Structure-Controllable Synthesis And Photocatalytic Properties Of Semiconductor Oxide Nanomaterials

Photocatalytic technology is an ideal way to solve the energy crisis and environmental pollution problems by converting the pollution-free and renewable solar energy into chemical energy through a simple reaction process catalyzed by semiconductor nanomaterials.The photocatalytic process is based on the absorbing photons by photocatalyst and generates excited states to complete energy conversion,so photocatalyst is the most critical part of photocatalytic technology.In this thesis,based on the characteristics of semiconductor materials(bismuth oxyhalide,cuprous oxide),some high-performance photocatalysts are constructed by controlling the morphology or loading quantum dots onto the semiconductor materials.These high-performance photocatalysts are applied to photocatalytic degradation of organic dyes,light-responsive nanoenzymes,sensing and organic synthesis.The specific work content includes:(1)We have developed a micelle-directed growth strategy for the preparation of high-efficiency photocatalysts of hollow open BiOCl nanocones.The opening angle and the halogen species of nanocones can be controlled via the fine adjustment of experimental conditions.Four batches of BiOCl nanocones with opening angles of 0°,32.3±0.6°,57.8±0.8° and 114.9±0.9° are successfully prepared.Meanwhile,BiOCl0.5Br0.5 and BiOBr nanocones also are successfully prepared.A series of photocatalytic experiments show that the asymmetric BiOCl nanocones have excellent photocatalytic activity compared with BiOCl nanoplates.It can completely degrade rhodamine B within 40 min even at a very low concentration,and the degradation kinetic constant is 7.8 times that of BiOCl nanoplates.Compared with some state-of-art photocatalysts and commercial photocatalysts(P25),BiOCl nanocones still have obvious advantages in terms of photocatalytic activity and synthesis process.(2)We have developed a bottom-up direct chemical synthesis method to synthesize the uniform and stable bismuth oxyhalide ultra-thin single crystal nanosheets and the activity of light-responsive nanoenzymes of nanosheets is studied for the first time.A series of experiments shows that the ultrathin bismuth oxyhalide nanosheets have light-controlled and high-efficiency oxidase activity in neutral aqueous solution,and can oxidize typical peroxidase substrates such as TMB,OPD and ABTS.A rapid and sensitive colorimetric method for the determination of glutathione concentration in solution is developed based on the bismuth oxyhalide nanosheets-TMB system,having good linearity in 1.5?15 ?M and a detection limit of 0.16 ?M.This work has broadened the application of bismuth oxychloride materials in the nanoenzyme field.(3)Cuprous oxide magnetic nanospheres(Fe3O4@Cu2O)are constructed via a one-step solvothermal method to overcome the problems in the synthesis of D-A cyclopropane,such as difficulty in the purification of the target product and high energy consumption.By optimizing the reaction conditions,the yield of the product reaches up to 82%.Besides,the catalytic system has good functional group tolerance and can convert different styrene derivatives into target products.The characterization of the used catalyst shows that the catalyst has good stability and can be used repeatedly.(4)Composite materials loaded with quantum dots,Fe3O4@Cu2O/CQDs/N-CQDs(FCCN),are constructed to overcome the problems in optical Fenton catalysts,such as narrow light response range,and only suitable for acidic conditions.A series of experiments show that the constructed composite materials have a wider visible light response range and a wider pH application range when compared with each component in the composite or the simple mixture of all components.The comparative experiments suggest the improved light response range is benefit from the up-conversion properties of quantum dots,and the wider pH application range is attributed to CQDs that can be used as active sites for photosensitive acids to adjust the local pH.Besides,this composite material can also be applied to the degradation of acid orange ??medium yellow 10 and complex dyes in actual industrial wastewater.Furthermore,the composite material has shown good stability for repeated use.