Synthesis of biomorphological mesoporous TiO 2 templated by mimicking bamboo membrane in supercritical CO 2

Abstract

A new approach is presented for preparing biomorphological mesoporous TiO 2 templated by mimicking bamboo inner shell membrane via supercritical CO 2 (SCCO 2) transportation through titanium tetrabutyloxide (TTBO). The analysis of wide-angle X-ray powder diffraction (XRD) showed the prepared TiO 2 in phase of anatase, and the small-angle XRD revealed the presence of mesopores without periodicity. The product exhibited the shape of crinkled films and extended in two dimensions up to centimeters. The electron microscopic observation showed that the TiO 2 films were around 200 nm in thickness, and across the films there were numerous round or ellipse-shaped mesopores, being 10–50 nm in diameter, which were formed by the close packing of TiO 2 particles. High-resolution transmission electron microscope (HRTEM) displayed that the single TiO 2 particle size was about 12.5 nm. The UV–vis absorption spectrum was transparent in the wavelength of 320–350 nm for suspensions of the prepared mesoporous TiO 2 in ethanol at the concentration of 5.0 mg/l. The mesoporous TiO 2 prepared with the aid of SCCO 2 exhibited an obvious blue shift compared with the TiO 2 prepared by sol–gel infiltration. The possible mechanism for the formation of the mesoporous TiO 2 is summarized into a biomimetic mineralization pathway. First, TTBO was transported to the membrane surface via SCCO 2, and then condensed. Hydrolysis reactions between the functional groups of organic membrane and TTBO took place to form the nuclear TiO 2, and the TiO 2 seeds grew around the organic membrane into TiO 2 mesoporous materials. The approach provides a low-cost and efficient route for the production of ceramics nanomaterials with unique structural features, which may have potential application in designing UV-selective shielding devices [S. Zhao, X.H. Wang, S.B. Xin, Q. Jiang, X.P. Liang, Rare Metal Mater. Eng. 35 (2006) 508–510].