Multifunctional TiO2/Ag composite nanowires are fabricated with a hydrothermal method by precipitating Ag nanoparticles （NPs） on the surfaces of TiO2 nanowires. This hierarchical one-dimensional （1D） nanostructure can be used as a surface enhanced Raman scattering （SERS） substrate with high sensitivity, for detecting the rhodamine 6G （R6G） in a wide range of low concentrations （from 1 × 10 6 M to 1 × 10-12 M）. In addition, the substrate can be self-cleaned under the irradiation of ultraviolet （UV） light due to the superior photocatalytic capacity of the TiO2/Ag composite nanostructure, making the recycled use of SERS substrates closer to reality. With both the evident SERS performance and high efficiency of photocatalytic capacity, such TiOz/Ag composite nanowires demonstrate considerable potential in the chemical sensing of organic pollutants.
Inner surface coating for tubular samples was realized by the grid enhanced plasma source ion implantation （GEPSII） method. In the GEPSII system, two electrodes, a central rod electrode and a coaxial grid electrode were coaxially assembled inside the tube. Plasma was generated between the electrodes by a radio-frequency （RF） oscillating power source. Plasma then diffused through the grid and realized inner surface ion implantation by a negative high voltage applied to the tube. The plasma was then divided, by the grid, into two regions, namely the source plasma region and the diffused plasma region. The plasma＇s self-bias between two RF power source electrodes was measured. At the same time, the electron temperature and plasma density in the GEPSII system were measured by a scattering spectrometer. Results showed that the plasma properties of the two regions were entirely different; the plasma self-bias, which might greatly affect the sputtering rate of the central titanium electrode, depended on the electrode structure, gas pressure and RF power.
Imaging properties of a two-dimensional rectangular-lattice photonic crystal (PC) slab consisting of air holes immersed in a dielectric are studied in this work. The field patterns of electromagnetic waves radiated from a point source through the PC slab are calculated with the finite-difference time-domain method. Comparing the field patterns with the corresponding equifrequency-surface contours simulated by the plane-wave expansion method, we find that an excellent-quality near-field image may be formed through the PC slab by the mechanisms of the simultaneous action of the self-collimation effect and the negative-refraction effect. Near-field imaging may be obtained within two different frequency regions in two vertical directions of the PC slab.
