February 1, 2022
Polymer-Induced Crystallization of Polymer-Grafted Nanoparticles
Crystallization is a ubiquitous process seen in most, if not all, classes of matter. Nanoparticles (NPs) are ideal systems for visualizing crystallization processes and can serve as building blocks for new classes of materials. A dazzling array of NP crystals has been achieved by engineering complementary interactions, e.g., attaching DNA ligands, controlling solvent evaporation, and slow cooling of concentrated solutions. However, it remains challenging to control the crystallization kinetics so that high-quality NP crystals can be rapidly and reliably fabricated.
In this talk, Yiwen will talk about a new strategy that a trace amount of polymeric impurities (<0.1 wt.%) leads to reproducible, rapid growth of 3D NP crystals in solution and on patterned substrates with high yield. This precipitation-induced NP crystallization process is applicable for a range of polymers, and the resultant 3-D NP crystals are tunable by varying polymeric additives loading, solvent evaporation rate, and NP size. STEM tomography, X-ray scattering and image analysis are used to elucidate how cohesive energy density and NP diffusivity are balanced to simultaneously favor nuclei formation energetically and kinetic growth to rapidly crystalize NPs over multiple length scales.
Yiwen Qian is a doctoral candidate in Materials Science and Engineering at UC Berkeley, where she studies nanoparticle assembly under Prof. Ting Xu in the Department of Materials Science and Engineering, and Department of Chemistry. Her focus is on nanoparticle synthesis and self-assembly, especially for single- and binary- nanoparticle superlattices formation, and their properties. Prior to UC Berkeley, she received a BS in Chemistry from Shanghai Jiao Tong University.