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.

Automated summary

Radial homomesocrystals consisting of rutile TiO2 nanorods were synthesized using TiO2 seed nanocrystals, which greatly reduced the synthesis temperature and time. The formation of these homomesocrystals involved the epitaxial generation of nanoneedle-like nuclei on the seed surface, the growth of TiO2 nanorods, and their radial self-assembling with the transformation of amorphous to rutile TiO2. Loading Au nanoparticles on these homomesocrystals resulted in higher visible-light activity for oxidation of organics compared to the usual Au/TiO2 nanoparticles, due to the formation of plasmonic hot spots near the edges and corners of the faceted Au nanoparticles and effective charge separation.