Application Of Noble Metal/semiconductor Composites: Surface Enhanced Spectroscopy(SES) Substrates And In-situ Monitoring

Noble metal nanoparticles(such as Au、Ag、Cu) have attracted much attentions due to their unique surface p lasmon resonance(SPR) property. SPR is a resonance phenomenon which happened while the vibration frequency of free electrons ascribed from the surface of metals is equal to the vibration frequency of incident light. Based on this distinct feature, noble metal nanoparticles possess the potential application prospects in the fields of surface enhanced spectroscopy, optoelectronic devices, biological/chemical sensors, and so on.Surface-enhanced Raman scattering spectroscopy(SERS) and surface-enhanced infrared absorption spectroscopy(SEIRA) are two major techniques to offers rich information of molecules. SERS is a common analytical tool with high sensitivity, high selectivity, non-destructivity, high reproducibility, and has widely applied in environmental science, biology science, trace analysis, chemical sensors, etc. In fact, how to enhance the activity of SERS substrates and broaden the SERS application fields are two crucial issues to solve.In this paper, we prepared several SERS substrates based on the noble metal-semiconductor composites. Besides, these compounds also employed as catalysts to degrade organic pollutants and catalyze cross coupling reactions. The main results were as follows:(1) CuS is an important semiconductor, which has draws considerable concerns due to its potential applications in various fields. The bi- functional Au/CuS composites with the catalytic activity and SERS performance were prepared. It could enhance the Raman signals of R6 G molecules with the enhancement factors of 2.53 × 105. Besides, it also employed as a catalyst for degrading R6 G and monitoring the degradation process.(2) The bi- functional Au/FeS composites were also fabricated. It exhibited superior SERS performance with the enhancement factor up to 1.81 × 106. The SERS technology was used to real- time and in-situ monitor the degradation process of R6 G molecules, employing the Au/FeS composites both as SERS substrates and catalysts.(3) The Au/PbS composites were employed as the SERS substrate and it showed extinctive SERS performance. In addition, the electromagnetic(EM) field and SERS performance of three semiconductors(CuS 、 PbS 、 FeS) were compared through experiments and FDTD theoretical studies. The results showed that the coupling interation between semiconductors and Au was stronger as the band gap of semiconductors got narrower, which will lead to the higher EM enhancement between nanoparticles and the interface between semiconductors and nanoparticles. Both the enhancement would make the SERS activity increased.(4) Cu/V2O5 composite was obtained via microwave-assisted reduction method. It exhibited excellent SERS sensitivity and reproducibility. Cu nanoparticles not only possess SERS activity, but also could use as catalysts for cross coupling reactions. Besides, the Lewis acid/base properties of V2O5 will improve the chemical enhancement of SERS via Lewis acid-base interaction. This SERS-active composite was hopeful in monitoring the catalytic reactions with in-situ SERS technology.(5) The Fe3O4/Au composites were fabricated and employed as SEIRA substrates. Firstly, the SPR resonance of Au would result in the enhanced infrared signal; on the other hand, surface density of Au nanoparticles are increased with increase of the magnetic intensities, which would lead to the larger EM enhancement and higher IR absorpation intensity. And the SEIRA could be adjusted by the external magnetic intensities. In this paper, Fe3O4/Au composites also were employed to identify the linkage form of-SH.