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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 19: Crystallization, Nucleation and Self-Assembly

CPP 19.10: Vortrag

Dienstag, 28. März 2023, 12:15–12:30, MER 02

Controlling internal structure of colloidal supraparticles - crystalline to amorphous — •Yashraj Wani¹, Melis Yetkin², Michael Kappl², Hans-Jürgen Butt², and Arash Nikoubashman¹ — ¹Institute of Physics, JGU Mainz, Germany — ²Max Planck Institute for Polymer Research, Mainz, Germany

Colloidal supraparticles made from smaller nanoparticles (NPs) are versatile materials whose properties can be tailored through the chemistry and ordering of their constituent NPs. Such supraparticles can be scalably fabricated using solvent-drying processes that assemble NPs inside liquid droplets. In charge stabilized dispersions, the interactions can be controlled by the salt concentration, which we systematically probed in experiments and simulations. In experiments at low salt concentrations, the dried supraparticles exhibited high crystalline order, whereas amorphous structures were found at high salinity. To understand this evaporation-induced structure formation, we first determined the interaction potentials between NPs via colloidal probe atomic force microscopy and dynamic light scattering experiments. Using these pair potentials, we carried out particle-based simulations to study the aggregation behavior in detail: At low salt concentrations, the effective NP-NP interactions remained purely repulsive until the end of drying, resulting in highly crystalline supraparticles. At higher salt concentrations, however, the electrostatic repulsion became screened, leading to the formation of small NP aggregates at early stages of drying, which then eventually merged into an amorphous supraparticles.