CHROMOGENIC WPA TIO2 HYBRID GELS AND FILMS

A novel low-temperature electrochromic and photochromic material in th e form of gels and thin solid films composed of H3PW12O40. nH(2)O (WPA ) incorporated in titanium oxide gel issued of Ti(OPri)(4) with additi on of acetic acid were made via the sol-gel route by the dip-coating t echnique. Gels in bulk and thin film forms have been studied with the help of FT-IR transmission, reflection absorption and Raman spectrosco py. Similarity of the characteristic band frequencies with pure WPA co nfirmed that entrapped Keggin salt is well preserved inside the gel. P hotochromism of WPA/TiO2 gels which appears after short exposure to UV (lambda = 366 nm) radiation is related to the excitation effect of br anched alcohol leading to formation of carbonyl modes due to the alcoh ol transformation to aldehyde. Electrochromic properties of WPA/TiO2 g el films were tested in aqueous 0.001M HClO4 and 0.1M LiClO4 electroly tes as well as in the sol-gel electrochromic device (ECD) composed of LiClO4 doped ormolyte and Sb:Mo:SnO2 counter electrode film with optic ally passive response. Slight improvement of the WPA/TiO2 intercalatio n/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).