Silver nanoparticle formation: Predictions and verification of the aggregative growth model

The mechanisms of growth of 5 -30 nm silver particles produced from the red uction of silver perchlorate by sodium borohydride are explored. Evidence i s provided that, within 5 s of mixing of silver perchlorate with borohydrid e, the concentration of ionic silver has dropped 2 orders of magnitude, ini tially resulting in the formation of similar to2.5 nm silver particles. We hypothesize that growth takes place over the next 20-50 min by an aggregati ve growth mechanism. This hypothesis is tested by comparing model predictio ns with experimental results of particle growth rates over a range of ionic strengths and reaction temperatures. The model assumes particles interact via electrostatic and van der Waals forces, and comparison of numerical sol utions to population balance models for aggregation and coalescence demonst rates that particle growth rates and final sizes can be predicted with surf ace potentials within 20% of those previously reported under reaction condi tions.