Characterization of molecular scale environments in polymer films by single molecule spectroscopy
Characterization of molecular scale environments in polymer films by single molecule spectroscopy
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DOI：
10.1021/jp992312y
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发表时间：
2000-01-20
影响因子：
3.3
通讯作者：
Higgins, DA
中科院分区：
文献类型：
--
作者：
Hou, YW;Bardo, AM;Higgins, DA
单分子光谱方法用于获得薄聚乙烯醇（PVA）和聚甲基丙烯酸甲酯（PMMA）薄膜中分子尺度环境的极性和刚性的详细信息。在这些实验中，尼罗河红被用作环境特性的高灵敏度光谱探针。记录了许多单分子的荧光光谱，并通过将光谱拟合到高斯函数来确定其峰的位置和宽度。利用尼罗红电荷转移跃迁与周围介质性质关系的新模型对光谱数据进行了分析。这个模型是基于Marcus (Marcus， R. A， J. Phys。化学，1990,94,4963)。分析所需的附加信息是通过广泛的体液相吸收和荧光研究获得的。发现PVA的环境分布具有广泛的不均匀性。结果表明，显著依赖于PVA膜的含水量，与水合膜的结果表明，刚性环境较少的存在。与PVA的结果相反，在PMMA薄膜中发现了两种不同的环境。在使用上述模型分析数据的基础上，可以得出结论，这两种环境的刚性不同，但极性几乎相同。
Single molecule spectroscopic methods are used to obtain detailed information on the polarity and rigidity of molecular-scale environments found in thin poly(vinyl alcohol) (PVA) and poly(methyl methacrylate) (PMMA) films. Nile Red is employed as a highly sensitive spectroscopic probe of environmental properties in these experiments. Fluorescence spectra are recorded fur numerous single molecules and their peak positions and widths determined by fitting the spectra to Gaussian functions. The spectral data are analyzed using a new model for the dependence of the Nile Red charge-transfer transition on the properties of the surrounding medium. This model is based on previous work by Marcus (Marcus, R. A, J. Phys. Chem. 1990, 94, 4963). Additional information required for the analysis is obtained fi om extensive bulk solution-phase absorption and fluorescence studies. A broad inhomogeneous distribution of environments is found fur PVA. The results are shown to depend significantly on PVA film water content, with the results for hydrated films indicating the presence of less rigid environments. In contrast to the PVA results, two distinct classes of environments are found in the PMMA films. On the basis of an analysis of the data using the aforementioned model, it is concluded that the two environments differ in rigidity but have nearly identical polarity.