenation to formate. [ABSTRACT FROM AUTHOR]

Au-n-octanedithiol-Au molecular junction (Au-SC8S-Au) has been investigated using density functional theory combined with the nonequilibrium Green's function approach. Theoretically calculated results are used to build the relationship between the interface binding structures and single-molecule quantum conductance of n-octanedithiol (SC8S) embodied in a gold nanogap with or without stretching forces. To understand the electron transport mechanism in the single molecular nanojunction, we designed three types of Au-SC8S-Au nanogaps, including flat electrode through an Au atom connecting (Model I), top-pyramidal or flat electrodes with the molecule adsorbing directly (Model II), and top-pyramidal Au electrodes with Au atomic chains (Model III). We first determined the optimized structures of different Au-SC8S-Au nanogaps, and then predicted the distance-dependent stretching force and conductance in each case. Our calculated results show that in the Model I with an Au atom bridging the flat Au (111) gold electrodes and the SC8S molecule, the conductance decreases exponentially before the fracture of Au–Au bond, in a good agreement with the experimental conductance in the literature. For the top-pyramidal electrode Models II and III, the magnitudes of molecular conductance are larger than that in Model I. Our theoretical calculations also show that the Au–Au bond fracture takes place in Models I and III, while the Au–S bond fracture appears in Model II. This is explained due to the total strength of three synergetic Au–Au bonds stronger than an Au–S bond in Model II. This is supported from the broken force about 2 nN for the Au–Au bond and 3 nN for the Au–S bond. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) and related spectroscopies are powered primarily by the concentration of the electromagnetic (EM) fields associated with light in or near appropriately nanostructured electrically-conducting materials, most prominently, but not exclusively high-conductivity metals such as silver and gold. This field concentration takes place on account of the excitation of surface-plasmon (SP) resonances in the nanostructured conductor. Optimizing nanostructures for SERS, therefore, implies optimizing the ability of plasmonic nanostructures to concentrate EM optical fields at locations where molecules of interest reside, and to enhance the radiation efficiency of the oscillating dipoles associated with these molecules and nanostructures. This review summarizes the development of theories over the past four decades pertinent to SERS, especially those contributing to our current understanding of SP-related SERS. Special emphasis is given to the salient strategies and theoretical approaches for optimizing nanostructures with hotspots as efficient EM near-field concentrating and far-field radiating substrates for SERS. A simple model is described in terms of which the upper limit of the SERS enhancement can be estimated. Several experimental strategies that may allow one to approach, or possibly exceed this limit, such as cascading the enhancement of the local and radiated EM field by the multiscale EM coupling of hierarchical structures, and generating hotspots by hybridizing an antenna mode with a plasmonic waveguide cavity mode, which would result in an increased local field enhancement, are discussed. Aiming to significantly broaden the application of SERS to other fields, and especially to material science, we consider hybrid structures of plasmonic nanostructures and other material phases and strategies for producing strong local EM fields at desired locations in such hybrid structures. In this vein, we consider some of the numerical strategies for simulating the optical properties and consequential SERS performance of particle-on-substrate systems that might guide the design of SERS-active systems. Finally, some current theoretical attempts are briefly discussed for unifying EM and non-EM contribution to SERS. [ABSTRACT FROM AUTHOR]

Photocatalytic or photoelectrocatalytic nitrogen fixation is considered as a very promising way to reduce energy requirements. Here, V o -BiOBr/TiO 2 nanocomposite photoelectrode was constructed by modifying TiO 2 nanotube arrays with BiOBr nanosheets with oxygen vacancies (V o) for photoelectrocatalytic nitrogen fixation. The oxygen vacancy promotes the adsorption and activation of N 2 on the catalyst surface. The Lewis basicity of nitrogen is enhanced by transferring the photogenerated electrons on the conduction band of BiOBr to the π anti-bonding orbit of N 2 , which is more beneficial for the addition of protons. On the other hand, the heterojunction between TiO 2 and V o -BiOBr facilitates the separation of photogenerated carriers. The photogenerated holes on the valence band of TiO 2 travelled to the counter electrode to produce oxygen at a negative potential, avoiding the further oxidation of NH 3. V o -BiOBr/TiO 2 displays a high NH 3 production rate of 25.08 μg h−1 cm−2 at −0.2 V which is 3.3 times higher than that of BiOBr/TiO 2. The synergistic effect between TiO 2 and V o -BiOBr results in enhanced light absorption and higher photoelectrocatalytic efficiency for the N 2 reduction reaction. Heterostructured V o -BiOBr/TiO 2 nanotube arrays shows remarkable NRR activity with an NH 3 yield of 25.08 μg h−1 cm−2 and the oxygen vacancies in BiOBr play an important role in promoting the N 2 adsorption and activation. [Display omitted] • Heterostructured V o -BiOBr/TiO 2 nanotube arrays is constructed. • The oxygen vacancies in BiOBr promote the N 2 adsorption and activation. • The NH 3 production rate of 25.08 μg h−1 cm−2 is achieved over V o -BiOBr at −0.2 V. • V o -BiOBr/TiO 2 shows high photoelectrocatalytic fixation nitrogen stability. [ABSTRACT FROM AUTHOR]

