A NaYF4:Gd3+/Yb3+/Er3+/Tm3+nanorods with infrared thermally enhanced upconversion luminescence for optical thermometers

A novel strategy for optical thermometers is reported based on the NaYF4:Gd3+/Yb3+/Er3+/Tm3+ nanorods which generate thermally enhanced near-infrared upconversion emission. The fluorescence intensity ratio (FIR) between the near-infrared emission of Tm3+ (3H4 & RARR;3H6) and the green emission of Er3+ (4S3/2 & RARR; 4I15/2) as a function of temperature are studied. The relative sensitivity (Sr) of FIR (3H4 & RARR;3H6/4S3/2 & RARR; 4I15/2) is compared with that of classical FIR (2H11/2 & RARR; 4I15/2/4S3/2 & RARR; 4I15/2). The results show that FIR (2H11/2 & RARR; 4I15/2/4S3/2 & RARR; 4I15/ 2) is suitable for low temperature, while FIR (3H4 & RARR;3H6/4S3/2 & RARR; 4I15/2) is suitable for high temperature. Using FIR with higher Sr at different temperature intervals can keep the Sr of the thermometer at a higher value (0.67-1.07 %K- 1) in the temperature range of 293-523 K. The results show that NaYF4:Gd3+/Yb3+/Er3+/Tm3+ nanorods can be used as high-quality candidates for thermometers with high sensitivity and wide temperature range.

Automated summary

A novel strategy for optical thermometers using NaYF4:Gd3+/Yb3+/Er3+/Tm3+ nanorods is reported, which generate thermally enhanced near-infrared upconversion emission. The fluorescence intensity ratio (FIR) between Tm3+ near-infrared emission and Er3+ green emission as a function of temperature is studied. Results show that NaYF4:Gd3+/Yb3+/Er3+/Tm3+ nanorods can be used as high-quality candidates for thermometers with high sensitivity and wide temperature range.