Continuous-flow Synthesis of Anisotropic Plasmonic Nanostructures

Owing to enhanced light-matter interactions and unique optical properties, plasmonic metal nanostructures have garnered extensive research interest and use in wide range of applications. A 3D-printed device for the synthesis of seed-mediated anisotropic gold (Au) nanoparticles (NPs) by droplet-based method is demonstrated. The miniaturized device was used to synthesize Au NPs by using three different reducing agents of different concentrations at two different flow rates and study the evolution of morphology of NPs. The device channel geometry and configuration allowed on-chip chemical syntheses of Au nanomaterials with good uniformity in shape and size. XRD and zeta potential measurement confirmed face-centered cubic structure and negative  surface charge of the synthesized nanomaterials. TEM studies confirmed flower-, urchin- and spindle-shaped morphologies of Au NPs synthesized on using different concentrations of reducing agent. Additionally, computational study to deduce the residence time of the droplets in the device and estimate the electric field distribution around the anisotropic Au NPs is also shown.