| At present, all the countries in the world are facing the problem ofenvironmental pollution in different extent. The reasons of serious water pollutionare hazardous wastes of industrial production, fertilizers and pesticides of agriculture,and the oil spill, etc. The reasons of air pollution are vehicle emissions and theburning of fossil fuels. The treatment of environmental pollution has drawn theworldwide attention. One of the main purposes of research on photocatalysis is tosolve the increasingly serious environmental and energy problems. Traditionalmethods of organic pollutants degradation mainly included biological degradation,physical chemistry method and oxidation method and so on. Compared with thesemethods, photocatalytic degradation has special advantages. For example:(1) theenergy of degradation derived from solar energy, energy consumption will be greatlydecreased;(2) the reusability of photocatalyst;(3) most photocatalysts ofsemiconductor material has stable chemical properties and without toxicity.Currently, most photocatalytic materials used semiconductor particles in micronor nano scale, it is due to the surface properties of materials have changed by paticlesizes, they have larger specific surface area and more surface active centers. As a newkind of green solvent, ionic liquids are also good surface active agents which act assolvents and surface modification agents in crystallization process of semiconductornanoparticles. Graphene oxide is also a semiconductor material, through combiningwith the other semiconductor material to promote the separation of photogeneratedelectrons. Graphene oxide has a lot of oxygen containing functional groups andnegative charges on the surface, therefore, it is easy to prepare composite materials byelectrostatic self-assembly.Based on above reasons, this research work includes the following contents:(1) Graphene oxide-cadmium sulfide (zinc sulfide, silver sulfide)nanocomposites were synthesized with surface modification method by ionic liquids,and the photoelectric conversion and photocatalytic properties were studied. Ionic liquids can be used as a solvent and a surface modification agent in crystalformation process of cadmium sulfide (silver sulfide, zinc sulfide), obtainingcadmium sulfide (zinc sulfide, silver sulfide) particles with positively charged surfacewhich can be well dispersed in water. Therefore, it’s easy to couple with grapheneoxide with negatively charged surface in water by electrostatic interaction. Theobtained graphene oxide-cadmium sulfide (zinc sulfide, silver sulfide)nanocomposites are very stable, and the synthesis method is simple and rapid. Wehave also studied the photoelectric conversion and photocatalytic properties.(2) Polymeric ionic liquids were used to modify cadmium sulfide by a similarmethod, the cadmium sulfide quantum dots were obtained with positively chargessurface, and study on the controllable particle size by polymeric ionic liquids and itsphase transfer. Their application in photoelectric conversion and photocatalysis werealso studied.Polymeric ionic liquids as a surface modification agent in crystal growth processof cadmium sulfide, obtaining cadmium sulfide quantum dots with positively chargedsurface. Due to the cation group of polymeric ionic liquid, we obtainedpolymeric-ionic-liquid-modified cadmium sulfide quantum dots with excellentdispersibility in water and better stability compared with ionic liquids as surfacemodification agent. This result provides a possibility in phase transfer by theinterchangeability of anion of polymeric ionic liquids. It is also found in our researchthat the addition of polymeric ionic liquids can affect the sizes of cadmium sulfidequantum dots. |
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