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Abstract: The adsorption and reorientation behavior of benzonitrile on an electrochemical roughened Pt electrode were studied by surface-enhanced Raman spectroscopy (SERS) over a wide potential range. The results revealed that benzonitrile was adsorbed on the surface in a vertical orientation through the nitrogen atom of CN group in the relative positive potential region (>−0.6V), while the benzonitrile molecule changed its orientation with the negative movement of potential (<−0.8V). In the hydrogen evolution region, the intensity of the Raman bands from the benzene ring and CN group decreased dramatically, and the frequency of CN red-shifted about 160cm−1. It indicated that the benzonitrile was adsorbed on the Pt electrode in a flat orientation by interacting with the electrode surface via CN and/or benzene ring. A schematic model about the adsorption configurations of benzonitrile in different potential regions was proposed. [Copyright &y& Elsevier]

The adsorption behaviour and the formation of a surface complex film of benzotriazole (BTAH) on Cu electrodes have been studied by in situ surface enhanced Raman spectroscopy in acetonitrile solution. A potential-dependent Raman study revealed that the adsorption and film formation process of BTAH involves the formation of a chemisorbed adlayer and a compact polymer film in two different potential regions in the acetonitrile solution. The results showed that BTA− ion can interact with the Cu surface through the two N atoms of the triazole ring to form a surface polymer complex of [Cu(BTA)]n, which suppressed the dissolution and oxidation of Cu effectively. When triphenylphosphine (pph3) was introduced into the solution, the formation of the surface polymer complex film was suppressed due to the formation of soluble . In solution, a complex of Cu with BTA− and pph3 was formed leading to a significant decrease of the surface inhibition efficiency. These two kinds of surface complexes were prepared by the direct electrochemical synthesis technique in similar solutions, and characterized by normal Raman spectroscopy and elemental analysis. The results showed that the final complexes were insoluble [Cu(BTA)]n polymer and CunBTAm(pph3)p complex with low solubility in the acetonitrile solution. [Copyright &y& Elsevier]

Co, Ni, Pt and Pd nano-wire arrays with diameter of about 50 nm were fabricated by means of template synthesis. By alternating current (AC) electrodeposition these metals were filled into channels of anodic aluminum oxide (AAO) film respectively. Nano-electrode arrays having good electric contact with the substrate was also fabricated by employing combined electroless deposition and the AC electrodeposition. Strong surface enhanced Raman scattering (SERS) was observed from both metal nano-wire arrays and nano-electrode arrays after partial removal of the AAO film. The SERS intensity of probe molecules adsorbed at the arrays depends critically on the length of the nano-wire explored at the surface. The experimental results agree well with the corresponding theoretic calculations based on electromagnetic enhancement. The lightning rod effect may play an important role for the enhancement of the Ni nano-rod under the favorable length. It has been shown that metal nano-wire arrays can be developed to a new generation of substrate exhibiting very high SERS activity, especially for transition metals. These well-ordered surface nano-structures can also be served as a proper model for the SERS mechanism study. [Copyright &y& Elsevier]

The dependence of the electrochemical reduction behavior of benzene on Pt and Rh electrodes on the acidity of electrolyte and the electrode potential has been studied by confocal microprobe Raman spectroscopy and electrochemical methods. The results show that benzene can be reduced directly to cyclohexane. The process is found to be significantly influenced by the acidity of the solution, the roughness of the electrode and the entity of the substrates. The catalytic efficiency of Rh electrode was found to be higher than that of Pt electrode. [Copyright &y& Elsevier]

