Preparation of Nano-Sized Zinc Oxide in Amphiphilic Polymer Gel Network and Evaluation of Luminescence Properties

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Nano-sized zinc oxide (ZnO) particles show the quantum size effect, and the luminescence intensity and wavelength depend on the particle size. The preparartion methods of nano-sized ZnO particles have been investigated actively. However, nano-particles grow or aggregate easily, and lose the properties of nano particles. In this study, the preparation of nano-sized ZnO particles in the polymer gel network was proposed, and the improvement of the stability of formed nano-sized ZnO particles in the gel and the capability of the control of particle size by the preparation composition of gel were examined.Amphiphilic N,N-dimethylacrylamide gel which are absolutely transparent was used. The gel was synthesized by a radical polymerization in ethanol, and the plate type gels of 2 mm thickness were prepared with various conmpositions of cross-linker. The effective network size was evaluated by measuring the relationship between the probe molecular size and the rejection efficiency. Polyethylene … More glycols of various molecular weights were used as the probe molecules. The preparation of nano-sized ZnO particles consists of the following two steps : (1)preparation of precursor by reacting zinc acetate with ethanol at 80℃ for 3 hours and (2)hydrolysis of the precursor with lithium oxide in a ultra-sonic bath. In the preparation of nano-sized ZnO particles in the gel, the dried gel was swollen in ethanol containing the desired amount of zinc acetate. The subsequent procedures were same as those mentioned above.The onset wavelength (λ_<onset>) of the absorption spectrum of ZnO colloid which is related to the particle size shifted to longer wavelength with time at 50℃. The colloid became opaque and the precipitate was observed within 2 days. On the other hand, the λ_<onset> of ZnO particles prepared in the gels scarcely changed over one month, and the gel was absolutely transparent. The λ_<onset> depended on the preparation composition of gel, i.e., the concentration of cross-linker. These results suggest that nano-sized ZnO particles formed in the gel are extremely stable and that the particle size can be controlled by the cross-linking density of gel. Less