Sol - Gel Process Samples And Their Optical Properties Study

Recent development in the process of oxide glass preparation by the sol-gel method which is an organic polymerization procedure based on the hydrolysis and condensation reactions opened the possibility to use these superior materials as an oxide matrix of organic dyes. RhB laser dyes, one of whose key problems in the investigation and application was the matrix which hosted the dye, were successfully embedded in SiOa gels.Many aspects of dye doped SiCb gels had been studied, but the photoluminescence (PL) during different periods of the sol-gel process and the effect of the refluence, etc., had not yet been reported. Those were the main problems that were involved in this series of experiments.In the first and second chapter, some basic problems, including the procedure of the sol-gel method, the effect factors of the process, and the advantage were discussed. The basic advantage of the sol-gel process is its ability to form inorganic structure (semiconductor, ceramics and glasses) at relatively low temperature.In the third chapter, the PL of dye doped SiO2 gels, the effect of refluence on PL, the degree of aggregation of dye, and the effect of intensity of RhB on PL, etc., were studied.The starting materials in all of the experiments were: tetraethylorthosilicate [Si(OC2H4)4, TEOS], deionized water[H2O], ethanol[C2H5OH], Rhodamine B[RhB], and nitric acid[HNO3] in which the ratio of the materials in volume was TEOS: C2H5OH: H2O=1:4:20. The addition of HNO3 making the PH of the solutionequal 1 was applied as catalyst for the hydrolysis of TEOS. (1) TEOS was hydrolyzed and polymerized using refluence method at 60癈 for 2 hours. The sol thus obtained was highly transparent and then it was sealed for 10 days. Subsequently, dried gel was prepared by baking the sample at about 90癈 for 7 days. During the course, the PL spectra of different periods of the sol-gel course were measured by RF-5301 (PC) S (Shimadzu corporation, made in Japan). The peaks of the PL of the embedded dyes exhibited red shift in the whole process while the intensity increased first and then decreased. (2) Another group of samples were made without refluence during the period of hydrolysis and polymerization process while all the other steps were the same. The PL spectra during the period of aging were also obtained. Red shift of the peak wavelength was observed while the degree of the shift without refluence was much stronger.Moreover, absorption spectra of RhB doped SiO2 gels were obtained. We found that the degree of aggregation of the dye decreases because the SiO2 may be regarded as a hydroxylic, relatively polar environment, less polar than water although controversy still exists on the role of water in causing aggregation.In addition, the effect of intensity of RhB which was doped in SiO2 gels on PL spectra was studied. It was found that with the increase of RhB, the peaks of the PL exhibited red shift, which is also the rule of RhB in water.In chapter four, the expectation of sol-gel method's application in some fields in the future was presented.