Function-guided Synthesis And Properties Of ZnO Nanostructures

Semiconductor nanomaterials have drawn extensive attentions in the worldwide,due to their unique optical, electrical, mechanical and magnetic properties differentfrom that of bulk materials. The main challenge in this area is how to precisely controlthe crystal structures, sizes, dimensionalities and compositions of nanomaterials forrational tailoring their physical or chemical properties. In this dissertation, a lot ofvaluable explorations had been carried out on the controllable growth of ZnO crystalplanes and modulation of their properties.Inspired by natural lotus leaves, we designed lotus leaf like ZnO nanostructure. Inthis nanostructure, the “stem” was hexagonal nanorod, and the “leaf” was broadenedZnO (0001) crystal plane on the top of hexagonal nanorod with high activity. A facilesolution based route was developed for the preparation of aligned lotus leaf like ZnOnanosturcure. In this approach, ZnO nanorod array served as both reactant anddispersed template, and the precursor for the growth of nanosheet came form thedissolution of ZnO nanorods. The component, morphology and crystal structure ofas prepared sample were characterized by XRD, XPS, SEM, TEM and SAED. Theresults comfirmed that the nanosheet, with a thickness of2~4nm, was the broadenedZnO (0001) crystal plane grown along <1010> direction.The sensor based on ZnO nanolotus leaves presented excellent sensing propertyto formaldehyde. Its sensitivities to formaldehyde with different concentration werenine times higher than the nanorods one. In addition, the sensor displayed a sensitiveresponse even in the case of1ppm, which is especially useful for low concentrationformaldehyde detection. The quartz crystal microbalance (QCM) coated with ZnOnanolotus leaves displayed special sensing property to ammonia. The frequency shiftto1ppm ammonia was about16.5Hz, and the response and recovery time were lowerthan30s. A new type of sensing mechanism was proposed and proved on the QCMcoated with ZnO nanolotus leave to explain its special sensing property to ammonia.Furthermore, a novel piezoelectrical behavior was discovered on the ZnOnanolotus leaves.A hexagonal cone like ZnO nanostructure with contracted ZnO (0001) plane wasdesigned for improving the superhydrophobicity of ZnO nanostructure. A low–temperature wet chemical route, composed of seed induced epitaxial growth andelectrochemical deposition, was developed to synthesize hierarchical ZnO nanocones.This new type of hierarchical ZnO nanostructure overcame the strong adhensivity ontraditional ZnO nanostructures. The static water contact angle was elevated to158o,the contact angle hysteresis was depressed to lower than10ofrom higher than100o,and water droplets easily rolled off the hierarchical nanostructure with a tilted angle of5.8o.The hydrophobicity mechanism of ZnO nanocrystal was carefully studied throughtheoretical and experimental approach. The adsorption property of ZnO nanocrystalwas calculated by The Fist Principle Calculation. A preferential adsorption of O2wasfound on O deficient ZnO (1010) plane. The effects of oxygen ambience on thehydrophobicity of ZnO nanorod array were also studied. A superhydrophobicitymechanism via preferential O2adsorption was proposed on the ZnO nanometerials.This study provided theoretical basis for design and application of ZnOnanomaterials based superhydrophobic surface.