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  • Novel ▫$polysilsesquioxane-I^-/I_3^-$▫ ionic electrolyte for dye-sensitized photoelectrochemical cells
    Jovanovski, Vasko ...
    A new sol-gel precursor, based on 1-methyl-3-š3-(trimethoxy-4-silyl)propylđimidazolium iodide (MTMSPI+I-), was synthesized and investigated as a potential novel quasi-solid-state ionic liquid redox ... electrolyte for dye-sensitized photoelectrochemical (DSPEC) cellsof the Graetzel type. MTMSPI+I- was hydrolyzed with acidified water, and the reaction products of the sol-gel condensation reactions were assessed withthe help of 29Si NMR and infrared spectroscopic techniques. Results of time-dependent analyses showed the formation of a positively charged polyhedral cubelike silsesquioxane species, which still contained a small amount of silanol end groups that were removed after heating at 200 C. After cooling, the material formed was a tough, yellowish, and transparent solid, consisting mainly of ladderlike polysilsesquioxane species. The specific conductivity () of the nonhydrolyzed MTMSPI+I- (no I2) was 0.23 mSžcm, while the activation energy (Ea), determined from the Vogel-Tamman-Fulcher (VTF) relation, was 0.29 kJžmol. After 56 days of aging the value of the hydrolyzedMTMSPI+I- dropped to 0.11 mSžcm but the viscosity had already increased to 7500 Pa s after 17 days, demonstrating that a quasi solid state was attained. Apparent diffusion coefficients (Dapp) of I- and I3- obtained from the voltammetric measurements were ~10-7 cm2žs and decreased to ~10-8 cm2žs after 15 days of sol aging. Time-dependent vibrational spectra, which served in assessing the hydrolysis and condensation reactions of MTMSPI+I-, were measured with the help of the attenuated total reflectance (ATR) IR spectroscopic technique. The results revealed that, in the course of condensation of sols, the refractive index of the modes attributed to the polysilsesquioxane species exhibited strong dispersion, which led to a shift of the vibrational band position in the experimental ATR spectra. This effect accompanies the sol-to-gel transformations and has not yet been considered as a possible error in analysis of the ATR spectra of sols and gels. The calculation procedure for obtaining the corresponding transmission spectra is briefly outlined, and the results are applied in this work.
    Vrsta gradiva - članek, sestavni del
    Leto - 2005
    Jezik - angleški
    COBISS.SI-ID - 3319834