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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Spatiotemporal Evolution of Fixed and Mobile Dopant Populations in Silica Thin-Film Gradients as Revealed by Single Molecule Tracking
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Spatiotemporal Evolution of Fixed and Mobile Dopant Populations in Silica Thin-Film Gradients as Revealed by Single Molecule Tracking

机译：硅薄膜梯度中固定和移动掺杂物种群的时空演化，如单分子跟踪所揭示的

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Investigations of single molecule diffusion and entrapment within sol-gel-derived silica thin film gradients are reported for the first time. Gradient films were prepared on silica-sublayer-coated substrates by infusion-withdrawal dip-coating [Chem. Mater. 2010,22,2970]. This method employs a sol of time- varying composition obtained by slowly mixing two different sols in the deposition reservoir. Tetramethoxysilane (TMOS) and methyltrimethoxysilane (MTMOS) were employed as precursor silanes. Films exhibiting macroscopic, unidirectional gradients in methyl content were obtained. Fourier transform infrared (FTCR) microscopy data provide proof of gradient formation, depicting an increase along the gradient in Si-CH3 absorption at 1275 cm~(-1) relative to Si-O-Si absorption at 1080 cm~(-1). Widefleld fluorescence videos recorded as a function of position for Nile Red-doped films depict spatially varying populations of immobile and mobile molecules. The immobile fraction is believed to be incorporated in the silica sublayer, while the mobile molecules reside in/on the gradient. Diffusion coefficients, D, measured from single molecule tracking data depict, on average, a gradual increase in molecular mobility between the TMOS and MTMOS ends of the gradient. The mobile fraction is observed to split into two separate populations toward the MTMOS end of the gradient. Simultaneously, the width of the D distribution for the most mobile population is found to increase. Comparison with simulated results suggests that the TMOS end of the film is relatively homogeneous, while the MTMOS end exhibits increased heterogeneity. It is concluded the MTMOS end may incorporate TMOS- and MTMOS-rich "domains". Plots of mean square displacement in time provide no evidence for confined diffusion, suggesting the molecules move freely between these domains.
机译：首次报道了溶胶-凝胶衍生的二氧化硅薄膜梯度中单分子扩散和截留的研究。通过注入-抽出浸涂法在二氧化硅底涂层的基材上制备梯度膜。母校2010,22,2970]。该方法使用通过在沉积容器中缓慢混合两种不同溶胶而获得的时变组成溶胶。四甲氧基硅烷（TMOS）和甲基三甲氧基硅烷（MTMOS）被用作前体硅烷。获得了在甲基含量上表现出宏观的单向梯度的膜。傅里叶变换红外（FTCR）显微镜数据提供了梯度形成的证据，描绘了相对于1080 cm〜（-1）的Si-O-Si吸收，沿1275 cm〜（-1）的Si-CH3吸收沿梯度的增加。尼罗红掺杂胶卷记录的宽荧光荧光视频是位置的函数，描述了固定和移动分子的空间变化。据信固定部分被结合在二氧化硅亚层中，而移动分子则驻留在梯度中/上。从单分子跟踪数据测得的扩散系数D平均表示梯度的TMOS和MTMOS端之间的分子迁移率逐渐增加。观察到流动部分在梯度的MTMOS末端分裂为两个单独的总体。同时，发现大多数流动人口的D分布宽度增加。与模拟结果的比较表明，薄膜的TMOS端相对均匀，而MTMOS端则显示出更高的异质性。可以得出结论，MTMOS端可以合并TMOS和MTMOS丰富的“域”。时间的均方位移图未提供有限扩散的证据，表明分子在这些结构域之间自由移动。

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