Photo-catalysis And Thermal-catalysis Test Of Au-Narrow Bandgap Semiconductor Hydrid Structure

Nobel metal-semiconductor hybrid materials have been extensively studied due to thesuperior catalytic properties compared to their individuals.The catalytic efficiency can be improved by adjusting the size,morphology,composition etc.Different from traditional investigations on catalytic properties of wide-bandgap semiconductors such as ZnO and TiO₂,here small-bandgap semiconductors CdS and MnO₂ have been studied,and Au nanoparticles?NPs?were deposited on the nanostructures.After that,photo-catalysis mechanism of Au-CdS nanostructure and thermal-catalysis mechanism of Au-MnO₂nanostructure were studied,respectively.The main content of this paper is divided into two parts:Part one1.The progress of photocatalysis research was reviewed briefly.The mechanism of surface plasmon resonance?SPR?was introduced and the concept of surface-enhanced Raman spectroscopy?SERS?was demonstrated.2.The cadmium sulfide?CdS?nanospheres with uniform particle size were prepared by hydrothermal method with cadmium acetate?Cd?CH₃CO₂?₂?as the cadmium source and thiourea?CH₄N₂S?as the sulfur source.3.The sodium citrate was used as reductant and the chloroauric acid?HAuCl₄?was used as Au source,uniform Au NPs were deposited on the surface of CdS nanospheres by using hydrothermal method.Followed by repeatedly reduction of HAuCl₄,the size of Au NPs on the surface of CdS increased.The excitation peak of Au was detected by UV-vis spectroscopy,demonstrating the appearance of Au NPs.4.The degradation of methylene blue?MB?by CdS covered with Au NPs?Au-CdS?presented superior photocatalytic properties compared with that of individual CdS nanospheres or individual Au NPs.5.The photocatalytic properties of Au NPs and Au-CdS samples was measured by SERS employing the oxidation of p-Aminothiophenol?PATP?as a model reaction.Combining the energy band analysis,the mechanism of superior photocatalytic properties of Au-CdS was concluded.Part two1.The MnO₂ nanostructures with K⁺ions or Na⁺ions doping were prepared by hydrothermal method,where manganese sulfate?MnSO₄?and potassium permanganate?KMnO₄?or sodium permanganate?NaMnO₄?were used,respectively.The variation of MnO₂ bandgap due to K⁺ion or Na⁺doped were confirmed.2.Sodium citrate was used as reductant,and chloroauric acid?HAuCl₄?was used as Au source.Uniform Au NPs were deposited on the surface of MnO₂?Au-MnO₂?.3.By comparing the temperature-dependent SERS of Au NPs and Au-MnO₂ samples,the influence of thermacatalysis effects due to the semiconductor bandgap were studied.