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

Abstract

Pore-size expansion of hexagonal-structured assembly of nanocrystalline titania (anatase) combined with cetyltrimethyammonium bromide (CH 3(CH 2) 15N +(CH 3) 3Br −, CTAB) (named as Hex-ncTiO 2/CTAB Nanoskeleton) was achieved with the aid of cosolvent organic molecules (COMs). The pore-size expanded Hex-ncTiO 2/CTAB Nanoskeleton was prepared through the sol–gel reaction of titanium oxysulfate sulfuric acid hydrate (TiOSO 4· xH 2SO 4· xH 2O, 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-ncTiO 2/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-ncTiO 2/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-ncTiO 2/CTAB/COM Nanoskeleton in aqueous media. Pore sizes (average diameters) of the Hex-ncTiO 2/CTAB/TMB Nanoskeleton and Hex-ncTiO 2/CTAB/TEB Nanoskeleton were enlarged up to 4.2 nm and 4.3 nm, respectively, while pore size (average diameter) of the Hex-ncTiO 2/CTAB Nanoskeleton prepared in the absence of any COMs was 2.9 nm. We also revealed that thermal stability of the Hex-ncTiO 2/CTAB/TMB Nanoskeleton became higher than that of Hex-ncTiO 2/CTAB Nanoskeleton. The hexagonally pore-structure of the Hex-ncTiO 2/CTAB/TMB Nanoskeleton was retained up to 400 °C, while the hexagonally pore-structure of the Hex-ncTiO 2/CTAB Nanoskeleton was kept up to 300 °C.