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UV–Vis Ratiometric Resonance Synchronous Spectroscopy for Determination of Nanoparticle and Molecular Optical Cross Sections

Nettles, Charles B., Zhou, Yadong, Zou, Shengli, Zhang, Dongmao
Analytical chemistry 2016 v.88 no.5 pp. 2891-2898
absorption, fluorescence, fluorescent dyes, light scattering, nanogold, nanoparticles, photons, quantum dots, solvents, spectroscopy, toluene, wavelengths, zinc sulfide
Demonstrated herein is a UV–vis Ratiometric Resonance Synchronous Spectroscopic (R₂S₂, pronounced as “R-two-S-two” for simplicity) technique where the R₂S₂ spectrum is obtained by dividing the resonance synchronous spectrum of a NP-containing solution by the solvent resonance synchronous spectrum. Combined with conventional UV–vis measurements, this R₂S₂ method enables experimental quantification of the absolute optical cross sections for a wide range of molecular and nanoparticle (NP) materials that range optically from pure photon absorbers or scatterers to simultaneous photon absorbers and scatterers, simultaneous photon absorbers and emitters, and all the way to simultaneous photon absorbers, scatterers, and emitters in the UV–vis wavelength region. Example applications of this R₂S₂ method were demonstrated for quantifying the Rayleigh scattering cross sections of solvents including water and toluene, absorption and resonance light scattering cross sections for plasmonic gold nanoparticles, and absorption, scattering, and on-resonance fluorescence cross sections for semiconductor quantum dots (Qdots). On-resonance fluorescence quantum yields were quantified for the model molecular fluorophore Eosin Y and fluorescent Qdots CdSe and CdSe/ZnS. The insights and methodology presented in this work should be of broad significance in physical and biological science research that involves photon/matter interactions.