Thermal Switching in a Ferrocenyl Nanojunction Is Observed in All-Atom Simulations

Nanoscale phononic materials are critical to next-generation devices for energy management and information technology. A nanojunction (NJ) consisting of two gold nanoparticles (AuNPs) bridged by ferrocenyl (Fc) molecules is one such material. We use molecular dynamics simulations to demonstrate that they can exhibit a thermal switching ratio of R > 200, allowing for directed control of heat transport. Both states─with electric field switched "ON" and "OFF"─are represented in the models through corresponding atomistic partial charges. We report the response of the NJ across a broad range of parameters by varying the electric field strength, temperature set point, AuNP size, AuNP-to-AuNP distance, and number of Fc molecules. We find a nonlinear relationship between the thermal switching ratio and the number of Fc molecules. The optimum performance of R > 300 is achieved when 2 to 4 Fc molecules bridge between the AuNPs. In a Medusa AuNP─with 140 Fc molecules on a 4 nm diameter AuNP─we can achieve R = 31, which is still larger than previously reported devices.