Synthesis of biocompatible and luminescent NaGdF 4 :Yb,Er@ Carbon nanoparticles in water-in-oil microemulsion
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Limin Wang Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004, People’s Republic of China
Zeye Wang Department of Materials Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004, People’s Republic of China
Zhengquan Lia) Department of Materials Physics and Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004, People’s Republic of China (Received 9 August 2010; accepted 30 September 2010)
Here we present a microemulsion route to prepare core–shell structured NaGdF4:Yb,Er@Carbon nanoparticles, in which a thin layer of hydrophilic carbon was covered on hydrophobic NaGdF4:Yb, Er nanocrystals. The prepared NaGdF4:Yb,Er@Carbon nanoparticles were uniform in a size of 25 nm, water-dispersible, and displayed good biocompatibility and strong upconversion fluorescence. Their potential for use as efficient cell-imaging probes is also demonstrated.
I. INTRODUCTION
Recently, synthesis and surface-modification of upconversion nanocrystals (UCNs) have attracted considerable attention because of their unique optical properties and promising applications in biological fields.1,2 Lanthanidedoped near-infrared (NIR)–to–visible UCNs, which can convert NIR excitation to visible light, are of particular interest.3 Since most biological species absorb minimally in the NIR window, their use in fluorescent imaging minimizes the induced autofluorescence and photodamage, as well as enables high penetration depth of light in tissues.4–6 UCNs exhibit superior photostability, as the lanthanide ions responsible for their fluorescence emission are doped within the nanocrystal core such that they are well shielded from the surroundings.7 Moreover, taking advantage of sharp emissions and long lifetime, the UCNs can also serve as efficient electron donors and improve the efficiency and sensitivity in fluorescence resonance energy transfer (FRET) detection, a popular technology widely used in biological detection.8,9 Among various host materials for lanthanide-doped UCNs, NaGdF4 nanocrystals are attractive because of the low photo energy associated with high upconversion efficiency.10,11 At the same time, Gd3+ ions possess a large number of unpaired electrons, and thus NaGdF4 nanocrystals can also serve as solid-state contrast agents in magnetic resonance imaging a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2010.36 82
J. Mater. Res., Vol. 26, No. 1, Jan 14, 2011
http://journals.cambridge.org
Downloaded: 10 Apr 2015
(MRI).12,13 Therefore, synthesis of high-quality and biocompatible NaGdF4 nanoparticles may support the development of multimodal bioimaging nanoplatform for diagnosis, detection, and therapy in future bionanotechnology. Many successful attempts have been made to synthesize NaGdF4 nanocrystals in the past years, but unfortunately high-quality and monodisperse nanocrystals are generally prepared from nonpolar solvents and bear a hydrophobic surface.10–13 To harness these hydrophobic nanocrystals to biological fields, surface modific
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