Tandem Protocol for Diversified Deuteration of Secondary Aliphatic Amines under Mild Conditions.

Deuteration of amine compounds has been widely of concern because of its practical role in organic reaction mechanisms and drug research; however, only limited deuteration label methods are accessible with D2O as a deuterium source. Herein, we propose a convenient deuteration protocol, including preparing D2 by the AlGa activation method, using PtRu nanowires as catalysts, and utilizing the elementary step in the couple reaction involving an imine unit, to realize the rapid preparation of a secondary amine with a diversified deuteration label. The self-coupling between nitriles not only provides a symmetric secondary amine with four α-D atoms but also produces high-valued ND3 in an atomic-economic way.

Insight into Multiphase Interlayer Molecular Packing and Stepwise Phase Transition in 4-(Phenylazo)benzoate Anion-Intercalated Layered Zinc Hydroxide.

The properties of layered intercalation hybrids are closely related to interlayer molecular packing. To develop functional intercalation hybrids, it is essential to gain deep insights into interlayer molecular packing. This work reports a new comprehensive insight into the controllable multiphase interlayer molecular packing in 4-(phenylazo)benzoate anion-intercalated layered zinc hydroxide (LZH-4-PAB intercalation hybrids). The new insight breaks up the general understanding that the interlayer molecular packing of anions is usually single-phase, lacking diversity and controllability. Furthermore, it uncovers an interesting stepwise rather than the generally expected continuous phase transition of the interlayer molecular packing. The intercalated 4-PAB anions initially organize into the horizontal monolayer packing (θ = 0°, Phase I), which stepwise transforms to the tilted interdigitated antiparallel bilayer packing (θ ≈ 50°, Phase II) along with an increased intercalation loading and eventually to the vertical interdigitated antiparallel bilayer packing (θ = 90°, Phase III). The LZH-4-PAB hybrids exhibited a greatly enhanced interlayer molecular packing-dependent UV-vis absorption. This study provides helpful guidance for developing property-tailored intercalation hybrids. It may attract new interest in more layered intercalation hybrids. New and rich intercalation chemistry might be discovered in more functional intercalation hybrids beyond the 4-PAB anion-intercalated layered zinc hydroxide.

Real-Time Monitoring of Surface Effects on the Oxygen Reduction Reaction Mechanism for Aprotic Na-O2 Batteries.

Discharging of aprotic sodium-oxygen (Na-O2) batteries is driven by the cathodic oxygen reduction reaction in the presence of sodium cations (Na+-ORR). However, the mechanism of aprotic Na+-ORR remains ambiguous and is system dependent. In-situ electrochemical Raman spectroscopy has been employed to study the aprotic Na+-ORR processes at three atomically ordered Au(hkl) single-crystal surfaces for the first time, and the structure-intermediates/mechanism relationship has been identified at a molecular level. Direct spectroscopic evidence of superoxide on Au(110) and peroxide on Au(100) and Au(111) as intermediates/products has been obtained. Combining these experimental results with theoretical simulation has revealed that the surface effect of Au(hkl) electrodes on aprotic Na+-ORR activity is mainly caused by the different adsorption of Na+ and O2. This work enhances our understanding of aprotic Na+-ORR on Au(hkl) surfaces and provides further guidance for the design of improved Na-O2 batteries.

[Surface Enhanced Raman Spectroscopic Studies on the Coupling Effect of Multilayer Au@SiO2 Film].

