Magnetic and optical properties of NaGdF4:Nd3+, Yb3+, Tm3+ nanocrystals with upconversion/downconversion luminescence from visible to the near-infrared second window

X. Zhang, Z. Zhao, X. Zhang, D.B. Cordes, B. Weeks, B. Qiu, K. Madanan, D. Sardar, J. Chaudhuri

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Abstract

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.

Original languageEnglish
Pages (from-to)636-648
Number of pages13
JournalNano Research
Volume8
Issue number2
Early online date9 Sept 2014
DOIs
Publication statusPublished - Feb 2015

Keywords

  • Near-infrared second
  • Window
  • Photoluminescence
  • Energy transfer
  • Nanocrystals

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