Synthesis And Properties Of Micro-/nanomaterials Based On ZnO

Zinc oxide(ZnO) is an important II-VI direct band gap semiconductor material, with a wide band gap(3.37 eV) and high exciton binding energy(60 meV). Zinc oxide nanomaterials possess excellent properties of both nano material and semiconductor material Zinc oxide micro/nanomaterials have much more siperior characteristics than general zinc oxide in photoelectric, piezoelectric and thermoelectric properties. In recent years, micro/nano ZnO have attracted great ateention at home and abroad.Hollow hamburger-like and other couple-layered ZnO microstructures have been fabricated by a facile solvothermal process using the mixture of water and alcohol as solvents. The volume ratios of water/glycerol play an important role for the morphologies of the microstructures. In the case of a volume ratio of 1/2, the hamburger-like ZnO microstructures are created by employing zinc glycerolate(C3H6O3Zn) as a sacrificial template. A possible formation process from precursor C3H6O3 Zn to ZnO is proposed by arresting a series of intermediate phase and the formation mechanism of the microstructures is proposed accordingly. The volume ratios of water/glycerol, such as 1/10, 1/6, 1/4, 1/2 and 1/1, were adjusted to create the microstructures with various morphologies. The results indicated that the morphologies of resulting samples changed from quasi-rhombic C3H6O3 Zn plates to various couple-layered ZnO microstructures, suggesting that water is responsible for the formation of couple-layered structures. In addition, the investigations on the formation of ZnO microstructures in the mixtures of water and various alcohols, including water/ethanol, water/isopropyl alcohol, water/n-butyl alcohol, water/ethylene glycol and water/glycerol, reveal that alcohols are crucial to control the morphologies of microstructures. The multi-hydroxyl alcohol, e.g. ethylene glycol and glycerol, favour the formation of hollow structures compared with the case of single-hydroxyl alcohol.A wet-chemical route has been demonstrated to investigate the chemical dependence of morphology and growth kinetic of high crystalline ZnO microstructures from zinc citrate microspheres created by Zn(Ac)2 and trisodium citrate as precursors. The Fourier-transform infrared spectroscopy and thermogravimetric analysis were used to determine optimal preparation parameters. The concentrations of precursor zinc citrate and the addition of trisodium citrate were key factors in the controlling of ZnO microphologies. Assembled growth resulted in the formation of ZnO microstructure with twin-cone and flower-like morphologies. The ZnO flower was consisted of cone petals. The shape of ZnO microstructures was further adjusted using trisodium citrate to created thin and thick hexagonal-plates. In the case of a high Zn concentration, thick hexagonal-plates were split into a flower-like morphology. The investigation of morphological evolution indicated that trisodium citrate is critical to control the growth rate of polar(0001) plane. The formation of a flower-like structure is ascribed to the assembly of crystal units with a high zinc citrate concentration.The synthesis of ZnO nanoflowers(NFs) by thermal decomposition in organic media has been studied in this work. The analysis was focused on parameters, like stirring rate, surfactant and reaction growth kinetics, given that they are crucial for scaling up the synthesis of ZnO NFs. These parameters have been shown to control nanoparticle size and morphology. ZnO NFs were prepared by thermal decomposition of zinc hydroxide in organic media at different stirring rates. Data showed that during ZnO synthesis, particle growth exhibits a oriented attachment behavior and a final oriented attachment process. The results indicated that the ZnO NFs exhibit an obvious improvement in response to acetone compared with the other structures. The uniform ZnO NFs-reduced grapheme oxide nanocomposites(ZnO-RGO NCs) are successfully synthesized via a facile method by intimately coating ZnO NFs with RGO. The photocatalytic test of degradation of Rhodamine B shows that the ZnO-RGO NCs exhibit an enhancement of photoactivity than ZnO NFs.A novel olvothermal process has been developed to synthesize uniform couple-layered ZnO microstructures and transition metal ions doped ZnO in ethylene glycol. The synthesis conditions have been carefully studied and the products have been extensively characterized by SEM. In particular, hysteresis loop of the Ni-doped ZnO microstructures prove that the Co atoms occupy the Zn sites of wurtzite ZnO. Also, cholamine improves the room temperature magnetic properities.