Spatial control of heat flow at the nanoscale using Janus particles

Janus Nanoparticles (JNP) feature heterogeneous compositions bringing opportunities in technological and medical applications. We investigate using non-equilibrium molecular dynamics simulations the temperature field generated around heated spherical Janus Nanoparticles to assess the performance of the particles in the generation of anisotropic heating. We demonstrate that the contrasting interfacial thermal conductances of the fluid-material interfaces arising from the heterogeneous composition of the JNP 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 simplified atomistic and complex models of gold nanoparticles passivated with hydrophobic and hydrophilic ligands 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.