Up-conversion luminescence of Lu6O5F8: 1%Er3+/10%Yb3+ nanoparticles for temperature sensing and Cu2+ detection

The ultra-small Lu6O5F8: 1%Er3+/10%Yb3+ up-conversion nanoparticles (UCNPs) were prepared via a co-precipitation method and used for detection of metal ions . Compared with other metal ions (Na+, Mg2+, Al3+, Fe2+, Co2+, Cd2+, etc), the up-conversion luminescence (UCL) intensity was reduced by 90% in the presence of Cu2+. Moreover, Strong quenching (65%) of the emission was observed upon the addition of Cu2+ in the concentration range of 0–10 μM. Meanwhile, the Cu2+ luminescence quenching mechanism was studied in detail. Under the 980 nm (1550 nm) excitation, the red UCL intensity of (Lu0.79Y0.1)6O5F8: 1%Er3+/10%Yb3+ and (Lu0.85Gd0.04)6O5F8: 1%Er3+/10%Yb3+ UCNPs enhanced about 4.67 (19.3) times and 3.95 (8.89) times than that of Y3+, Gd3+-absent samples, respectively. The temperature-sensing effect of Lu6O5F8: 1%Er3+/10%Yb3+ was also studied in detail, including not only this thermally coupled level (Er3+ 2H11/2, 4S3/2), but also the non-thermally coupled levels (Er3+ 2H11/2, 4F7/2). The absolute (S a ) and relative sensitivity (S r ) of Lu6O5F8: 1%Er3+/10%Yb3+ based on non-thermally coupled levels is much higher than that based on thermally coupled levels in the 293–473 K range. The maximum S a and S r is 0.087 and 0.0185 K −1  at 293 K. These meaningful results indicate that Lu6O5F8: 1%Er3+/10%Yb3+ materials have broad prospects in UCL multifunctional applications.