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

Abstract

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 (⁴S_3/2 + ⁴I_15/2 → ⁴I_9/2 + ⁴I_13/2) and energy back transfer (⁴S_3/2 + ⁴F_7/2 → ⁴I_13/2 + ⁴F_5/2) 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.