Controlled synthesis, formation mechanism, and great enhancement of red upconversion luminescence of NaYF4:Yb3+, Er3+ nanocrystals/submicroplates at low doping level

Strong red upconversion luminescence of rare-earth ions doped in nanocrystals is desirable for the biological/biomedical applications. In this paper, we describe the great enhancement of red upconversion emission (4F9/2 --> I15/2 transition of Er3+ ion) in NaYF4:Yb3+, Er3+ nanocrystals at low dop...

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Vydáno v:The journal of physical chemistry. B Ročník 112; číslo 49; s. 15666 - 15672
Hlavní autoři: Zhao, Junwei, Sun, Yajuan, Kong, Xianggui, Tian, Lijin, Wang, Yu, Tu, Langping, Zhao, Jialong, Zhang, Hong
Médium: Journal Article
Jazyk:angličtina
Vydáno: United States 11.12.2008
Témata:
Cations
Citric Acid - chemistry
Color
Erbium - chemistry
Luminescence
Metal Nanoparticles - chemistry
Metal Nanoparticles - ultrastructure
Microscopy, Electron, Scanning
Microscopy, Electron, Transmission
Spectroscopy, Fourier Transform Infrared
Temperature
X-Ray Diffraction
Ytterbium - chemistry
ISSN:1520-6106
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Shrnutí:Strong red upconversion luminescence of rare-earth ions doped in nanocrystals is desirable for the biological/biomedical applications. In this paper, we describe the great enhancement of red upconversion emission (4F9/2 --> I15/2 transition of Er3+ ion) in NaYF4:Yb3+, Er3+ nanocrystals at low doping level, which is ascribed to the effectiveness of the multiphonon relaxation process due to the existence of citrate as a chelator and cross relaxation between Er3+ ions. The dissolution-recrystallization transformation, governing both the intrinsic crystalline phase (cubic and/or hexagonal phase) and the growth regime (thermodynamic vs kinetic), is responsible for the phase control of the NaYF4 crystals. The possible formation mechanism of the NaYF4 crystals and the role of trisodium citrate which acts as a chelating agent and shape modifier are discussed in detail. It is also found that the alpha --> beta phase transition is favored by the high molar ratio of fluoride to lanthanide and high hydrothermal temperature as well as long hydrothermal time.
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ISSN:1520-6106
DOI:10.1021/jp805567k