Magnetic and optical properties of NaGdF4:Nd3+, Yb3+, Tm3+ nanocrystals with upconversion/downconversion luminescence from visible to the near-infrared second window
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We have designed and synthesized NaGdF4:Nd3+, Yb3+, Tm3+ magnetic nanophosphors with combined dual-mode downconversion (DC) and upconversion (UC) photoluminescence upon 800 nm excitation. Hexagonal-phase NaGdF4:Nd3+, Yb3+, Tm3+ nanocrystals (NCs) with an average size of 21 nm were synthesized using a solvothermal approach. Nd3+, Yb3+, Tm3+ triple-doped NaGdF4 NCs exhibit a broad range of photoluminescence peaks covering a near infrared first/second window (860–900, 1,000, and 1,060 nm), and visible emission including blue (475 nm), green (520 and 542 nm) and yellow (587 nm) after excitation at 800 nm. A mechanism involving circulation of energy over Gd3+ sublattices as bridge ions and final trapping by the initial activator ions (Nd3+) has been proposed. Penetration depth studies indicate that NIR emission is easily detected even at a large tissue thickness of 10 mm. These paramagnetic nanophosphors demonstrate a large magnetization value of 1.88 emu/g at 20 kOe and longitudinal relaxivity value of 1.2537 mM−1·S−1 as a T 1-weighted magnetic resonance imaging contrast agent. These NaGdF4:Nd3+, Yb3+, Tm3+ NCs are promising for applications in biological and magnetic resonance imaging.
Zhang , X , Zhao , Z , Zhang , X , Cordes , D B , Weeks , B , Qiu , B , Madanan , K , Sardar , D & Chaudhuri , J 2015 , ' Magnetic and optical properties of NaGdF 4 :Nd 3+ , Yb 3+ , Tm 3+ nanocrystals with upconversion/downconversion luminescence from visible to the near-infrared second window ' Nano Research , vol 8 , no. 2 , pp. 636-648 . DOI: 10.1007/s12274-014-0548-2
© Tsinghua University Press and Springer-Verlag Berlin Heidelberg 2014. The final publication is available at Springer via http://dx.doi.org/10.1007/s12274-014-0548-2
The authors acknowledge the support of the National Science Foundation (NSF) Grant #MRI0922898 for the TEM work. We also thank the support from the Anhui Provincial Natural Science Foundation of China (1308085QA06) and the National Science Foundation Partnership for Research and Education in Materials (NSF-PREM) grant (No. DMR-0934218).
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