Heterogeneous Catalysis. In their Communication (e202405379), Jun Cheng et al. use machine learning molecular dynamics to demonstrate anomalous entropic effect on catalysis via surface pre‐melting of nanoclusters...By Fu‐Qiang Gong; Yun‐Pei Liu; Ye Wang; Weinan E; Zhong‐Qun Tian and Jun ChengReported by Author; Author; Author; Author; Author; Author [Extracted from the article]

Precise control and accurate understanding of the ordering degree of bimetallic nanocatalysts (BNs) are challenging yet crucial to acquire advanced materials for the oxygen reduction reaction (ORR). AuCu BNs with various ordering degrees were synthesized to evaluate the influence of ordering degree on the ORR at a molecular level using in situ Raman spectroscopy. The activity of AuCu BNs was improved by over 2 times after a disorder‐to‐order transition, making the performance of highly ordered AuCu BNs exceed that of benchmark Pt/C. Direct Raman spectroscopic evidence of key intermediate (*OH) demonstrates that the active site is the combination site of Au and Cu. Moreover, two distinct *OH species are observed on the ordered and disordered structure, and the ordered site is more beneficial for ORR due to its lower affinity to *OH. This work deepens the understanding on the important role of ordering degree on BNs and enables the design of improved catalysts. [ABSTRACT FROM AUTHOR]

Precise control and accurate understanding of the ordering degree of bimetallic nanocatalysts (BNs) are challenging yet crucial to acquire advanced materials for the oxygen reduction reaction (ORR). AuCu BNs with various ordering degrees were synthesized to evaluate the influence of ordering degree on the ORR at a molecular level using in situ Raman spectroscopy. The activity of AuCu BNs was improved by over 2 times after a disorder‐to‐order transition, making the performance of highly ordered AuCu BNs exceed that of benchmark Pt/C. Direct Raman spectroscopic evidence of key intermediate (*OH) demonstrates that the active site is the combination site of Au and Cu. Moreover, two distinct *OH species are observed on the ordered and disordered structure, and the ordered site is more beneficial for ORR due to its lower affinity to *OH. This work deepens the understanding on the important role of ordering degree on BNs and enables the design of improved catalysts. [ABSTRACT FROM AUTHOR]

Abstract: Silver-7, 7, 8, 8-tetracyanoquinodimethane (AgTCNQ) microrods are synthesized through the photoelectrochemical catalysis of TiO2 nanoparticles. When illuminated by UV light, Ag nanoclusters deposit on TiO2 nanoparticles dispersed in the AgNO3/alcohol solution. When illuminated by visible light, the metallic Ag on TiO2 nanoparticles will dissolve in the solution as Ag+ while the released electron will be accepted by TCNQ to form TCNQ−. Consequently, AgTCNQ microrods are obtained through a photoinduced bipolar mechanism, which is valuable in the chemical synthesis involving cooperative effect or coupling processes. [Copyright &y& Elsevier]

As important irradiation defects, helium bubbles will threaten the stability and reliability of reactor structural materials. Extensive research has been conducted on the dynamic response of helium bubbles under thermal annealing, irradiation, or tension, but the behavior and mechanisms of helium bubble evolution under compression remain to be understood. Here, by adopting in-situ cyclic nanocompression testing on Fe9Cr1.5W0.4Si F/M steel containing helium bubbles at 673 K, we present direct experimental evidence for the shrinkage and coalescence behavior of helium bubbles under the coupling effect of compression stress and temperature for the first time. Unlike the stress-free condition where the bubble size shows an increasing trend, compressive stress causes the bubble to shrink. Moreover, the large-sized bubbles show a greater change in size than small-sized bubbles. At 673 K, there is no thermal motion of the bubbles in F/M steel, and it is the deformation and mutual squeezing of bubbles under compression that causes the coalescence of tightly arranged bubbles. Furthermore, helium bubbles can act as dislocation sources to emit dislocations under compression, and the emitted dislocations can in turn envelope around the helium bubbles, thus hindering bubble coalescence and leading to the formation of deformed bubbles. [ABSTRACT FROM AUTHOR]

