Fluorescence Probing of Solvent Accessibility and Micropolarity on Silica and Alkylated Silica Surfaces

Abstract

The highly solvatochromic probe “Fluoroprobe”, which fluoresces in a wide range of the visible spectrum, was covalently attached to silica and alkylated silica particles to study solvent accessibility and surface micropolarity. A two step attachment method was used which was found to lead to a quite homogeneous distribution of the probes without extensive local clustering. On silica the probe experiences a local dielectric constant of ϵ = 6, while its solvent accessibility is ca. 30%. On alkylated silica this reduces to ϵ = 3.4 and ca. 23% respectively.