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

Abstract

Radial homomesocrystals consisting of rutile TiO2 nanorods (NRs) were hydrothermally synthesized with TiO2 seed nanocrystals (rad-TiO2 HOMCs). The addition of the seeds greatly reduces the synthesis temperature and time. Transmission electron microscopic analyses show that the formation of rad-TiO2 HOMCs proceeds via epitaxial generation of nanoneedle-like nuclei on the seed surface, the growth of TiO2 NRs in the [001] direction, and their radial self-assembling with the transformation of amorphous to rutile TiO2. Au nanoparticles (NPs) with similar sizes and amounts were 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 precipitation method. As a test reaction for the evaluation of the plasmonic photocatalytic activity, degradation of 2-naphthol was examined by using it as a model water pollutant under illumination of weak visible light (λex > 430 nm, AM-1.5, 12.5 mW cm–2). In the Au/TiO2 systems, a positive correlation holds between the photocatalytic activity and the faceting probability of Au NPs on TiO2. The photocatalytic activity of Au/rad-TiO2 HOMCs much higher than those of Au/TiO2 NPs can stem from the plasmonic hot spot formation near the corners and edges of the faceted Au NPs and effective charge separation characteristics of the Au/rad-TiO2 HOMC system.