Quantum sensing of temperature increase due to thermoplasmonic effects using fluorescent nanodiamonds

In addition to the nanoscale electric field enhancement in plasmonic structures, there is an increase in the local temperature at the nanoparticle surface due to light absorption at resonance, resulting in Thermoplasmonics effects. Therefore, understanding and quantifying the local heating and resultant effects with nanoscale spatial resolution is crucial for engineering plasmonic devices for various applications. Here we report plasmonic heating of Au nanoparticles using a resonant light illumination and an estimation of associated temperature rise using Nitrogen-Vacancy (NV) centers in nanodiamonds (NDs). A custom-built wide field measurement setup detects and analyses the modulation of fluorescence spectra from the NDs close to the plasmonic hotspots. The plasmonic resonance absorption in Au nanoparticles and associated local heating is also studied using COMSOL Multiphysics which matches closely with our experimental results and validates our measurement system. This setup allows to make a thermal map of the system without being limited by diffraction and can be extended to other systems.