The color tuning and mechanism of upconversion emission from green to red in NaLuF4:Yb3+/Ho3+ nanocrystals by codoping with Ce3+

• The color tuning and mechanism of upconversion emission from green to red in NaLuF4:Yb3+/Ho3+ nanocrystals by codoping with Ce3+.
• Sliced TRES spectra of 500–700 nm UC emissions, the peak intensity is changed with the time increased.
• Two efficient cross relaxation processes between Ho3+ and Ce3+ are found to be dominant UC pathways for tuning the emission color from green to red in single NaLuF4:Yb3+/Ho3+ nanocrystals.

The upconversion (UC) luminescence nanocrystals of hexagonal phase NaLuF4:Yb3+/Ho3+ were prepared by a solvothermal process at 300 °C. The visible upconversion emission from green to red in Yb3+ and Ho3+ codoped β-NaLuF4 nanoparticles is successfully achieved by tridoping with Ce3+ ions (0–12 mol%) and the red emission intensity is enhanced gradually with the increasing Ce3+ concentration. In this work, results of XRD, SEM, EDS and TRES upconversion data demonstrate that Ce3+ ions are successfully incorporated into NaLuF4:Yb3+/Ho3+ nanoparticles. UC emissions at 541 nm and 644 nm of all prepared nanoparticles under 980 nm excitation correspond to the transitions of 5S2/5F4 → 5I8 and 5F5 → 5I8 of Ho3+ ions respectively. The decay curves of 541 nm emission under 980 nm pulse excitation are detected. The 541 nm emission decays fast when Ce3+ concentration increases. All results show that tuning from green to red upconversion can be realized in NaLuF4:Yb3+/Ho3+ nanocrystals via tridoping with different concentration of Ce3+ ions.