The Scalable Synthesis of Metal Hybrid Nanoparticles for Use in Targeted Drug Delivery, Catalysis, and Biosensors

Abstract

The functionalization of gold nanoparticles (GNPs) for numerous applications from targeted cancer therapy to homogenous catalysis has exploded in the literature alongside the use of GNP seed-mediated growth strategies for the synthesis of larger gold geometries such as nanoshells and nanorods. However, many strategies for producing novel gold geometries and gold hybrid nanoparticles are time intensive and unscalable. Therefore, the primary focus of this study is to design scalable procedures that both synthesize and control the properties of gold hybrid nanoparticles. The surface plasmon resonance and catalytic properties that make GNP functionalization attractive are readily transferable to larger gold geometries. The full and partial nanoshells formed around these particles make them good candidates for use in applications such as catalysis, targeted drug delivery, and bio-imaging while more novel gold nanorings may have application as ultrasensitive biosensors. Herein, gold hybrid nanoparticles were synthesized via a two-step procedure of Flash Nanoprecipitation (FNP) to produce GNP-seeded polymer nanoparticle cores followed by gold electroless plating to reduce gold onto the surface of the particles. The gold seeds on the core particles served as nucleation points for subsequent gold growth and directed the formation of each geometry. Optimal strategies for electroless gold reduction as well as optimal concentrations of gold precursor and reducing agents were determined for each gold hybrid geometry. Smooth nanoshells were produced using each of five different reducing agents. Continuous Janus half-shell coatings have not yet been achieved, but progress has been made in controlling gold growth on one side of the particles. Finally, electroless plating as been shown to be an effective method of synthesizing rigid nanorings. Further questions remain regarding how to optimize these systems for application, yet the success of the seed-mediated strategy for gold reduction has been extended to include two more novel systems.