Light-Activated Self-thermophoretic Janus Nanopropellers

TL;DR

This paper demonstrates a novel light-driven, fuel-free self-thermophoresis mechanism in gold-silica Janus nanoparticles, enabling controlled nanoscale motion by optical excitation, advancing active matter research.

Contribution

It introduces a reversible, tunable, and fuel-free method for inducing active motion in nanometer-sized particles using optical excitation, with direct experimental evidence of self-thermophoresis.

Findings

Direct evidence of self-thermophoresis in Janus nanoparticles

Light-driven active motion distinguished from thermal noise

Potential for nanoscale active matter manipulation

Abstract

Achieving controlled and directed motion of artificial nanoscale systems in three-dimensional fluid environments remains a key-challenge in active matter, primarily due to the prevailing thermal fluctuations that rapidly randomize the particle trajectories. While significant progress has been made with micrometer-sized particles, imparting sufficient mechanical energy, or self-propulsion, to nanometer-sized particles to overcome Brownian diffusion and enable controlled transport remains a major issue for emerging applications in nanoscience and nanomedicine. Here, we address this challenge by demonstrating the fuel-free, reversible, and tunable active behavior of gold-silica (Au-SiO2) Janus nanoparticles (radius R=33 nm) induced by optical excitation. Using single particle tracking, we provide direct experimental evidence of self-thermophoresis, clearly distinguishing active motion from thermal noise. These light-driven Janus nanoparticles constitute a minimal yet robust photothermal system for investigating active matter and its manipulation at the nanoscale.