Temperature sensing and bio-imaging applications based on polyethylenimine/CaF2 nanoparticles with upconversion fluorescence

Publication date: 1 July 2017
Source:Talanta, Volume 169
Author(s): Guofeng Liu, Zhen Sun, Zuoling Fu, Li Ma, Xiaojun Wang
Rare earth ion-doped upconversion nanoparticles (UCNPs) have become a research hotspot for their applications such as nano-thermometry and bio-imaging. Here we report one pot solvothermal synthesis of polyethylenimine (PEI) coated CaF2: 1%Er³⁺, 2%Yb³⁺ UCNPs with good water-solubility and biocompatibility. The nanoparticles show a spherical shape with an average size of 40nm and display intense green light (Yb³⁺ and Er³⁺) under the 980nm irradiation. The maximum sensitivity of temperature sensing in the biological temperature range is obtained to be 0.00215K⁻¹ using the fluorescence intensity ratio (FIR) technique. Furthermore, after the UCNPs are incubated with Hela cancer cells for 6h, the obvious green sign from Er³⁺ can be observed under the excitation at 980nm. All the experimental results imply that the PEI/CaF2: 1%Er³⁺, 2%Yb³⁺ nanoparticles are excellent candidates for nano-thermometry and have good potential for biological applications.

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