Colloidal stabilization via nanoparticle halo formation

Abstract

We present a detailed numerical study of effective interactions between micron-sized silica spheres, induced by highly charged zirconia nanoparticles. It is demonstrated that the effective interactions are consistent with a recently discovered mechanism for colloidal stabilization. In accordance with the experimental observations, small nanoparticle concentrations induce an effective repulsion that counteracts the intrinsic van der Waals attraction between the colloids and thus stabilizes the suspension. At higher nanoparticle concentrations an attractive potential is recovered, resulting in reentrant gelation. Monte Carlo simulations of this highly size-asymmetric mixture are made possible by means of a geometric cluster Monte Carlo algorithm. A comparison is made to results obtained from the Ornstein-Zernike equations with the hypernetted-chain closure.

Stabilization of Weakly Charged Microparticles Using Highly Charged Nanoparticles

“…Steric stabilization typically occurs through the use of polymer chains which are either adsorbed, grafted, or otherwise attached to the surface of the dispersed particles [18][19][20][21][22]. The polymer chains extend away from the particle surface and physically inhibit the particles from approaching other particles close enough to be in the range of the van der Waals attraction.…”

“…A more recent development in colloidal stability is through a nanoparticle-microparticle interaction described as "nanoparticle haloing" [7,20,[23][24][25][26][27][28][29][30]. This behavior requires a system of two different types of particles that are highly different from each other in size and surface potential.…”

Investigation of stabilization mechanisms for colloidal suspension using nanoparticles.

“…26 The electrostatic repulsion is calculated using the Hogg-HealyFuerstenau (HHF) formula 39 , which is well known to calculate the double layer interactions at constant surface potential between dissimilar surfaces and has been utilized to study mechanisms of nanoparticle halo in several other works. 106,107 We assume that the effective zeta potential is the same for both silica sphere and plate, and a continuum assumption is made for the overlapping of effective double layers as silica sphere approaching the plate. The depletion force is estimated using Piech and Walz's approximation.…”

“…The HHF approximation is well known to calculate the double layer interactions at constant surface potential between dissimilar surfaces, and has been utilized to investigate mechanisms of nanoparticle halo in several other works. 106,107 We assumed the effective zeta potential was the same for both silica microsphere and plate, and a continuum assumption was made for the overlapping of the effective double layers as the charged layers associated with silica surfaces were approaching.…”

“…Subsequently, by using Monte Carlo simulations, Liu and coworkers showed that the formation of halo was caused by a weak attraction between a colloidal microsphere and nanoparticle at low concentrations ( 10 -4 ). 106,107 Besides, the previous chapters have shown our CP-AFM measurement of interactions between weakly charged colloidal surfaces in the presence of highly charged nanoparticles. It is found that charged nanoparticle are able to induce a charged layer over the negligible charged colloidal surface, thus improving the stability of colloidal suspensions.…”