NSF-DFG Confine: Drying-induced assembly of colloidal supraparticles from anisotropic nanoparticles

Auburn University, Auburn AL

Investigators

Abstract

This project was awarded through the “Chemistry and Transport in Confined Spaces (NSF-DFG Confine)" opportunity, a collaborative solicitation that involves the National Science Foundation and Deutsche Forschungsgemeinschaft (DFG). Colloidal supraparticles - micrometer-sized spheres made from smaller nanoparticles (NPs) - are versatile materials. Porous supraparticles with internal voids are particularly valued for their catalytic, photonic, drug delivery, and physical absorption properties. While supraparticles can be fabricated at scale using solvent drying to assemble NPs inside liquid droplets, these processes are poorly understood. This project will use computer modeling to address this knowledge gap in how porous supraparticles form and how their properties can be engineered. Furthermore, the nanoparticle shape and surface property effects on the assembly process and the characteristics of the product supraparticles will be investigated. The models that will be developed have significant potential to shorten the research & development cycle of new materials in both academic and industrial settings. This international collaboration will train a globally competitive work force. The project will also integrate activities to (1) broaden participation in computational science through a summer research experience for undergraduates underrepresented in STEM, (2) develop a virtual-reality educational activity on diffusion for K-12 students, and (3) disseminate open-source software and training materials. The goal of this project is to develop mathematical models to investigate the drying-induced assembly of nanoparticles (NPs) with interaction or shape anisotropy into colloidal supraparticles. This process is poorly understood because it involves complex molecular thermodynamics and nonequilibrium transport in confinement. Complementary particle-based and continuum models - based on the multiparticle collision dynamics and classical dynamic density functional theory approaches, respectively - will be developed and validated. The models will be applied to “patchy” NPs with anisotropic attraction and rodlike NPs with anisotropic shape that have significant untapped potential for realizing new porous supraparticle assemblies. The local NP density and orientational order will be characterized to systematically interrogate how both the NP properties and the processing conditions (such as the drying speed) determine the porosity distribution in the supraparticle. The proposed research will not only improve our ability to engineer supraparticles but also advance fundamental understanding of confined advection-diffusion processes for NPs, including related processes such as freeze drying, filtration, and sedimentation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.