Invited Article: Optical trapping of ultrasmooth gold nanoparticles in liquid and air

Optical manipulation of gold nanoparticles has emerged as an exciting avenue for studies in nanothermometry, cell poration, optical binding, and optomechanics. However, conventional gold nanoparticles usually depart from a spherical shape, making such studies less controlled and leading to potential artifacts in trapping behavior. We synthesize ultrasmooth gold nanoparticles, which offer improved circularity and monodispersity. In this article, we demonstrate the advantages of such nanoparticles through a series of optical trapping experiments in both liquid and air. Compared to their conventional counterparts, ultrasmooth gold nanoparticles exhibit up to a two-fold and ten-fold reduction in standard deviation for trap stiffness measurements in liquid and air, respectively. They will enable more controlled studies of plasmon mediated light-matter interactions.