Synthesis of metal–cadmium sulfide nanocomposites using jingle-bell-shaped core-shell photocatalyst particles

Photocatalytic deposition of gold (Au) and silver (Ag) nanoparticles was investigated using jingle-bell-shaped silica (SiO₂)-coated cadmium sulfide (CdS) nanoparticles (SiO₂/CdS), which each had a void space between the CdS core and SiO₂ shell, as a photocatalyst. A size-selective photoetching technique was used to prepare the jingle bell nanostructure of SiO₂/CdS. Nanoparticles of Au and Ag were deposited by irradiation of the photoetched SiO₂/CdS in the presence of the corresponding metal complexes under deaerated conditions. Chemical etching of Au-deposited particles enabled the selective removal of CdS without any influence on the surface-plasmon absorption of Au. TEM analyses of the resulting particles suggested that some particles were encapsulated in hollow SiO₂ particles, while other Au particles were deposited on the outer surface of the SiO₂ shell. Emission spectra of the photoetched SiO₂/CdS showed that the metal deposition developed a broad emission with a peak around 650 nm originating from surface defect sites, the degree being dependent on the kind of metal nanoparticles and their amount of deposition. This fact can be explained by the formation of metal–CdS binary nanoparticles having defect sites at the interface between metal and CdS.