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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.

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.

The rapid recombination of carriers on plasmon metal nanoparticles leads to relatively low efficiency of traditional photocatalysts. The combination of a metal and a semiconductor allows to the separation of hot electrons and holes to improve photocatalytic efficiency. In this study, Au nanoparticles were integrated with semiconductor TiO2 nanoparticles of different sizes to improve the photocatalytic activity. Various techniques have been developed to study the mechanism of catalytic activity, the significance of band bending in the space-charge region within metal–semiconductor nanocomposites, and the built-in electric field. The results provide theoretical and experimental evidence for the design of a high-performance surface plasmon resonance (SPR) photocatalyst. To reveal the interface band structure, surface-enhanced Raman spectroscopy (SERS) was employed to analyze the band structure of the TiO2–metal composites. This approach was based on the electrochemical Stark effect and a molecular probe strategy, combined with X-ray photoelectron spectroscopy (XPS), Electrochemical impedance spectroscopy (EIS), and other techniques at the molecular level. The results demonstrated that charge transfer occurred spontaneously between the Au nanoparticles and TiO2, and that the TiO2–metal interface constitutes a Schottky barrier. Moreover, the size of the TiO2 nanoparticles affects the degree of band bending. Optimal state matching was achieved with TiO2 (60 nm)–Au, improving the photocatalytic activity of the nanocomposite. The photocatalytic coupling reaction of p-aminothiophenol (PATP) acted as a probe to study the catalytic performance of TiO2–metal nanocomposites. The results revealed that the introduction of TiO2 improves the SPR catalytic activity of Au, mainly through the efficient separation of electrons and holes at the TiO2–metal interface.

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-situelectrochemical 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–O2batteries.

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 D2by 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 ND3in an atomic-economic way.

The surface coordination chemistry of benzotriazole (BTAH) on a Cu electrode was investigated by electrochemical synthesis of surface complexes and in situ electrochemical surface-enhanced Raman spectroscopy (SERS) in nonaqueous solution. Two different surface complexes were prepared in solution with or without triphenylphosphane (PPh3). A new mixed-valence Cu–N cluster compound containing BTAH was synthesized by direct electrochemical oxidation of Cuin nonaqueous solutions with PPh3. The final product, Cu5Cl(BTA)5(PPh3)4 was crystallized and characterized by microanalysis and Raman spectroscopy together with X-ray crystallographic determinations. The complex crystallized in a monoclinic space group (P21/n) with lattice parameters a = 16.739(2) Å, b = 18.919(2) Å, c = 31.042(4) Å, β = 103.194(3)°, V = 9571.0(19) Å3, R1 = 0.0704, wR2 = 0.1643. The results showed that the complex was a pentanuclear compound. The central CuII atom is coordinated to four equatorial and one axial BTA– ligands to form a distorted tetragonal pyramidal coordination polyhedron, whereas each surrounding CuI ion is in a distorted tetrahedral environment. The in situ SERS studies revealed that the BTA– ion was coordinated to a Cu surface through its 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. The introduction of PPh3 blocked the surface coordination of BTAH with the electrode, and a complex of BTA– and PPh3 with Cu was formed in the bulk solution.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The electrochemical adsorption and hydrogenation of benzene on a roughened Pt electrode were studied by confocal Raman microscopy. Some forbidden vibrational bands of benzene were detected owing to the lowering of the symmetry upon adsorption. The results infer that benzene is adsorbed on the Pt surface in a flat orientation by its ring. By comparison, its adsorption was carried out on an ultrathin Pt film-coated Au electrode exhibiting higher SERS activity. It has been shown that benzene reacts with the adsorbed hydrogen, then is hydrogenated to cyclohexane on the Pt surface at negative potentials in acidic solution. This preliminary study provides evidence to support the fact that even weak adsorbates on pure transition metals can be studied by SERS spectroscopy. Copyright © 2003 John Wiley & Sons, Ltd.

Applying the probe molecule strategy, surface-enhanced Raman spectroscopy has been used, for the first time, as a diagnostic tool of the electronic properties of metal nanorods; the vibrational frequency of the probe molecule SCN⁻ at Cu nanorods is shown to critically depend on the nanorod’s diameter in the range from 50 to 15 nm; the up-shifting of the Fermi level with a decrease of the nanorod’s diameter is interpreted based on the change of cohesive energy owing to the high ratio of surface to bulk atoms.