Electrodeposition Synthesis And Properties Of Quasi-2D ZnO-based Nanostructures

Nanostructures have became a mature field during the last decades and expanded with remarkable progress into many areas of physics, chemistry, biology, environment, medicine, materials science, etc., and have provided an ever-increasing number and promising applications. The nature of the nanomaterials is not only related to their chemical composition and size, but also involved in their crystal structure, electronic structure, surface state, micromorphology, assembly mode and so on. Research on nanostructures mainly include preparation, microstructure, properties and their applications, in those aspects the synthesis method is the prerequisite supporting technology as well as the significant and predominant object to focus on. Our research is intended to prepare high performance nanomaterials, based on ZnO by specific ultra thin liquid layer electrodeposition combined with other methods to synthesize quasi-two-dimensional semiconductor nanostructures with unique morphology and superior performance. The main contents are as follow:Study on ultrathin liquid layer electrodeposition synthesized multi-functional ZnO nanosheets(NSs) film. The ZnO nanosheets film was obtained through ultra thin liquid layer electrodeposition on Si/SiO2 substrates, and the formation was caused by the cyclic variation of the frontal sediment. The surface of the nanosheets was porous, rough and with special exposure facet, plenty of vacancy oxygen. In terms of above characteristics, the ZnO nanosheets film was investigated from two aspects: for gas sensor, the film exhibited intensive selectivity and quick response/recovery for detecting NO2 at a low working temperature; for surface-enhanced Raman scattering(SERS), the film showed high sensitivity and conspicuous enhancement to 4-Mpy molecules.Study on Au decorated ZnO nanosheets synthesized by ultra thin liquid layer electrodeposition and replacement method for recyclable SERS application. The obtained dendritic Zn/ZnO nanosheets consisted of polycrystalline Zn microwires and single crystal ZnO nanosheets. Further, replacement reaction between Zn and HAuCl4 led to Au nano-particles decorated on ZnO heterostructure nanosheets. The size and density of Au nano-particles could be modulated by changing the concentration of the HAuCl4 solutions. Moreover, the Au decorated ZnO nanosheets were promising as high SERS-active substrates with UV catalytic decomposed cleanable and regenerated property.Study on ZnO/ZnSe heterostructure parallel arrays and their optoelectronic properties. Through quasi-2D electrochemical deposition system and thermal process, ZnO/ZnSe heterostructure parallel arrays were prepared; the corresponding mechanism is that, selective and alternate deposition for Zn and ZnSe followed by high temperature oxidation, and the periodic change of the deposition potential and the ion concentration at the tip of deposited substrate. The ZnO/ZnSe heterostructure is “Type Ⅱ”, which means there is indirect electronic transition between the valence band of ZnSe and ZnO at the interface, that contribute to the optical absorption range enlarging and the optical response broadening from the ultraviolet to visible light.Study on ZnO nanosheets on plastic substrate and optoelectronic properties of the flexible substrate for the first time. It was found that the optoelectronic properties basically kept unchanged after the plastic substrate bending with curve radius r=1.3, r=1.6 and r=2.1cm respectively.