STUDY OF 1-NAPHTHOL AS A FLUORESCENT-PROBE FOR THE SOL TO GEL TO XEROGEL REACTION OF MIXED ALUMINUM AND SILICON SYSTEMS

The fluorescence spectrum of 1-naphthol was observed, as a function of time, during the sol to gel to xerogel reaction of a mixed system composed of tetraethyl orthosilicate and diisobutoxyalumino triethoxy silane (silicon to aluminium ratio of approximately 9:1) catalysed by HCl. It was found that the fluorescence of 1-naphthol shifts to the red (predominant emission originating from the 1L(a) state) in the first stage of the reaction. This red shift reflects the increase in the polar nature of the matrix surrounding the doped 1-naphthol molecules. In the next stage of the reaction, the spectrum shifts to the blue (predominant emission originating from the 1L(b) state). This blue shift reflects the increase in the viscosity around the doped 1-naphthol molecules. The change in the fluorescence spectrum of 1-naphthol provides a sensitive means of probing the structural, chemical and physical characteristics which occur around the probe molecules during the sol-gel process.