Morphology control and multicolor up-conversion luminescence of GdOF:Yb3+/Er3+, Tm3+, Ho3+ nano/submicrocrystals

In this paper, well defined GdOF:Yb(3+)/Er(3+), Tm(3+), Ho(3+) nano/submicrocrystals with multiform morphologies were prepared via the urea-based precipitation method without using any surfactants. The morphologies of the GdOF products, including spindles and spheres with different sizes (30-550 nm), could be easily modulated by changing the fluorine sources, and the possible formation mechanism has been presented. XRD, FT-IR, SEM, TEM, as well as up-conversion (UC) photoluminescence spectra were used to characterize the prepared samples. Under 980 nm NIR excitation, the relative emission intensities and emission colors of Yb(3+)/Er(3+), Yb(3+)/Tm(3+) and Yb(3+)/Ho(3+) doped GdOF could be precisely adjusted over a wide range by tuning the Yb(3+) doping concentration. The strategies for color tuning of UC emission proposed in the current system may be helpful to achieve efficient multicolor luminescence under 980 nm laser excitation. In addition, the corresponding UC mechanisms in the co-doping GdOF systems were analyzed in detail based on the emission spectra and the plot of luminescence intensity to pump power.