Characterization of colloidal stability during precipitation reactions

Methods of characterizing colloidal interaction potentials of nanoscale sil ver particles during their formation are discussed. Silver sols are produce d by the borohydride reduction of silver perchlorate, and their colloidal s tability is found to vary both with reaction conditions and over the course of the reaction. Stability ratios are estimated using two independent tech niques for a variety of reaction conditions and interpreted in terms of pai r potentials consisting of van der Waals attractions and electrostatic repu lsions. At low temperatures (< 15 degreesC), the particles are highly charg ed. At higher temperatures (> 15 degreesC), surface potentials decrease. At the end of the reaction where borohydride is converted to berate by oxidat ion with water, the particle surface changes, possibly forming an oxide lay er resulting in a decrease in surface potential.