Plasmonic metals under photoexcitation can generate energetic hot electrons to directly induce chemical reactions. However, the capability and fundamental insights of the transportation of these hot electrons at plasmonic metal‐2D material interfaces remain unclear. Herein, hot‐electron transfer at Au‐graphene interfaces has been in situ studied using surface‐enhanced Raman spectroscopy (SERS) with atomic layer accuracy. Combining in situ SERS studies with density functional theory calculations, it is proved that hot electrons can be injected from plasmonic Au nanoparticles to graphene and directly penetrate graphene to trigger photocatalytic reactions. With increasing graphene layers, the transportation of hot electrons decays rapidly and would be completely blocked after five layers of graphene. Moreover, the transfer of hot electrons can be modulated by applying an external electric field, and the hot‐electron transfer efficiency under electrochemical conditions is improved by over three times in the presence of a monolayer of graphene. [ABSTRACT FROM AUTHOR]

Plasmonic metals under photoexcitation can generate energetic hot electrons to directly induce chemical reactions. However, the capability and fundamental insights of the transportation of these hot electrons at plasmonic metal‐2D material interfaces remain unclear. Herein, hot‐electron transfer at Au‐graphene interfaces has been in situ studied using surface‐enhanced Raman spectroscopy (SERS) with atomic layer accuracy. Combining in situ SERS studies with density functional theory calculations, it is proved that hot electrons can be injected from plasmonic Au nanoparticles to graphene and directly penetrate graphene to trigger photocatalytic reactions. With increasing graphene layers, the transportation of hot electrons decays rapidly and would be completely blocked after five layers of graphene. Moreover, the transfer of hot electrons can be modulated by applying an external electric field, and the hot‐electron transfer efficiency under electrochemical conditions is improved by over three times in the presence of a monolayer of graphene. [ABSTRACT FROM AUTHOR]

With a combined molecular dynamics simulation and first-principles calculations, we have investigated a metal surface immersed in aqueous solution at room temperature using a Pt(111) electrode as an example. With the inclusion of thermal average effects at room temperature, the calculated averaged work function is found to be in good agreement with the experimental measurements. The electron redistribution at the interface of the topmost Pt( 111) slab layer and the first water layer plays an important role in controlling the work function. A broad distribution of calculated work functions caused by the thermal motions of the dipolar solvents is obtained from statistical sampling, which implies that the chemical reactivity of a metal electrode in aqueous solution is a dynamic property at least in the nanoscale. Such a microscopic understanding helps to understand the behavior of complex electrochemical double layers. [ABSTRACT FROM AUTHOR]

Since the mid-1990s good quality surface-enhanced Raman spectra have been obtained from many transition metal (TM) electrodes. It has been observed quite often that SERS band intensities, i.e., the relative intensities of different vibrational modes, of the adsorbate are very sensitive to the nature of the metal. Since transition metals interact with adsorbed molecules much more strongly than the typical SERS substrates, i.e., Au, Ag, and Cu, it is desirable to give a detailed and quantitative explanation of the spectroscopic behavior on TM electrodes. In the present study, a hybrid density functional approach with 6-311+G/LanL2DZ basis sets and the B3LYP nonlocal exchange-correlation functionals has been used for the Raman intensity analysis on totally symmetric modes of pyridine adsorbed at transition metal electrodes, e.g., iron, cobalt, nickel, palladium, and platinum. Among all studied metal electrodes, iron and cobalt are predicted to be the most effective SERS substrates involving chemical enhancement, a result in good agreement with the experiments. The chemical bonding enhancement plays a role in pyridine interaction with the transition metal electrodes. The charge transfer enhancement as the most common chemical mechanism is also discussed for comparison. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au@RuO x core–shell nanostructures are fabricated to amplify the Raman signals. • Electroreduction of RuO x is in-situ studied using the borrowing SERS strategy. • Direct evidences of OH intermediate are obtained during RuO x electroreduction. • A two-step molecular pathway is proposed for RuO 2 electroreduction. RuO 2 is one of the most promising catalysts for oxygen evolution reaction (OER), a key reaction in water electrolysis. However, the fundamental insights about the structural evolution of RuO 2 under different electrochemical environments remain unclear. Herein, the molecular reaction pathways of the electroreduction of RuO x in alkaline and neutral conditions are identified using in-situ electrochemical surface-enhanced Raman spectroscopy. Au@RuO 2 core–shell nanostructures are fabricated to amplify the Raman signals of species adsorbed on RuO x surfaces. Using such core–shell nanostructures, direct spectroscopic evidences of OH intermediate during the RuO 2 electroreduction process are obtained, which is further confirmed by D 2 O isotopic substitution experiments. A molecular pathway that RuO 2 is reduced to Ru through a two-step reduction process has been proposed. This work provides insightful information on the structural evolution of RuO x with electrochemical environments. [ABSTRACT FROM AUTHOR]

