Versatility of one-pot, single-step synthetic approach for spherical porous (metal) oxide nanoparticles using supercritical alcohols

We developed a rapid, one-pot, single-step synthetic method for preparing spherical porous (metal) oxides, titanium dioxide, silica, zirconium dioxide, cerium dioxide, and zinc oxide with large surface areas in a supercritical alcohol containing formic acid or phthalic acid as organic additive in a very short reaction time (10 min). A new type of hollow TiO2 nanoparticle was obtained by slowly heating the reaction mixtures. The shell thickness of hollow TiO2 nanoparticles was controlled by adjusting the heating rate. The method proved highly versatile for synthesizing solid and hollow spherical meso/microporous nanoparticles. The spherical mesoporous TiO2 nanoparticles photocatalytically degraded methylene blue in water under UV irradiation, and successfully transported DNA under biolistic bombardment.