Upconversion luminescence, scintillation properties and optical thermometry behaviors of Tm3+, Yb3+: Gd2Zr2O7 nanocrystals

Abstract

The development of multifunctional nanocrystals has attracted growing interest lately in the biological and medical sciences. Herein, the dual-mode luminescence properties and optical thermometric performances of Tm3+, Yb3+: Gd2Zr2O7 nanocrystals synthesized by a facile hydrothermal method are investigated systematically. Upon 980 nm excitation, the upconversion (UC) luminescence spectra of the obtained samples consist of blue (485 nm), red (655 and 681 nm), and near-infrared (785 nm) emission bands of Tm3+ ions. Diversely, the X-ray excited luminescence (XEL) spectra contain a strong ultraviolet (UV) emission from Gd3+ ions (314 nm), a weak defect-related emission band (400–600 nm), and several tiny emissions from Tm3+ ions. To realize the optical thermometry in the biological window, the luminescence intensity ratio (LIR) between 3F2,3 → 3H6 (681 nm) and 1G4→3F4 (655 nm) transitions is employed for temperature sensing, giving high absolute and relative sensing sensitivities (Sa-max = ∼1064 × 10−4 K−1, Sr-max = ∼2.32%K−1). Therefore, the present Tm3+, Yb3+: Gd2Zr2O7 nanocrystals could be useful in optical thermometry, photodynamic therapy, and X-ray imaging.