Developing advanced characterization techniques for single‐atom catalysts (SACs) is of great significance to identify their structural and catalytic properties. Raman spectroscopy can provide molecular structure information, and thus, the technique is a promising tool for catalysis. However, its application in SACs remains a great challenge because of its low sensitivity. We develop a highly sensitive strategy that achieves the characterization of the structure of SACs and in situ monitoring of the catalytic reaction processes on them by shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) for the first time. Using the strategy, Pd SACs on different supports were identified by Raman spectroscopy and the nucleation process of Pd species from single atoms to nanoparticles was revealed. Moreover, the catalytic reaction processes of the hydrogenation of nitro compounds on Pd SACs were monitored in situ, and molecular insights were obtained to uncover the unique catalytic properties of SACs. This work provides a new spectroscopic tool for the in situ study of SACs, especially at solid–liquid interfaces. [ABSTRACT FROM AUTHOR]

Developing advanced characterization techniques for single‐atom catalysts (SACs) is of great significance to identify their structural and catalytic properties. Raman spectroscopy can provide molecular structure information, and thus, the technique is a promising tool for catalysis. However, its application in SACs remains a great challenge because of its low sensitivity. We develop a highly sensitive strategy that achieves the characterization of the structure of SACs and in situ monitoring of the catalytic reaction processes on them by shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) for the first time. Using the strategy, Pd SACs on different supports were identified by Raman spectroscopy and the nucleation process of Pd species from single atoms to nanoparticles was revealed. Moreover, the catalytic reaction processes of the hydrogenation of nitro compounds on Pd SACs were monitored in situ, and molecular insights were obtained to uncover the unique catalytic properties of SACs. This work provides a new spectroscopic tool for the in situ study of SACs, especially at solid–liquid interfaces. [ABSTRACT FROM AUTHOR]

Surface enhanced Raman spectroscopy (SERS) is a non‐destructive, highly sensitive, and rapid analytical tool, which has been widely used in different fields, especially for trace quantities of analyte. However, using SERS for reliable quantitative sample analysis is still a great challenge. Herein, a new approach to quantitative SERS analysis at nanostructured substrates that does not require an internal standard or well‐ordered nanostructured SERS substrates is developed. This method is based on the kinetics of chemisorption, that is, on a homogeneous surface, the time taken for adsorption of an adsorbate (adenine or melamine) to reach equilibrium negatively correlates with the concentration of the adsorbate. Quantitative analysis is achieved by using in situ SERS to acquire the adsorption profile of the adsorbate and enabling the adsorption equilibrium time to be calculated. There is excellent correlation between the adenine and melamine SERS response over adsorption equilibrium time with concentration, and the correlation coefficients are 0.9906 and 0.9682, respectively. Moreover, milk sample spiked with the melamine is also studied, and the standard recovery rate is 106%. This work demonstrates a novel, non‐destructive, and cost‐effective quantitative SERS detection technique, which can broaden applications across multiple fields. [ABSTRACT FROM AUTHOR]

Molecular electronics is a promising subject to overcome the size limitation of silicon‐based electronic devices. In the past decades, various micro/nanofabrication techniques have been developed for constructing molecular junctions, and a number of breakthroughs are made in the characterizations and applications of the single‐molecule device. The history and progress are reviewed in this article, laying emphasis on the recent works on the combination of micro/nanofabrication techniques with other techniques such as electrochemical deposition and surface‐enhanced Raman spectroscopy (SERS). Some prototypical single‐molecule devices such as molecular transistors are presented. Finally, the challenges and prospects in the fabrication of single‐molecule devices are discussed. [ABSTRACT FROM AUTHOR]

Elucidating hydrogen oxidation reaction (HOR) mechanisms in alkaline conditions is vital for understanding and improving the efficiency of anion‐exchange‐membrane fuel cells. However, uncertainty remains around the alkaline HOR mechanism owing to a lack of direct in situ evidence of intermediates. In this study, in situ electrochemical surface‐enhanced Raman spectroscopy (SERS) and DFT were used to study HOR processes on PtNi alloy and Pt surfaces, respectively. Spectroscopic evidence indicates that adsorbed hydroxy species (OHad) were directly involved in HOR processes in alkaline conditions on the PtNi alloy surface. However, OHad species were not observed on the Pt surface during the HOR. We show that Ni doping promoted hydroxy adsorption on the platinum‐alloy catalytic surface, improving the HOR activity. DFT calculations also suggest that the free energy was decreased by hydroxy adsorption. Consequently, tuning OH adsorption by designing bifunctional catalysts is an efficient method for promoting HOR activity. [ABSTRACT FROM AUTHOR]

