Studies on the effect of organic additives on the monolithicity and optical properties of the rhodamine 6G doped silica xerogels

Rhodamine 6G (R6G) laser dye doped silica xerogels were prepared by sol-gel processing using tetraethylorthosilicate [TEOS, Si(OC2H5)(4)] precursor, citric acid (CTA) catalyst and ethanolic R6G in the presence of various organic additives such as formamide (FA), N'methylformamide (N'MF), dimethylformamide (DMF), acetamide (AA), glycerol (GLY), oxalicacid (OXA), ethyleneglycol (EG) and diethyleneglycol (DEG). The organic additive/TEOS molar ratio was varied from 0.001 to 0.1 by keeping the TEOS/EtOH/H2O/CTA/R6G molar ratio constant at 1:5:7:1.2x10(-3):9.2x10(-6). It was found from the spectral studies of the additive modified R6G doped silica xerogels that the absorption maxima at 530 nm and emission maxima at 565 nm were increased with the addition of organic additive and with the increase of the additive/TEOS molar ratio. The transparency of the R6G doped silica xerogels was increased with the increase of additive/TEOS molar ratio from 0.001 to 0.1 with OXA, DEG and EG and in the case of DMF, N'MF, FA, AA and GLY, the transparency of the samples increased up to 0.014 of additive/TEOS molar ratio and then decreased for >0.014 of additive/TEOS molar ratio. Monolithic samples were obtained with all the organic additives. The percentage volume shrinkage of the samples was less EG and DEG and more with OXA additives. (C) 2003 Elsevier Science B.V All rights reserved.