Silver nanoparticle–clay composites

Abstract

Composite materials of the alumino silicate minerals, kaolinite and halloysite, with silver nanoparticles have been successfully synthesised. This was achieved by a layer-by-layer deposition process in which kaolinite or halloysite was dispersed in successive solutions of the cationic polymeric linker polydiallyldimethylammonium chloride and anionic polymethacrylic acid capped silver nanoparticles. The optical properties of the metallic nanoparticles were retained in the composites and attractively coloured powders were produced. Electron microscopy revealed the silver to be nanospheres, ranging in diameter from 5–40 nm depending on the method of preparation. The chemical and physical characterisation of the resultant composites, particularly the mode of bonding between the nanoparticles and clays, was undertaken through X-ray diffraction, X-ray photoelectron spectroscopy and solid state NMR. The composites showed effective anti-microbial activity against Staphylococcus aureus bacteria.