Surface Plasmon Enhanced Chemical Reactions on Metal Nanostructures

Noble metal nanomaterials as plasmonic photocatalysts can strongly absorb visible light and generate localized surface plasmon resonance (SPR), which in turn depends on the size, shape, and surrounding of the plasmonic metal nanomaterials (PMNMs). Remarkably, the high-efficiency conversion of solar energy into chemical energy was expected to be achieved by PMNMs. Therefore, researchers have chosen PMNMs to improve the photocatalytic activity toward targeted molecules. This enhancement can be achieved by the effective separation of photogenerated electrons and holes of the PMNMs in the presence of light. Surface-enhanced Raman spectroscopy (SERS) has been performed for obtaining information about the photochemically transformed surface species at molecular levels. A profound understanding of kinetic mechanisms is needed for the development of novel plasmonic catalysts toward various chemical transformations of targeted molecules. In this chapter, based on the above discussions, the participation of SPR excitation in PMNMs and photocatalysis toward chemical transformations of SERS-active organic molecules such as aromatic amino and nitro compounds based on PMNMs have been discussed in detail through theoretical and experimental studies. Eventually, a summary and the future directions of this study are discussed

Hybrid molecular dynamics and first-principles study on the work function of a Pt(111) electrode immersed in aqueous solution at room temperature

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.National Basic Research Program of China [2011CB808505, 2010CB923300, 2009CB930703]; National Natural Science Foundation of China [20620130427, 20925311]; Goran Gustafsson Foundation for Research in Natural Sciences and Medicine; Swedish National Infrastructure for Computing (SNIC

Trans-Anastomotic Drainage Tube Placement After Hand-Sewn Anastomosis in Patients Undergoing Intersphincteric Resection for Low Rectal Cancer: An Alternative Drainage Method

Anastomotic leakage (AL) is a common complication after intersphincteric resection (ISR). It significantly reduces quality of life and causes great distress to patients. Although traditional drainage (e.g., anal and pelvic catheters) may reduce the impact of AL to some extent, their role in reducing the incidence of AL remains controversial. In this study, we developed a novel drainage technique involving the placement of drainage tubes through the gap between sutures during handsewn anastomosis, to reduce the occurrence of anastomotic leakage. We retrospectively analyzed 34 consecutive patients who underwent intersphincteric resection requiring handsewn anastomosis between February 1, 2017, and January 1, 2021. Patients were classified into the trans-anastomotic drainage tube group (TADT, n = 14) and the non-TADT group (n = 20) based on whether trans-anastomotic tube placement was performed. The incidence of postoperative complications, such as AL, was compared between the two groups, and anal function of patients at 1-year post-ISR was evaluated. Six cases of AL occurred in the non-TADT group, while none occurred in the TADT group; this difference was statistically significant (p=0.031). The TADT group also had a shorter hospital stay (p=0.007). There were no other significant intergroup differences in operation time, blood loss, pain score, anastomotic stenosis, intestinal obstruction, or incidence of wound infection. In the 30 patients (88.2%) evaluated for anal function, there were no significant intergroup differences in stool frequency, urgency, daytime/nocturnal soiling, Wexner incontinence score, or Kirwan grading. Taken together, trans-anastomotic tube placement is a novel drainage method that may reduce AL after ISR requiring handsewn anastomosis and without adversely affecting anal function

From plasmon-enhanced molecular spectroscopy to plasmon-mediated chemical reaction

该论文在田中群教授指导下完成，第一作者为iChEM中心2013级博士生战超。 表面等离激元效应可以在时间和空间上实现光子、电子和热能的重新分配。表面等离激元增强分子光谱由于其具有超高的灵敏度在过去四十年里引起了人们的广泛关注并得到快速发展。近年，表面等离激元效应介导的化学反应得到广泛的关注。该综述系统介绍了表面等离激元效应、表面等离激元增强分子光谱和表面等离激元介导化学反应的背景和基础理论，并与传统热化学、光化学和光催化进行对比。通过将表面等离激元介导化学反应与表面等离激元增强分子光谱以及其它反应类型进行比较，归纳出表面等离激元介导化学反应的独特科学内涵，展示了较完整的表面等离激元介导化学反应的物理化学图像。系统深入地分析了表面等离激元介导化学反应的特色和优势、影响因素及其之间的关联性，进而讨论高效利用表面等离激元来介导化学反应的策略，并对该领域做了展望。【Abstract】The excitation of surface plasmons (SPs), collective oscillation of conduction electrons in nanostructures, can redistribute photon, electron and heat energy in time and space. Making use of this ability, plasmon-enhanced molecular spectroscopies (PEMS) with ultra-high sensitivity and surface selectivity have attracted much attention and developed significantly in the past four decades. Recently, SPs have impacted the discipline of chemistry, through plasmon-mediated chemical reactions (PMCR). PMCR exhibit some obvious differences from, and potential advantages over traditional thermal-chemistry, photo-chemistry and photo-catalysis. Our physicochemical understanding of PMCR is still far from complete. In this review, we analyze the common ground and distinctive features of PEMS and PMCR; comparing as well, PMCR and traditional photo-chemical and thermal-chemical reactions. We then discuss how to advance PMCR by rationally designing and fabricating plasmonic nanostructures, selecting suitable surface/interface mediators and teaming them synergistically.We are deeply grateful to M. Moskovits for his very helpful suggestions and careful academic and English editing throughout the manuscript. This work is financially supported by the National Natural Science Foundation of China (21533006, 21621091, 91427304 and 21403180) and the Ministry of Science and Technology of China (2015CB932300). 研究工作得到国家自然科学基金委(21533006、21621091、91427304）和科技部重大科学研究计划（2015CB932300）的支持

