AbstractA simple, rapid (10 min), one-pot, single-step method for the preparation of solid and hollow spherical porous TiO2 nanoparticles with large surface areas (100–211 m2/g) was developed in supercritical alcohols using carboxylic acids as organic additives. The shell thickness of the hollow TiO2 nanoparticles (20–280 nm) was controlled by adjusting the heating rate (2.0–10.0 °C/min). The preparation of different spherical porous metal oxide nanoparticles, including CeO2, SiO2, TiO2, ZrO2, and ZnO, demonstrated the versatility of the synthetic approach. In addition, several rare earth-doped spherical mesoporous metal oxide nanoparticles, including CeO2:Er, CeO2:Er,Yb, ZrO2:Er, and TiO2:Er, which exhibit energy upconversion emission, were successfully prepared using this one-pot, single-step, supercritical methanol method. The obtained spherical mesoporous CeO2:Er and CeO2:Er,Yb nanoparticles emit green light upon excitation, even when irradiated with a low-power IR laser (980 nm, 10 mW) without calcination. Several other (metal) elements were also easily doped into spherical, mesoporous TiO2 nanoparticles, such as Eu, Ce, Yb, Fe, and N, using a similar procedure. Furthermore, the spherical mesoporous TiO2 nanoparticles were successfully applied as a new material for the transport of DNA via biolistic bombardment.
Versatility of one-pot, single-step synthetic approach for spherical porous (metal) oxide nanoparticles using supercritical alcohols
