title: Characterization of the Dynamics of Photoluminescence Degradation in Aqueous CdTe/CdS Core-Shell Quantum Dots.
abstract: We investigate the effects of the excitation power on the photoluminescence spectra of aqueous CdTe/CdS core-shell quantum dots. We have focused our efforts on nanoparticles that are drop-cast on a silicon nitride substrate and dried out. Under such conditions, the emission intensity of these nanocrystals decreases exponentially and the emission center wavelength shifts with the time under laser excitation, displaying a behavior that depends on the excitation power. In the low-power regime a blueshift occurs, which we attribute to photo-oxidation of the quantum dot core. The blueshift can be suppressed by performing the measurements in a nitrogen atmosphere. Under high-power excitation the nanoparticles thermally expand and aggregate, and a transition to a redshift regime is then observed in the photoluminescence spectra. No spectral changes are observed for nanocrystals dispersed in the solvent. Our results show a procedure that can be used to determine the optimal conditions for the use of a given set of colloidal quantum dots as light emitters for photonic crystal optical cavities.
authors.affiliation: Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil. cgpanki@gmail.com.|DISSE - INCT de Nanodispositivos Semicondutores, Rio de Janeiro, Brazil. cgpanki@gmail.com.
authors.forename: C G
authors.identifier: http://orcid.org/0000-0002-6243-1653
authors.initials: CG
authors.lastname: Pankiewicz
authors.affiliation: Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: P-L
authors.initials: PL
authors.lastname: de Assis
authors.affiliation: Departamento de Biofísica e Radiobiologia, Universidade Federal de Pernambuco, 50670-901, Recife, Pernambuco, Brazil.
authors.forename: P E Cabral
authors.initials: PE
authors.lastname: Filho
authors.affiliation: Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: C R
authors.initials: CR
authors.lastname: Chaves
authors.affiliation: Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.|INCT em Nanomateriais de Carbono, Belo Horizonte, Brazil.
authors.forename: E N D
authors.initials: EN
authors.lastname: de Araújo
authors.affiliation: Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: R
authors.initials: R
authors.lastname: Paniago
authors.affiliation: Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.|DISSE - INCT de Nanodispositivos Semicondutores, Rio de Janeiro, Brazil.
authors.forename: P S S
authors.initials: PS
authors.lastname: Guimarães
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D008027:Light; D008163:Luminescent Measurements; D045663:Quantum Dots / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*; D013691:Tellurium / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D013440:Sulfides; C034939:cadmium sulfide; D014867:Water; D013691:Tellurium; C028337:cadmium telluride
keywords: Colloidal nanocrystals; Emission decay; Mercaptosuccinic acid; Photoluminescence; Spectral shift