LAUSR

For the first time, La2O2CN2:Yb3+/Tm3+ upconversion luminescence nanofibers and nanobelts were successfully fabricated via cyanamidation of the respective relevant La2O3:Yb3+/Tm3+ nanofibers and nanobelts which were obtained by calcining the electrospinning made PVP/[La(NO3)3+Yb(NO3)3+Tm(NO3)3] composite nanofibers and nanobelts. The morphologies, structures, and properties of the nanofibers and nanobelts are investigated. The diameters of La2O2CN2:Yb3+/Tm3+ nanofibers and width of La2O2CN2:Yb3+/Tm3+ nanobelts with the thickness of 112 nm are 109 ± 4.3 nm and 1.8 ± 0.2 μm at 95% confidence level, respectively. Upconversion luminescent analysis manifests that La2O2CN2:Yb3+/Tm3+ nanofibers and nanobelts emit intense blue emissions around 476 nm corresponding to 1G4→3H6 energy level transitions of Tm3+ ions under the excitation of a 980-nm diode laser. For the La2O2CN2:30%Yb3+/x%Tm3+ nanofibers, the blue emission intensity increases when the Tm3+ concentration is increased from 0.1 to 0.5% and then decreases as the Tm3+ concentration is further increased from 0.5 to 1.0%, so the Tm3+ optimum concentration is 0.5%. For the La2O2CN2:y%Yb3+/0.5%Tm3+ nanofibers, when the concentration of Tm3+ is fixed at 0.5%, the blue emission intensity increases when the Yb3+ concentration is increased from 5 to 30% and then decreases as the Yb3+ concentration is further increased from 30 to 40%. Therefore, the optimum concentration of Yb3+ is 30%. Thus, the optimum molar concentration ratio of Yb3+ to Tm3+ ions is 60:1 in the as-prepared La2O2CN2:Yb3+/Tm3+ nanofibers. The formation mechanisms of the La2O2CN2:Yb3+/Tm3+ nanostructures are also proposed. The novel technique can be applied to prepare other rare earth oxycyanamide nanostructures of various morphologies.