White up-conversion efficiency of Yb3+/Er3+/Tm3+ co-doped β-NaYF4 nano-crystals

In this paper, Yb3+/Er3+, Yb3+/Tm3+ and Yb3+/Er3+/Tm3+ co-doped β-NaYF4 up-conversion fluorescent nanoparticles (UCNPs) with an average diameter of 50 nm were successfully synthesized through a thermal decomposition method. The Yb3+/Er3+ co-doped UCNPs possess bright and tunable luminescence varying from green to red as the ratio of Yb3+ and Er3+ doping increases. Remarkably, white up-conversion luminescence can be successfully achieved through the incorporation of Tm3+. The white light up-conversion efficiency of Yb3+/Er3+/Tm3+ co-doped UCNPs dispersed in the solvent have been calculated, suggesting the potentials of the efficient white up-conversion emissions for the multispectral imaging and potential bio-applications.