Based on the requirements of the lower detection limit for the low-volume gaseous effluent, we have designed an automatic separation apparatus of krypton (Kr). The principle of the apparatus is based on both the adsorption and desorption mechanism in the traps with the activated carbon particles and gas chromatography with 5A molecular sieves. The separation efficiency and overall recovery rate could be maintained at about (90.4 ± 4.2)% and (24.3 ± 1.3)%. The 85Kr could be radioassayed on a liquid scintillation counter following the automatic separation and loading into the cryogenic count vial. The detection limit based the low-volume of 3 L is about 9.5 Bq m−3, and the expanded relative uncertainties are in the range of 13–18% for typical measurements. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) studies of electrode/solution interfaces are important for understanding electrochemical processes. However, revealing the nature of reactions at well-defined single crystal electrode surfaces, which are SERS-inactive, remains challenging. In this work, shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) was used for the first time to study electrochemical adsorption and hydrogenation reactions at single crystal surfaces in nonaqueous solvents. A roughened Au surface was also studied for comparison. The experimental results show that the hydrogenation of adsorbed p-ethynylaniline (PEAN) on roughened Au electrode surfaces occurred at very negative potentials in methanol because of the catalytic effect of surface plasmon resonance (SPR). However, because “hot electrons” were blocked by the silica shell of Au@SiO 2 nanoparticles and aprotic acetonitrile was an ineffective hydrogen source, surface reactions at Au(111) were inhibited in the systems studied. Density functional theory (DFT) calculations revealed that the PEAN triple bond opened, allowing adsorption in a flat configuration on the Au(111) surface via two carbon atoms. This work provides an advanced understanding of electrochemical interfacial processes at single crystal surfaces in nonaqueous systems. [ABSTRACT FROM AUTHOR]

CuI N-heterocycle thiolate clusters efficiently catalyze the acceptorless dehydrogenation of alcohols at 70 °C. A variety of secondary/primary benzylic, allylic, and aliphatic alcohols are dehydrogenated to the corresponding ketones and aldehydes in high yields of isolated product upon release of H2. This simple catalytic system is involved in the synthesis of imines through the one-pot reaction of alcohols and amines. [ABSTRACT FROM AUTHOR]

Traditional “sandwich” structure immunoassay is mainly based on the self-assembly of “antibody on solid substrate-antigen-antibody with nanotags” architectures, and the sensitivity of this strategy is critically depended on the surface enhanced Raman scattering (SERS) activities and stability of nanotags. Therefore, the rational design and fabrication on the SERS nanotags attracts the common interests to the bio-related detecting and imaging. Herein, silica encapsulated Au with mercaptobenzoic acid (MBA) core-shell nanoparticles (Au-MBA@SiO 2 ) are fabricated instead of the traditional naked Au or Ag nanoparticles for the SERS-based immunoassay on human and mouse IgG antigens. The MBA molecules facilitate the formation of continuous pinhole-free silica shell and are also used as SERS labels. The silica shell is employed to protect MBA labels and to isolate Au core from the ambient solution for blocking the aggregation. This shell also played the similar role to BSA in inhibiting the nonspecific bindings, which allowed the procedures for constructing “sandwich” structures to be simplified. All of these merits of the Au-MBA@SiO 2 brought the high performance in the related immunoassay. Benefiting from the introduction of silica shell to encapsulate MBA labels, the detection sensitivity was improved by about 1– 2 orders of magnitude by comparing with the traditional approach based on naked Au-MBA nanoparticles. This kind of label-embedded core-shell nanoparticles could be developed as the versatile nanotags for the bioanalysis and bioimaging. [ABSTRACT FROM AUTHOR]

A large surface-enhanced Raman scattering (SERS) effect is critically dependent on the gap distance of adjacent nanostructures, i.e., “hot spots”. However, the fabrication of dynamically controllable hot spots still remains a remarkable challenge. In the present study, we employed an external magnetic field to dynamically control the interparticle spacing of a two-dimensional monolayer film of Fe 3 O 4 @Au nanoparticles at a hexane/water interface. SERS measurements were performed to monitor the expansion and shrinkage of the nanoparticles gaps, which produced an obvious effect on SERS activities. The balance between the electrostatic repulsive force, surface tension, and magnetic attractive force allowed observation of the magnetic-field-responsive SERS effect. Upon introduction of an external magnetic field, a very weak SERS signal appeared initially, indicating weak enhancement due to a monolayer film with large interparticle spacing. The SERS intensity reached maximum after 5 s and thereafter remained almost unchanged. The results indicated that the observed variations in SERS intensities were fully reversible after removal of the external magnetic field. The reduction of interparticle spacing in response to a magnetic field resulted in about one order of magnitude of SERS enhancement. The combined use of the monolayer film and external magnetic field could be developed as a strategy to construct hot spots both for practical application of SERS and theoretical simulation of enhancement mechanisms. [ABSTRACT FROM AUTHOR]

