Seedless Gold Nanostars: A Hands-On Educational Approach to Explore Plasmonic Effects at the Nanoscale

Gold nanostars (AuNS) are plasmonic nanoparticles whose optical properties can be tuned by controlling their morphology. In this hands-on educational laboratory activity, we exemplify how students can synthesize AuNS through a simple, seedless method to investigate how nanoparticle shape influences plasmonic behavior on the nanoscale. By systematically varying the anisotropic features of the gold nanoparticles through colloidal chemistry, students observe different color (extinction) variations corresponding to different AuNS morphologies. Furthermore, they also examine how changes in the surrounding environment, specifically the refractive index of the medium, affect the optical properties of the colloidal suspension. Overall, this hands-on activity is well-suited for undergraduate students with little or no prior practical experience in wet lab work as it relies on inexpensive reagents with low toxicity.