Fluorescence Spectroelectrochemical Sensor for 1-Hydroxypyrene

A spectroelectrochemical sensor was demonstrated for an organic compound whose oxidation proceeds through an electron transfer−chemical reaction−electron transfer (ECE) mechanism to generate new chemical species that are used for detection by fluorescence. The polycyclic aromatic hydrocarbon 1-hydroxypyrene (1-PyOH) served as a representative model analyte. The spectroelectrochemical properties of 1-PyOH in solution were explored with an optically transparent thin layer electrode. Electrochemical oxidation of 1-PyOH under acidic conditions proceeds via the ECE mechanism to a diquinonepyrene, which shows reversible electrochemistry and fluoresces at 425 nm in its reduced form, dihydroxypyrene. The sensor consisted of a tin-doped indium optically transparent electrode coated with a Nafion thin-film (20 nm) that rapidly preconcentrated the analyte at the sensor surface. Fluorescence in the film was excited by the evanescent wave from attenuated total reflection spectroscopy. Electrochemical modulation of dihydroxypyrene fluorescence at 425 nm in the 500 to −200 mV (vs Ag/AgCl) potential range was used for indirect detection of 1-PyOH. The spectroelectrochemical sensor calibration curve had a range of 5 × 10−9 to 1 × 10−6 M with a calculated detection limit of 1 × 10−9 M.