Synthesis and Characterization of Hierarchical Biomorphic Mesoporous TiO2 Nanosheets Using Caltrop-Stem as Biotemplate

Biomorphic TiO2 nanosheets with hierarchical mesoporous structures were synthesized through facile infiltration and thermal decomposition using caltrop stems as biotemplates. Thermo-gravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscope, atomic force microscopy, N-2 adsorption-desorption equipment and UV-visible diffuse reflectance spectra were applied to characterize the microstructures of the samples. Results indicate that the as-synthesized TiO2 nanosheets with thickness of about 5 nm are composed of anatase phase. The surfaces of TiO2 nanosheets were constructed by a large number of mesopores, which pore diameter is in the range of 3.5-9 nm. Compared to TiO2 powders (P25), the as-synthesized TiO2 nanosheets exhibit a clear red shift (20 nm) showing an enhanced visible photocatalytic activity. The photocatalytic activity of the TiO2 nanosheets for the decolorization of methylene blue under sunlight irradiation is superior to P25 powders.