Preparation, Structure And Property Of Zinc Oxide With Different Morphology

Nanomaterial is a very important research area of nanoscience and nanotechnology. ZnO, which is an important direct band gap semiconductor material, has been attracting a great deal of attention due to its unique structures and excellent electrical, magnetic, optical and piezoelectric properties as well as great potential applications in nanogenerators, sensors, optoelectronic devices and biodetectors. Many studies have proved that ZnO with different morphologies have different properties. Morphology-controlled synthesis of multiple ZnO micro/nanostructures and studying their morphology-related properties would be an interesting work. Many methods have been developed to synthesize various ZnO micro/nanostructures. For instance, ZnO nanobelts, microspheres, nanowires and nanorods have been prepared by physical vapor deposition (PVD), hydrothermal method, molecular beam epitaxy (MBE) and magnetron sputtering method, respectively. To date, ZnO yolk-shell nanostructures have rarely been reported.In our work, zinc citrate microspheres with different morphologies were synthesized by solution chemistry method. And ZnO yolk-shell nanospheres were prepared using zinc citrate microspheres as precursor.(1) Amorphous zinc citrate microspheres could be successfully prepared from zinc nitrate, hexamethylenetetramine (HMT) and tripotassium citrate solution at90℃for20min and an ageing process. As the ageing time increases from0to12h, the morphology of the zinc citrate particles transforms from solid microspheres through yolk-shell microspheres to hollow microspheres. On the basis of experimental results, the Ostwald ripening mechanism is employed to understand the evolution of morphology for zinc citrate microspheres.(2) By calcination of amorphous zinc citrate at600℃for2h, the crystalline ZnO solid nanospheres, yolk-shell nanospheres and hollow nanospheres were prepared. The SEM and TEM observations reveal that the obtained ZnO nanospheres have a certain decrease in size but the morphologies are perfectly inherited after calcination.(3) Compared with ZnO solid nanospheres and hollow nanospheres, ZnO yolk-shell nanospheres exhibit the largest visible emission which can be attributed to the maximal number of radiative defects at the interfaces of the ZnO yolk-shell nanospheres. ZnO yolk-shell nanospheres show the highest photocatalytic activity for the degradation of MO due to their largest surface area.(4) Spindle-like and twined hexagonal rod-like ZnO were prepared form zinc nitrate and dimethylamineborane (DMAB) solution by hydrothermal method at120℃for10h. By adjusting the reaction time, the formation mechanism of twined hexagonal rod-like ZnO is studied. ZnO with different morphologies could be prepared by adding different soluble salts into the reaction solution and their photoluminescence properties are studied.