title: Determination of the Dipole Geometry of Fluorescent Nanoparticles Using Polarized Excitation and Emission Analysis.
abstract: We demonstrate that the geometries of the absorption dipole μab and emission dipole μem of nano-emitters such as quantum dots can be determined simultaneously by far-field polarimetry. The method involves plotting the emission polarization ratio against the absorption polarization ratio of single nano-emitters. Using Monte Carlo simulation, we show that these plots depend sensitively on the aspect ratio of the dipole shape. For example, the so-called 3D-2D dipole combination, that is, μab of radius ratio 1:1:1 and μem of ratio 1:1:0, would give rise to a vertical line plot. Polarization ratios of commercial cadmium selenide/zinc sulfide (CdSe/ZnS) quantum dots are measured and plotted. The empirical data points are best-fitted to yield μab of radius ratio 1:1:0.28 and μem of ratio 1:1:0.
authors.affiliation: Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Jianan
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China.
authors.forename: Ka-Cheung
authors.initials: KC
authors.lastname: Kwok
authors.affiliation: Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China nhcheung@hkbu.edu.hk.
authors.forename: Nai-Ho
authors.initials: NH
authors.lastname: Cheung
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry; D008856:Microscopy, Fluorescence / Q000379:methods*; D009010:Monte Carlo Method; D045663:Quantum Dots / Q000737:chemistry*; D018036:Selenium Compounds / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; D013440:Sulfides; D017967:Zinc Compounds; C058667:cadmium selenide; C031238:zinc sulfide
keywords: Dipole geometry; polarimetry; quantum dots