Understanding adsorption behavior of silica nanoparticles over a cellulose surface in an aqueous medium

• BD study delineates the mechanism of suspension and adsorption of nanoparticles.
• The electrostatic screening length controls particles׳ suspension and adsorption.
• Adsorbed particles form a monolayer, independent of their bulk concentration.
• The monolayer is either gas or liquid like, depending on their bulk concentration.

The suspension and adsorption of silica nanoparticles on a cellulose surface, in an aqueous medium is investigated using Brownian dynamic simulations. The inter particle and particle–surface interactions are modeled within the framework of the DLVO theory. Our analysis predicts the accumulation of negatively charged nanoparticles near a negatively charged surface depending on the Debye screening length of the medium. A crossover from the suspension to the adsorption of negatively charged silica nanoparticles onto a negatively charged cellulose surface has been reported as the screening length (k−1k−1) of the medium increases. The crossover is observed at k−1=100nm, due to the interplay between the nanoparticle–nanoparticle and the nanoparticle–surface interactions. The adsorption behavior of nanoparticles is explained using the potential of mean force analysis. The amount of nanoparticles adsorbed depends on their bulk volume fraction (ϕ) and the screening length of the medium. Further, the effects of electrical potentials of nanoparticle (ΨP) and surface (ΨS) on the adsorption are reported. The data suggests that the adsorption of nanoparticles increases either with increasing ΨP magnitude, or/and, with decreasing ΨS magnitude. The adsorbed particles form a disordered monolayer, and undergo subdiffusive motion. We have also observed a transition from the gas-like structure to the liquid-like structure of nanoparticles in the adsorbed monolayer as their bulk volume fraction increases.