CHEMISTRY OF NANOSIZED SILICA-COATED METAL PARTICLES EM-STUDY

Colloidal gold and silver are difficult to manipulate. The surfaces ar e normally coated with organic acids or polymers, and conventional met hods for thin metal oxide coatings normally result in clumping and het erocoagulation. We have recently developed a method to silica-coated g old and silver particles which avoids any particle coalescence. The me thod can be applied to a wide range of nanoparticles [1, 2]. In this r eport we present some results from studies into chemical reactions of nanosized coated metal particles using high resolution transmission el ectron microscopy. The chemical reactions were carried out on silica-c oated silver and gold nanoparticles in aqueous solution. The reaction of a single Ag@SiO2 nanoparticle with I-2 to form AgI was monitored di rectly by transmission electron microscopy. As well the dissolution of Au cores by cyanide ion led to the creation of monodisperse, hollow, nanosized silica particles.