The SiO2 shell with the thickness of 4 nm was attached onto high surface enhanced Raman spectroscopy (SERS) active Au core nanoparticles to obtain Au@SiO2 core shell nanoparticles by the hydrolysis of sodium silicate solution with the boiling water bath. The inert shell of SiO2 isolated the direct interaction of Au nanoparticles and probe molecules. The stable, compact and uniform monolayer nanoparticles film was self assembled at water/oil interface, and one to six monolayers film was transferred to Si wafer as SERS substrates through layer by layer technique. The relationship between the SERS activities and layers of the monolayer nanoparticles film on Si surface was investigated. The SERS mapping was developed to determine the layers of the Au@SiO2 film. The coupling effect among the Au@SiO2 films was explored by changing the adsorption location of the probe on the multilayer films. The result revealed that the monolayer film was a favourable candidate with high-quality performances for the SERS application. The SERS signal was distributed on the surface with high uniformity at the same monolayer film, and it was enhanced in the intensity with the increase in film layers. It reached the maximun intensity as the film was over five layers. It indicated that the SERS signal was contributed mainly by the first five monolayers. The probe molecules were immobilized onto the first monolayer nanoparticles film, and the SERS signal from the probe approached to the maximum as the second monolayer covered the probe modified first nanoparticles film. It was dominated by the coupling effect ("hot spots") of the adjacent layers. The SERS signal decreased in intensity when the third layer was transferred onto the second layer, and it disappeared after the fouth layer was covered, mainly duo to the shield of the nanoparticles film to the incident laser and Raman signal. The preliminary results provided guidance for fabricating optimal SERS substrates.

Hydrophilicity Dependent Distribution of Water at Ionic Liquids/Metal Interface Monitored by Electrochemical SERS.

The understanding of the interfacial processes is critically important for extending the practical application of ionic liquids, particularly for the role of interfacial water. In the electrochemical system based on ionic liquid electrolytes, small amounts of water at the interface generate a significant change in the electrochemical behaviors of ionic liquids. Therefore, the investigation on the interfacial behavior of water is highly desired in ionic liquids with different anions, water content, and hydrophilicity. Herein, based on the probe strategy, in situ surface enhanced Raman spectroscopy (SERS) combined with electrochemical control (EC-SERS) was developed to investigate the influence of hydrophilicity/hydrophobicity of ionic liquids on the interfacial water. The water-sensitive transformation reaction of 4,4'-dimercaptoazobenzene (DMAB) to para-aminothiophenol (PATP) was employed as a probe reaction for investigating the behavior of interfacial water. The changes of relative SERS intensities of DMAB to PATP served as an indication of the quantity variation of interfacial water. The results show that the transformation reaction efficiencies were critically dependent on the additional water contents, potential, and hydrophilicity of ionic liquids. With a very low molar fraction of additional water (Xw = 0.01), transformation efficiency of DMAB (the amount of interfacial water) followed the sequence of [BMIm]BF4 < [BMIm]PF6 < [BMIm]Tf2N. It was in agreement with the hydrophobicity order of the ionic liquids. With the increase in additional water content, the potential for the full transformation was positively moved, and the efficiency increased significantly. The stronger hydrophobicity allowed more water molecules to migrate to the interface, which was attributed to the difference in interactions between water and the anions of ionic liquids. It demonstrated that the small amount of water tended to gather at the interface in hydrophobic ionic liquids. Compared to traditional cyclic voltammetry, the EC-SERS technique combined with probe reactions is more sensitive to interfacial water. It is anticipated to develop as a promising tool for the investigating water-related issues at interfaces and to provide guidance to screen ionic liquids for practical application.

Magnetic separation of heavy metal ions and evaluation based on surface-enhanced Raman spectroscopy: copper(II) ions as a case study.

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.

Resolving nanostructure and chemistry of solid-electrolyte interphase on lithium anodes by depth-sensitive plasmon-enhanced Raman spectroscopy.

The solid-electrolyte interphase (SEI) plays crucial roles for the reversible operation of lithium metal batteries. However, fundamental understanding of the mechanisms of SEI formation and evolution is still limited. Herein, we develop a depth-sensitive plasmon-enhanced Raman spectroscopy (DS-PERS) method to enable in-situ and nondestructive characterization of the nanostructure and chemistry of SEI, based on synergistic enhancements of localized surface plasmons from nanostructured Cu, shell-isolated Au nanoparticles and Li deposits at different depths. We monitor the sequential formation of SEI in both ether-based and carbonate-based dual-salt electrolytes on a Cu current collector and then on freshly deposited Li, with dramatic chemical reconstruction. The molecular-level insights from the DS-PERS study unravel the profound influences of Li in modifying SEI formation and in turn the roles of SEI in regulating the Li-ion desolvation and the subsequent Li deposition at SEI-coupled interfaces. Last, we develop a cycling protocol that promotes a favorable direct SEI formation route, which significantly enhances the performance of anode-free Li metal batteries.

