The Research On The Synthesis And Properties Of The ZnO Based One Dimensional Nanocomposites

Today the synthesis and the application of nanomaterials has become one of the key research areas for countries all over the world. One dimensional nanomaterials are now the hop spot of research of nanotechnologies because of their fresh new physical, chemical and biological properties and their potential usage in the nano-instruments. So we conducted a systematic reasearch on the synthesis of one dimensional ZnO based nanomaterials and their gas sensitivity and photocatalytic properties.The traditional hydrothermal solution method was modified and a simple precursor ultrasonic-assisted-hydrothermal solution method was designed. At the temperature of 120℃, the ZnO nanorods were synthesized with this method, the nanorods with high output were uniform in structure and well dispersed. The results show that the output and uniformity of the nanorods could be improved if the precursor solution was ultrasound treated and some ZnO crystal nucleus thus produced as crystal seeds had been reacted in hydrothermal-solution reaction. We systematically studied the influence factors like assistants, reaction temperatures and reaction time that affected the ZnO nano morphologies and structures. The results demonstrate that the cationic surfactant CTAB and the organic macromolecule surfactant PEG400 are the best assistants for control synthesis of one-dimensional ZnO.The solid ZnAc₂·2H₂O and NaOH were creatively used as raw materials, and were put into the alcoholic solution that contained PEG400 as assistants and at the low temperature of 120℃, ZnO nano wires and nanorods could be synthesized at one step, their diameters were around 20 nm. The percentage of NaOH plays a key role in controlling the length of ZnO nanomaterials. Thus we suggest that the ZnO nanorods and nanowires' growth mechanism is dissolution-alcoholysis-nucleation mechanism.The gas sensing properties of ZnO nanomaterials with different structures were measured by mixing detected gas and air in static state. In comparison with ZnO nanoparticles, one- dimensional ZnO nanomaterials have higher gas sensitivity and better gas sensing stability. One-dimensional ZnO nanostucture was higher in gas sensitivity than zero dimensional structure. Through analysis with SEM photographs and data of specific surface area, we concluded the main reason to be that after the gas sensor had been sintered through high temperature, one dimensional ZnO may retain its morphology and form large amount of gas channels that provided relatively high effective surface area.The creative modification with Pd and Pt quantum dots (QDs) method on oxide gas sensing materials had effectively increased the sensitivity and selectivity of the sensors. Pd and Pt QDS were synthesized with solution-grown method and the study found that the modification with Pd and Pt QDS method was more effective and convenient than the traditional doped method. We used Pd QDs to modify ZnO nanowires, thus we got the highly sensitive and highly selective H₂S gas sensor. The sensor can detect H₂S gases of ppb grade. After being modified by Pt QDs, the gas sensitivity of the ZnO nanowires had improved considerably, the minimum amount of alcohol and HCHO it could detect had lowered.A simple photochemical precipitation method was used to synthesize a new gas sensitive material of Ag-doped ZnO nanorods. The results show that this new type of material had outstanding gas sensing capability and can detect alcohol at ppm grade.Since ZnO and WO3 can both be synthesized into one-dimensional nanomaterials and have good photocatalytic properties, their compound ZnWO₄ might be synthesized into one-dimensional nanomaterials and could have good photocatalytic properties. A simple precipitation-hydrothermal method was used without any assistants to synthesize the ZnWO₄ nanorods that were uniform in structures, well dispersed, of high output and had the diameter of 20 nm and length of around 200 nm. We systematically studied the influence of reaction temperature and time on the formation and degree of crystallization of one-dimensional nanostructure. And we propose the growth mechanisms of the ZnWO₄ nanorods to be nucleation-nanorods forming-crystallization. We studied the photoluminescence performance of the ZnWO₄ nanorods synthesized under different conditions and their photocatalytic degradation efficiency of the organic dye RhB. We found that at the temperature of 200℃with reaction time of 16 hours, the products we got was of small diameters, uniform in morphologies, high in fluorescence emissive power, of high crystallization and its photocatalytic degradation efficiency of RhB was so high that it was almost comparable to the highly efficient catalyst TiO₂ (Degussa P-25).