Wang Jun-Ling, He Zhi-Qun, Wang Yong-Sheng, Mu Lin-Ping, Ye Shi, Jing Xi-Ping
Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2009 Jul;29(7):1740-4.
Thin nano-porous silica films doped with high concentrations of fluorescent material, 2, 5-bis (5-tert-butyl-2-benzoxazolyl)-thiophene (BBOT) were prepared via a sol-gel process. Uniform and bright blue fluorescence was observed. Light emission properties of these organic molecule doped inorganic silica films, i.e., hybrid films, were measured using ultraviolet-visible (UV-Vis) absorption spectroscopy, steady and time-resolved fluorescence spectroscopy as well as optical microscopy. Features of these materials were revealed in this investigation: Firstly, photoluminescence intensity from BBOT doped silica films increased linearly as the concentrations of BBOT increased if the dopant concentration was relatively low and below 6 x 10(-3) mol x L(-1); Secondly, no molecular aggregation or phase separation was observed using optical microscopy when the BBOT concentration was below 6 x 10(-3) mol x L(-1) in BBOT doped silica films. Thirdly, the fluorescence lifetimes of BBOT in the doped silica films were longer than that in a dilute dioxane solution (1.957 ns), which was contradicted to our general understanding that the fluorescence lifetime may be reduced in a condensed matter due to molecular interactions or quenching. It was further found that the fluorescence lifetime also varied with the gelation conditions. Taking a BBOT concentration of 6 x 10(-3) mol x L(-1) for an example, the lifetime of BBOT in doped silica films was about 2.45 ns for a specimen polymerized at 50 degrees C; while the lifetime was increased to 3.04 ns for a specimen polymerized at 90 degrees C. This work demonstrates no concentration quenching when the BBOT dopant concentrations increased to as high as 6 x 10(-3) mol x L(-1) in the silica matrix. In comparison with the changes in time-resolved photoluminescence of BBOT in dioxane solution and that of the BBOT doped nano-porous silica in relation to their concentration dependence and the gelation conditions, it was found that concentration quenching can be effectively suppressed by the nano-porous silica matrix. A stable fluorescent organic-inorganic hybrid material is thus obtained.
通过溶胶 - 凝胶法制备了掺杂高浓度荧光材料2,5 - 双（5 - 叔丁基 - 2 - 苯并恶唑基） - 噻吩（BBOT）的薄纳米多孔二氧化硅薄膜。观察到均匀且明亮的蓝色荧光。使用紫外 - 可见（UV - Vis）吸收光谱、稳态和时间分辨荧光光谱以及光学显微镜对这些掺杂有机分子的无机二氧化硅薄膜，即混合薄膜的发光特性进行了测量。本研究揭示了这些材料的特性：首先，如果掺杂剂浓度相对较低且低于6×10⁻³ mol·L⁻¹，BBOT掺杂二氧化硅薄膜的光致发光强度随BBOT浓度的增加呈线性增加；其次，当BBOT掺杂二氧化硅薄膜中BBOT浓度低于6×10⁻³ mol·L⁻¹时，用光学显微镜未观察到分子聚集或相分离。第三，掺杂二氧化硅薄膜中BBOT的荧光寿命比在稀二氧六环溶液中的荧光寿命（1.957 ns）长，这与我们通常的理解相反，即由于分子相互作用或猝灭，凝聚态中的荧光寿命可能会降低。进一步发现荧光寿命也随凝胶化条件而变化。以BBOT浓度为6×10⁻³ mol·L⁻¹为例，在50℃聚合的样品中，掺杂二氧化硅薄膜中BBOT的寿命约为2.45 ns；而在90℃聚合的样品中，寿命增加到3.04 ns。这项工作表明，当二氧化硅基质中BBOT掺杂剂浓度增加到高达6×10⁻³ mol·L⁻¹时，不存在浓度猝灭。与二氧六环溶液中BBOT的时间分辨光致发光变化以及BBOT掺杂纳米多孔二氧化硅的时间分辨光致发光变化与其浓度依赖性和凝胶化条件的关系相比，发现纳米多孔二氧化硅基质可以有效抑制浓度猝灭。从而获得了一种稳定的荧光有机 - 无机杂化材料。
