Ag-PVA和Ag-PVA/TiO_2复合超薄膜的制备及性能研究

Fabrication and Characteristics of Ag-PVA and Ag-PVA/TiO_2 Ultrathin Composite Films

用3种方法制备了银纳米粒子-聚乙烯醇复合体系,其中用加热还原法所得体系中Ag纳米粒子的尺寸较大(15nm),其表面等离子体共振吸收峰较宽,最大吸收波长位于420nm;用室温硼氢化钠还原法得到的复合体系的吸收峰蓝移至409nm,且峰形较窄,Ag纳米粒子的平均粒径为8.7nm;低温NaBH4还原法所得体系吸收峰进一步蓝移至397nm,此时Ag纳米粒子粒径最小(3.5nm).将室温还原法所得Ag-PVA复合体系旋涂成膜,所得薄膜光滑、透明、均匀性好,该法适用于制备多层薄膜,以调控薄膜的厚度和光谱性质.将Ag-PVA复合体系与钛酸四丁酯(Ti(OnBu)4)的乙醇溶液交替旋涂得到Ag-PVA/TiO2有机/无机复合薄膜.紫外-可见吸收光谱研究表明,随着Ag-PVA层数的增加,薄膜的表面等离子体共振吸收强度呈线性增加,但是TiO2层数的增加对吸收光谱没有明显影响.Ag-PVA/TiO2有机/无机复合薄膜将金属纳米粒子、有机高分子与无机半导体材料结合在一起,这种多层纳米结构在光电、催化功能薄膜等方面具有潜在的应用前景.

Ag nanoparticle-PVA composite systems were prepared by three methods. In the heatinginduced reduction, Ag nanoparticles formed had a diameter of 15 nm, and showed a broad surface plasmon resonance absorption band at λmax 420 nm. In the ambient reduction by NaBH4, the surface plasmon resonance absorption of Ag nanopartieles blue-shifted to 409 nm, and became narrower. The average diameter of Ag nanoparticles produced was 8.7 nm. When the reduction process was carried out at low temperature （0 ℃ ） , the absorption of Ag nanoparticles further blue-shifted to 397 nm, and 3.5 nm Ag nanoparticles were obtained. Smooth, transparent and uniform thin films were fabricated by spin-coating the Ag nanoparticle-PVA composite systems on substrates. This approach is suited for preparation of uniform multilayer films of varied thicknesses and spectroscopic properties. When Ag-PVA composite system and Ti（OnBu）4 ethanolie solution were alternatively spin-coated on substrate, Ag-PVA/TiO2 composite films were obtained. UV-Visible spectra showed a regular film growth and enhancement of film absorption with increasing the number of Ag-PVA layers. In contrast, no significant effect of TiO2 layers was observed on the absorption spectrum of film. Such organic/inorganic nanostructured multilayer films may be promising in optical, electronic, and catalytic applications.