Cai’e Cui

Excellent optical thermometry based on single-color fluorescence in spherical NaEuF 4 phosphor

Temperature-dependent luminescence of spherical NaEuF₄ phosphors with different particle sizes was studied. The thermally coupled ⁵D₀ and ⁵D₁ level of Eu³⁺ was observed. The linear dependence of emission intensities of ⁵D₀ level of NaEuF₄ phosphor on temperature confirmed the excellent temperature sensing performance. Sensitivity up to 0.43% is achieved via decreasing the particle size, which is higher than that of reported thermometry based on upconversion of lanthanide ions. Moreover, the original luminescent intensity of 90% was recovered after 10 temperature-changed cycles, indicating good sensing stability. Therefore, spherical NaEuF₄ phosphor might be a promising candidate for optical temperature sensors.

Multifunctional CaSc2O4:Yb3+/Er3+ one-dimensional nanofibers: electrospinning synthesis and concentration-modulated upconversion luminescent properties

In this paper, an electrospinning technique was developed to prepare CaSc2O4:Yb3+/Er3+ one dimensional (1D) nanofibers for the first time. X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy and nitrogen adsorption/desorption were utilized to characterize the structure and morphology of the as-prepared nanofibers, indicating that single phase mesoporous CaSc2O4:Yb3+/Er3+ 1D nanofibers with a uniform size and morphology can be prepared via the electrospinning technique. The as-prepared CaSc2O4:Yb3+/Er3+ 1D nanofibers exhibit strong UCL under the excitation of 980 nm. The cross-relaxation (4S3/2 + 4I15/2 → 4I9/2 + 4I13/2) and energy back transfer (4S3/2 + 4F7/2 → 4I13/2 + 4F5/2) processes are found to be responsible for the concentration-dependent UCL properties, confirmed by rate equation modeling. Optical thermometry in the temperature range of 298–623 K was recorded using the FIR technique with two green UC emissions in the as-prepared CaSc2O4:Yb3+/Er3+ 1D nanofibers. The dependence of the sensitivity on the doping concentration of the Yb3+ and Er3+ ions is found. The above results suggest that the as-prepared CaSc2O4:Yb3+/Er3+ 1D nanofibers have great potential for the applications of drug delivery and optical thermometers.