THE PREPARATION AND STABILITY OF COLLOIDAL METAL DISPERSIONS PREPARED BY A 2-PHASE NONAQUEOUS ROUTE

Stable suspensions of small metal Au, Ru, Pt, Pd, Rh, Co and Ni particles dispersed in n-heptane and n-dodecane have been prepared using a novel two-phase system, involving the formation of the particles in a methanolic phase and subsequent phase transfer of the particles to the alkane medium. The dispersions consisted of small particles having diameters in the range of 8-30 nm (the gold sols were very polydisperse having average diameters of ca.34 nm). The phase transfer of the particles and their subsequent colloid stability were effected by the presence of dissolved dispersant in the hydrocarbon phase (either Oloa 1200 or Hypermer LP 8). In the case of Oloa 1200, a widely-used polyisobutylene succinimide automotive engine dispersant, it is proposed that the amine groups adsorb strongly to the acidic surface of the particles, and the 70-carbon polyisobutylene chains extend into the hydrocarbon medium sufficiently to maintain the separation of adjacent particles by steric and possibly also by electrical repulsion.