A fluorescence gas sensor based on Förster Resonance Energy Transfer between polyfluorene and bromocresol green assembled in thin films

An innovative gas sensor based on Forster Resonance Energy Transfer (FRET) has been developed. It comprises the optimization of thin blend films composed of a conjugated semiconducting polymer (host) and a conveniently chosen pH indicator dye (guest) as sensing agent for acid vapors. Spectroscopic characterization of the films demonstrates that upon exposure to HCl gas, quenching of the polymer emission due to energy transfer process is enlarged. Hence, the dramatic spectral change experienced by the dye in acid atmospheres even at low concentration constitute the principle to achieve a quantitative and sensitive detector using the Forster mechanism modulation of the polymer fluorescence as transduction signal. At low and moderate acid concentration, the detector shows relatively fast response and repeatability after consecutive exposure-recovery cycles, whilst these features wipe away at higher acid vapor contents. The concentration dependence of the fluorescence can be described by an appropriate model that takes into account resonant and non-resonant contributions to the observed photoluminescence.