Morphology control, luminescence and energy transfer properties of NaCeF4 and NaCeF4:Tb3+/Yb3+ nanocrystals

Abstract

Oil-dispersible monodispersed NaCeF₄, NaCeF₄:Tb³⁺ and NaCeF₄:Yb³⁺ nanoparticles were prepared through a thermal decomposition method. Phase purity, morphology and luminescence properties were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution TEM (HRTEM), and photoluminescence (PL) spectra, respectively. The starting amount of NaF is crucial for phase purity, and the reaction time had an effect on the morphology of the products. Products with rectangles, rods, and their mixtures could be obtained at different reaction times. Under UV excitation, energy transfer from Ce³⁺ to lanthanide ions Tb³⁺ and Yb³⁺ could be observed in both NaCeF₄:Tb³⁺ and NaCeF₄:Yb³⁺. Energy transfer from Ce³⁺ to Tb³⁺ was proposed to be of a resonant type (ET) by luminescent dynamic studies with a theoretically calculated efficiency of up to 93%. Energy transfer from Ce³⁺ to Yb³⁺ was demonstrated to be a cooperative (CET) process, and the CET efficiency and total theoretical quantum efficiency were found to be 79% and 158%, respectively.