Elucidating hydrogen oxidation reaction (HOR) mechanisms in alkaline conditions is vital for understanding and improving the efficiency of anion‐exchange‐membrane fuel cells. However, uncertainty remains around the alkaline HOR mechanism owing to a lack of direct in situ evidence of intermediates. In this study, in situ electrochemical surface‐enhanced Raman spectroscopy (SERS) and DFT were used to study HOR processes on PtNi alloy and Pt surfaces, respectively. Spectroscopic evidence indicates that adsorbed hydroxy species (OHad) were directly involved in HOR processes in alkaline conditions on the PtNi alloy surface. However, OHad species were not observed on the Pt surface during the HOR. We show that Ni doping promoted hydroxy adsorption on the platinum‐alloy catalytic surface, improving the HOR activity. DFT calculations also suggest that the free energy was decreased by hydroxy adsorption. Consequently, tuning OH adsorption by designing bifunctional catalysts is an efficient method for promoting HOR activity. [ABSTRACT FROM AUTHOR]

The surface‐enhanced Raman scattering (SERS) effect was discovered by Richard Van Duyne et al. in 1977. He and coworkers also first utilized an innovative strategy that used SERS to record spectra on such SERS‐inactive substrate surfaces as n‐gallium arsenide (100) surfaces, which were modified by silver nano‐islands. This nanostructure‐enhanced Raman spectroscopy on flat surfaces (NERSoFS) enabled such SERS applications to be expanded to a variety of materials by virtue of SERS‐active nanostructures such as Au or Ag nanoparticles and shell‐isolated nanoparticles. However, most of such systems, although yielding Raman spectra, produce rather low enhancements, especially when used to record spectra on flat surfaces of SERS‐inactive materials. In this work, along with the direction of Van Duyne's borrowing‐SERS strategy and on the basis of the strategy of cascading optical coupling, we consider a theoretically designed optical configuration, based on an attenuated total reflection‐cascading nanostructure to produce enhanced Raman spectroscopy (ATRc‐NERS) on flat surfaces. This system can effectively harvest the incident light, thereby boosting the local optical field of the incident light and also moderately increasing the radiation field of the Raman‐scattered signals. In this way, one can gain 1–2 additional orders of magnitude in Raman enhancement over present NERSoFS systems both on metallic and nonmetallic flat surfaces, which are otherwise SERS‐inactive. This ATRc‐NERS strategy can potentially be used to develop ultrasensitive and versatile tools for surface science, material science, catalysis, electrochemistry, and micro‐electronics and micro‐LED industries. [ABSTRACT FROM AUTHOR]

Surface‐enhanced Raman spectroscopy (SERS) is a powerful surface analytical technique; however, its lack of material and morphological generality is a longtime limitation. The invention of shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) using silica shell‐encapsulated Au nanoparticles (NPs) overcomes these problems. Whereas, it is difficult to obtain a silica shell (less than 1 nm thick) without pinholes for generating extremely high SERS enhancements. Graphene is one of the most promising two‐dimensional materials, which has a single‐atom layer thickness. Moreover, graphene can provide additional SERS chemical enhancement. Herein, we prepared graphene‐coated Au (Au@G) NPs via chemical vapor deposition (CVD). The graphene shell thickness could be controlled from a few layers to multilayers, and the Au@G SERS activities were characterized using mercaptobenzoic acid (MBA) as a probe molecule. Both the pH and high‐temperature stabilities of the Au@G nanoparticles were characterized. Also, Pt‐on‐Au@G satellite structures were developed via a self‐assembly method. Whereby Au@G nanoparticles were coated with Pt nanocatalysts, and this bifunctional SERS substrate could be used to monitor in situ catalytic reaction mechanisms occurring on the Pt surface. [ABSTRACT FROM AUTHOR]

Keywords: Carbon Dioxide Conversion; Heterogeneous Catalysis; Materials Science; Reaction Mechanisms; Reduction EN Carbon Dioxide Conversion Heterogeneous Catalysis Materials Science Reaction Mechanisms Reduction 1 1 1 10/31/23 20231106 NES 231106 B CO SB 2 sb hydrogenation to formate b is an attractive route for the utilization of this greenhouse gas. Comprehensive mechanism studies reveal that selective production of formate is enabled at MoS SB 2 sb edge sulfur vacancies via a new water-mediated hydrogenation mechanism. Carbon Dioxide Conversion, Heterogeneous Catalysis, Materials Science, Reaction Mechanisms, Reduction. [Extracted from the article]

