Microscopic vs. macroscopic structural evolution of SiO2 sols and gels employing a tailor-made fluorescent reporter dye
Microscopic vs. macroscopic structural evolution of SiO2 sols and gels employing a tailor-made fluorescent reporter dye
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使用定制荧光报告染料观察 SiO2 溶胶和凝胶的微观与宏观结构演化
DOI：
10.1039/b501622c
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发表时间：
2005
影响因子：
--
通讯作者：
U. Resch‐Genger
中科院分区：
文献类型：
--
作者：
B. Unger;K. Rurack;R. Müller;H. Jancke;U. Resch‐Genger
用荧光光谱、动态光散射(DLS)、~(29)Si核磁共振和重量分析等方法研究了温和条件下制备的溶胶-凝胶材料的短期和长期结构演化和老化过程。结合前者，介绍了一种新开发的具有两个不同强度和拓扑结构的亲酸中心的给体-受体取代的荧光探针。它在微观尺度上检测极性、亲水性和孔体积等参数的变化方面的性能与其他两种染料以及DLS、核磁共振和重量法揭示的宏观变化进行了比较。在溶胶-凝胶过程的早期阶段，荧光法、DLS和核磁共振显示了类似的变化，这是具有不同合成参数的SiO_2溶胶结构演变的典型特征。在溶胶老化的后期，DLS和核磁共振反映了网络的生长，并表明所有的溶胶都接近相似的结构平衡。荧光测定法通过发出高质子活度的可移动物种逐渐减少的信号来支持这些发现。只有从DLS结果中才能很明显地看到凝胶化后形成的跨团簇，而荧光团的局部环境基本保持不变。然而，这种荧光染料即使在长期老化过程中也能够报告微观变化。用荧光法和重量法可以很容易地观察到凝胶的干燥，并有明显的溶剂化毛孔收缩。在反应后期，量身定制的染料的荧光性质仍然对环境敏感。
The short- and long-term structural evolution and aging of sol–gel materials prepared under mild conditions are studied by fluorometry, dynamic light scattering (DLS), 29Si NMR and gravimetry. In combination with the first, a newly developed donor–acceptor-substituted fluorescent probe with two acidophilic sites of different strength and topology is introduced. Its performance in detecting changes in parameters such as polarity, proticity, and pore volume on the microscopic scale is compared to two other dyes and to the macroscopic changes revealed by DLS, NMR and gravimetry. At early stages of the sol–gel process, fluorometry, DLS and NMR reveal similar changes which are typical of the structural evolution of SiO2 sols having different synthesis parameters. During later times of sol aging, DLS and NMR reflect the growth of the network and indicate that all sols approach similar structural equilibria. Fluorometry supports these findings by signalling a gradual decrease in mobile species with high proton activity. The formation of the spanning cluster upon gelation is strongly evident only from DLS results while the local environment of the fluorophore remains largely unchanged. However, the fluorescent dye is able to report microscopic changes even during long-term aging. Drying of the gels with a pronounced contraction of solvated pores is readily observable by fluorometry and gravimetry. During the late reaction stages, the fluorescence properties of the tailor-made dye are still sensitive toward the environment.