Colloidal nanoparticles, due to their large sizes, are all relatively strong light scatterers in comparison to small chemical reagents in solutions. Many photoactive nanoparticles are also photon absorbers and emitters. Experimental quantification of the fundamental optical constants of colloidal nanoparticles in terms of their photon absorption, scattering, and emission cross-sections are critical for developing a mechanistic understanding of the correlation between material optical properties and its structural parameters including sizes, shapes, and chemical compositions. Such information holds to key for rational nanoparticle design and applications. However, experimentally decoupling the complex interplay of material photon absorption, scattering, and emission is challenging with existing spectroscopic methods. Introduced in this talk is the recent polarized resonance synchronous spectroscopic (PRS2) technique for evaluation of the optical activities of colloidal nanoparitcles in solutions. The model nanoparticles includes polystyrene nanoparticles that are approximately pure light scatterers with no significant photon absorption and emission in the UV-vis region, plasmonic gold and silver nanoparticles that are simultaneous photon absorbers and scatterers with no signfiicant emission, and fluorescent quantum dots that are simultaneous absorbers, scatterers, and emitters. Besides quantification of nanoparticle photon absorption, scattering, emission cross-sections, and scattering and fluorescence depolarization, PRS2 application for in-situ non-invasive monitoring nanoparitcle size and shape variations will also be discussed.

Quantification of the optical properties of colloidal nanoparticles in solutions: Challenges and opportunities

2019 Spring National Meeting

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