Optimization of the specific surface area of ordered mesoporous TiO2 yields a high response to humidity

Owing to their unique surface adsorption characteristics, the controlled synthesis of highly ordered mesoporous materials with high adsorption traits is of utmost importance. In the present work, ordered mesoporous TiO2 (OMT) with tunable channels was prepared via a facile soft-templet evaporation-induced self-assembly (EISA) method. The effect of phenol-formaldehyde resins (PF) and the ratio of triblock copolymer (F127) and tetrabutyl titanate (TBOT) on the OMT surface was studied by BrunauerEmmettTeller (BET) and scanning electron microscopy (SEM) analysis. The samples without PF resol did not offer any ordered mesoporous formation, while a highly ordered mesoporous structure was obtained for samples with PF resol. For the prepared samples, the specific surface area SSA∼141–254 m2/g, average pore size SP∼5.3–9.8 nm and pore volume VP∼0.29–0.45 cm3/g were obtained by controlling the ratio of F127 and TBOT. For 95% relative humidity (RH), the OMT with optimum specific surface area (SSA∼220 m2/g) and small pore size (SP∼5.3 nm) showed a high response (SR∼3.5 ×105), fast response time (26 s) and good long-term stability (over 90 days). Finally, the structure, morphology and chemical composition of the samples were determined by XRD, SEM, HRTEM, and XPS techniques to predict and authenticate the plausible sensing mechanism.