Photosensing by a fluorescing probe covalently attached to the silica

Starting from aminopropyl silicagel, an anthracene fluorophore has been covalently grafted on the surface of silica, the secondary amino group being left in the linking arm. When one fifth of the initial amino functions are grafted, the silica behaves as a pH probe, the fluorescence of which switches on when the amino groups are protonated. On the contrary, if the silica loading is almost complete, the pH probing is no longer possible. In this case, an excimeric versus monomeric emission can be used in sensing the solvent water content. An anthracene fluorophore covalently grafted on aminopropyl silicagel, behaves as a pH probe when grafting is kept at low level and shows potential as a water probe when the silica loading is almost complete.