Thermometric Calibration of the Ultrafast Relaxation Dynamics in Plasmonic Au Nanoparticles

TL;DR

This study developed a method to measure the real-time temperature changes in plasmonic gold nanoparticles during ultrafast laser excitation, providing new insights into their relaxation dynamics.

Contribution

We introduced a thermometric calibration technique to track the ultrafast temperature evolution of plasmonic nanoparticles during relaxation processes.

Findings

Identified optical signatures of equilibrium and off-equilibrium states.

Established a calibration scale for dynamic temperature measurement.

Demonstrated real-time temperature tracking of nanoparticles.

Abstract

The excitation of plasmonic nanoparticles by ultrashort laser pulses sets in motion a complex ultrafast relaxation process involving the gradual re-equilibration of the system's electron gas, lattice and environment. One of the major hurdles in studying these processes is the lack of direct measurements of the dynamic temperature evolution of the system subcomponents. We measured the dynamic optical response of ensembles of plasmonic Au nanoparticles following ultrashort-pulse excitation and we compared it with the corresponding static optical response as a function of the increasing temperature of the thermodynamic bath. Evaluating the two sets of data, the optical fingerprints of equilibrium or off-equilibrium responses could be clearly identified, allowing us to extract a dynamic thermometric calibration scale of the relaxation process, yielding the experimental ultrafast temperature evolution of the plasmonic particles as a function of time.