Fluorescence resonance energy transfer from Fluorescein to Safranine T in solutions and in micellar medium

Energy transfer by dipole–dipole interaction between anionic dye Fluorescein and cationic dye Safranine T (3,6 diamino-2,7-dimethyl-5-phenyl phenazinium chloride) solubilised in aqueous solution and micellar solution of cetyl trimethyl ammonium bromide (CTAB) was studied where donor–acceptor Förster critical radius (R0) is larger than the micellar diameter (dm). The mechanism of quenching of fluorescence of Fluorescein by Safranine T in aqueous solution and in normal micellar medium has been related to the non-radiative energy transfer processes. The value of overlap integral and critical energy transfer distance is higher in CTAB micellar medium compared to that in the aqueous solution. The variation of quantum yield and efficiency of energy transfer between two dyes in micellar medium and aqueous solution has been compared. Effect of viscosity on the fluorescence resonance energy transfer (FRET) between the dye pairs has been determined from fluorescence anisotropy study.