Plasmon-Mediated Chemical Reactions on Nanostructures Unveiled by Surface-Enhanced Raman Spectroscopy.

Surface plasmons (SPs) originating from the collective oscillation of conduction electrons in nanostructured metals (Au, Ag, Cu, etc.) can redistribute not only the electromagnetic fields but also the excited carriers (electrons and holes) and heat energy in time and space. Therefore, SPs can engage in a variety of processes, such as molecular spectroscopy and chemical reaction. Recently, plenty of demonstrations have made plasmon-mediated chemical reactions (PMCRs) a very active research field and make it as a promising approach to facilitate light-driven chemical reactions under mild conditions. Concurrently, making use of the same SPs, surface-enhanced Raman spectroscopy (SERS) with a high surface sensitivity and energy resolution becomes a powerful and commonly used technique for the in situ study of PMCRs. Typically, various effects induced by SPs, including the enhanced electromagnetic field, local heating, excited electrons, and excited holes, can mediate chemical reactions. Herein, we use the para-aminothiophenol (PATP) transformation as an example to elaborate how SERS can be used to study the mechanism of PMCR system combined with theoretical calculations. First, we distinguish the chemical transformation of PATP to 4,4’-dimercaptoazobenzene (DMAB) from the chemical enhancement mechanism of SERS through a series of theoretical and in situ SERS studies. Then, we focus on disentangling the photothermal, hot electrons, and "hot holes" effects in the SPs-induced PATP-to-DMAB conversion. Through varying the key reaction parameters, such as the wavelength and intensity of the incident light, using various core-shell plasmonic nanostructures with different charge transfer properties, we extract the key factors that influence the efficiency and mechanism of this reaction. We confidently prove that the transformation of PATP can occur on account of the oxygen activation induced by the hot electrons or because of the action of hot holes in the absence of oxygen and confirm the critical effect of the interface between the plasmonic nanostructure and reactants. The products of these two process are different. Furthermore, we compare the correlation between PMCRs and SERS, discuss different scenario of PMCRs in situ studied by SERS, and provide some suggestions for the SERS investigation on the PMCRs. Finally, we comment on the mechanism studies on how to distinguish the multieffects of SPs and their influence on the PMCRs, as well as on how to power the chemical reaction and regulate the product selectivity in higher efficiencies

Spectroelectrochemical flow cell with temperature control for investigation of electrocatalytic systems with surface-enhanced Raman spectroscopy

We describe a method for investigating the reaction mechanism of fuel cell systems by designing a spectroelectrochemical cell with functions of temperature and flow control to mimic the reaction condition of fuel cell systems and utilizing Au core Pt shell (Au@Pt) nanoparticles to enhance the Raman signal of the surface species on the surface of electrocatalysts. The cell consists of three parts: a thin-layer spectroelectrochemical reaction chamber with an optical window for Raman measurement, the heating chamber right beneath the reaction chamber, and a long spiral flow channel to preheat the solution to the desired temperature and effectively exchange the solution. The temperature of the solution can be easily controlled from room temperature to 80 degrees C, and the flow rate can be as high as 945 mu l s(-1). The temperature and flow control is demonstrated by monitoring the changes in the cyclic voltammograms and the Raman signals. By synthesizing Au@Pt nanoparticles and assembling them on a Pt substrate, we can significantly enhance the Raman signal of surface species on the Pt shell surface, which allows us to detect strong signal of CO as the dissociative product of formic acid as well as the intermediate species of the oxidation process. The further development and perspectives of using SERS to study the electrocatalytic systems are discussed

