Studies of adhesion of metal particles to silica particles based on zeta potential measurements

The zeta-potentials of silica, copper, platinum and gold particles have bee n measured as a function of pH. The isoelectric points were found to be at pH 3.0, 5.8, 3.0 and 3.5, respectively. In the pH range 3.0 to 5.8 copper a nd silica particles are oppositely charged and accordingly the coating of s ilica with copper particles could be demonstrated. In the case of gold and platinum the sign of the charge is such that direct adhesion to silica part icles cannot be expected and this was also demonstrated in the case of plat inum.