Designing Nanoparticle Colloidal Shells for Selective Transport

Abstract

We present a theoretical model that relates transport through a colloidal shell to the shell thickness, packing density, the colloidal particle size, and polydispersity. The model addresses two cases: Self-assembled monolayer shells and fused shells. In the former case, the shell thickness is equal to the colloidal particle diameter, and the packing density is determined by adsorption thermodynamics. In the latter case, the shell thickness may be several times that of the particle dimensions, and the packing density is set by the fusion process. We find that the pores formed by close-packing of the particles in the shell enable size exclusion, namely, prohibit transport of diffusants larger than a critical size. As may be expected, the critical dimension for size selectivity is proportional to the colloidal particle radius, and decreases with packing density. For diffusants smaller than the size-exclusion limit, we find that the rate of transport decreases with increasing packing density of particles in the shell. In the case of self-assembled monolayers the transport rate is independent of the particle dimensions, while in the case of thick multi-layered ones the rate decreases with decreasing particle size.

Keywords:

• Colloidosome
• Polydispersity
• Self-assembly
• Size selectivity

Acknowledgment

Thanks to NSF/IDBR award number 0649897 for financial support. RTR acknowledges the NSF-IGERT DGE-0654313 fellowship.