Grafting Mechanism of Electrochromic PAA–WO₃ Composite Film

ISSN： 0022-4596

Source： Journal of Solid State Chemistry, Vol.142, Iss.2, 1999-02, pp. : 368-373

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Abstract

A micro-Raman spectroscopic study has been carried out to investigate the electrochromic process in a porous and nanocrystalline tungsten oxide film. The film was prepared by dipping the tin-doped indium oxide glass into an aqueous mixture solution of PAA (polyacrylic acid) and WO₃–NH₄OH. After heating at low temperature, around 100°C, the film was treated in 1 N HCl in order to achieve polycondensation, where the ammonium ion was replaced with a proton. In the micro-Raman spectra for the bleached and colored PAA–WO₃ films, it was evident that the coloration accompanies a peak reduction at ∼960 cm^-1 and a peak enhancement at ∼810 cm^-1. Based upon the present Raman observation, we can confirm that the electrochromism of the nanocrystalline tungsten oxide is dominated by the grafting process, i.e., the surface modification of –W^VI=O bonds into –W^V=O^(1-δ)+—M^δ+ (M=H, Li) ones.