Potential and film thickness dependence of the photoluminescence of aryl amine polymers

• Published in: Electrochimica acta 2004-09, Vol.49 (22), p.3687-3692
• Main Authors: Antonel, P.S., Andrade, E.M., Molina, F.V.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conducting polymers; Exact sciences and technology; Fluorescence; Metallic quenching; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Photoluminescence; Physics; Redox switching; Solid organic materials; Voltammetry
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2003.11.036

The fluorescence of polyaniline (PANI) and poly(2-methoxyaniline) (PMOA) films has been studied as a function of potential and film thickness. The fluorescence measurements were conducted on polymer films of different thicknesses on platinum electrodes. Absorption spectra were also recorded, using PANI films on semitransparent gold electrodes. The fluorescence emission intensity, in the reduced state as a function of polymer film thickness (measured through the voltammetric charge) shows a complex behaviour. For low thicknesses, none or minimum emission is observed; this is attributed to the metallic quenching of the fluorescence. Beyond a critical thickness, the emission increases sharply, then reaches a maximum and finally decays slightly towards a limiting value. The decay is interpreted as due to the attenuation of the waves reflected on the metal surface: both the excitation wave absorbed after being reflected, and the emitted one reaching the detector after reflection are exponentially attenuated as the film thickness increases. In the case of PMOA, a polymer that, depending on the synthesis conditions, shows either conducting or non-conducting (redox) behaviour, the conducting form has a fluorescence response similar to that of PANI, whereas the non-conducting form shows low emission.