Synthesis And Chracteration Of Oriented One-dimensional ZnO Micro/nanorod Arrays By A Solution Route

Due to its excellent optical properties and electron transportation ability, one-dimensional(1-D) ZnO nanomaterials have shown great potential in the field of electronic nano-devices and optoelectronic nano-devices. Especially, 1-D ZnO nanowire/rod arrays grown on substrates can be used in short wave lasers and Graetzel solar battery, which has received considerable attention among many researchers. At present, highly aligned ZnO nano-arrays are usually synthesized through vapor-phase processes or solution processes. Despite the products synthesized by vapor-phase processes have high purity, profect crystallization and controllable sizes,the reaction conditions involve in expensive apparatus, higher temperature and complicated procedures, so it is very hard to prepare ZnO nano-arrays in large scale, which constrains its applications in many nanodevices. Compared with vapor-phase process, the solution method is more advantageous in perpendicularly orientated growth of ZnO nano-arrays, owing to its simple process, low temperature and non-pollution, which makes it an effective method for preparing large-scale ZnO nanowire/rod arrays. In this paper, we report a simple solution route to grow well-aligned c-oriented 1-D ZnO micro/nanorod arrays on ITO glass. Firstly, we prepare ZnO nanoparticle seeds on ITO glass using Zn(NO3)2 and (CH2)6N4 as raw materials. Then, we synthesized well-defined 1-D ZnO micro/nanorod arrays on the above substrates in strong basic solution, using Zn(NO3)2 and NaOH as growth resources. It is proved to be a mild and profit method with low temperature(85℃) and short reaction time(1h), which provides an experimental ground for the industrialized of production.The main contents of the thesis are summarized as followed:(1) Preparation of 1-D ZnO micro/nanorod arrays1-D ZnO micro/nanorod arrays were synthesized on ZnO-seed-coated substrates in Zn(NO3)2/Zn(Ac)2-NaOH solution. In order to find the optimum way to prepare 1-D ZnO arrays, the effects of different experimental conditions were also investigated. Results show that the kind of salts, the original zinc concentration, the molar ratio of zinc to base, the reaction temperature and time, all have functions on the product. Among them, the original zinc concentration and the reaction time are the key factors to obtain well-defined 1-D ZnO arrays.(2) The influences of ZnO seeds preparation conditions on 1-D ZnO micro/nanorod arraysOn the basis of the optimum conditions to grow 1-D ZnO micro/nanorod arrays, the influences of ZnO seeds on the products were studied by preparing them in Zn(NO3)2 and (CH2)6N4 system. Both direct aging method and immerse-coating method were carried out to fabricate ZnO seeds; and the optimum way was established. Results show that the density and sizes of the ZnO seeds on substrate are the key factors to determine the growth of 1-D ZnO micro/nanorod arrays.(3) The roles of surfactant in the fabrication of 1-D ZnO micro/nanorod arrays Using the direct aging method to prepare ZnO seeds, the influences of different ionic surfactants on the 1-D ZnO micro/nanorod arrays were studied. The experiments indicate that the cation surfactant CTAB with low concentration can promote the c-axis orientation and the uniformity of the product. Anionic surfactants SDS and SDBS can reduce the size of ZnO nanorods significantly; SDS can enhance the orientation of the arrays, while SDBS markedly decrease the orientated growth along c-axis. This is due to the difference in the spacial structures of SDS and SDBS.