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arXiv · 2602.17548

Light-Activated Self-thermophoretic Janus Nanopropellers

Henri Truong·Chiara Moretti·Lionel Buisson·Benjamin Abecassis·Eric Grelet
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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.

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Henri Truong, Chiara Moretti, Lionel Buisson, Benjamin Abecassis, Eric Grelet. 2026-02-19. Light-Activated Self-thermophoretic Janus Nanopropellers. https://doi.org/10.1039/d5nr04182a

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