本論文提出以簡易的化學反應,製備銀奈米粒子之研究。 奈米粒子之製備可約略分為三大類,第一類為雷射消熔法(laser ablation method);第二類為金屬氣相合成法(metal vapor synthesis method);第三類為化學還原法(chemical reduction method)。本實驗是以化學還原法製備奈米銀粒子,使用過氯酸銀、硝酸銀加入還原劑及保護劑來控制奈米銀粒子之大小。由於奈米銀能提供二氧化鈦粒子捕捉電子與電洞的基位,使得受光激發後的電子與電洞對不易再結合,故二氧化鈦粒子之光催化活性能夠提升。而二氧化鈦可藉由煅燒來改善奈米粉體的結晶度;煅燒過程使二氧化鈦的結晶度提高,消除非晶形成份後,光催化活性得以提高。將二氧化鈦粉末沉浸在奈米銀溶液中,以化學吸附的方式讓奈米銀自然吸附在二氧化鈦粒子之表面,再比較以化學還原奈米銀至二氧化鈦粒子之表面方式,藉著奈米銀可降低電子與電洞對再結合之能力而使二氧化鈦粒子光催化活性提高,而由對亞甲基藍光催化測試結果證實其真實性。將產物進行TEM、XRD、UV-VIS、粒徑分析儀等儀器的特性分析。
Preparations of nanoparticles could be classified into three categories. The first is 〝laser ablation method〞; the second is 〝metal vapor synthesis method" ; and the third is〝chemical reduction method〞. In the present study, synthesis of Ag nanoparticles was carried out by simple chemical reduciton methods. Sodium borohydride (NaBH4), silver perchlorate(AgClO4) and silver nitrate (AgNO3) was employed as starting precursors. It is found that protective reagent such as sodium citrate is important for the controlling size of silver nanoparticles. It was also found that silver nanoparticles improved the catalystic effect of TiO2. Nano silver on TiO2 offers an longer duration for the recombination of electron and hole and the catalystic activity of TiO2 was enhanced. Silver nanoparticles adsorbed onto the surface of porous TiO2 was achieved via chemical adsorption and chemical reduction process. Photocatalytic activity of TiO2 and Ag-coated TiO2 was evaluated by degrading methylene blue solution. X-ray, UV/Vis spectrophotometer was employed to characterize the synthesized products. The size and morphology of silver adsorbed onto the surface of TiO2 were observed by TEM.