Fluorescence of polyaniline films on platinum surfaces. Influence of redox state and conductive domains

Fluorescence of polyaniline films on electrode surfaces: Thickness dependence and surface influence

“…A Teq-03 potentiostat under computer control was employed. Both the electropolymerization and the fluorescence experiments were conducted in a specially constructed cell, allowing to perform electrochemical processes with simultaneous fluorescence or absorbance measurements [37]. It is a rectangular cell (5.94 cm  9.03 cm, wall thickness 0.50 cm), made of high density polyethylene.…”

“…As discussed previously [37], in the analysis of photoluminescence of solid films, it must be considered the absorption of both the excitation and emission beams by the film material, as well as the reflective properties of the supporting surface in order to have quantitatively correct results. When a fluorescent film of thickness L, supported on a reflective surface, is irradiated with an excitation beam of intensity I 0 (of wavelength k 0 ), the corrected emission intensity I m,c is related to the intensity measured at the detector I m , at a given emission wavelength k e , by where f 0 and f e are the metal reflectance values at k 0 and k e respectively, a 0 and a e are the respective absorption coefficients, h 0 is the incidence angle of I 0 and h e is the angle of emission [37].…”

“…When a fluorescent film of thickness L, supported on a reflective surface, is irradiated with an excitation beam of intensity I 0 (of wavelength k 0 ), the corrected emission intensity I m,c is related to the intensity measured at the detector I m , at a given emission wavelength k e , by where f 0 and f e are the metal reflectance values at k 0 and k e respectively, a 0 and a e are the respective absorption coefficients, h 0 is the incidence angle of I 0 and h e is the angle of emission [37]. For platinum supported films, Eq.…”

“…More recently [36,37], the fluorescent emission of PANI in different redox states was studied, measuring the quantum yield of the base forms of LE and EM in solution with NMP as solvent. The leucoemeraldine base spectrum in NMP shows an emission maximum at a wavelength k em = 384 nm.…”

“…In the case of PANI films in the salt form, for small thicknesses no emission was observed; as the film thickness increased, the observed intensity increased, reached a maximum and afterwards decreased slightly. The fluorescent behaviour of PANI films as a function of applied potential was also studied [37], applying a correction to account for absorption in the film and reflection at the metal surface. It was observed a decrease in emission intensity as the polymer film is oxidized (going from 0.1 to 0.6 V vs. RHE), leaving a small but not null emission when the polymer is in the emeraldine state.…”