High-pressure entrapment of rhodamine 6G into a silica matrix

The entrapment of organic dyes with interesting optical properties in silica produced by sol-gel method, has been studied over the last years, aiming to obtain a new class of optical materials. The monoliths produced by this method present cracks, large shrinkage during the silica gelation and drying, and a great porosity, which decreases their optical performance. In a previous work, to overcome these difficulties, a high pressure (4.5 GPa) technique at room temperature was used to produce compacts of silica gel doped with rhodamine 6G (R6G). In this work, we extended this study to pressures up to 7.7 GPa to verify the effect of high pressure in the fluorescence spectra of the R6G and in the density and hardness of the compacts. High density (98% of the silica density), transparent and crack-free compacts were produced, being resistent to polishing. The fluorescence spectra were similar to the ones observed in ethanol solutions. These new class of materials are potentially useful for optical applications.