Expanding generality of surface-enhanced Raman spectroscopy with borrowing SERS activity strategy

Surface-enhanced Raman scattering (SERS) was discovered three decades ago and has gone through a tortuous pathway to develop into a powerful diagnostic technique. Recently, the lack of substrate, surface and molecular generalities of SERS has been circumvented to a large extent by devising and utilizing various nanostructures by many groups including ours. This article aims to present our recent approaches of utilizing the borrowing SERS activity strategy mainly through constructing two types of nanostructures. The first nanostructure is chemically synthesized Au nanoparticles coated with ultra-thin shells (ca. one to ten atomic layers) of various transition metals, e.g., Pt, Pd, Ni and Co, respectively. Boosted by the long-range effect of the enhanced electromagnetic (EM) field generated by the highly SERS-active Au core, the originally low surface enhancement of the transition metal can be substantially improved giving total enhancement factors up to 10(4)-10(5). It allows us to obtain the Raman spectra of surface water, having small Raman cross-section, on several transition metals for the first time. To expand the surface generality of SERS, tip-enhanced Raman spectroscopy (TERS) has been employed. With TERS, a nanogap can be formed controllably between an atomically flat metal surface and the tip with an optimized shape, within which the enhanced EM field from the tip can be coupled (borrowed) effectively. Therefore, one can obtain surface Raman signals (TERS signals) from adsorbed species at Au(110), Au(111) and, more importantly, Pt(110) surfaces. The enhancement factor achieved on these single crystal surfaces can be up to 106, especially with a very high spatial resolution down to about 14 nm. To fully accomplish the borrowing strategy from different nanostructures and to explain the experimental observations, a three-dimensional finite-difference time-domain method was used to calculate and evaluate the local EM field on the core-shell nanoparticle surfaces and the TERS tips. Finally, prospects and further developments of this valuable strategy are briefly discussed with emphasis on the emerging experimental methodologies

Thermal effects on electronic properties of CO/Pt(111) in water

Ministry of Science and Technology [2009CB930703, 2010CB923300, 2011CB808505]; Natural Science Foundation of China [20973143, 20925311]; Goran Gustafsson Foundation for Research in Natural Sciences and MedicineStructure and adsorption energy of carbon monoxide molecules adsorbed on the Pt(111) surfaces with various CO coverages in water as well as work function of the whole systems at room temperature of 298 K were studied by means of a hybrid method that combines classical molecular dynamics and density functional theory. We found that when the coverage of CO is around half monolayer, i.e. 50%, there is no obvious peak of the oxygen density profile appearing in the first water layer. This result reveals that, in this case, the external force applied to water molecules from the CO/Pt(111) surface almost vanishes as a result of the competitive adsorption between CO and water molecules on the Pt(111) surface. This coverage is also the critical point of the wetting/non-wetting conditions for the CO/Pt(111) surface. Averaged work function and adsorption energy from current simulations are consistent with those of previous studies, which show that thermal average is required for direct comparisons between theoretical predictions and experimental measurements. Meanwhile, the statistical behaviors of work function and adsorption energy at room temperature have also been calculated. The standard errors of the calculated work function for the water-CO/Pt(111) interfaces are around 0.6 eV at all CO coverages, while the standard error decreases from 1.29 to 0.05 eV as the CO coverage increases from 4% to 100% for the calculated adsorption energy. Moreover, the critical points for these electronic properties are the same as those for the wetting/non-wetting conditions. These findings provide a better understanding about the interfacial structure under specific adsorption conditions, which can have important applications on the structure of electric double layers and therefore offer a useful perspective for the design of the electrochemical catalysts

Experimental and Theoretical Study of Surface-Enhanced Raman Spectra of Sulfadiazine Adsorbed on Nanoscale Gold Colloids.

Sulfadiazine, as a class of antibiotics, has been widely used in the world for decades; however, its surface-enhanced Raman spectra (SERS) on gold colloids are obviously different from ordinary Raman spectra in the solid powder and liquid solution. To explore the reasons for such significant differences, we used density functional theory calculations and normal-mode analysis to investigate the effects of the configuration, conformation, protonation, hydrogen-bonding interaction, and adsorption configurations of sulfadiazine on gold clusters to check these different effects on the vibrational assignments. Our calculated results can be summarized as two points. First, the Raman spectra strongly depend on the configuration, conformation, protonation, and hydrogen bonding of sulfadiazine. Second, the wagging vibration displays a significant vibrational frequency shift and a very strong SERS peak responsible for the observed SERS signal when sulfadiazine is adsorbed on gold clusters through the terminal amino group. This is different from another adsorption configuration through two oxygen atoms of the -SO2NH- group on gold clusters. Finally, we further investigate the potential energy surfaces along the wagging vibration and the binding interaction of -NH2 adsorbed on different sites of gold surfaces

