Transient Enhancement and Spectral Narrowing of The Photothermal Effect of Plasmonic Nanoparticles Under Pulsed Excitation

Metal plasmonic NPs are the best converters of light into heat through the mechanism of surface plasmon resonance.[1,2] This unique photothermal (PT) property was developed to allow precise manipulations of thermal energy at nanoscale through engineered plasmon resonances.[3–6] Enhancement of the PT efficacy and spectral selectivity of such engineered NPs is associated with several principal limitations. Most commonly, stationary optical excitation creates high thermal losses[7–9] that, in turn, require additional excitation energy, while the pulsed excitation involves high optical intensities that destroy NP structure that provides optical absorbance.[10–13] Spectral width of absorption spectra of single NPs is tens of nanometers at best, while random clustering of NPs further broadens their spectra to hundreds of nanometers.[2,14–16] An ability to deliver high PT efficacy with high spectral resolution and minimal thermal losses will therefore significantly improve current applications of plasmonic materials.