An Isotropic Vapor-Phase Catalytic Approach for Deep-Blue Light-Emitting Au Nanoparticles-on-In₂O_3-x Mesocubes

We report a one-step fabrication of nearly uniform cubic bixbyite-type indium sesquioxide (c-In2O3) mesocubes (MCs) with a statistical average crystallite size of 115 nm with which Au nanoparticles (NPs, 5–10 nm) were decorated. The Au NP-decorated In2O3-x MCs displayed a distinct room-temperature deep-blue (DB) photoluminescence (PL) emission at 410 nm (3.02 eV). Compared with the previously reported results from the pure In2O3 nanocubes showing broad PL emission peaks centered at 450 nm, this could be ascribed to the formation of the In2O3-x MCs with oxygen vacancies and the plasmon-enhanced PL of Au NPs. Furthermore, an isotropic vapor–liquid–solid growth model was proposed. (i) Based on the ‘octa-twin’ In2O3 nucleation embryos at the initial growth stage, the eutectic Au–In alloy droplets first formed in the Au–In/In2Ox/In2O3-x inclusions as the preferred absorption sites for the incoming In2Ox/In vapor. (ii) At ∼950 °C, the higher partial pressure of metastable In2O weakens the effect of the classical surface energy difference on the facet’s growth rate, resulting in the dominant copious nanoscale nucleation of the particulate phase on the substrate, finally leading to the growth of c-In2O3 MCs via morphology evolution. The hybrid semiconductor Au NPs-on-In2O3-x MCs hold great promise as potential mesoscale functional photocatalysts with DB luminescence.