In this paper, a series of silver-deposited TiO2 (Ag−TiO2) nanoparticles (NPs) with a varying content of Ag were prepared by a photoreduction method and were attempted to serve as SERS-active substrates for the first time. SERS signals of 4-MBA molecules adsorbed on Ag−TiO2 NPs were further enhanced considerably relative to those enhancements on pure TiO2 NPs. The surface-deposited Ag on TiO2 can inject additional electrons into molecules adsorbed on the TiO2 surface through the conduction band of TiO2 NPs because of plasmon resonance absorption of Ag under incident visible laser, besides the intrinsic TiO2-to-molecule charge-transfer (CT) contribution. The two contributions mentioned are responsible for the whole SERS intensity of the molecules adsorbed on Ag−TiO2 NPs. This work is valuable in developing nanosized TiO2 used as a promising, nontoxic and biologically compatible SERS-active substrate as well as in studying the CT mechanism between Ag and TiO2 for potential photoelectrochemical applications.

The ZnO/PATP/Ag sandwich structure and its reverse Ag/PATP/ZnO were fabricated using ZnO nanorods and silver nanoparticles with functional molecules 4-aminothiophenol (PATP) through layer-by-layer selfassembly techniques. Under near-IR excitation (1064 nm, far from the surface plasmon resonance of the Ag nanoparticles in the assemblies), the enhancement of surface-enhanced Raman spectra (SERS) from the chargetransfer mechanism can be readily observed only in the former structure. The considerably larger enhancement of the b 2 modes, relative to those of the a 1 modes, is ascribed to the charge transfer between the silver nanoparticles and ZnO tunneling through the interconnecting PATP molecules. This is not observed in the second structure. The result demonstrates for the first time that directional charge transfer between nanoscale metal and semiconductor tunneling through the interconnecting molecules may be examined by SERS.

We have studied the spreading of liquid drops on a solid surface by molecular-dynamics simulations of Lennard-Jones systems of liquid, vapor, and solid. As the attraction between liquid and solid increases we observe a smooth transition from partial wetting to terraced wetting, with distinct molecular layers spreading with different velocities. In the terraced case the layers are ordered but not solid, with substantial molecular diffusion both within and between layers, and a growth rate that disagrees with experiments with nonvolatile liquids as well as recent calculations.

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In this work, 5, 15, and 30 nm Ag island films over CuO thin films (AgFOCuF) were prepared as SERS substrates. The spectra of 4-mercaptopyridine (4-Mpy) adsorbed on these AgFOCuF and bare Ag island films are compared. The Raman spectrum of a bare 5 nm Ag island film is weak. However, the Raman signal of 4-Mpy from 5 nm AgFOCuF substrate is enhanced and can be readily ascribed to surface plasma resonance of silver and charge transfer between the silver and CuO nanoparticles. Moreover, the difference between the spectra of 4-MPY adsorbed on CuO film partially covered with Ag island film and CuO film entirely covered with Ag film confirms that the observed Raman scattering arises from the interaction between CuO film and Ag island film.

Ag nanoparticles were exclusively deposited inside the pores of the porous anodic alumina (PAA) template through the deposition cycle including the incubation and the subsequent reduction of Ag(NH 3 ) + 2 . Both the density and size of the produced Ag nanoparticles increased as the deposition cycle number increased. A field-emission scanning electron microscopeand an ultraviolet-visible spectrometer were applied, respectively, to study the morphology and the extinction spectra of the Ag nanoparticles. The optimum deposition number was found from the scanning electron microscope (SEM) analysis. Surface enhanced Raman scattering (SERS) spectra of p-aminothiophenol recorded on the Ag-PAA substrates prepared under increasing number of deposition cycles, manifested an enlarging trend of peak intensity. A point-by-point SERS mapping of p-aminothiophenol on the Ag-PAA substrate was acquired to characterise the homogeneity of the substrate.

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