A novel optical thermometry strategy based on upconversion emission of Tm3+/Yb3+ codoped Na3GdV2O8 phosphors

Abstract

In the last few years, huge progress has been devoted to the development of remote optical thermometry, due to their non-contact, high-sensitivity and fast measurement characteristics, which is especially important for various industrial and bio-applications. For these purposes, lanthanide-doped particles seem to be the most promising luminescence thermometers. In this study, Na3GdV2O8 (NGVO): Tm3+/Yb3+ phosphors are prepared by sol gel method. Under 980 nm excitation, the upconversion emission spectra are composed of two visible emission bands arising from the Tm3+ transitions 1G4→ 3H6 (475 nm), 1G4→ 3F4 (651 nm), a strong emission at 800 nm (3H4→ 3H6) in the first biological window and an emission in the third biological window at 1625 nm (3F4 → 3H6). Accordingly, the luminescence intensity ratio (LIR) between the Tm3+ LIR1( 3H4/ 1G4) and LIR2 ( 3F4/1G4)) transitions demonstrates excellent relative sensing sensitivity values (4.2 % K−1 – 2% K−1 ) and low-temperature uncertainties (0.4 K–0.5 K) over a wide temperature sensing range of 300 K to 565 K, which are remarkably better than those of many other luminescence thermometers. The NGVO: Tm3+ , Yb3+ exhibit a stronger NIR emission at low excitation density that has potential uses in deep tissue imaging, optical signal amplification and other fields. The results indicate Tm3+/Yb3+: NGVO is an ideal candidate for optical thermometer and particular for biological applications.