The plasmon catalyzed surface reaction has been attracted considerable attention due to its promising application in heterogeneous catalysis. This kind of plasmon catalysis played bilateral roles in driving the unconventional reactions or destructing the surface molecule layer. The acceleration or inhibition on this catalysis is still remained significant challenge. In this paper, monolayer film of Au nanoparticles was fabricated at air/water interface as substrates both for surface enhanced Raman spectroscopy (SERS) and plasmon catalyzed surface reaction. The influence from several issues, involving surfactants, coadsorption species, the solvent and water, were systemically investigated to probe the acceleration and inhibition on the plasmon catalysis reaction. The concentration and molecular weight of surfactant polyvinylpyrrolidone (PVP) exhibited significant influence in the reactive activity for the plasmon catalyzed dimerization of para-nitrothiophenol (PNTP) to p,p′-dimercaptoazobenzene (DMAB). A suitable molecular weight of 10,000 and concentration of 10 mg/mL were beneficial for improving the conversion efficiency of PNTP to DMAB. The higher molar ratio of coadsorbed 1-octanethiol and the aprotic solvents resulted in the inhibition of dimerization because 1-octanethiol occupied the surface sites to isolate the adsorbed PNTP molecules with a larger distance and lack of proton source. The plasmon catalysis occurred in ionic liquids suggested that water was essential for the dimerization of PNTP, in which it was used to accelerate the reaction rate and severed as the hydrogen source. [ABSTRACT FROM AUTHOR]

Room temperature ionic liquids (RTILs) played an important role in the electrochemistry because of the advantageous properties. Due to the different electrochemical behavior from the dilute solution, it was still remained a significant challenge to obtain the insight into the interfacial structure. Although the spectroelectrochemistry offered the rich spectroscopic information for obtaining the interfacial structure at molecular level, the lack of the spatial information of those techniques at nano/subnanometer scale led the difficulties in the determination of the spatial structure of double layer. Here, the surface enhanced Raman spectroscopy (SERS) Stark tuning rates of CN stretching frequency were employed to determine the electric double layer structure on Au electrode, and probes with different lengths, involving cyanide ion (CN − ), thiocyanate (SCN − ), 3-aminopropanenitrile (3-APN) and 6-aminohexanenitrile (6-AHN), were used as rulers to measure the spatial structure of double layer. In this approach, SERS combined with electrochemical control was performed to distinguish the orientation of surface species and detect the vibrational frequency of the nitrile stretching mode. For shorter probes (such as CN − and SCN − ), the nitrile group were located in the electric double layer region, resulting in measureable Stark tuning rates (d ν CN /d E ), while for longer probe molecules (such as 3-APN and 6-AHN), the interfacial potential completely decayed before reaching the nitrile group location, resulting in the negligible Stark tuning rates. The vibrational Stark tuning rates suggested that the potential drop occurred over a range of 5–6 Å from the metal surface into the bulk phase of ionic liquids. The results demonstrated that the overall potential mostly dropped across the first layer and only a small fraction across the second layer. The preliminary results allowed us to obtain an insight into the physical picture of the interfacial structure of RTILs/metal system. [ABSTRACT FROM AUTHOR]

The surface plasmon resonance (SPR) catalyzed reaction has attracted considerable attention due to its promising application in heterogeneous catalysis. The acquirements on mechanism of the conversion reaction are still in challenge. It was found that the cyclic conversion of para-aminothiophenol (PATP) and 4,4′-dimercaptoazobenzene (DMAB) was critically dependent on the interfacial environments, such as hydrogen, oxygen and water, which were of the fundamental issues in electrochemistry. Here, the in situ surface enhanced Raman spectroscopy (SERS) combined with electrochemical control was developed to investigate the cyclic conversion of PATP and DMAB at the interface of [BMIm]BF 4 /Ag electrode and to probe the interfacial structure of water. The surface-catalyzed coupling reaction of PATP commonly occurred to produce DMAB in a fast rate with the illumination of laser. The results revealed that water played the vital role in the reduction of DMAB. The expected reduction of DMAB was absent in the extremely negative potential due to the lack of the free water at the interface in the “dried” [BMIm]BF 4 . The similar experiments were performed in the [BMIm]BF 4 /H 2 O mixtures with the water molar fraction of 0.01, 0.1, 0.3, 0.5, 0.7 and 0.9 respectively. The trace water in the [BMIm]BF 4 /H 2 O mixture ( x w < 0.1) was mainly mixed with RTILs through the hydrogen bonding between water and RTILs. It hindered the diffusion of trace water to interface which resulted in the absence of the reduction of DMAB. With the increase of water content, the formation of clusters network water allowed the diffusion of water to the interface to facilitate the reduction. The surface reaction behavior was similar to that in the aqueous solution as the interface was completely surrounded by larger water clusters in solutions with high water content ( x w = 0.7–0.9). By this strategy, the electrochemical reduction of DMAB could be served as the probe to monitor the water structure in the [BMIm]BF 4 /H 2 O mixtures, and it was believed that SERS could be developed as the powerful tool for monitoring the interfacial reaction and to resolve the interfacial structure in RTILs, particularly for the water structure. [ABSTRACT FROM AUTHOR]