[Preparation of core-shell magnetic nanoparticles and its application in separation and spectral detection].

Magnetic nanoparticles as well as core-shell magnetic nanocomposites are of great interest for researchers due to their potential applications in lots of areas. In the present review, the authors summarized several universal synthetic methods of nanocomposites and their specific properties. In the following, the authors focused on the applications of functionalized magnetic nanoparticles in separation and spectral detection, along with the introduction of some work in the authors' lab. At last, the questions remaining in magnetic nanoparticles and the application perspectives of magnetic nanocomposites were discussed.

[Fabrication of reproducible surface enhanced Raman scattering substrate and its application].

Gold nanoparticles were homogeneously coated with silica using the silane coupling agent (3-aminopropyl)-trimethoxysilane to functionalize the gold surface and sodium silicate solution as the precursor of silica. The shell thickness could be well controlled by changing the amount of sodium silicate, reaction temperature and time. The Au@SiO2 core-shell nanoparticles with a suitable silica shell thickness exhibited optimal SERS activity and were self-assembled onto an ITO substrate in order to get a stable and reproducible SERS substrate. The conditions for preparing SERS substrates can be optimized by investigating the relationship between the intensity of SERS signals and the thickness of silica shell. The reproducible SERS measurements were performed by using 1,4-BDT and 4,4'-bipyridine as probe molecules. Within a certain concentration range, the linear relationship between the SERS intensities and the logarithm of concentration was obtained. The results revealed that the Au@SiO2 substrate assembled on ITO surface could be developed as a reproducible substrate for the quantitative analysis.

Plasmonic Core-Shell Nanomaterials and their Applications in Spectroscopies.

Plasmonic core-shell nanostructures have attracted considerable attention in the scientific community recently due to their highly tunable optical properties. Plasmon-enhanced spectroscopies are one of the main applications of plasmonic nanomaterials. When excited by an incident laser of suitable wavelength, strong and highly localized electromagnetic (EM) fields are generated around plasmonic nanomaterials, which can significantly boost excitation and/or radiation processes that amplify Raman, fluorescence, or nonlinear signals and improve spectroscopic sensitivity. Herein, recent developments in plasmon-enhanced spectroscopies utilizing core-shell nanostructures are reviewed, including shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), plasmon-enhanced fluorescence spectroscopy, and plasmon-enhanced nonlinear spectroscopy.

Exploring electrosorption at iron electrode with in situ surface-enhanced infrared absorption spectroscopy.

Surface-enhanced infrared absorption spectroscopy (SEIRAS) in attenuated total reflection (ATR) configuration has been extended to the Fe electrode/electrolyte interface in neutral and weakly acidic solutions for the first time. The SEIRA-active Fe film electrode was obtained through a potentiostatic electrodeposition of a virtually pinhole-free 40 nm-thick Fe overfilm onto a 60 nm-thick Au underfilm chemically predeposited on the reflecting plane of an ATR Si prism. The infrared absorption for CO adlayer at the Fe film electrode measured with ATR-SEIRAS was enhanced by a factor of larger than 34, as compared to that at a Fe bulk electrode with external infrared absorption spectroscopy in the literature. More importantly, the unipolar band shape enabled the reliable determination of the Stark tuning rates of CO adlayer at Fe electrode. In situ ATR-SEIRAS was also applied to study the electrosorption of a typical corrosion inhibitor benzotriazole (BTAH) on Fe electrode as a function of potential, providing additional spectral information at positive potentials in support of the formation of a polymer-like surface complex Fe(II)(m)(BTA)(n) as the corrosion-resistant layer.

