High performance temperature sensing and optical heating of Tm3+- and Yb3+- codoped SrBi4Ti4O15 up-conversion luminescence nanoparticles

Abstract Up-conversion (UC) phosphors with multiple functions are highly desirable for many potentially technological applications which can stimulate the miniaturization and multipurpose of modern devices. In this work, Tm3+- and Yb3+-codoped SrBi4Ti4O15 (SBT:xTm3+/Yb3+) nanoparticles have been first synthesized by a convenient EDTA-citrate method. The structures and morphologies of SBT:xTm3+/Yb3+ were measured by powder X-ray diffraction, Fourier transform infrared reflectivity spectra and scanning electron microscope. Under 980 nm excitation, SBT:xTm3+/Yb3+ exhibited strong near-infrared (NIR) and weak visible emissions. The UC emissions were unveiled to be tightly related to the Tm3+ concentration and the optimum concentration was determined as x = 0.01. The possible UC mechanism was proposed. Importantly, based on thermo-responsive fluorescence intensity ratio approach, the optical thermometric properties were characterized in the temperature range between 313 and 573 K. The maximum sensitivity of SBT:0.01Er3+/Yb3+ UCNPs was obtained as 7.5 × 10−4 K-1. Besides, excellent repeatability and stability were also realized by the thermal-cycling measurement. Furthermore, prominent photo-thermal (PT) effect was also achieved with a temperature coefficient being 0.81 °C∙mm2/mW. Under periodic laser stimulation, the PT effect of the sample displayed regular response, indicating that the PT effect can be expediently controlled by 980 nm laser. These results indicate that SBT:xTm3+/Yb3+ UCNPs could be potential candidates for temperature sensors and PT agents.