Fluorescence probing of solvent accessibility and micropolarity on silica and alkylated silica surfaces

The highly solvatochromic probe "Fluoroprobe", which fluoresces in a wide r ange of the visible spectrum, was covalently attached to silica and alkylat ed silica particles to study, solvent accessibility and surface micropolari ty. A two step attachment method was used which was found to lead to a quit e homogeneous distribution of the probes without extensive local clustering . On silica the probe experiences a local dielectric constant of epsilon = 6, while its solvent accessibility is ca. 30%. On alkylated silica this red uces to epsilon = 3.4 and ca. 23% respectively.