Upconversion Luminescence of Er $^{3+}$ –Yb $^{3+}$ Codoped NaYF

NaYF₄: 0.02ErmiddotxYb-PVP composite nanofibers with the diameter of ~400 nm have been prepared by electrospinning. Field emission scanning electron microscope and X-ray diffraction have been utilized to characterize morphology and structure of the as-prepared electrospun nanofibers. Their up-conversion luminescence is investigated under a 980-nm excitation. Green (538 and 520 nm), red (655 nm), and blue (405 nm) emissions are observed in the up-conversion luminescence spectra, and the intensity of these three emissions changes differently with the variety of Yb content, which has been interpreted successfully in this letter. The color of NaYF₄: 0.02ErmiddotxYb-PVP nanofibers under a 980-nm excitation can be changed from green rarr white rarr yellow gradually via changing the Yb content.