Keywords: Carbon Dioxide Conversion; Heterogeneous Catalysis; Materials Science; Reaction Mechanisms; Reduction EN Carbon Dioxide Conversion Heterogeneous Catalysis Materials Science Reaction Mechanisms Reduction 1 1 1 10/31/23 20231106 NES 231106 B Sn-based perovskite oxides b have shown intriguing potential in CO SB 2 sb electroreduction. Carbon Dioxide Conversion, Heterogeneous Catalysis, Materials Science, Reaction Mechanisms, Reduction In their Research Article (e202307086), Jiawei Zhu and co-workers report an effective strategy to promote CO SB 2 sb -to-HCOOH conversion of Sn-based perovskite oxides by A-site-radius-controlled Sn-O bond lengths. [Extracted from the article]

As energy demands increase, electrocatalysis serves as a vital tool in energy conversion. Elucidating electrocatalytic mechanisms using in situ spectroscopic characterization techniques can provide experimental guidance for preparing high-efficiency electrocatalysts. Surface-enhanced Raman spectroscopy (SERS) can provide rich spectral information for ultratrace surface species and is extremely well suited to studying their activity. To improve the material and morphological universalities, researchers have employed different kinds of nanostructures that have played important roles in the development of SERS technologies. Different strategies, such as so-called borrowing enhancement from shell-isolated modes and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS)-satellite structures, have been proposed to obtain highly effective Raman enhancement, and these methods make it possible to apply SERS to various electrocatalytic systems. Here, we discuss the development of SERS technology, focusing on its applications in different electrocatalytic reactions (such as oxygen reduction reactions) and at different nanostructure surfaces, and give a brief outlook on its development. [ABSTRACT FROM AUTHOR]

The adsorption and electrooxidation of CO molecules at well‐defined Pt(hkl) single‐crystal electrode surfaces is a key step towards addressing catalyst poisoning mechanisms in fuel cells. Herein, we employed in situ electrochemical shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) coupled with theoretical calculation to investigate CO electrooxidation on Pt(hkl) surfaces in acidic solution. We obtained the Raman signal of top‐ and bridge‐site adsorbed CO* molecules on Pt(111) and Pt(100). In contrast, on Pt(110) surfaces only top‐site adsorbed CO* was detected during the entire electrooxidation process. Direct spectroscopic evidence for OH* and COOH* species forming on Pt(100) and Pt(111) surfaces was afforded and confirmed subsequently via isotope substitution experiments and DFT calculations. In summary, the formation and adsorption of OH* and COOH* species plays a vital role in expediting the electrooxidation process, which relates with the pre‐oxidation peak of CO electrooxidation. This work deepens knowledge of the CO electrooxidation process and provides new perspectives for the design of anti‐poisoning and highly effective catalysts. [ABSTRACT FROM AUTHOR]

The adsorption and electrooxidation of CO molecules at well‐defined Pt(hkl) single‐crystal electrode surfaces is a key step towards addressing catalyst poisoning mechanisms in fuel cells. Herein, we employed in situ electrochemical shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) coupled with theoretical calculation to investigate CO electrooxidation on Pt(hkl) surfaces in acidic solution. We obtained the Raman signal of top‐ and bridge‐site adsorbed CO* molecules on Pt(111) and Pt(100). In contrast, on Pt(110) surfaces only top‐site adsorbed CO* was detected during the entire electrooxidation process. Direct spectroscopic evidence for OH* and COOH* species forming on Pt(100) and Pt(111) surfaces was afforded and confirmed subsequently via isotope substitution experiments and DFT calculations. In summary, the formation and adsorption of OH* and COOH* species plays a vital role in expediting the electrooxidation process, which relates with the pre‐oxidation peak of CO electrooxidation. This work deepens knowledge of the CO electrooxidation process and provides new perspectives for the design of anti‐poisoning and highly effective catalysts. [ABSTRACT FROM AUTHOR]

Scanning electrochemical microscopy (SECM) is one of the most important instrumental methods of modern electrochemistry due to its high spatial and temporal resolution. We introduced SECM into nanomachining by feeding the electrochemical modulations of the tip electrode back to the positioning system, and we demonstrated that SECM is a versatile nanomachining technique on semiconductor wafers using electrochemically induced chemical etching. The removal profile was correlated to the applied tip current when the tip was held stationary and when it was moving slowly (<20 μm s−1), and it followed Faraday's law. Both regular and irregular nanopatterns were translated into a spatially distributed current by the homemade digitally controlled SECM instrument. The desired nanopatterns were "sculpted" directly on a semiconductor wafer by SECM direct‐writing mode. The machining accuracy was controlled to the sub‐micrometer and even nanometer scales. This advance is expected to play an important role in electrochemical nanomachining for 3D micro/nanostructures in the semiconductor industry. [ABSTRACT FROM AUTHOR]