[Study of regeneration based on SERS labelled immunoassay].

Labelled immunoassay by surface enhanced Raman scattering (SERS) has great research and application value. It combines SERS which has the high sensitivity and high selectivity with specific adsorption in immunology. The present paper mainly studies the regeneration about SERS labelled immunoassay, striving to develop the recycling value of it. The authors used glycine-HCl eluent for the sandwich structure including solid matrix antibody, antigen and labelled immuno-gold colloids, then the authors had got expected result. The complex of antibody and antigen would be separated by changing the pH scale. It could elute the most antigen and the labelled immuno-gold colloids. Also the authors could assemble it again and distinguish the characteristic SERS spectrum of the reporter molecules. Under this condition, we researched the stability and reusing of this technology. The authors found that it has better stability and it retained activity after 10 recycles of applications.

[Self-assembly of two kinds of nanoparticles and their surface enhanced Raman spectroscopic study].

Two kinds of nanoparticles (gold nanoparticles and Au core Pt shell nanoparticles) on silicon surfaces which were silanization were electrostatically self-assembled. The density of nanoparticles was controlled by changing the time of the substrate immersed in colloids. The substrate was characterized by scanning electron microscope (SEM), and the results indicated that Au and Au@Pt particles were dispersed on the substrate with mono/submonolayers. The authors used pyridine (Py) as a probing molecule, and surface enhanced Raman spectroscopy (SERS) effect was investigated on pure Au and Au-Au@Pt mixed nanoparticle surfaces under the excitation line of 632.8 nm. The results revealed that there is a significant shift of the two characteristic peaks of Py, but the enhancement factors of Au dropped off precipitously with the introduction of the Au@Pt nanoparticles. The authors attributed this effect to the introduction of metal d-states from the metal, which would serve effectively to quench the surface plasmon excitation necessary for large (electromagnetic) enhancements in Raman spectroscopy.

A study on 85Kr measurement with an internal gas proportional counter.

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.

[UV-Vis studies on the course of reaction of Au/Ag alloy colloid with hydrogen tetrachloroaurate(III) hydrate].

Using citrate as protector, Au-Ag alloy nanoparticles with different molar ratios were prepared with hydrazine as the reducer. One plasmon band between monometallic Ag and Au was observed in their UV-Vis spectra. And the peak of alloy shifted linearly with the ratio of Au changing in the alloy. By UV-Vis spectra, the course of reaction of the alloy colloid with HAuCl4 was studied. The result shows that the UV-Vis spectra of the alloy colloid changed regularly with the adding volume of HAuCl4 increasing. And there is a linear interval in it with the change in the calculated ratio of Au. With the former studies, the course can be attributed to the dealloy of Au/Ag alloy.

[Study of surface enhanced raman spectra of SCN- adsorbed on the Au-Ag complex substrate].

Ag and Au nanoparticles were self-assembled on a silicon substrate simultaneously. The density of Ag and Au nanoparticles was controlled by changing the volume ratio of Au to Ag colloids. The substrate was characterized by UV-Vis diffuse reflectance and SEM, and the results indicated that Ag and Au nanoparticles were dispersed on the substrate with mono/submono layers. Using SCN as a probing molecule, surface enhanced Raman spectroscopic (SERS) effect was investigated on pure Au, pure Ag and Au-Ag mixed nanoparticle surfaces. After a series of calibration, the results revealed that the SERS spectral features of SCN from the mixture system were similar to those from the pure Ag nanoparticles, indicating the coupling effect between the Ag and Au nanoparticles, which results in the property of Au inclining to Ag.

[Studies of surface-enhanced Raman spectroscopy on bare Ti electrode].

