Excitation energy transfer between acriflavine and rhodamine 6G as a pH sensor

Excitation energy transfer between acriflavine (donor) to rhodamine 6G (acc eptor) molecules in water with varying pH has been studied by using steady state measurements. From absorption and fluorescence spectra of donor and a cceptor, overlap integrals for donor fluorescence and donor absorption (Ome ga(DD)) as well as donor fluorescence and acceptor absorption (Omega(DA)) h ave been calculated. The corresponding critical transfer distances for dipo le-dipole Forster mechanism of excitation energy transfer between donor-don or (R-0D) and donor-acceptor (R-0A). reduced concentration and efficiency o f energy transfer have also been calculated. It has been found that the Ome ga(DA) change with pH whereas Omega(DD) remain unchanged, resulting in chan ge in energy transfer from donor to acceptor with pH, bur no change in ener gy migration. The efficiency of excitation energy transfer is maximum For a highly basic solution and it decreases with a decrease in pH. The energy t ransfer efficiency, reduced concentration, and overlap integrals show a lin ear dependence on pH. It has been proposed that the system may be used as a wide range (1.4 to 12) pH sensor with an accuracy of 0.01. (C) 2000 Elsevi er Science S.A. All rights reserved.