Photoionization of methylphenothiazine and photoluminescence of erbium 8-hydroxyquinolinate in transparent mesoporous silica films by spin-coating on silicon

Abstract

Transparent mesoporous silica films were successfully prepared by spin-coating on silicon wafers at room temperature. The X-ray diffraction patterns of the films indicate that both hexagonal and cubic mesoporous films can be formed by varying the surfactant to silicon mole ratio. These films have reasonable thermal stability and are calcinable up to 670 degreesC and crack free when thickness is less than 0.5 mum. The calcined films have a thickness of 433+/-2 nm as measured by cross-sectional scanning electron microscopy. Methylphenothiazine was incorporated into the mesoporous silica films and after photoionization by ultraviolet light, the radical cation photoproduced was characterized by electron spin resonance spectroscopy. Erbium 8-hydroxyquinolinate was incorporated into the mesoporous silica films and the mesoporous silica films with incorporated Er(III) were characterized by photoluminescence and isothermal nitrogen physisorption studies. The characteristics of the silica films were studied by X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy, high resolution transmission electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy and isothermal nitrogen physisorption. (C) 2003 Elsevier Inc. All rights reserved.