Thermal sensitivity and stability of NaYF4:Yb3+, Er3+ upconversion nanowires, nanorods and nanoplates

• NaYF4:Yb3+, Er3+ nanowires, nanorods and nanoplates exhibit excellent temperature sensing properties.
• All the upconversion particles show high thermal stability.
• Thermal sensitivity depends on the particle shapes and sizes.

In this paper, temperature sensing properties of NaYF4:Yb3+, Er3+ upconversion (UC) nanowires, nanorods and nanoplates were studied compared to their corresponding bulk materials. Heating–cooling cycle tests show that the as-prepared samples have high thermal stability. The natural logarithm of intensity ratio (RHS) between 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions of all the samples shows a good linear relation to the inverse temperature, indicating their potential for temperature sensing applications. Based on the exponential relationship between RHS and temperature, the fitted energy difference (ΔE) of 2H11/2 and 4S3/2 energy levels of Er3+ ions depends on the shapes and sizes of UC samples, which leads to improvements of thermal sensitivity of NaYF4:Yb3+, Er3+ particles with the increase of surface to volume ratios.