Spatial Control of Heat Flow at the Nanoscale Using Janus Particles

Controlling the magnitude and direction of heat transfer in nanoscale materials is an outstanding objective of thermoplasmonics. Advances in achieving this objective will significantly impact biomedical applications, particularly thermal therapies for cancer treatments (killing cancer cells with nano heaters), drug delivery, imaging, and catalysis.

Our work demonstrates that nanoparticles with internal heterogeneous composition provide a route to tuning thermal transport spatially. With this purpose, we investigated plasmonic metallic Janus nanoparticles (JNPs) coated with ligands of different hydrophilicity, which results in contrasting thermal conductances on opposite sides of the JNP. Furthermore, we quantified the heat transferred locally around the nanoparticle using large scale Non-Equilibrium Molecular Dynamics Simulations of coarse-grained and fully atomistic models of JNPs. We also introduce in our work a continuum model based on classical heat transfer theory that predicts the anisotropic heating of JNP in a wide range of system sizes, from few nm to 0.1 um. Our model can be easily implemented in experimental settings to quantify the thermal transport anisotropy emerging from the heating of nanoparticle using optical probes.

We anticipate that our work will impact the general area of thermoplasmonics, particularly thermal therapy and catalytic applications, which require fine control of the temperature increase and spatial temperature distribution at the surface of plasmonic nanoparticles.

Image detail: Gold Janus nanoparticle coated with hydrophlic mercaptohexanol ligands (cyan) and hydrophobic octanethiol ligards (red).Water molecules around the nanoparticles are coloured in ice-blue and the gold atoms in yellow.

Authors: Juan D. Olarte-Plata; Jordan Gabriel; Pablo Albella; Fernando Bresme

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