Effect of particle size on the sticking probability

In the literature the transport of particles toward an oppositely charged c ollector in stagnation point flow is described theoretically with the Smolu chowski-Levich solution of the convective-diffusion equation. Using optical reflectometry, the initial adsorption rate in the case of adsorption of ne gatively charged polystyrene latex particles onto a glass collector covered with positively charged poly(propylene imine) dendrimers was studied at lo w ionic strength and constant pH, For latex particle sizes varying from 10 to 100 nm, the experimentally obtained values for the initial adsorption ra te are systematically lower than the theoretical predictions, The deviation s are captured by a sticking probability or collision efficiency that incre ases linearly from 0.5 to 0.8 within the experimental window, This can be e xplained by the fact that with particle size the contact area between the i ncoming particles and the amorphous collector increases and with this the n umber of sites involved in binding. (C) 2001 Academic Press.