Solvation and spectra of a charge transfer solute in ethanol confined within nanoscale silica pores.

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.