Encapsulation of methyl orange pH-indicator into a sol-gel matrix

The acid catalyzed sol-gel reaction was used to encapsulate methyl orange pH-indicator into transparent monolithic silica matrices. Tetraethylorthosilicate was used for the entrapment of the methyl orange indicator. The immobilized methyl orange shows similar behavior as its solution counterpart. It retains its structure during the sol-gel reactions in terms of response to pH. The surface morphology indicates that the methyl orange molecules are weakly interacted within the host silica network. This study shows that the methyl orange pH-indicator can be doped into sol-gel silica matrix and used for sensing pH as a solid indicator. (C) 2005 Elsevier B.V. All rights reserved.