Quantum size effect and catalytic activity of nanosized single-crystalline spherical β-Ga2O3 particles by thermal annealing of liquid metal nanoparticlesElectronic supplementary information (ESI) available: Histogram of diameter, Brus equation, fluorescence and reflectance spectra. See DOI: 10.1039/c6ra26085c

We report on the synthesis of nanosized single-crystalline spherical β-Ga 2 O 3 particles ( GONP ) by thermal annealing of gallium nanoparticles ( GaNP ), which previously has been prepared under ultrasonication. GONP displayed a spherical morphology and the particle size reflected that of GaNP . The nanoparticles have been confirmed as crystalline β-Ga 2 O 3 by powder X-ray diffraction. The selected area electron diffraction patterns obtained from a whole particle of one GONP represented production of single-crystalline nanoparticle. Furthermore, the dispersibility and stability of GONP in solvent dramatically improved through silica coating ( GO@SiO 2 NP ). Photoluminescence spectroscopy indicated that the GO@SiO 2 NP exhibited a light blue emission at 445 nm under excitation at 240 nm. Diffuse reflectance spectroscopy demonstrated that the band gap of GO@SiO 2 NP ( E g = 4.89 eV) was hypsochromically shifted compared to that of bulk Ga 2 O 3 ( E g (bulk) = 4.56 eV) due to the quantum size effect of β-Ga 2 O 3 . Additionally, silica particle-supported GONP ( GONP/MCM-41 ) showed catalytic activity for the benzylation of benzene with benzyl chloride. Thus, the GONP presented here will have potential applications in LED phosphors, optoelectronic devices, and supported catalysts. Nanosized single-crystalline spherical β-Ga 2 O 3 particles were readily prepared from liquid metal gallium.