Seed-Assisted Hydrothermal Synthesis of Radial TiO₂ Homomesocrystals and the Application as a Support for Plasmonic Photocatalysts

Radial homomesocrystals consisting of rutile TiO2 nanorods(NRs) were hydrothermally synthesized with TiO2 seed nanocrystals(rad-TiO2 HOMCs). The addition of the seeds greatly reducesthe synthesis temperature and time. Transmission electron microscopicanalyses show that the formation of rad-TiO2 HOMCs proceedsvia epitaxial generation of nanoneedle-like nuclei on the seed surface,the growth of TiO2 NRs in the [001] direction, and theirradial self-assembling with the transformation of amorphous to rutileTiO(2). Au nanoparticles (NPs) with similar sizes and amountswere highly dispersed on rad-TiO2 HOMCs (Au/rad-TiO2 HOMCs) and two kinds of commercially available rutile TiO2 NPs (Au/TiO2 NPs) by the deposition precipitationmethod. As a test reaction for the evaluation of the plasmonic photocatalyticactivity, degradation of 2-naphthol was examined by using it as amodel water pollutant under illumination of weak visible light (lambda(ex) > 430 nm, AM-1.5, 12.5 mW cm(-2)). IntheAu/TiO2 systems, a positive correlation holds between thephotocatalytic activity and the faceting probability of Au NPs onTiO(2). The photocatalytic activity of Au/rad-TiO2 HOMCs much higher than those of Au/TiO2 NPs can stemfrom the plasmonic hot spot formation near the corners and edges ofthe faceted Au NPs and effective charge separation characteristicsof the Au/rad-TiO2 HOMC system. Radial TiO2 mesocrystals were hydrothermallysynthesized with TiO2 seed nanocrystals. Loading Au nanoparticles(NPs) on them gives rise to visible-light activity for oxidation oforganics much higher than those of the usual Au/TiO2 NPsdue to the plasmonic hot spot formation near the edges and cornersof the faceted Au NPs and effective charge separation characteristicof the former system.