Eco-friendly sonochemical synthesis of BaTiO3/Ag nanocomposite particles: Investigation of Ag-nanoparticle formation and growth behavior under ultrasound irradiation

This study synthesizes BaTiO3/Ag nanocomposite particles using an eco-friendly sonochemical method and investigates the mechanism of Ag-nanoparticle deposition. BaTiO3 and Ag2O were ultrasonically irradiated in methanol at 20 ˚C, and samples and solvents were characterized using X-ray diffraction, scanning electron microscopy, scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy, ultraviolet-visible spectroscopy, Brunauer-Emmett-Teller method, X-ray photoelectron spectroscopy and gas chromatography-mass spectrometry. Nanocomposite particles uniformly decorated with fine Ag nanoparticles were obtained via ultrasonication (>45 kHz) for 3 h. The average size of the Ag nanoparticles increased with increasing irradiation time, which was presumed to be due to the thermal and physical effects of the ultrasound. Even at 10 vol% Ag loading, nanocomposites exhibited uniform particle distribution. Ultrasound irradiation produced nanocomposite particles with finer Ag nanoparticles and accelerated the reduction of Ag2O compared with mechanical stirring. In this deposition reaction, Ag2O was presumed to be reduced by methanol and its radical derivatives, and BaTiO3 exhibited catalytic activity for Ag2O reduction. This study not only contributes to the understanding of the mechanism of Ag-nanoparticle deposition in alcohol-Ag2O systems but also offers a promising room-temperature and waste-reducing synthesis route for nanocomposite particles toward a sustainable society.