A Chemical Mechanism for the Bistable-to-Oscillatory Transition in Colloidal Aggregates of Silver Phosphate

Abstract

We previously reported collective behavior in colloidal aggregates of silver phosphate in H₂O₂ and under UV light. Diffusiophoretic interactions between aggregates lead to non-linear behavior such as oscillations and synchronization, in which oscillation frequencies increase with H₂O₂ concentration. The aggregates transition between schooling and dispersed behaviors with incipient spatiotemporal correlations. We identified a kinetic model that maps the chemical species that are thought to underlie non-linear phenomena in the colloidal aggregates, i. e. adsorbed oxygen species *OOH⁻ and *O. We investigate the emergent dynamics for the simplest case, the coupling of two otherwise bistable clusters. Two coupling schemes are proposed and we find that – depending on whether the coupling is excitatory or inhibitory – the clusters may oscillate with zero or π phase shift.