https://doi.org/10.1140/epje/s10189-023-00386-4
Regular Article - Soft Matter
Induced phase transformation in ionizable colloidal nanoparticles
1
Department of Materials Science and Engineering, Northwestern University, 60208, Evanston, IL, USA
2
Department of Chemistry, Northwestern University, 60208, Evanston, IL, USA
3
Department of Physics and Astronomy, Northwestern University, 60208, Evanston, IL, USA
Received:
7
September
2023
Accepted:
22
November
2023
Published online:
7
December
2023
Acid–base equilibria directly influence the functionality and behavior of particles in a system. Due to the ionizing effects of acid–base functional groups, particles will undergo charge exchange. The degree of ionization and their intermolecular and electrostatic interactions are controlled by varying the pH and salt concentration of the solution in a system. Although the pH can be tuned in experiments, it is hard to model this effect using simulations or theoretical approaches. This is due to the difficulty in treating charge regulation and capturing the cooperative effects in a colloidal suspension with Coulombic interaction. In this work, we analyze a suspension of ionizable colloidal particles via molecular dynamics (MD) simulations, along with Monte Carlo simulations for charge regulation (MC-CR) and derive a phase diagram of the system as a function of pH. It is observed that as pH increases, particles functionalized with acid groups change their arrangement from face-centered cubic (FCC) packing to a disordered state. We attribute these transitions to an increase in the degree of charge polydispersity arising from an increase in pH. Our work shows that charge regulation leads to amorphous solids in colloids when the mean nanoparticle charge is sufficiently high.
To Fyl Pincus, with admiration for his groundbreaking contributions to charged colloids and polyelectrolytes that have inspired us. The Soft-matter community celebrates his enduring legacy and ongoing influence on our understanding of complex systems.
© The Author(s) 2023
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