Low-Temperature Reverse Microemulsion Synthesis, Characterization, and Photocatalytic Performance of Nanocrystalline Titanium Dioxide

Nanocrystalline titanium dioxide (<svg style="vertical-align:-3.13504pt;width:31.25px;" id="M1" height="14.7125" version="1.1" viewBox="0 0 31.25 14.7125" width="31.25" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(1.25,0,0,-1.25,0,14.7125)"> <g transform="translate(72,-60.23)"> <text transform="matrix(1,0,0,-1,-71.95,63.41)"> <tspan style="font-size: 12.50px; " x="0" y="0">T</tspan> <tspan style="font-size: 12.50px; " x="7.5268059" y="0">i</tspan> <tspan style="font-size: 12.50px; " x="11.00264" y="0">O</tspan> </text> <text transform="matrix(1,0,0,-1,-51.92,60.28)"> <tspan style="font-size: 8.75px; " x="0" y="0">2</tspan> </text> </g> </g> </svg>) was synthesized in microemulsions by using cetyltrimethylammonium bromide (CTAB) as surfactant. In order to investigate the crystal transformation and photoactivity at low temperature, the as-prepared precipitates were aged at 65°C or calcined at various temperatures. Analyses using powder X-ray diffraction (XRD) and Fourier transform infrared microscopy (FT-IR) showed that precursors without aging or calcination were noncrystal and adsorbed by surfactant. After aging for 6 h, the amorphous <svg style="vertical-align:-3.13504pt;width:31.25px;" id="M2" height="14.7125" version="1.1" viewBox="0 0 31.25 14.7125" width="31.25" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(1.25,0,0,-1.25,0,14.7125)"> <g transform="translate(72,-60.23)"> <text transform="matrix(1,0,0,-1,-71.95,63.41)"> <tspan style="font-size: 12.50px; " x="0" y="0">T</tspan> <tspan style="font-size: 12.50px; " x="7.5268059" y="0">i</tspan> <tspan style="font-size: 12.50px; " x="11.00264" y="0">O</tspan> </text> <text transform="matrix(1,0,0,-1,-51.92,60.28)"> <tspan style="font-size: 8.75px; " x="0" y="0">2</tspan> </text> </g> </g> </svg> began to change into anatase. The obtained catalysts, which were synthesized in microemulsions with weight ratios of n-hexanol/CTAB/water as 6 : 3 : 1 and calcined at 500°C, presented the highest photocatalytic degradation rate on methyl orange (MO), while the catalysts, which were aged at 65°C for 90 h, also exhibited an outstanding photocatalytic performance and a little higher than that of the commercial titania photocatalyst Degussa P25.