Plasmonic Heating Effects in Tip-Enhanced Raman Spectroscopy (TERS)

Tip-enhanced Raman spectroscopy (TERS) is a spectroscopy technique that possesses single-molecule sensitivity and subnanometer spatial resolution. These unique properties are achieved thanks to the extremely high electromagnetic field confinement at the apex of the scanning probe. However, such strong field confinement can lead to photodecomposition and thermal decomposition of the analytes. Here, we demonstrate that the use of an aqueous solvent as tip-sample junction mediator drastically reduces possible molecule degradation. Using a combination of electrodynamic and heat transport simulations, we provide some theoretical insight into the plasmonic heating of the TERS system. The simulations of a realistic model system show that upon illumination of the tip-sample junction the temperature at the tip apex can increase by -180 K when TERS is performed in air with optical powers of -100 mu W. On the other hand, in aqueous media, the temperature increase of the tip remains significantly lower (a few kelvins) thanks to the higher thermal conductivity of water.