Nobuaki Negishi

Study of 1-naphthol as a fluorescent probe for the sol to gel to xerogel reaction of mixed aluminium and silicon systems

Abstract 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 1La 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 1Lb 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.

Photoluminescence properties of La2O3 methane coupling catalysts

La2O3 catalysts prepared at 923 K (La2O3-LT) and 1073 K (La2O3-HT) exhibit different photoluminescence properties due to notably different concentrations of ions in position of low coordination at the surface or coordinatively unsaturated surface sites (cus). The catalyst which exhibits the higher yields of photoluminescence due to the higher concentration of cus corresponds to the one which gives the higher C2+ selectivity in the oxidative methane coupling reaction.