Pore-size expansion of hexagonal-structured nanocrystalline titania/CTAB Nanoskeleton using cosolvent organic molecules

Pore-size expansion of hexagonal-structured assembly of nanocrystalline titania (anatase) combined with cetyltrimethyammonium bromide (CH3(CH2)15N+(CH3)3Br−, CTAB) (named as Hex-ncTiO2/CTAB Nanoskeleton) was achieved with the aid of cosolvent organic molecules (COMs). The pore-size expanded Hex-ncTiO2/CTAB Nanoskeleton was prepared through the sol–gel reaction of titanium oxysulfate sulfuric acid hydrate (TiOSO4·xH2SO4·xH2O, TiOSAH) in an aqueous solution initiated by CTAB swollen micelles pre-prepared with the addition of COMs into aqueous CTAB micellar solutions at 60 °C (the product was named as Hex-ncTiO2/CTAB/COM Nanoskeleton). Long-chain alcohol (1-hexadecanol, C16OH), normal alkane (n-decane, C10) and benzene derivatives (benzene, Bz; 1,3,5-trimethylbenzene, TMB; 1,3,5-triethylbenzene, TEB; 1,3,5-triisopropylbenzene, TiPB) were used as COMs to evaluate the effects of COM solubilization site in CTAB micelles and COM molecular size on the pore-size expansion of the Hex-ncTiO2/CTAB/COM Nanoskeleton. We found that 1,3,5-trimethylbenzene (TMB) and 1,3,5-triethylbenzene (TEB) act as effective COMs for pore-size expansion of the Hex-ncTiO2/CTAB/COM Nanoskeleton in aqueous media. Pore sizes (average diameters) of the Hex-ncTiO2/CTAB/TMB Nanoskeleton and Hex-ncTiO2/CTAB/TEB Nanoskeleton were enlarged up to 4.2 nm and 4.3 nm, respectively, while pore size (average diameter) of the Hex-ncTiO2/CTAB Nanoskeleton prepared in the absence of any COMs was 2.9 nm. We also revealed that thermal stability of the Hex-ncTiO2/CTAB/TMB Nanoskeleton became higher than that of Hex-ncTiO2/CTAB Nanoskeleton. The hexagonally pore-structure of the Hex-ncTiO2/CTAB/TMB Nanoskeleton was retained up to 400 °C, while the hexagonally pore-structure of the Hex-ncTiO2/CTAB Nanoskeleton was kept up to 300 °C.