In recent years, surface-enhanced Raman scattering (SERS) of a molecule/metal-semiconductor hybrid system has attracted considerable interest and regarded as the synergetic contribution of the electromagnetic and chemical enhancements from the incorporation of noble metal into semiconductor nanomaterials. However, the underlying mechanism is still to be revealed in detail. Herein, we report an irreversible accumulated SERS behavior induced by near-infrared (NIR) light irradiating on a 4-mercaptobenzoic acid linked with silver and silver-doped titanium dioxide (4MBA/Ag/Ag-doped TiO 2) hybrid system. With increasing irradiation time, the SERS intensity of 4MBA shows an irreversible exponential increase, and the Raman signal of the Ag/Ag-doped TiO 2 substrate displays an exponential decrease. A microscopic understanding of the time-dependent SERS behavior is derived based on the microanalysis of the Ag/Ag-doped TiO 2 nanostructure and the molecular dynamics, which is attributed to three factors: (1) higher crystallinity of Ag/Ag-doped TiO 2 substrate; (2) photo-induced charge transfer; (3) chargeinduced molecular reorientation.

The properties of the localized surface plasmon resonance (LSPR) and the surface enhanced Raman scattering (SERS) of the core-shell bimetallic nanostructures, that is the monodisperse Au@Ag core-shell nanorods with different thickness of Ag shell, are theoretically and experimental researched. The UV-vis-NIR absorption spectra of the Au@Ag core-shell nanorods are measured and displayed their blue-shifts of the longitudinal plasmon resonance peaks with increasing of Ag concentrations in the colloidal solution. And the absorption spectra of the Au@Ag core-shell nanorods are simulated by the Finite Element Method (FEM), which are in agreement with the experimental measurements and reveal their LSPR mechanism as the varying structures. In addition, Rhodamine 6G, as a Raman reporter molecule, is used to investigate SERS of gold nanorods and Au@Ag core-shell nanorods. It is found that Au@Ag core-shell nanorods have better SERS responses, comparing with those of Au nanorods, and their SERS intensities are increased with the increases of the Ag shell thickness, which demonstrate that the chemisorptive bond effect and the morphology of the nanoparticle play key roles to the SERS signals. It is significant to design the biosensor based on the properties of Au@Ag core-shell nanorods.

Hollow sea-urchin gold nanoparticles (HSU-GNPs) were successfully prepared through a novel one-step galvanic replacement strategy, and their corresponding optical properties was studied in detail. During the synthesis process, the sizes of the interior hollows of the HSU-GNPs could be changed by adjusting the amount of silver nitrate added into hydrogen tetrachloroaurate trihydrate solution. The absorption spectra of the HSU-GNPs showed that the localized surface plasmon resonance (LSPR) peaks were red-shifted with increasing size of the interior hollows in the HSU-GNPs. When the added amount of silver nitrate was up to 6 μl, the LSPR peak of the synthesized HSU-GNP reached 726 nm as a maximum red-shift. Furthermore, the absorption spectra of the HSU-GNPs with different morphologies were theoretically simulated by the finite element method, which was consistent with the experimental results and explained the origin of the red-shift of the LSPR peaks. In addition, the surface-enhanced Raman scattering (SERS) of the sea urchin gold nanoparticles were also investigated using 4-mercaptobenzoic acid as a Raman reporter molecule. Both the experimental and calculated results showed that the HSU-GNPs had stronger SERS enhancement than the solid sea-urchin gold nanoparticles. In particular, the HSU-GNPs prepared by adding 6 μl silver nitrate exhibited a maximum SERS enhancement factor, EF = 1.1 × 10(9), due to the LSPR peak at 726 nm which is near to the excitation wavelength, 785 nm. This feature is significant for designing a biosensor with a super-high sensitivity based on the morphology of the HSU-GNPs.

The synthesis of a series of conjugated aromatic polyoxadiazoles (PODn) characterized by having moderate chain flexibility and highly flexible lateral substituents is reported. The majority of these polymers are soluble in a mixture of chloroform and trifluoroacetic acid and have inherent viscosities up to 0.9 dL/g. The glass transition temperature, T g , lies in the range 165-230 °C and depends on the side-chain length. The PODn show a good thermal stability in nitrogen up to 270 °C. Wide-angle X-ray diffractograms reveal a "comblike" organization of the polymeric chains. Homogeneous thin films of such a material were prepared by the spin-coating technique. Films spun on fused silica were characterized by spectroscopic analysis in the whole UV-vis-NIR range showing a high transmission in the NIR region which is the typical telecommunication band (1300-1500 nm). Furthermore, the refractive index and the film thickness have been measured using the coupled modes technique in a planar guiding structure having POD as the core. It has then been prepared a device consisting of the said polymer sandwiched between two electrodes on top of a glass substrate. The electron conductivity of the polymer has been found to be higher than that of terephthalic poly(1,3,4-oxadiazole).