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

Y Arita,K Dholakia,N Mcreynolds,W Edwards,E R Kay,G Tkachenko,N Marro

doi:10.1063/1.5030404

Y Arita, K Dholakia + Show 5 more

Open Access

https://doi.org/10.1063/1.5030404

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Journal: APL Photonics	Publication Date: Jul 1, 2018
Citations: 9	License type: cc-by

Affiliation: Chiba University, University of St Andrews

Abstract

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.

Highlights

Optical manipulation of mesoscopic particles has facilitated a wide range of innovative science and applications
Size distribution and circularity of the imaged gold NPs are summarized in Table I, where the diameter is the majoraxis length and circularity is defined as the ratio between the actual area of an object and the area expected from its maximum Feret’s diameter
Our US particles exhibit significantly improved circularity and monodispersity both in shape and in size compared to conventional NS particles of the corresponding size

Summary

Introduction

Optical manipulation of mesoscopic particles has facilitated a wide range of innovative science and applications. Though the majority of studies have focused upon the use of micron sized dielectric objects, in 1994 it was established by Svoboda and Block that gold nanoparticles (NPs) of sizes below 100 nm could readily be trapped.[1] Trapping at this size scale is perhaps surprising at first given the cubic dependency of the polarizability (and the optical gradient force) on the particle size for dielectric particles. The trapping behavior is explained by gold’s large polarizability leading to very strong optical gradient forces and three-dimensional trapping[2,3,4] for such small particles. Subsequent investigations have shown a vast array of fascinating studies using gold NPs, with many exploiting the surface plasmon resonance, leading to a strong wavelength dependence of their trapping behavior.[5,6,7] Notably, the chemical properties of gold lead to routes for custom functionalization for biomedically relevant applications. Laser-induced breakdown of gold NPs can be used for cell poration.[10]

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