Optimization of Ormosil films for optical sensor applications

Recent work has indicated that Ormosil films, fabricated from organically m odified precursors, produce better sensor performance for some specific app lications, compared to films fabricated from conventional sol-gel precurors such as TEOS or TMOS. This paper aims to compare film properties and senso r behavior for films fabricated from tetraethoxysilane (TEOS) and tetrameth oxysilane (TMOS) silica precursors and both methyltrimethoxysilane (MTMS) a nd methyltriethoxysilane (MTES) organically modified precursors. Microstruc tural differences, for example, porosity changes due to the different precu rsor backbone structures, are interrogated by monitoring oxygen gas and aqu eous-phase sensor response. Oxygen sensing using these films is enabled by incorporating in the films an oxygen-sensitive ruthenium dye whose fluoresc ence is quenched in the presence of oxygen. Film properties such as thickne ss, thickness stabilization time, as well as sensor response, are discussed in terms of relative hydrolysis and condensation behaviour for the differe nt precursors. Film hydrophobicity, an issue which has been identified as b eing of crucial importance for optimum dissolved oxygen sensor response, is discussed and contact angle measurements are used to investigate the degre e of hydrophobicity for different film types. The main motivation for this work is film optimization for optical gas-phase and dissolved oxygen sensor s.