二氧化鈦是一種能將有害物質降解為水和二氧化碳的光觸媒之一。在本研究中以溶膠凝膠法製備二氧化鈦溶膠，其中以四氯化鈦為前驅物而過氧化氫作為塑解劑在95度高溫下將氫氧化鈦水溶液轉換成二氧化鈦溶膠。本研究之目的最主要著重於提高二氧化鈦溶膠之穩定性以及加強二氧化鈦在可見光範圍之光催化應用。加入維生素C溶液可形成電荷轉移之複合物，此有著特殊彎曲的Ti-O鍵會使二氧化鈦的光吸收度紅移至可見光區並可有效降低顆粒凝聚現象，達到系統的穩定性。本研究透過X光粉末繞射分析儀 (XRD)、雷射粒徑分析儀 (DLS)、超高真空場發射掃描式電子顯微鏡 (SEM)、穿透式電子顯微鏡 (TEM)、高解析掃描穿透式電子顯微鏡 (HRTEM)、傅立葉紅外線光譜儀 (FTIR)以及紫外光-可見光分光光度計 (UV-vis)來分析二氧化鈦溶膠和改質二氧化鈦溶膠。從XRD圖譜、選區繞射圖 (SAED)和HRTEM的晶格距離 (lattice distance)可得知樣品所對應二氧化鈦中之銳鈦礦相。而DLS和SEM呈現改質後二氧化鈦的粒徑較未改質二氧化鈦小，此外，DLS也可由ζ電位 (Zeta potential) 確認維生素C增強二氧化鈦溶膠的穩定性。維生素C-二氧化鈦溶膠所形成之Ti-O鍵可由FTIR來判定，其圖譜會出現所對應之波峰。本研究之維生素C-二氧化鈦溶膠的光降解活性使用亞甲基藍染料作為測試，經過UV-vis分析可得到：無論在紫外光或可見光的照射下，維生素C與二氧化鈦之莫爾比等於0.75比1 (AT3)的光催化效果最好。;Titanium dioxide, a kind of photocatalyst is one of the best ways to degrade harmful materials into H2O and CO2 and it has been studied by the researches. In this study, TiO2 sol was prepared by a sol-gel method using TiCl4 as precursor and H2O2 as peptizing agent in order to induce the formation of TiO2 nanoparticles that converted from Ti(OH)4 under 95 ℃. The objective of this study was to find a method to enhance the stability of the sol and improve the photocatalytic activity of TiO2 under visible light irradiation. Adding ascorbic acid solution into TiO2 sol would form a charge-transfer complex, leading to red shift TiO2 up to visible light region and decrease the agglomeration to attain the stable environment due to the formation of specific Ti-O band with large curvature. TiO2 and AA-modified TiO2 nanoparticles were characterized by XRD, DLS, SEM, TEM, HRTEM, FTIR, and UV-vis spectroscopy. XRD patterns, SAED, lattice distance of HRTEM confirm that all of samples were in anatase phase. While DLS and SEM presented that the particle size of AA-modified TiO2 was smaller than that of pure TiO2 and DLS also ensured that surface modifier would enhance the stability of TiO2 sol. The new binding of AA-modified TiO2, Ti-O-C was demonstrated by FTIR spectra. AT3 (the molar ratio of AA: TiO2= 0.75:1) showed high activity both under UV light and visible light irradiation for the photocatalytic degradation of methylene blue dye.
