Thermal sensitivity and stability of NaYF_4:Yb~(3+) , Er~(3+) upconversion nanowires, nanorods and nanoplates

摘要

In this paper, temperature sensing properties of NaYF_4:Yb~(3+) , Er~(3+) 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 (R_(HS)) between ~2H_(11/12)→~4I_(15/2) and ~4S_(3/2)→~4I_(15/2) 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 R_(HS) and temperature, the fitted energy difference (ΔE) of ~2H_(11/12)and ~4S_(3/2) energy levels of Er~(3+) ions depends on the shapes and sizes of UC samples, which leads to improvements of thermal sensitivity of NaYF_4:Yb~(3+) , Er~(3+) particles with the increase of surface to volume ratios.