Study On Optical Characters Of Dye Doped Silica Gels

The sol-gel process was an effective and feasible method in the preparation of organic dyes doped the inorganic matrix, which promoted the research of organic-inorganic optical composite system. This field was always active, especially in the solid laser dye materials. In recent years many organic dyes such as fluorescence dyes, laser dyes, nonlinear optical dyes and phototropic dyes were inducted into the inorganic matrix or ormosils.Silica gels have lots of unique capabilities, nicer heat-insulating property, low density with porous structure, good transparency, low reflect index, nice mechanical elasticity, big surface area, for instance. These properties made it to be applied in many fields as optics, catalysis, sensor, high-energy physics, mechanism and so on. With the development of the sol-gel process the crazing problem in the bulk of aerogel has been settled.Silica gels were provided with even far-reaching applications foreground.In this paper dyes doped silica gels were prepared by sol-gel method in order to find the relationship between the character and the structure of the composite. Techniques and theories will be attributed to the fabricating the excellent solid tunable dye lasers material.In the first chapter the application and development of organic-inorganic composite and the existent questions were introduced in the brief. The question for discussion was brought forward. Some basic problems, including the principle of the sol-gel method, the effect factors of the process, the measure to avoid crazing and the advantage, were discussed.In chapter two, we selected the appropriate experiment conditions andsuccessfully prepared the sample with dense structure and lesser aperture.In the third chapter, the optical properties of dyes doped silica gels were studied. Owing to the shield of silica network, the stability of organic dyes increased. Doped in silica gels, the dye molecules were isolated and adsorbed in the tiny pores of the inorganic network steadily. Most of them existed in the form of monomer, so the spectra were similar to that of a single molecule.The polyvinyl alcohol(PVA) in precursor can improve the porosity and make the aperture distribution narrower. So the gels were not easily crazing when drying. Simultaneously the fluorescence intensity of the dyes increased as a result of the probabilities of radiationless transitions. From the emission spectra of coumarin 102(C102) in different conditions, it showed that C102 molecule existed single in both the composite material films. The sample catalyzed by acid had flat surface and dense structure but it had hackly surface and open structure catalyzed by the alkali.In the fourth chapter, the fluorescence spectra for Coumarin 102(the donor) at a concentration of 2 10-3niol/L and Rhodamine 6G (the acceptor) at various concentrations in ethylene glycol and in silica films were measured. The results displayed that the spectra were wider than that of one single dye and there were energy transfer between C102 and Rh6G.In silica films the energy transfer efficiency was higher than that in ethanol solutions. All the results showed that the material we made can be better used in the solid laser dye materials.