Cysteine-assisted overgrowth of gold nanorods to prepare highly branched gold nanoantennas with tunable morphological and plasmonic properties

Abstract

In this work, gold nanoantennas with high branching properties were prepared by cysteine-assisted overgrowth of gold nanorods (AuNRs). These Au nanoantennas are a kind of multi-branched anisotropic structured nanoparticles, whose central core is a cylindrical NR and branches protrude from the ends of the NR. In particular, the morphological evolution of the AuNPs can be well controlled by optimizing the reaction parameters such as the concentration of cysteine, seed, and HAuCl₄, as well as the reaction time. We achieved a series of precise controlled Au nanoantennas with defined but varied branch numbers (n = 2, 4, 6, 8, and 10), dimensions and aspect ratios. On the other hand, UV-vis-NIR spectra analysis demonstrated that the Au nanoantennas reveal distinctive intense broad localized surface plasmon resonance (LSPR) peaks that can be tuned in the NIR region by varying the characteristics of the surface branches of NPs, such as the number, length, width and aspect ratio of branches. This method provides a simple, reproducible, and large-scale method for the preparation of highly branched Au nanoantennas.