Despite their use in a myriad of imaging applications, the mechanism of photoinduced light emission from metallic plasmonic nanoparticles remains an open question. Photoluminescence and electronic Raman scattering views have both been proposed to explain this phenomenon. We have used our expertise in the design, synthesis, and quantitative study of gold nanostructures to systemically probe their emission, focusing on the hypothesis that Purcell Effect enhanced photoluminescence is the primary mechanism. This talk will serve as a brief overview of this work. We have shown that varied excitation wavelengths and excitation photon flux change the energy distribution of hot carriers and impact the emission spectral lineshape. The plasmonic resonance quality factors, tuned by nanorod crystallinity, determine the Purcell enhancement effect and have a linear relation with the emission quantum yield. Another important factor in determining the emission quantum yield is the inter-/intraband emission contributions, which we have shown can be tuned by varying the nanorod size. By studying the upconverted emission of gold nanorods and comparing intensities with Stokes emission we find temperature distributions that can only be explained by an excited electron population. Additionally, the anti-Stokes emission shows a nonlinear power dependence based on the number of photons participating. The central role of hot carriers in the systematical study on gold nanorods as a model system supports a Purcell effect enhanced hot carrier photoluminescence mechanism.

Light emission from plasmonic nanorods

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ACS Fall 2022

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