Structural changes induced by the catalyst in hybrid sol-gel films: a micro-Raman investigation

The effect of acid catalysts on the structure and properties of zirconia-ba sed hybrid organic-inorganic thin films obtained by sol-gel, starting from gamma -glycidoxypropyl-trimethoxysilane (GLYMO) and zirconium n-propoxide Z r(C3H7)(4), is studied by means of micro-Raman spectroscopy. The kind of ne twork formed during the polymerisation process depends on the catalyst: thi s modifies the reactivity of the organic moiety of the GLYMO and a glass fo rmer behaviour is obtained only when the epoxy ring of the GLYMO is cleaved . Unopened epoxy rings, on the other hand, may protect the guest luminescen t molecules. like the azo-dyes, to acid attacks. Nitric and acetic acids ar e reported as examples. (C) 2001 Elsevier Science B.V. All rights reserved.