(167an) Designing Hybrid Colloids: A Study of Gold Adsorption atop Polystyrene to Control Morphology of Reactive Nanoparticles

Hybrid nanoparticles, or nanoparticles that contain both an inorganic and organic component, hold promise for improving groundwater remediation techniques that employ colloids to degrade or remove harmful contaminants. Hybrid nanoparticles have the ability to stabilize reactive, inorganic materials against aggregation, enhancing their ability to pervade small spaces and travel longer distances to degrade contaminants in situ. However, fabrication of these hybrid materials often requires multiple steps and often does not specifically address a method to control their precise morphology or reactivity. We demonstrate a simple, two-step fabrication method for hybrid gold-polystyrene nanoparticles in which we produce polystyrene nanoparticles using Flash NanoPrecipitation (FNP) and incubate them with citrate-stabilized gold nanocatalysts. Despite the absence of notable attractive interactions, we find that the presence of a good solvent remaining from the FNP process during incubation enables gold adsorption to polystyrene, thus producing hybrid gold-polystyrene nanoparticles. Furthermore, we reveal that changing process parameters, such as gold incubation time, and molecular parameters, such as polymer molecular weight and polymer end-group charge, provides control over the resultant nanocatalyst loading and dispersal atop hybrid nanoparticles. Through close analysis of the sizes of gold nanocatalyst clusters on the surfaces of polystyrene nanoparticles, we can quantify the obtained morphologies into three distinct regimes: aggregated, disperse, or internalized. Finally, we show that the emergence of these regimes has key implications for controlling reaction rates in applications such as heterogeneous catalysis or groundwater remediation because hybrid nanoparticles with gold nanocatalysts embedded below the surfaces of polystyrene nanoparticles exhibit slower bulk catalytic reduction capacity than their disperse, surface-decorated counterparts. Taken together, our work reveals a simple way by which hybrid nanoparticles can be fabricated and presents a unique method to control catalytic reactions using these nanomaterials.