Various roughening methods for the bare Ti electrode such as mechanical roughening, electrochemical oxidation-reduction method and chemical etching were tried to obtain surface-enhanced Raman spectra (SERS) successfully for the first time. The results of the experiments proved that mechanical roughening and electrochemical oxidation-reduction method could be successfully employed in roughening titanium electrode, however, surfaces roughened in such ways showed no SERS-activity in Raman detection. Finally, chemical etching with hydrofluoric acid was proved to be an effective way to get SERS-active titanium surface, and surface-enhanced Raman spectra of pyridine adsorbed on a titanium surface was observed for the first time. In order to get the most effective titanium surface, roughening conditions, including concentration of the acid, the time of etching and the external potential, were investigated. As illustrated, Raman activity varies with conditions changing in roughening processes and the most reasonable condition for roughening was indicated. The result showed that at the concentration of hydrofluoric acid 0.33% (Wt) and 5 min for etching, the most SERS-active rough titanium surface could be obtained. In addition, with an external potential to speed up corrosion, the surface of titanium electrode tended to form a thin film of oxide, which prevented further corrosion and caused SERS-activity decrease. Thus, in this paper, the surface-enhanced Raman spectra of pyridine (pyridine 0.01 mol L(-1), and electrolyte KCl 0.1 mol L(-1)) adsorbed on bare roughed Ti electrode were observed at open circuit potential. Referring to the calculations of enhancement factor of pyridine on electrode, the enhancement factor is about 102 on the roughened titanium electrode.

[Template preparation of metal-molecule-metal junction and its SERS investigation].

In the present paper, the authors reported the assembly and SERS studies of a simple device unit of a metal nanowire-molecule-metal nanoparticles junction in an anodic aluminum oxide (AAO) template. The AAO template was fabricated by two-step electrochemical oxidation. Metals were filled into the pores by AC deposition. Then the AAO template with metal nafiowires was immersed into the solution of 1,4-benzenedithiol (1,4-BDT), which was followed by the immersion into silver nanoparticles with appropriate diameter. 1,4-BDT served as the probe molecule for SERS detection as well as the molecule for linking the metal nanowires and metal nanoparticles. The simple junction of metal-molecule-metal embedded in AAO template was built successfully. The SERS effect of the junction was investigated through the dissolution of AAO template to expose the junctions in the same orientation (standing on the substrate vertically). The giant enhancement from the former junction might be attributed to the coupling effect in the junction. The authors' preliminary results revealed that SERS might be a characteristic tool for the junction and the construction on the junction will be beneficial to the investigation of the complex SERS mechanism.

[Preparation and surface enhanced raman spectroscopic studies on Au-Ag alloy nanoparticles].

Using citrate as protector, Au-Ag alloy nanoparticles with different molar ratios were prepared by using hydrazine as the reducer, One plasmon band between that of monometallic Ag and Au observed in their UV-Vis spectra indicated the formation of Au-Ag alloy nanoparticles. TEM results showed diameters about 25 nm and homogeneous color of the alloy nanoparticles without clear core-shell contrast. By using Pyridine as the probe molecules, SERS studies were performed. The results indicated the spectra of Pyridine adsorbed on alloy is different from that of Ag and Au.

[Surface enhanced Raman spectroscopic studies on the coadsorption of N-methylimidazole and 2,2'-bipyridine at Cu electrode].

The adsorption behavior and coadsorption of N-methylimidazole (NMIM) and 2,2'-bipyridine(2,2'-bipy) at copper electrode were investigated by in situ electrochemical surface enhanced Raman spectroscopy (SERS) in the acetonitrile solution. In situ SERS studies revealed that NMIM can adsorb stably onto Cu electrode in a quite different potential range, but the potential range for adsorbing 2,2'-bipy is narrow. With the introduction of 2,2'-bipy into the solution, the SERS could be divided into three parts: (a) under -0.8 V, NMIM molecule adsorption, (b) near the open potential, 2,2'-bipy molecule adsorption with cis-conformation, (c) at positive potential region, both NMIM and 2,2'-bipy were coadsorbed at Cu surface, and the SERS data also suggested that the NMIM bound to copper surface with a tilted orientation, while the 2,2'-bipy was adsorbed through cis-conformation to the surface.