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

In this paper, Yb 3+ /Er 3+ , Yb 3+ /Tm 3+ and Yb 3+ /Er 3+ /Tm 3+ co-doped β -NaYF 4 up-conversion fluorescent nanoparticles (UCNPs) with an average diameter of 50 nm were successfully synthesized through a thermal decomposition method. The Yb 3+ /Er 3+ co-doped UCNPs possess bright and tunable luminescence varying from green to red as the ratio of Yb 3+ and Er 3+ doping increases. Remarkably, white up-conversion luminescence can be successfully achieved through the incorporation of Tm 3+ . The white light up-conversion efficiency of Yb 3+ /Er 3+ /Tm 3+ 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.