Abstract
A novel low-temperature electrochromic and photochromic material in the form of gels and thin solid films composed of H3PW12O40·nH2O (WPA) incorporated in titanium oxide gel issued of Ti(OPr i )4 with addition of acetic acid were made via the sol-gel route by the dip-coating technique. Gels in bulk and thin film forms have been studied with the help of FT-IR transmission, reflection absorption and Raman spectroscopy. Similarity of the characteristic band frequencies with pure WPA confirmed that entrapped Keggin salt is well preserved inside the gel. Photochromism of WPA/TiO2 gels which appears after short exposure to UV (λ=366 nm) radiation is related to the excitation effect of branched alcohol leading to formation of carbonyl modes due to the alcohol transformation to aldehyde. Electrochromic properties of WPA/TiO2 gel films were tested in aqueous 0.001M HClO4 and 0.1M LiClO4 electrolytes as well as in the sol-gel electrochromic device (ECD) composed of LiClO4 doped ormolyte and Sb:Mo:SnO2 counter electrode film with optically passive response. Slight improvement of the WPA/TiO2 intercalation/deintercalation kinetics was obtained with the films exhibiting one order of magnitude higher electronic conductivity which were made with addition of in situ polymerized pyrrole with Fe(NO3)3.
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