An optical pH sensor based on excitation energy transfer in Nafion® film

Excitation energy transfer, between a dye pair (acriflavine and rhodamine 6G) doped in an ion exchange polymer matrix (Nafion®), has been investigated from the viewpoint of fabrication of an optical pH sensor. The study is done by steady state as well as time domain fluorescence measurements. Using fixed donor–acceptor concentration, excitation energy transfer in the pH range 2–12 has been found to follow Förster function for dipole–dipole interaction. Further, pH has been calibrated by the energy transfer parameters, e.g. overlap integral ΩDA, energy transfer efficiency ηT, rate of energy transfer KR, critical transfer distance R0A and reduced concentration γ0A in the range 2–12 and is found to show an approximately linear dependence. These results in Nafion® matrix are similar to those found by us in solution [Sens. Actuators: B Chem. 63 (2000) 18]. The system appears to be attractive for optical pH sensor with reversibility and sensitivity of 0.01 pH units.