Colloid particle adsorption on partially covered (random) surfaces

The random sequential adsorption (RSA) approach was used to model irreversi ble adsorption of colloid particles at surfaces precovered with smaller par ticles having the same sign of surface charge. Numerical simulations were p erformed to determine the initial flux of larger particles as a function of surface coverage of smaller particles theta (s) at various size ratios lam bda = alpha (1)/alpha (s). These numerical results were described by an ana lytical formula derived from scaled particle theory. Simulations of the lon g-time adsorption kinetics of larger particles have also been performed. Th is allowed one to determine upon extrapolation the jamming coverage theta ( infinity)(1) as a function of the lambda parameter at fixed smaller particl e coverage theta (s). It was found that the jamming coverage theta (infinit y)(1) was very sensitive to particle size ratios exceeding 4. Besides yield ing theta (infinity)(1), the numerical simulations allowed one to determine the structure of large particle monolayers at the jamming state which devi ated significantly from that observed for monodisperse systems. The theoret ical predictions suggested that surface heterogeneity, e.g., the presence o f smaller sized contaminants or smaller particles invisible under microscop e, can be quantitatively characterized by studying larger colloid particle adsorption kinetics and structure of the monolayer. (C) 2001 Academic Press .