Scanning electrochemical microscopy (SECM) is one of the most important instrumental methods of modern electrochemistry due to its high spatial and temporal resolution. We introduced SECM into nanomachining by feeding the electrochemical modulations of the tip electrode back to the positioning system, and we demonstrated that SECM is a versatile nanomachining technique on semiconductor wafers using electrochemically induced chemical etching. The removal profile was correlated to the applied tip current when the tip was held stationary and when it was moving slowly (<20 μm s−1), and it followed Faraday's law. Both regular and irregular nanopatterns were translated into a spatially distributed current by the homemade digitally controlled SECM instrument. The desired nanopatterns were "sculpted" directly on a semiconductor wafer by SECM direct‐writing mode. The machining accuracy was controlled to the sub‐micrometer and even nanometer scales. This advance is expected to play an important role in electrochemical nanomachining for 3D micro/nanostructures in the semiconductor industry. [ABSTRACT FROM AUTHOR]

Nanostructure-based surface-enhanced infrared absorption (SEIRA) spectroscopy has attracted tremendous interest as an ultrasensitive detection tool that supplies chemical-fingerprint information. The interactions between molecular vibrations and plasmons lead to not only the enhancement of spectral intensity, but also the distortion of spectral Lorentzian lineshapes into asymmetric Fano-type or more complicated lineshapes in the SEIRA spectra; this effect hampers the correct readout of vibrational frequencies and intensities for an accurate interpretation of the measured spectra and quantitative analysis. In this work, we investigate the Fano interference between molecular vibrations and plasmons based on exact electrodynamic simulations and theoretical models. We report that, even if the molecular vibrational energy is equal to the plasmon resonant energy, the molecule–nanostructure distance-dependent dipole–dipole interactions, the plasmon-mediated coherent intermolecular interactions and the decay rates of plasmons have a significant impact on the SEIRA lineshapes. This study paves the way for controllable Fano interference at the nanoscale and more studies on plasmon-dressed molecular electronic or vibrational excited states. [ABSTRACT FROM AUTHOR]

The spillover of hydrogen species and its role in tuning the activity and selectivity in catalytic hydrogenation have been investigated in situ using surface‐enhanced Raman spectroscopy (SERS) with 10 nm spatial resolution through the precise fabrication of Au/TiO2/Pt sandwich nanostructures. In situ SERS study reveals that hydrogen species can efficiently spillover at Pt‐TiO2‐Au interfaces, and the ultimate spillover distance on TiO2 is about 50 nm. Combining kinetic isotope experiments and density functional theory calculations, it is found that the hydrogen spillover proceeds via the water‐assisted cleavage and formation of surface hydrogen–oxygen bond. More importantly, the selectivity in the hydrogenation of the nitro or isocyanide group is manipulated by controlling the hydrogen spillover. This work provides molecular insights to deepen the understanding of hydrogen activation and boosts the design of active and selective catalysts for hydrogenation. [ABSTRACT FROM AUTHOR]

The spillover of hydrogen species and its role in tuning the activity and selectivity in catalytic hydrogenation have been investigated in situ using surface‐enhanced Raman spectroscopy (SERS) with 10 nm spatial resolution through the precise fabrication of Au/TiO2/Pt sandwich nanostructures. In situ SERS study reveals that hydrogen species can efficiently spillover at Pt‐TiO2‐Au interfaces, and the ultimate spillover distance on TiO2 is about 50 nm. Combining kinetic isotope experiments and density functional theory calculations, it is found that the hydrogen spillover proceeds via the water‐assisted cleavage and formation of surface hydrogen–oxygen bond. More importantly, the selectivity in the hydrogenation of the nitro or isocyanide group is manipulated by controlling the hydrogen spillover. This work provides molecular insights to deepen the understanding of hydrogen activation and boosts the design of active and selective catalysts for hydrogenation. [ABSTRACT FROM AUTHOR]

Understanding the structure‐activity relationship of catalytic reactions at a molecular level still remains a great challenge. Herein, shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) is employed to in‐situ study the catalytic hydrogenation of para‐nitrothiophenol (pNTP) on Pt‐based nanocatalysts with different size and composition. The nanocatalysts are assembled on pinhole‐free shell‐isolate nanoparticles (SHINs), which work as Raman amplifiers to enhance the Raman signals of species on the catalysts, allowing the in‐situ monitoring of catalytic reactions carried out on the catalysts. Using this strategy, we find that the catalytic activity of the Pt nanocatalysts shows a volcanic trend with the Pt size, and that PtM (M=Ni or Cu) bimetallic nanocatalysts display much higher performance compared with Pt due to better activation of the nitro group. This work demonstrates that SHINERS is a promising technique for in‐situ study of nanocatalysis thus can deepen the understanding of the behaviors of different catalysts. [ABSTRACT FROM AUTHOR]

