Spatial Control of Heat Flow at the Nanoscale Using Janus Particles
JD Olarte-Plata and J Gabriel and P Albella and F Bresme, ACS NANO (2021).
Janus nanoparticles (JNPs) feature heterogeneous compositions, bringing opportunities in technological and medical applications. We introduce a theoretical approach based on nonequilibrium molecular dynamics simulations and heat transfer continuum theory to investigate the temperature fields generated around heated spherical JNPs covering a wide range of particle sizes, from a few nm to 100 nm. We assess the performance of these nanoparticles to generate anisotropic heating at the nanoscale. We demonstrate that the contrasting interfacial thermal conductances of the fluid-material interfaces arising from the heterogeneous composition of the JNPs can be exploited to control the thermal fields around the nanoparticle, leading to a temperature difference between both sides of the nanoparticle (temperature contrast) that is significant for particles comprising regions with disparate hydrophilicity. We illustrate this idea using coarse-grained and atomistic models of gold nanoparticles with hydrophobic and hydrophilic coatings, in water. Furthermore, we introduce a continuum model to predict the temperature contrast as a function of the interfacial thermal conductance and nanoparticle size. We further show that, unlike homogeneous nanoparticles, the interfacial fluid temperature depends on the interfacial thermal conductance of Janus nanoparticles.
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