Preparation,Optical And Photoelectric Performance Of Gold Manoparticles-titanium Dioxide Composite Structures

Titanium dioxide（TiO₂）has shown great application potentials in the fields of optics,photocatalysis and optoelectronics due to its some advantages,such as high stability,low cost and non-toxicity.However,the wide band gap and high carrier recombination efficiency of TiO₂ limit its applications as photocatalyst and optoelectronic material.Since Au nanoparticles（Au NPs）can support strong localized surface plasmon resonance（LSPR）in visible region,combining them with TiO₂ not only could broaden the photoresponse range of the composite structures,but also could help to reduce the recombination of TiO₂ carriers due to the Schottky junction formed at the interface between TiO₂ and Au NPs,and therefore could improve the photocatalytic and photoelectric performance of the composite structures.In this dissertation,based on the controllable preparations of TiO₂ nanoparticles with different crystal structures and Au NPs with different particle sizes,Au-TiO₂ composite powders and Au-TiO₂ composite films have been respectively prepared by electrostatic self-assembly method and spraying method.The effects of various preparation parameters on the optical,photocatalysis and photoelectric performance of the composite structures have been investigated,and the concrete results are shown below.1.The sol-gel procedure for TiO₂ preparation has been optimized by adding a washing process,through which the maximum weight loss rate can be reduced by83.3%,and the TiO₂ yield can be increased by 22.2%.Subsequently,the photocatalytic performance of anatase and rutile TiO₂ have been respectively investigated,and the results indicate that the rutile TiO₂ with higher crystallinity can show higher photocatalytic efficiency.2.Au NPs have been prepared by a liquid-phase reduction method,and the effects of reductant addition,protectant addition,reaction temperature and solvent type on the particle size and surface plasma performance of Au NPs have been investigated.The results indicate that,on one hand,the size-dependent surface plasmon performance of Au NPs prepared in aqueous solution agree well with Mie theory,indicating that the LSPR peak of Au NPs gradually blue-shifts with the increasing of reductant addition;blue-shifts then red-shifts,and then slightly blue-shifts again with the increasing of protectant addition;gradually red-shifts with the increasing of reaction temperature.on the other hand,Au NPs with high stability have been successfully prepared in ethylene glycol solution thanks to the optimized procedure..3.Au-TiO₂ composite powders have been successfully prepared by an electrostatic self-assembly method,and the effects of Au loading on the optical and photocatalytic performance have been investigated.Both optical characterizations and finite element simulations indicate that strong interaction will happen between Au NPs and TiO₂under excitation.On one hand,the carrier yield of Au-TiO₂ composite powders can be greatly enhanced due to the LSPR sensitization effect and the near-field enhancement effect of Au NPs.On the other hand,the carrier recombination efficiency of TiO₂ can be dramatically reduced due to the Schottky junction formed at the interface between TiO₂and Au NPs.When the Au NPs have been 0.66%loaded,the photocatalytic efficiency of Au-TiO₂ composite powders could reach 2 times and 1.2 times of that of TiO₂ under visible light and sunlight irradiation,respectively.4.TiO₂ films and Au-TiO₂ composite films have been successfully prepared by a spraying method,which can be employed to realize large-scaled production,and the effects of heat treatment temperatures,spraying times and Au contents on their optical and photoelectric performance have been investigated.It has been demonstrated that the photocurrent density and photoresponse speed of the 400°C treated TiO₂ film have been greatly improved due to its higher carrier yield and faster carrier transport rate,and the results indicate that the photoresponse time of such treated TiO₂ film is about 0.1 s and its photocurrent density is about 4.2 times of that of unheated TiO₂ film.As the spray time goes on,there is obvious inverse correlation between the photocurrent density and roughness of the TiO₂ films,which could be due to the denser TiO₂ films are,the lower carrier recombination can be achieved.The photocurrent density of Au-TiO₂ composite films reaches the maximum when the Au content is 0.66%,which is about 1.4 times of that of TiO₂ film,due to the cooperative effect of Schottky junction and LSPR sensitization.