| Summary: | 碩士 === 臺灣大學 === 化學研究所 === 98 === In this work, three-dimensional branched Au nanomaterials were produced at high yield by reacting an aqueous solution of sodium tetrachloroaurate with a tea extract at ambient temperature and pressure. By varying the tea concentrations at a constant amount of sodium tetrachloroaurate, different size and shape of Au nanomaterials were separately prepared. We also synthesized other noble metal nanoparticles such as Ag, Pt and Pd by tea extract. UV-vis absorption, energy dispersive X-ray, X-ray diffraction, and transmission electron microscopy measurements were conducted to characterize the as-prepared Au nanomaterials. The results revealed that the branched Au nanomaterials (50 nm) were formed through the self-assembly of short nanorods (8 nm in width and 12 nm in length). According to the experiments, we find out that the polyphenols in tea extract play an important role of reducing Au3+ ion to Au and stabling the branched Au nanomaterials. By conducting Raman measurements, we found that the branched Au nanomaterials was useful on enhanced signal further than 10 times through surface-enhanced Raman scattering (SERS) effect and Ag nanoshells when adopting 4-mercaptobenzoic acid as report. We believe the Au/Ag nanomaterials have the potential to be good SERS substrates because of the stable signal and clean surface. Through the interaction of polyphenol and Titanium metal (ligand to metal charge transfer), the branched Au nanomaterials were easily deposited on the surface of TiO2 nanomaterials. On the photocatalysis, we have found the photodegradation of the methylene blue is further enhanced in TiO2(P25) about 2.50 folds and TiO2(P210) about 2.05 folds through the deposition of the branched Au nanomaterials. Consequently, we believe the branched Au materials have the potential to be good SERS substrates and photocatalysis enhancers because of the stable signal and clean surface.
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