CHEMISTRY OF SILVER AGGREGATES IN AQUEOUS-SOLUTION - NONMETALLIC OLIGOMERS AND METALLIC PARTICLES

Metals and semiconductors experience drastic changes in their optical and catalytic properties when they are prepared as extremely small particles (approximately 1 nm) in aqueous solution as a transition takes place from metallic or semiconducting to molecular behaviour. In recent years, the changes have been studied thoroughly for a great number of semiconductor materials. In the case of the metals, such studies were hampered as there was no method available for the preparation of oligomeric non-metallic clusters in solution. However, silver clusters have recently been found to be formed as long-lived intermediates during the reduction of silver ions when the reduction is carried out in the presence of a polyanion. Some chemical reactions of these clusters as well as of larger metallic silver particles (approximately 4 nm) are described.