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Nano Lett ; 17(12): 7487-7493, 2017 12 13.
Artigo em Inglês | MEDLINE | ID: mdl-29160715


Upon photo- or electrical-excitation, colloidal quantum dots (QDs) are often found in multicarrier states due to multiphoton absorption, photocharging, or imbalanced carrier injection of the QDs. While many of these multicarrier states are observed in single-dot spectroscopy, their properties are not well studied due to random charging/discharging, emission intensity intermittency, and uncontrolled surface defects of single QDs. Here we report in situ deciphering of the charging status, precisely assessing the absorption cross section, and determining the absolute emission quantum yield of monoexciton and biexciton states for neutral, positively charged, and negatively charged single core/shell CdSe/CdS QDs. We uncover very different photon statistics of the three charge states in single QDs and unambiguously identify their charge signs together with the information on their photoluminescence decay dynamics. We then show their distinct photoluminescence saturation behaviors and evaluate the absolute values of absorption cross sections and quantum efficiencies of monoexcitons and biexcitons. We demonstrate that the addition of an extra hole or electron in a QD not only changes its emission properties but also varies its absorption cross section.

Zhongguo Yi Miao He Mian Yi ; 15(3): 208-10, 2009 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-20084882


OBJECTIVE: To know the epidemiological characteristics of rubella case reported in Songyang County in 2004, and to know new ways of rubella control. METHOD: To analyze the epidemiology on the rubella cases reported in Songyang County in 2004. RESULTS: In 2004, 195 rubella cases were reported, and the reported rubella incidence was 84.42/100,000. The rubella cases were mainly primary and middle school students,which were 180 cases. The rubella cases occurred from January to June, and 64.10% cases occurred in April. There were 12 rubella outbreaks with 181 cases in the rural areas. For the immunity history of rebulla vaccine of 181 cases, 48.07% cases were unvaccinated, 51.93% cases were unknown. The immunization coverage rate of rubella vaccine of students in rural areas (20%) was obviously lower than that of students in the urban areas (92%). CONCLUSION: The main reasons of the high rubella incidence in Songyang County in 2004 were the low coverage rate of rubella vaccine and poor living accommodation for the primary and middle school students in the rural areas, and it was effective to adopt comprehensive measures such as emergent vaccination to control rubella outbreak.

Rubéola (Sarampo Alemão)/epidemiologia , Adolescente , Distribuição por Idade , Criança , Pré-Escolar , China/epidemiologia , Surtos de Doenças , Feminino , Humanos , Lactente , Masculino , Rubéola (Sarampo Alemão)/imunologia , Rubéola (Sarampo Alemão)/prevenção & controle , Vacina contra Rubéola/administração & dosagem , Vacina contra Rubéola/imunologia , Adulto Jovem