UV-Vis and Raman Spectral Analysis of Polyaniline/Gold Thin Films as a Function of Applied Potential

Abstract

Polyaniline and polyaniline/gold films were prepared by potentiodynamic oxidation of aniline in 1 M H₂SO₄ aqueous solution, and their electrochromic properties were investigated by UV-Vis and Raman spectroscopy. Both tetrachloroaurate and gold nanoparticles were used to deposit gold onto or inside the polyaniline film based on the deposition technique used. Polyaniline films showed multiple color changes (blue to green to yellow) depending on the electrochemical reactions in the potential range −0.2 to 0.8 V vs. Ag/AgCl. The color of polyaniline films changed from transparent green to yellow at the anodic peak around 0.2 V and gradually changed from green to dark blue at potentials higher than 0.5 V. The deterioration of electrochromic properties is caused by hydrolysis of the diimine structure formed by oxidation at 0.8 V. Furthermore, the polyaniline films showed enhanced Raman characteristics (due to SERS) depending on the treatments with gold and the potentials applied to the films to control the oxidation state.

Acknowledgments

This work was supported by grants from the National Institutes of Health, RIMI program, Grant P20 MD001085, and the Department of Defense, Grant W911NF-06-1-0433 whose supports are greatly appreciated.