Anti Stokes Thermometry of Plasmonic Nanoparticle Arrays

Metallic nanoparticles possess strong photothermal responses, especially when illuminated as ensembles due to collective effects. However, accurately quantifying the temperature increase remains a significant challenge, impeding progress in several applications. Anti Stokes thermometry offers a promising solution by enabling direct and non-invasive temperature measurements of the metal without the need for labeling or prior calibration. While Anti Stokes thermometry is successfully applied to individual nanoparticles, its potential to study light-to-heat conversion with plasmonic ensembles remains unexplored. In this study, the theoretical framework and the conditions that must be fulfilled for applying Anti Stokes thermometry to ensembles of nanoparticles are discussed. Then, this technique is implemented to measure the light-induced heating of square arrays of Au nanodisks. The obtained temperature measurements are validated using wavefront microscopy, demonstrating excellent agreement between the two thermometry methods. These results showcase the extension of Anti Stokes thermometry to plasmonic ensembles, highlighting its potential for implementation in the diverse photothermal applications involving these systems. Plasmonic nanoparticles present strong photothermal responses, but precisely measuring their temperature is challenging. Anti Stokes thermometry is a label-free technique that is mostly applied to single particles. Here, the theoretical framework is introduced to apply it to the collective heating of ensembles. Temperature measurements of arrays of Au nanodisks are demonstrated and validated with wavefront microscopy, with excellent agreement.image