Hydrothermal Synthesis Of Nano-Sized Zno And Its Polymer Hybrid Material By Polyacrylate As Stabilizer And Controller

Nano-sized ZnO has become an important basic material because it possesses many advantages such as low price, nice chemical stability, wide band gap (3.2eV) and large excition binding energy of60meV. It has been widely applied in areas such as biology, medicine, chemistry, electronics and ceramics. At present the synthesis of nano-sized ZnO can be divided into physical and chemical approaches. Hydrothermal approach, one kind of chemical approaches, is favored by the researchers for the merits of simple operation, elimination of expensive devices and low cost.In this study, my primary work is as follows:(1) First, sodium/potassium polyacrylate is synthesized from acrylate and sodium hydroxide/potassium hydroxide by aqueous solution polymerization with ammonium persulfate as catalyst. Through changing the concentration and feeding methods, sodium/potassium polyacrylate with different molecular weight is prepared.(2) Through a hydrothermal approach with sodium/potassium polyacrylate as the stabilizer and controller, ZnO nano-particles are synthesized from zinc acetate dehydrate and aqueous ammonia. The sizes of the particles are in the range of two nanometers to five nanometers with good distribution. The steric repulsion by the molecular chains of polyacrylate and the electrostatic stabilization by the charges on the chain confine the growth of the ZnO nano-crystallines and prevent the aggregation of ZnO nano-particles.(3) The ZnO nano-particles are packed by sodium/potassium polyacrylate and they form nano-microspheres together. The preferred growth direction of nano-particles is parallel to the [001] crystallographic direction (c-axis).(4) Nano-microspheres consisted of ZnO and sodium/potassium polyacrylate can be synthesized in the presence of different molecular weight sodium/potassium polyacrylate in a certain concentration range. As the concentration of sodium/potassium polyacrylate increases, the diameters of the nano-microspheres decrease.(5) The nano-microspheres can disperse stably in aqueous solution for dozens of days without any deposition. The stably distribution of ZnO nano-particles in aqueous solution is achieved. After adding the precipitating solvent of acetone into the aqueous solution, the nano-microspheres are deposited. The precipitates can dissolve in water again and stable aqueous solution with good distribution is obtained. (6) Acrylamide and ammonium persulfate are dissolved in the aqueous solution with ZnO nano-particles in it. After the polymerization of acrylamide and volatilization of water, nano-sized ZnO/poly acrylamide hybrid material is obtained.