二氧化鈦做為光觸媒是利用二氧化鈦半導體的性質。當二氧化鈦吸收了紫外光可產生電子電洞對，電子電洞分別具有強還原及氧化能力將反應物還原或氧化。但太陽光的波長大多為可見光，希望能將二氧化鈦的能隙縮小，將吸收光波長由紫外光的範圍延伸至可見光的部份，以有效利用太陽光進行光催化反應。本研究是利用溶膠凝膠法合成含過渡金屬離子Cr3+、V4+及Fe3+奈米級二氧化鈦粒子的鍍膜液。以雷射光散射粒徑儀，X光繞射儀，感應耦合電漿原子放射光譜儀及X光光電子能譜儀鑑定合成的產物。以浸漬鍍膜法將二氧化鈦在玻璃基材上，200℃鍛燒後其晶型主要為銳鈦礦。摻雜過渡金屬離子的二氧化鈦中，以摻雜釩離子對可見光的吸收能力最好。以水楊酸水溶液進行可見光光催化分解反應測試，結果發現摻雜少量鉻、鐵離子的二氧化鈦可見光光催化效果未經改質的二氧化鈦相當或稍高，而摻雜釩離子的二氧化鈦光催化活性最低。

　　　　　Titanium oxide is a semi-conducting photo-catalyst. Under UV irradiation, electrons and holes are generated in the valence band and conduction band respectively. Electrons and holes are strong reductants and oxidants. It can decompose the pollutants by irradiation of UV light. However, the solar spectrum contains a large portion of visible light. Decrease the band gap of titanium oxide in order to use solar light is the topic of recent research. In this report, nano-particles of titanium oxide doped with Cr3+、Fe3+ and V4+ were synthesized by sol-gel method. The products are characterized by laser light scattering, XRD, ICP-AES and XPS. Solutions containing titanium oxide nano-particles were coated on glass by dip-coating method. Anatase structures of TiO2 and modified TiO2 wer obtained after annealing at 200℃. Titanium oxide modified with V4+ ions obsorbs a large amount of visible light. The photo-decomposition activities of salicylic acid solution over Cr3+ and Fe3+ modified TiO2 were similar to or slightly higher than TiO2. The photo-decomposition activity is lowest over V4+ modified TiO2.