Organic amines (decylamine, dodecylamine, octodecylamine) and titanium iso-propoxide (Ti( i OPr) 4 ) were purchased from Aldrich, and used without further treatment. Doubly distilled water and absolute ethanol were used as solvents.
Synthesis: For the synthesis of mesoporous TiO 2 , 0.01 mol Ti( i OPr) 4 was dissolved in 10 mL absolute ethanol. The molar ratio of organic amine to Ti( i OPr) 4 was fixed to 1:3. The organic amine was dissolved in absolute ethanol together with the Ti( i OPr) 4 , then added slowly to doubly distilled water. Typically, 0.0033 mol organic amine was dissolved in 10 mL ethanol, followed by the addition of 0.01 mol Ti( i OPr) 4 . The resulting solution was added slowly to 40 mL distilled water under sonication (volume ratio of ethanol/water = 1:4). After the addition, the suspension was sonicated at ambient temperature for 6 h by a high-intensity ultrasonic probe (Misonix, XL sonifier, 1.13 cm diameter Ti horn, 20 kHz, 100 W/cm 2 ). During sonication, the temperature of the suspension rose to 80 C. The powder was separated by centrifugation. For the removal of the surfactant, the as-prepared sample was post-treated by extraction with dilute solution of HNO 3 in ethanol, washed three times with ethanol, then dried overnight under vacuum. Calcination at 350 C for 8 h under vacuum, or at 450 C for 4 h under air were also used for the removal of the organic amine. Evidence for the complete removal of the amine and other organic residues is obtained from Fourier transform infrared (FTIR) measurements that will be reported elsewhere.
Characterization: Low-angle (2 ~10) and wide-angle X-ray powder diffraction (XRD) patterns were obtained using a Bruker D8 diffractometer, using Cu Ka irradiation. High-resolution transmission electron microscopy (HRTEM) studies were carried out on a Phillips CM-120 electron microscope. The samples for HRTEM were prepared by dispersing the final powders in ethanol; this dispersion was then dropped on carbonยฑcopper grids. The nitrogen adsorption and description isotherms at 77 K were measured using Micromeritics (Gemini 2375) after the samples dried at 170 C for 1 h. BrunauerยฑEm-mettยฑTeller (BET) surface areas were calculated from the linear part of the BET plot. Pore-size distributions were calculated using the BarretยฑJoynerยฑHalenda (BJH) model with Halsey equation [26]. The pore volume was measured at the P/P 0 = 0.9947 signal point.