Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, USA.
J Phys Chem B. 2012 May 10;116(18):5414-24. doi: 10.1021/jp210737c. Epub 2012 Apr 27.
The free energy and electronic fluorescence spectra of a model solute solvated by ethanol in a nanoscale silica pore are examined as a function of the solute position, with the aim of improving our understanding of solvation in nanoconfined environments. The results indicate that the position distribution of the solute depends on its dipole moment as well as on the surface interactions of the silica pore, i.e., hydrophilic or hydrophobic (uncharged). Further, the solute fluorescence spectrum is a function of the solute position in the hydrophilic pore, but is independent of position in the hydrophobic pore. The origins of these results are investigated, including by decomposition of the free energy as a function of solute position into the contributing interactions. The implications for time-dependent fluorescence (TDF) experiments, used commonly to probe solvation dynamics in nanoconfined solvent systems, are considered. The possible role of chromophore diffusion in TDF measurements, and chemistry in nanoconfined liquids more broadly, is given particular emphasis.
考察了模型溶质在纳米二氧化硅孔中被乙醇溶剂化的自由能和电子荧光光谱随溶质位置的变化，旨在增进对纳米受限环境中溶剂化的理解。结果表明，溶质的位置分布取决于其偶极矩以及二氧化硅孔的表面相互作用，即亲水性或疏水性（不带电）。此外，溶质的荧光光谱是亲水孔中溶质位置的函数，但与疏水孔中的位置无关。研究了这些结果的起源，包括通过将自由能作为溶质位置的函数进行分解，以确定贡献相互作用。考虑了用于探测纳米受限溶剂体系中溶剂化动力学的时间分辨荧光（TDF）实验的含义。特别强调了发色团扩散在 TDF 测量中的可能作用以及更广泛的纳米受限液体中的化学作用。