Rhodium as a Ubiquitous Substrate for Surface Enhanced Raman Spectroscopy

本文简要介绍了将铑电极用于表面增强拉曼光谱 (SERS)研究的方法 .具有较强活性的铑电极可以通过对电极施加方波电流进行恒电流粗糙获得 .对模型分子吡啶进行的表面拉曼光谱研究表明 ,该电极具有很好的稳定性和可逆性 ,并且其表面增强因子可达 4 0 0 0 .在对铑电极上一氧化碳的氧化过程进行的拉曼光谱研究中同时检测到桥式和线型吸附的C O和Pt C振动的拉曼信号 .本研究表明铑电极可作为多用的SERS基底 ,拉曼光谱可作为界面研究的通用工具 .Raman Spectroscopy is a powerful technique in characterizing the molecular structure at the molecular level. However, only after the discovery of surface enhanced Raman scattering (SERS) effect, has it become one of the most widely used technique in surface sciences. The limitation that only Ag, Au and Cu can produce prominent SERS signal of practical significance, greatly hinders the application of this technique. Recently our group has made great progress in extending SERS to pure transition metal surfaces, such as Pt, Ni, Fe, Co etc [1] . Rh, due to its special application as catalysts in the catalytic or electrochemical reaction has made it one of the most important materials in surface sciences. It will be of great help for understanding the interfacial phenomenon and possibly the SERS mechanisms if we can extend SERS to the Rh surface. However, It has been found that, Rh is very difficult to be roughened since it will grow naturally in air an oxide layer which will retard the further formation of surface oxides. Furthermore, Rh is very easily oxidized to various forms of rhodium oxides as can be found from the phase diagram of Rh [2] . How to select a method to roughen the surface and to extend SERS to Rh seems not an easy task. In our previous study, we found that Rh could not be successfully roughened using controlled?potential roughening procedure as has been used for Pt. In the present study we developed a method to roughen the Rh surface for obtaining strong Raman scattering based on the work of Shibata [3] . It reveals that the etching of Rh is possible by applying a pulse current with a suitable frequency. With the pulse current, we can easily polarize the electrode to a high potential with a high current density, that makes the deep oxidation of Rh surface possible. After the systematic work of our group, we found that an Rh electrode with reasonable good SERS activity could be obtained by applying the current between -30 mA to +50 mA with a frequency ranging between 200 to 800 Hz. The roughened Rh surface presents a quite uniform surface structure. The most important feature is the electrochemical behavior of this kind of electrode is almost the same as that of the smooth surface, see Fig. 1. It can be clearly seen that both cyclic voltammograms present the oxidation of Rh at positive potentials and the hydrogen adsorption/desorption at negative potentials, and at very negative potentials, the hydrogen evolution occurs on the surface. This ensures the Raman spectra obtained is in representative of that from bulk electrodes, which is distinctly different from Ag, Cu and Au surfaces that after roughened in KCl solution, the electrochemical behavior changed dramatically. Using this kind of surface, we selected pyridine as the model molecule to check the applicability of this method for the surface Raman study. The Raman spectra were acquired on a LabRam I spectrometer that has very high detection sensitivity. The solution used was 0.01 mol/L pyridine + 0.1 mol/L NaClO 4. It could be seen from Fig. 2 that the surface Raman signal of pyridine is very strong, with characteristic bands appearing at 1 003 , 1 208 and 1 590 cm -1 respectively. The relative band intensity and the band position is very close to that of Pt electrode while distinctively different from that of noble metal and Fe and Ni electrodes. This indicates a different interaction of pyridine with different transition metal surfaces. This kind of surface shows quite good stability. It is very stable even after a long time exposure in air. Upon very negative or positive potential excursion of the electrode then back to -0.8 V, the pyridine signal reduced to about 20% and 50% that of the freshly prepared Rh surface. One might think that the reversibility of this electrode is not as good as that of the Pt surface. However, before or after each experiment, when it was cleaned in 0.1 mol/L H 2SO 4 solution until reproducible cyclic voltammograms obtained, the pyridine signal can be recovered to about 80% compared with that作者联系地址：厦门大学固体表面物理化学国家重点实验室!化学系福建厦门361005,厦门大学固体表面物理化学国家重点实验室!化学系福建厦门361005,厦门大学固体表面物理化学国家重点实验室!化学系福建厦门361005Author's Address: Dept. of Chem. and State Key Lab for Phys. Chem. of Solid Surfaces, Xiamen Univ., Xiamen 361005, Chin