Controlled synthesis of ytterbium ion and erbium ion codoped gadolinium oxyfluoride hollow nanosphere with upconversion
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ng Liu, Xuesi Wang, and Hongwei Songb) State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, People’s Republic of China (Received 8 June 2012; accepted 2 January 2013)
Uniform ytterbium ion and erbium ion codoped gadolinium oxyfluoride (GdOF: Yb31, Er31) hollow nanospheres of 100-nm diameter were synthesized via the nanoscale Kirkendall approach, using colloidal nanospheres of ytterbium ion and erbium ion codoped gadolinium hydroxide [Gd(OH)3: Yb 31, Er 31] as sacrificial templates and titanium tetrafluoride as fluorine source under hydrothermal condition. The shell thickness of the as-synthesized GdOF: Yb31, Er 31 hollow nanospheres can be facilely tuned from 31 to 13 nm by controlling reaction temperature and reaction time. The upconversion emission color could be adjusted from red to yellow to green when the host lattices variedfrom gadolinium (III) oxide to gadolinium oxyfluoride to gadolinium fluoride. Furthermore, the formation mechanism of the hollow GdOF: Yb 31, Er 31 nanospheres was found to depend on the fluorine source. I. INTRODUCTION
Nanomaterials have continuously attracted worldwide interest because their morphology, dimensionality, and size greatly affect the physical and chemical properties.1–23 Due to their low effective density and high specific surface area, uniform, mondisperse hollow inorganic nanospheres are more important than solid nanospheres in some applications,24–33 such as catalysis,29 photonic devices,30 electrochemical cell,31 and biotechnology.32 Among these inorganic nanomaterials, the lanthanide oxides and lanthanide fluorides are promising host matrices for down- and upconversion (UC) luminescence because of their good chemical and thermal stability.34–40 Monodisperse rare-earth-doped lanthanide oxide and lanthanide fluoride hollow nanospheres are in high demand as both fluorescence and magnetic resonance imaging (MRI) labels34 in biomedical field and application in drug-release field because of their low density and high surface area. It is a promising candidate for labeling the location, local environments of the drug carriers in vivo and monitoring the drug delivery conditions instantaneously using the hollow lanthanide oxide and fluoride nanospheres as drug carrier.35 When compared with the nanospheres of lanthanide oxides and lanthanide fluorides, the nanospheres
Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2013.12 848
J. Mater. Res., Vol. 28, No. 6, Mar 28, 2013
of lanthanide oxyfluorides have been more intensively studied due to their unique chemical bonding between metal cations and fluoride anions.41–44 However, to the best of our knowledge, there are few reports on the synthesis of hollow uniform and monodisperse nanospheres of lanthanide oxides and lanthanide fluorides45–50 and almost no reports on the synthesis of uniform, monodisperse gadolinium oxyfluoride (GdOF) hollow nanospheres doped with rare earth activators of100-nm
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