Synchronized motion of gold nanoparticles in an optothermal trap

TL;DR

This study explores the complex behavior of gold nanoparticles in an optothermal trap, revealing synchronized motion and confinement effects that differ from traditional optical binding, with implications for nanoscale assembly.

Contribution

It uncovers novel synchronized rotational diffusion and confinement phenomena of nanoparticles in an optothermal trap, expanding understanding beyond known optical and thermophoretic effects.

Findings

Observed unexpected radial confinement of nanoparticles.

Detected synchronized rotational diffusion at micrometre separations.

Identified forces beyond traditional optical binding and thermophoresis.

Abstract

Optical tweezers have revolutionized particle manipulation at the micro- and nanoscale, playing a critical role in fields such as plasmonics, biophysics, and nanotechnology. While traditional optical trapping methods primarily rely on optical forces to manipulate and organize particles, recent studies suggest that optothermal traps in surfactant solutions can induce unconventional effects such as enhanced trapping stiffness and increased diffusion. Thus, there is a need for further exploration of this system to gain a deeper understanding of the forces involved. This work investigates the behaviour of gold nanoparticles confined in an optothermal trap around a heated anchor particle in a surfactant (CTAC) solution. We observe unexpected radial confinement and synchronized rotational diffusion of particles at micrometre-scale separations from the anchor particle. These dynamics differ from known optical binding and thermophoretic effects, suggesting unexplored forces facilitated by the surfactant environment. This study expands the understanding of optothermal trapping driven by anchor plasmonic particles and introduces new possibilities for nanoparticle assembly, offering insights with potential applications in nanoscale fabrication and materials science.