Abstract—

Nanostructured titanium dioxide (TiO₂) with a crystallite size from 10 to 85 nm, photocatalytically active for organic reactions under illumination with visible light, has been prepared by a sol–gel process using a titanium tetrabutoxide solution in ethanol with an initial pH of 6. According to X-ray diffraction characterization results, the as-prepared titanium dioxide was amorphous. Annealing in a hydrogen atmosphere for 1 h at 400°C led to the formation of an anatase phase, and annealing in the temperature range from 600 to 800°C resulted in the anatase–rutile phase transition. The crystallite size of titanium dioxide increased from 10 to 75 nm as the annealing temperature was raised from 400 to 1000°C (furnace annealing for 1 h) and from 60 to 85 nm as the annealing time at a temperature of 800°C was increased from 30 to 240 min. Diffuse reflection spectra showed that the band gap of TiO₂ decreased from 3.3 to 2.6 eV as the annealing temperature was raised from 200 to 1000°C. The specific surface area data obtained by BET measurements showed that the samples annealed at the highest temperature (1000°C) had the smallest surface area, which dropped from 307 to 1 m²/g. The efficiency of the synthesized TiO₂ tested as a catalyst for oxidative \(S_{{\text{N}}}^{{\text{H}}}\) cross-coupling of acridine with indole demonstrated an in crease in product yield from 35 to 80% as the annealing temperature was raised to 800°C. Varying the 800°C annealing time from 30 to 180 min had no effect on the reaction product yield, which ranged from 70 to 80%.

中文翻译：

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光催化活性增强的纳米TiO 2的合成及理化性质

摘要—

纳米二氧化钛（TiO ₂）具有10至85 nm的微晶尺寸，在可见光照射下对有机反应具有光催化活性，这是通过溶胶-凝胶法，使用四丁醇钛的乙醇溶液（初始pH为6）制备的。衍射表征结果，所制备的二氧化钛为无定形。在氢气气氛中于400°C退火1小时导致形成锐钛矿相，在600至800°C的温度范围内退火导致锐钛矿-金红石相变。随着退火温度从400升高到1000°C（炉退火1小时），二氧化钛的微晶尺寸从10增大到75 nm，而随着在800℃温度下的退火时间的增加，二氧化钛的微晶尺寸从60增大到85 nm 30至240分钟。随着退火温度从200℃升高到1000℃，₂从3.3 eV降低到2.6 eV。通过BET测量获得的比表面积数据表明，在最高温度（1000℃）下退火的样品具有最小的表面积，从307降至1m ² / g。测试合成的TiO ₂作为催化剂对a啶与吲哚的氧化\（S _ {{\ text {N}}} ^ {{\ text {H}}} \）的交叉偶联的效率证明了产品的增加退火温度提高到800°C时，产率从35％增至80％。将800°C的退火时间在30至180分钟之间变化对反应产物的收率没有影响，反应产物的收率范围为70％至80％。