title: Measurement of the hydrodynamic radius of quantum dots by fluorescence correlation spectroscopy excluding blinking.
abstract: One of the most important properties of quantum dots (QDs) is their size. Their size will determine optical properties and in a colloidal medium their range of interaction. The most common techniques used to measure QD size are transmission electron microscopy (TEM) and X-ray diffraction. However, these techniques demand the sample to be dried and under a vacuum. This way any hydrodynamic information is excluded and the preparation process may alter even the size of the QDs. Fluorescence correlation spectroscopy (FCS) is an optical technique with single molecule sensitivity capable of extracting the hydrodynamic radius (HR) of the QDs. The main drawback of FCS is the blinking phenomenon that alters the correlation function implicating in a QD apparent size smaller than it really is. In this work, we developed a method to exclude blinking of the FCS and measured the HR of colloidal QDs. We compared our results with TEM images, and the HR obtained by FCS is higher than the radius measured by TEM. We attribute this difference to the cap layer of the QD that cannot be seen in the TEM images.
authors.affiliation: †Department of Quantum Electronics, Institute of Physics "Gleb Wataghin", State University of Campinas/UNICAMP, 13083-859 Campinas, São Paulo, Brazil.
authors.forename: A A
authors.initials: AA
authors.lastname: de Thomaz
authors.affiliation: †Department of Quantum Electronics, Institute of Physics "Gleb Wataghin", State University of Campinas/UNICAMP, 13083-859 Campinas, São Paulo, Brazil.
authors.forename: D B
authors.initials: DB
authors.lastname: Almeida
authors.affiliation: †Department of Quantum Electronics, Institute of Physics "Gleb Wataghin", State University of Campinas/UNICAMP, 13083-859 Campinas, São Paulo, Brazil.
authors.forename: V B
authors.initials: VB
authors.lastname: Pelegati
authors.affiliation: ‡Department of Structural and Functional Biology, Institute of Biology, State University of Campinas/UNICAMP, 13083-865 Campinas, São Paulo, Brazil.|§National Institute of Photonics Applied to Cell Biology (INFABIC), 13083-865 Campinas, São Paulo, Brazil.
authors.forename: H F
authors.initials: HF
authors.lastname: Carvalho
authors.affiliation: †Department of Quantum Electronics, Institute of Physics "Gleb Wataghin", State University of Campinas/UNICAMP, 13083-859 Campinas, São Paulo, Brazil.|§National Institute of Photonics Applied to Cell Biology (INFABIC), 13083-865 Campinas, São Paulo, Brazil.
authors.forename: C L
authors.initials: CL
authors.lastname: Cesar
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry; D004058:Diffusion; D057446:Hydrodynamics; D010316:Particle Size; D045663:Quantum Dots / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013691:Tellurium / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D013691:Tellurium; C028337:cadmium telluride