Light-directed on-chip shape transformation of a single gold nanoparticle

Abstract

The plasmonic optical properties of metallic nanoparticles strongly rely on their sizes, shapes, and compositions, and the tuning strategies are mostly based on the chemical engineering of their synthesis or physical deposition, which reflects the ensemble properties of the batch. However, these traditional approaches show poor capability to modify a single nanoparticle at the desired location, which is highly desired for device miniaturization and integration. Here, we demonstrate the laser-induced shape transformation of a single gold nanoparticle (Au NP) based on Au dissolution and re-deposition driven by plasmonic hot carriers. The competition between oxidative etching and regrowth results in the shape transformation of the spherical Au NP into a faceted nanocrystal. The balance of these competing processes can be altered by adjusting the concentration of HAuCl₄, which leads to enlarged particle size or the complete etching of the Au NP. This strategy is extendable to the shape modification of non-spherical Au NPs such as Au bipyramids and nanorods. These findings provide a versatile on-chip approach for the shape modulation of single Au NPs and shed light on the plasmon-driven fine adjustment of plasmonic NP chemistry.