Establishing Surface Charge as a Key Control Parameter for Linker-Driven Tip-Specific Ordering of Anisotropic Gold Nanoparticles

Abstract

Here, we show that nanoparticles’ surface charge is a key factor that determines their tip-specificity in a covalently linked assembly of anisotropic plasmonic nanoparticles. We developed a strategy to controllably tune the surface charge of gold nanoparticles over a broad ζ potential range between −5 and −35 mV using simple acid–base chemistry and showed that dithiol-driven, end-to-end linked dimers of gold nanorods were formed reproducibly within a ζ potential range between −10 and −17 mV in acetonitrile medium. Below this ζ potential range, nanoparticles collapse together to form large clusters without any tip-specificity. For ζ potentials above this range, electrostatic repulsion prevents them from binding to each other. Our approach of using the surface charge of nanoparticles as a key control parameter for achieving tip-specificity is quite versatile and works for different anisotropic nanoparticles including gold nanorods of different aspect ratios and gold nanobipyramids.