A new approach was developed for the magnetic separation of copper(II) ions with easy operation and high efficiency. p-Mercaptobenzoic acid served as the modified tag of Fe2O3@Au nanoparticles both for the chelation ligand and Raman reporter. Through the chelation between the copper(II) ions and carboxyl groups on the gold shell, the Fe2O3@Au nanoparticles aggregated to form networks that were enriched and separated from the solution by a magnet. A significant decrease in the concentration of copper(II) ions in the supernatant solution was observed. An extremely sensitive method based on surface-enhanced Raman spectroscopy was employed to detect free copper(II) ions that remained after the magnetic separation, and thus to evaluate the separation efficiency. The results indicated the intensities of the surface-enhanced Raman spectroscopy bands from p-mercaptobenzoic acid were dependent on the concentration of copper(II) ions, and the concentration was decreased by several orders of magnitude after the magnetic separation. The present protocol effectively decreased the total amount of heavy metal ions in the solution. This approach opens a potential application in the magnetic separation and highly sensitive detection of heavy metal ions. [ABSTRACT FROM AUTHOR]

Highlights: [•] A facile approach has been developed to fabricate multifunctional Fe3O4@AuAg nanoparticles. [•] The nanocompositions integrated the stronger magnetism and tunable SERS effect. [•] The combination of magnetism, SERS and microfluidic chip improved the enrichment efficiency and detection sensitivity. [ABSTRACT FROM AUTHOR]

Abstract: The corrosion inhibition behavior of benzotriazole (BTAH) on Ag electrodes and the influence of triphenylphosphane (pph3) were investigated by electrochemical method, in situ surface-enhanced Raman spectroscopy (SERS) and direct electrochemical synthesis of surface complexes in nonaqueous solution. The results indicated that the BTA− ion was coordinated to the Ag surface to form a highly cross-linked surface polymer complex of [Ag(BTA)] n , which suppressed the dissolution and oxidation of Ag effectively. The introduction of a neutral ligand of pph3 blocked the surface coordination processes of BTAH with the Ag electrode. It resulted in a decrease of inhibition efficiency to Ag surface. The ligand of pph3 played a negative role on the corrosion inhibition of BTAH to the Ag electrode. The SERS results were well consistent with the cyclic voltammetry and polarization curves measurements. For modeling, two different surface complexes were prepared in acetonitrile with and without pph3 by direct electrochemical synthesis. A polymer-like complex of [Ag(BTA)] n attached to the Ag surface was obtained in the absence of pph3, which suppressed the dissolution and oxidation of Ag effectively. A new binuclear compound, Ag2(BTA)2(pph3)4, was produced in acetonitrile with pph3 and the final coordination process occurred in solution leading to difficulties in forming a compact surface film, thus decreasing the corrosion inhibition efficiency of BTAH. The role of pph3 and the mechanism were proposed. [Copyright &y& Elsevier]

Abstract: Surface-enhanced Raman scattering (SERS)-active substrates of polyvinyl alcohol/gold–silver (PVA/Au–Ag) nanofibers were prepared using a simple approach involving electrospinning. The tunable surface plasmon resonance (SPR) of gold–silver alloy (Au–Ag alloy) nanoparticles (NPs) was achieved by controlling the feed ratio between gold and silver precursors. A higher concentration of Au–Ag alloy NPs could be obtained than the conventional methods, using 1wt% of PVA as the stabilizer. The Au–Ag alloy structure was demonstrated by HRTEM and STEM-EDX. After the electrospinning, the Au–Ag alloy NPs were successfully embedded in PVA nanofibers, as shown in the SEM and TEM images. Raman spectra displayed an apparent enhancement in the signal of 4-mercaptobenzoic acid (4-MBA), pyridine, and thiophenol molecules pre-absorbed from their ethanol solution onto the PVA/Au–Ag nanofibers. Different SERS effects were achieved by varying the Au content or excitation wavelength. [Copyright &y& Elsevier]

