Quantification of the optical properties of fluorescent quantum dots (QDs) is challenging with existing spectroscopic methods because of the complex interplay of the photon absorption, scattering, and emission that can concurrently occur in QD samples. Presented herein is the polarized resonance synchronous spectroscopic (PRS2) method and its application for quantification of the QD optical constants including absorption, scattering, and on-resonance-fluorescence (ORF) cross-section spectra as well as Stokes’-shifted fluorescence depolarization spectra quantified by polarized Stokes’-shifted fluorescence spectroscopy. The ORF and light scattering contributions are separated in the PRS2 spectra, and the UV-vis extinction spectra are decomposed into absorption and scattering components. The core-shell-ligand structured QDs with different shell volume and geometry are investigated. Scattering and absorption cross-section increased with increasing QD shell volume. The ORF cross-section monotonically decreases as the volume increases, indicating for a unit mass of QD, the increment of QD shell volume render the QD a stronger scatter and absorber, but a less efficient ORF emitter. The ORF quantum yield for rod-shape QDs (~10%) is significantly higher than that of the dot-shape QDs (&lt;3%), which offers a new way to differentiate QD geometry. SSF depolarization is strongly dependent on the QD aspect ratio, which decreases from ~1 to ~0.6 when the aspect ratio changes from 1 to 16.8. The new insights provided by the presented technique relate the QD geometry to its optical properties, which can be constructive for QD design and in-situ monitoring QD synthesis.<br/>

New insights to optical properties of fluorescent quantum dots by polarized resonance synchronous spectroscopy and polarized Stokes’-shifted fluorescence spectroscopy

2019 Spring National Meeting

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