Effect of method of preparation on photophysical properties of Rh-B impregnated sol-gel hosts

Rhodamine-B (Rh-B) impregnated sot-gel samples have been prepared using two different methods - mentioned as the dope and dip methods. Two types of dye impregnated samples were prepared using the dope method and one type using the dip method. A comparative study of photophysical properties of the three types of samples were carried out with the lapse of time of preparation up to about an year. The two types of samples prepared by dope method showed degradation in absorption/fluorescence properties with the lapse of time whereas no such degradation was observed with those samples prepared by dip method. The change in the absorption/fluorescence properties of Rh-B in dope samples has been associated with the increasing acid environment during sol-gel-xerogel transitions resulting in conversion of molecular form from cation to weakly fluorescent higher protonated form of Rh-B. On the other hand, Rh-B in dip samples have very stable absorption/fluorescence properties with high fluorescence quantum yield value equal to 0.98(+/-0.1). On the basis of a comparative study of the three types of Rh-B impregnated samples, Rh-B dipped samples were found to have the best performance and may be useful as laser active materials in solid state dye lasers. (C) 2002 Elsevier Science B.V. All rights reserved.