Theoretical Analysis of Metallic-Nanodimer Thermoplasmonics for Phototactic Nanoswimmers

TL;DR

This paper provides a theoretical analysis of metallic nanodimers as phototactic nanoswimmers, revealing that identical nanodimers can effectively propel themselves via thermophoresis, with properties tunable by light wavelength.

Contribution

It demonstrates that symmetric nanodimers made of identical metallic nanoparticles can serve as efficient phototactic nanoswimmers, challenging the assumption that asymmetry is necessary for self-propulsion.

Findings

Identical nanodimers are effective for phototactic self-thermophoresis.

Thermophoretic force depends strongly on incident light wavelength.

Symmetric nanodimers can be as effective as asymmetric ones for propulsion.

Abstract

We assess the potentiality of several geometries of metallic nanodimers (one of the simplest thermoplasmonic systems) as candidates for active particles (nanoswimmers) propelled and controlled by light (phototaxis). The studied nanodimers are formed by two spherical nanoparticles of gold, silver, or copper with radii ranging from 20 to 100 nm. Contrary to most proposals, which assume the asymmetry of the systems as a requirement for self-propulsion, our results show that nanodimers made of identical nanoparticles are excellent candidates for phototactic self-thermophoretic systems. Nonsymmetrical nanodimers, although having a tunable effective diffusion, possess much lower or zero average thermophoretic forces. We show that the effective diffusion and the net thermophoretic force in both types of systems depend strongly on the wavelength of the incident light, which makes these properties highly tunable. Our study may be useful for the design of simple-to-make but controllable self-propelled nanoparticles. This can find numerous applications ranging from autonomous drug-carrying to controlling the self-assembly of complex nanomaterials.