The interfacial electron transfer capability of Si/SiO2 wafer supported single layer graphene is optimized by thermal annealing in an inert gas environment, which facilitates its applications in both electrochemical and electronic devices. [ABSTRACT FROM AUTHOR]

Deep‐learning‐based spectral identification received intensive interests benefiting from the availability of large scale spectral databases. However, for the identification of spectroscopic data such as Raman, the massive experimental data remained challenging, impeding the application of deep neural networks. Here, we describe a new approach with a transfer‐learning model pretrained on a standard Raman spectral database for the identification of Raman spectra data of organic compounds that are not included in the database and with limited data. Our results show that, with transfer learning, classification accuracy improvement of our convolutional neural network reaches 4.1% and that of our fully connected deep neural network reaches 5.0%. By investigating the influence of the source datasets, we find that our transfer learning method is able to incorporate both relevant and seemingly irrelevant source datasets for pretraining, and the relevant source dataset brings better classification accuracy than that of the seemingly irrelevant source dataset. This study demonstrates that the transfer learning technique has great potential in the effective identification of Raman spectra when the number of Raman data is limited. [ABSTRACT FROM AUTHOR]

Conversion of carbon monoxide to high value‐added ethylene with high selectivity by traditional syngas conversion process is challenging because of the limitation of Anderson‐Schulz–Flory distribution. Herein we report a direct electrocatalytic process for highly selective ethylene production from CO reduction with water over Cu catalysts at room temperature and ambient pressure. An unprecedented 52.7 % Faradaic efficiency of ethylene formation is achieved through optimization of cathode structure to facilitate CO diffusion at the surface of the electrode and Cu catalysts to enhance the C−C bond coupling. The highly selective ethylene production is almost without other carbon‐based byproducts (e.g. C1–C4 hydrocarbons and CO2) and avoids the drawbacks of the traditional Fischer–Tropsch process that always delivers undesired products. This study provides a new and promising strategy for highly selective production of ethylene from the abundant industrial CO. [ABSTRACT FROM AUTHOR]

Conversion of carbon monoxide to high value‐added ethylene with high selectivity by traditional syngas conversion process is challenging because of the limitation of Anderson‐Schulz–Flory distribution. Herein we report a direct electrocatalytic process for highly selective ethylene production from CO reduction with water over Cu catalysts at room temperature and ambient pressure. An unprecedented 52.7 % Faradaic efficiency of ethylene formation is achieved through optimization of cathode structure to facilitate CO diffusion at the surface of the electrode and Cu catalysts to enhance the C−C bond coupling. The highly selective ethylene production is almost without other carbon‐based byproducts (e.g. C1–C4 hydrocarbons and CO2) and avoids the drawbacks of the traditional Fischer–Tropsch process that always delivers undesired products. This study provides a new and promising strategy for highly selective production of ethylene from the abundant industrial CO. [ABSTRACT FROM AUTHOR]

This article seeks to encourage the adoption of modern methods of surface analysis in teaching contexts by introducing the use of attenuated total reflection infrared spectroscopy (ATRIRS) in analysis of adsorption reactions at hydrous metal oxide thin films. The first experiment shows how outer-sphere adsorption of perchlorate ion is distinguished from inner-sphere adsorption of ethanedioate (oxalate) ion at TiO2 surfaces. The second experiment shows how the nature of adsorption of sulfate ion to iron oxide surfaces changes with pH. In the third experiment, the variation of the amount of benzene-1,2-diol (catechol) adsorbed to TiO2 with solution concentration enables an adsorption constant to be derived from the adsorption isotherm. [ABSTRACT FROM AUTHOR]

It is vital to understand the oxygen reduction reaction (ORR) mechanism at the molecular level for the rational design and synthesis of high activity fuel‐cell catalysts. Surface enhanced Raman spectroscopy (SERS) is a powerful technique capable of detecting the bond vibrations of surface species in the low wavenumber range, however, using it to probe practical nanocatalysts remains extremely challenging. Herein, shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) was used to investigate ORR processes on the surface of bimetallic Pt3Co nanocatalyst structures. Direct spectroscopic evidence of *OOH suggests that ORR undergoes an associative mechanism on Pt3Co in both acidic and basic environments. Density functional theory (DFT) calculations show that the weak *O adsorption arise from electronic effect on the Pt3Co surface accounts for enhanced ORR activity. This work shows SHINERS is a promising technique for the real‐time observation of catalytic processes. [ABSTRACT FROM AUTHOR]