Synthesis And Study On The Luminescence And Photocatalysis Of ZnTi-based Nanomaterials

In resent years,the semiconductor and their composite structures have attracted much attention due to their advantages of non-toxic,low cost,unique physical and chemical properties. With the characteristics of both nano materials and semiconductor materials,this new type of semiconductor material has already been one of the most important multifunctional materials.Thanks to their superior characters,ZnO,ZnS, TiO2and their composite micro/nano materials can be well applied in many areas such as photoelectron,chemistry and biology sensors,energy storage (e.g. solar cells and nanogenerator),decomposition of organic pollutants,wastewater purification and hydrogen production by photo-catalysis. However,the properties of micro/nano materials are affected by the composition,structure,and microscopic size of the materials. Therefore,there is a great significance to study their properties including composition,structure,and microscopic size by adjusting the parameters, which could improve the properties of materials and develop their applications areas.In this article,ZnS nanorods were studied systematically. ZnS nanorods and their composite were synthesized by a simple hydrothermal method. The composition,structure,morphology,formation mechanism and optical properties were characterized. We have studied the effects of ion doping on capture,transfer and separation process of photon-generated carriers on (or near) the surface of semiconductor.ZnO nanoparticles with different sizes were synthesized by direct precipitation method.The concentration of the reactants,pH value of the system and illumination intensity have direct effect on their photo-catalytic activity. In order to resolve the problem of recycling of photocatalyst, TiO2composite photocatalyst was prepared using float bead fly ash as carriers.The efficiency of semiconductor photocatalysis can be enhanced by reducing recombination probability of electron hole pairs using the composition of semiconductors and polyacid-modified method. Recombination time of electron hole pairs can be reduced and efficiency of hydroxyl radical can be enhanced by auxiliary coupled effect of field effect and the ultrasonic field effect of the surfactant solution,and thus the photocatalytic property of floating type composite photocatalyst was further improved.The main research content and results of this paper include the following four aspects:(1)Synthesis and study on luminescence properties of ZnS nano-compositesTransition metal (Mn,Fe,Cu) doped ZnS nanorods were prepared by hydrothermal method.The structure,morphology and microscopic size of the ZnS:Mn2+,ZnS:Cu2+,ZnS:Fe2+,ZnS:Mn2+Cu2+,ZnS:Mn2+Fe2+,ZnS: Mb2+Cu2+Fe2+nanorods were adjusted by adjusting the composition and proportion of the elements.The structure,morphology, Luminescent properties were characterized;three layers of core-shell structure composite system of ZnS:TM2+(Mn,Fe,Cu) nanorod/ZnO quantum dot/SiO2were prepared by Stoeber method,the effect of thickness of the shell on the optic properties of samples was studied by varying the ratio of nanorods and quantum dot.The effects of microstructure,micro morphology and micro size on the capture, transfer and separation process and properties of photon-generated carrier on or near the surface of semiconductor were studied.(2) Synthesis of Size-controlled ZnO nanoparticles and study on the photocatalytic performance ZnO nanoparticles with different sizes were prepared by direct precipitation method. Experimental results show that the photocatalytic performance of ZnO not only depends on its crystal size but also its crystallization property.The20nm ZnO nanopartides shows the best photocatalytic property when the calcination temperature was500℃.The effects of catalyst loading, initial dye concentration,the illuminating distance (the distance between the light and the solution surface) and dye initial pH on the rate constant were investigated by using the methyl orange as the model pollutant.The results show that the reaction rate constant is proportional to the scale of catalyst (koc[ZnO]0.62).The reaction rate constant is inversely proportional to the initial concentration and illumination distance of the dye,and their relation is koc[C0]-1.18and koc[D]-0.88, respectively.With the increase of pH,the rate of photocatalytic degradation will decrease.(3) The preparation and photocatalytic properties of TiO2composite photocatalystI. Poly acid-modified TiO2composite photocatalyst (phosphor-tungstic acid/TiO2/floating bead) was prepared by sol-gel method using phosphotungstic acid as modifier.And the catalytic activity of the TiO2composite photocatalyst and influencing factors were studied. With phosphotungstic acid as modifier and malachite green dye as model wastewater, the catalytic activity of the TiO2composite photocatalyst and influencing factors were studied, and the degradation rate of malachite green reached90%within80minutes.Ⅱ. Floating type photocatalyst was prepared by loading MoO3/TiO2thin film on float bead fly ash using sol-gel method.The photocatalysis activity of composite photocatalyst was characterized by degrading methylene blue wastewater.The photocatalysis properties of semiconductor composite TiO2composite photocatalyst were also studied. The composite photocatalysts (MoO3/TiO2/floating bead) were under the visible light within30minutes, so that degradation rate of methylene blue reached90%, and its degradation rate increased with the increasing of Mo content. When the Mo content was9wt%, its degradation rate reached95.6%under visible light irradiation for15minutes.(4) Design and application research of field effect assisted TiO2composite photocatalysis systemI.TiO2/floating bead photocatalyst,which can float on waste water,was prepared by sol-gel method.Ultrasonic assisted photocatalytic reactor was designed and fabricated by ourselves.Photocatalysis properties of ultrasonic field assisted TiO2composite photocatalyst were studied using methylene blue as model wastewater. The degradation rate of methylene blue within10minutes increased the38.51%more than that without ultrasound assisted conditions.II. Ce3+ion doped Ce3+-TiO2/floating bead floating type composite photocatalyst was synthesized by sol-gel method.The composite system was constructed by using sodium dodecyl sulfate as anionic surfactant. We discussed the activity of photocatalytic degradation of composite photocatalyst and photocatalytic reaction mechanism of composite TiO2composite system with surfactant using methylene blue as pollution of organic dye. Under the visible light irradiation for240minutes, the composite system of0.05g SDS and0.1g Ce3+-TiO2/floating bead made the photocatalytic degradation rate of methylene blue dye in solution reached93.49%.