Preparation, characterisation and properties of groups VIII and IB metal nanoparticles

Vapour synthesis techniques have been used to prepare nanoparticulate dispersions of ruthenium, rhodium, palladium, platinum, silver and gold in non-aqueous solvents. The dimensions of these solvent-stabilised particles, which can be controlled within the 1-3 nm size regime, effectively encompass the areas of molecular chemistry (as typified by high-nuclearity metal clusters) and the smaller colloidal metals. The nanostructures have been characterised by high-resolution transmission electron microscopy and evidence for face-centred cubic (f.c.c.) octahedral, f.c.c. cuboctahedral and icosahedral metal particles obtained; quasi-molten states have also been observed in a number of these systems. In addition to discrete particles, larger aggregates of the small primary particles have been observed, some of which appear to be organometallic in nature. Gold nanoparticles differ from those of the Group VIII metals in exhibiting unusual time and concentration-dependent behaviour. A regime of preparative conditions under which 1-3 nm size gold particles, which are stable with respect to aggregation as a function of time, is defined. Some preliminary results of attempts to use laser mass spectrometry as a rapid method for the molecular mass determination of some of these materials are also described.