醇热技术制备TiO2纳米晶的荧光光谱及荧光量子产率

Fluorescence Spectra and Quantum Yield of TiO_2 Nanocrystals Synthesized by Alcohothermal Method

采用钛酸四丁酯醇热技术制备了TiO2纳米晶溶胶,透射电子显微镜(TEM)照片显示其为粒径小于10nm的类球形形貌。该纳米晶在最大激发波长375nm激发下,在450nm处产生稳定的强荧光。不同浓度TiO2纳米晶的荧光光谱和吸收光谱表明,该发光带不仅受粒子量子尺寸效应的影响还与带内缺陷能级和表面态的电子跃迁有关,是三者共同作用的结果。以硫酸奎宁在激发波长313nm的荧光量子产率0.55为标准,测得TiO2纳米晶在不同激发波长下的荧光量子产率。结果表明,TiO2纳米晶在激发波长330～370nm范围内有较高的荧光量子产率(约为0.20),远高于文献报道值(10-3数量级)。据此,TiO2纳米晶有望成为一种有前途的无机纳米荧光探针。

Fluorescence spectra and fluorescence quantum yield of TiO2 nanocrystals were studied. Using tetra n-butyl titanate as a starting material, a facile alcohothermal technique was used to synthesize TiO2 nanocrystals. As can be seen from the transmittance electron microscopy （TEM） image, TiO2 nanocrystals with a relatively uniform particle size distribution of 〈10 nm are present in the transparent sol. The transparent sol presents a strong stable fluorescence emission with a maximum at 450 nm, which is greatly dependent on the size quantization effects, defect energy level and the surface state of TiO2 nanocrystals. The quantum yield （γ） of TiO2 was determined by the relative comparison procedure, using freshly prepared analytical purity quinine sulfate in 0.05 mol·L^-1 H2SO4 as a relative quantum yield standard. The emission quantum yield of TiO2 nanocrystals prepared in alcoholic media was calculated to be about 0.20 at wavelengths ranging from 330 to 370 nm, which was much higher than the values reported in previous works. So, it is supposed that nano-TiO2 will be applied as a potential quantum dots fluorescence probe in biological analysis.