Effect of Colloidal Particle Size on Adsorbed Monodisperse and Bidisperse Monolayers

Abstract

Coating hydrogel films or microspheres by an adsorbed colloidal shell is one synthesis method for forming colloidosomes. The colloidal shell allows control of the release rate of encapsulated materials, as well as selective transport. Previous studies found that the packing density of self-assembled, adsorbed colloidal monolayers is independent of the colloidal particle size. In this paper we develop an equilibrium model that correlates the packing density of charged colloidal particles in an adsorbed shell to the particle dimensions in monodisperse and bidisperse systems. In systems where the molar concentration in solution is fixed, the increase in adsorption energy with increasing particle size leads to a monotonic increase in the monolayer packing density with particle radius. However, in systems where the mass fraction of the particles in the adsorbing solutions is fixed, increasing particle size also reduces the molar concentration of particles in solution, thereby reducing the probability of adsorption. The result is a nonmonotonic dependence of the packing density in the adsorbed layer on the particle radius. In bidisperse monolayers composed of two particle sizes, the packing density in the layer increases significantly with size asymmetry. These results may be utilized to design the properties of colloidal shells and coatings to achieve specific properties such as transport rate and selectivity.

Colloidosomes: Synthesis, properties and applications

“…Alternatively, a bimodal distribution of small and large spheres could be utilized such that the former are selected to fit within the interstices formed by the latter. 75 Duan et al 35 used CdTe nanoparticles as probes in order to examine how packing defects Biggs and co-workers 65 reported that covalently cross-linked colloidosomes exhibit tunable permeability to fluorescently-labeled dextran (70 x10 3 g mol -1 ). 78 At low pH, the polyaminebased steric stabilizer is protonated and hence highly cationic.…”

On Packing, Connectivity, and Conductivity in Mesoscale Networks of Polydisperse Multiwalled Carbon Nanotubes

“…Other studies show that the packing densities of polydisperse spheres are slightly higher than their monodisperse or bidisperse counterparts. 28,29 In our system, the measured volume fractions of the compacts were at the lower end of the macroscopic data. We attribute this increased porosity to the nonstraightness of the CNTs ( Figure S3), which has been shown to decrease the packing density.…”

Random sequential adsorption of polydisperse mixtures on lattices

“…Polydispersity of incident particle size is observed in a large number of processes, specially in (but not restricted to) colloidal particle and macromolecule deposition. The simplest RSA models that account for polydispersity effects are those with binary particle size distribution [11][12][13][14][15], which were already used to explain real system properties [16,17]. Uniform distributions of particle size were also considered in continuum [18,19] and lattice [20][21][22] models, showing interesting features such as the effects of particle shape on the maximal surface coverage and on the form of concentration decay.…”