本研究是以含浸法(Impregnation)與光沉積法(Photodeposition)二種方式將金沉積在二氧化鈦光觸媒表面，利用金奈米粒子本身之特性及可以補捉二氧化鈦被光激發電子的能力，有效減少電子電洞再結合速率，達成以簡易方式製備-高活性的光觸媒之目的。探討不同金含量、金粒徑、二氧化鈦粒徑及製備方式對於二氧化鈦光催化效率之影響，進一步研究金的表面電漿共振(surface plasmon resonance，SPR)現象與光催化效率之關連性。
研究工作分為物性分析與光催化效率測試兩部分，物性分析以穿透式電子顯微鏡(TEM)、X光繞射儀(XRD)、反射式紫外-可見光光譜儀(UV-VIS-DRS)、X-ray光電子能譜儀(XPS)、感應耦合電漿原子放射光譜儀(ICP-AES)、螢光光譜儀(PL)等儀器為主，而光催化效率測試則是在(a)單光源照射(UV-A)(b)雙光源照射(UV-A+GLED)下光催化降解甲基橙水溶液。PL結果顯示當二氧化鈦經由金改質後，金能有效補捉二氧化鈦照光後所躍遷到傳導帶的電子，而有效減少電子電洞再結合速率，進而增加二氧化鈦的光催化效率。UV-VIS-DRS結果顯示，Au-TiO2在波長530 ~ 570 nm左右會出現由金的表面電漿共振現象所引起之吸收峰，其峰強度大致上正比於金含量。於光催化效率測試可發現，當Au-TiO2照到綠光(GLED)會激發金產生表面電漿共振，而伴隨而來的強「電場」對於二氧化鈦於UV-A光下所激發之電子電洞對的生成量有所助益，而可以增進光催化反應活性，而SPR的行為受二氧化鈦的粒徑、性質、表面金粒子顆粒尺寸與數量影響，進而對於光催化活性有不同影響，實驗結果可知藉由改變參數以調整SPR之位置符合綠光激發光源範圍時，並增強SPR吸收強度，可以有效地增加Au-TiO2在雙光源系統下的光催化活性。

In this study, the gold-loaded titanium dioxide was prepared by photodeposition and impregnation methods for the better activity. The gold nanoparticles can capture the photoexcited electron of titanium dioxide to reduce the recombination rate of electron and hole.
In this research, the effects of content of gold, particle size of gold, particle size of titanium dioxide, and preparation methods on surface plasmon resonance (SPR) phenomenon and the photocatalytic efficiency are investigated in detail. The transmission electron microscopy (TEM) , X-ray diffraction (XRD), UV-Visible-diffuse reflectance spectra (UV-VIS-DRS), X-ray photoelectron spectra (XPS), inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and photoluminescence (PL) spectroscopy were applied to observe the morphology, crystal structure, light absorption, surface composition, gold content, and emission from the recombination of photoexcited electron and hole, respectively. The photocatalytic activity was evaluated by the decolorisation of methyl orange solution over the modified titania under illuminations of UV-A and UV-A/GLED.
The PL intensity decrease greatly with the presence of Au on TiO2 due to the electrons will be trapped by gold nanoparticles, resulting in the improvement of photocatalytic activity. The Au-TiO2 will have an absorption peak (530-570 nm) due to the surface plasma resonance effect. The SPR absorption increases with the increase of gold content. The results of photocatalytic experiments indicate the UV-photocatalytic reaction rate will be enhanced by using the illumination of green light simultaneously. The strong electric field, resulting from the surface plasma resonance excitation, is generated as Au-TiO2 is irradiated by green light. It then improves the generation rate of photoexcited electron and hole of titanium dioxide under UV irradiation. Therefore, the photoactivity of Au-TiO2 in the double beam system (UV/GLED) is better than that in single beam system (UV). The SPR phenomenon is affected by particle size of gold and TiO2, amount of gold, and coherence properties between TiO2 and Au. The experiment results show that synergistic effect between UV and green light for the improvement of photoactivity will be increased by increasing the SPR-absorption of Au-TiO2 and adjusting the wavelength of SPR to the green-light region.

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