Picosecond Studies of Electronic Relaxation in Triphenylmethane Dyes by Fluorescence-Upconversion

Abstract

The electronic relaxation in solution of triphenylmethane dyes, TPM(Fig. 1), such as crystal violet (CV) and malachite green (MG), has been studied in several ways and is found to show a significant dependence on solvent viscosity. The fluorescence quantum yield, Q, is very small (<0.1) in fluid solvents, but increases to about 30% in extremely viscous media [1–3]. Both fluorescence yield studies and picosecond spectroscopic kinetic measurements [4–8] of the decay of excited state absorption (ESA) and of the rates of ground state repopulation (GSR) show that increased solvent viscosity leads to reduced rates of electronic relaxation.