Synthesis of Au/SnO2 core-shell structure nanoparticles by a microwave-assisted method and their optical properties

Au/SnO₂ core-shell structure nanoparticles were synthesized using the microwave hydrothermal method. The optical and morphological properties of these particles were examined and compared with those obtained by the conventional hydrothermal method. In microwave preparation, the peak position of the UV-visible plasmon absorption band of Au nanoparticles was red-shifted from 520 to 543 nm, due to the formation of an SnO₂ shell. An SnO₂ shell formation was complete within 5 min. The thickness of the SnO₂ shell was 10-12 nm, and the primary particle size of SnO₂ crystallites was 3-5 nm. For the core-shell particles prepared by a conventional hydrothermal method, the shell formed over the entire synthesis period and was not as crystalline as those produced, using the microwave method. The relationship between the morphological and spectroscopic properties and the crystallinity of the SnO₂ shell are discussed.