Abstract: A facile approach was developed to prepare novel multifunctional Fe2O3/Au/Ag nanostructures integrated with isolated functions involving magnetic and optical properties. The Fe2O3/Au/Ag hybrid nanoparticles with different thicknesses of Ag shell were prepared by adjusting the amount of the AgNO3. Surface structures were varied from the rough with pinhole to smooth and pinhole free surfaces with increasing amounts of AgNO3. The surface plasmon resonance was tuned in a very wide region from that of Au to Ag. Surface enhanced Raman scattering (SERS) effects were also investigated, employing thiophenol (TP) and aminothiophenol (PATP) as probe molecules. It was revealed that the SERS intensity was strongly depended on the molar ratio of Ag and Au. With an increase in the Ag molar fractions, SERS signals were enhanced to the maximum due to the surface plasmon resonance of the pinhole structure. The magnetic enrichment for on line SERS monitoring the molecules with low concentration was performed based on the magnetic core and the SERS activity of the bimetallic shells. This enrichment procedure improved efficiently the limits of the SERS detection. It was shown that the multicomponent nanoparticles have potential applications in the fields of optical devices and magnetic separation. [Copyright &y& Elsevier]

Abstract: The adsorption of three cyanopyridine isomers on Pt electrodes was investigated using electrochemical surface-enhanced Raman spectroscopy (SERS) within a wide potential region. It was revealed that the adsorption configurations depend on the applied potential and on the positions of CN group. The 4-cyanopyridine (4-CP) and 3-cyanopyridine (3-CP) molecules adsorb on Pt surfaces via the N atoms of the pyridine ring, while the 2-cyanopyridine (2-CP) molecules attach to the surface with the N atoms of both the pyridine ring and the CN group. In the case of 4-CP, the tilted adsorption mode is dominant under the potential of −0.8–0V. It is converted to the vertical mode when the potential is moved to 0–0.8V. For 3-CP, the vertical adsorption mode is found to be preferential in the full potential window. The Cing vibrational band of 2-CP is absent in the observed SER spectra. This is mainly caused by the characteristic π-electron delocalization as both N atoms are anchored to the Pt surface to form a heterogeneous ring. The hydrogen atoms are co-adsorbed with the cyanopyridine isomers on the Pt surface in extremely negative potential region. [Copyright &y& Elsevier]

Abstract: The complexes of benzotriazole (BTAH) with Ag, Cu, Fe, Zn and Ni were prepared respectively in the non-aqueous solution by the direct electrochemical synthesis and characterized by microanalysis and normal Raman spectroscopy. The influence of the neutral ligand of triphenylphosphine (pph3) on the coordination process was deduced by the normal Raman spectroscopy and electrochemistry. The metals were classified into two categories. For the first type, such as Cu and Ag, CuBTA and AgBTA were obtained in the solution without pph3. The introduction of pph3 led to its participation in the coordination processes of BTAH with Cu or Ag and appeared in the final complex. Fe, Zn and Ni belonged to the second type, there was no influence on the coordination of BTAH with Zn, Ni and Fe, i.e., the final complexes were Fe(BTA)2, Zn(BTA)2 and Ni(BTA)2, respectively, in the solution with/without pph3. The electrochemical results revealed that the BTAH can inhibit the corrosion of all the above metals, and the introduction of pph3 resulted in the decrease of inhibition efficiency to Cu surface, while no influence was observed on the Ni surface. The different role of pph3 was explained in terms of hard/soft acids and bases rule and coordination mechanism was proposed. [Copyright &y& Elsevier]

A measurement method of 85Kr using an internal gas proportional counter (IGPC) is presented in this study. The operation conditions of the IGPC were determined and optimized, including the operating voltage, pressure, sample volume, interference from other gas components such as nitrogen or air, and mitigation of the memory effect. The IGPC was calibrated using certified standards, and the detection efficiency was approximately 58% for typical samples. A lower limit of detection of approximately 0.11 MBq/m3(Kr) was achieved after counting for 5 h with 1 mL pure Kr, corresponding to the atmospheric activity concentration of 0.18 Bq/m3 (air). It was shown that the IGPC could be used effectively for measuring 85Kr. • A measuring setup of krypton-85 with an internal proportional counter is described. • Operating conditions were tested and optimized. • The performance of the method is presented. [ABSTRACT FROM AUTHOR]