Five-photon UV upconversion emissions of Er^3+ for temperature sensing

Abstract

Under 980 nm excitation, the temperature dependence of five-photon UV (256 and 276 nm) upconversion luminescence in Yb³⁺-Er³⁺ codoped β-NaLuF₄ nanocrystals was studied from 303 K to 523 K. The ⁴D(7/2) and ⁴G(9/2) levels of Er³⁺ are confirmed to be thermally coupled levels. They are the highest energy states for optical thermometry known so far. By using fluorescence intensity ratio technique, optical temperature sensing characteristics based on the ⁴D(7/2)/⁴G(9/2) → ⁴I(15/2) transitions of Er³⁺ were reported here for the first time. The obtained sensitivity of this UV-based sensor is higher than that of green-based optical thermometer in low temperature range.

Luminescent nano-thermometer based on up-conversion luminescence behavior of transparent Ba2ErF7 nano-glass ceramics

“…The Er 3? ion was reported to have two couples of adjacent thermally coupled energy levels (TCL), 2 H 11/2 and 4 S 3/2 , and 4 D 7/2 and 4 G 9/2 , whose relative emission intensity is strongly temperature-dependent [20][21][22][23]. In the photoluminescence process, TCL of the Er 3?…”

Concentration-Dominated Temperature-Dependence of Upconversion Luminescence in Gd6WO12 Nanophosphor Co-Doped with Er3+ and Yb3+

“…17 Previous investigations have formed a well-known consensus that Er 3+ /Yb 3+ co-doped fluorides such as NaYF 4 :Er 3+ /Yb 3+ and NaLuF 4 :Er 3+ /Yb 3+ exhibited the highest UC luminescence yields. [18][19][20] However, these fluoride materials usually require relatively completed preparative procedures. In addition, their stability is worse than that of oxides.…”

Highly efficient upconversion of Er3+ in Yb3+ codoped non-cytotoxic strontium lanthanum aluminate phosphor for low temperature sensors

“…Moreover, the UC intensity of SLA:Er is too low to be used practically in comparision to the SLA:Er/Yb samples. From literature it is also evident that the sensitivity of SLA:Er and SLA:Er/Yb phosphors are also in accordance to the low phonon hosts such as fluorides, rare earth oxides etc that are highly used in bio-imaging due to their high UC efficiencies in spite of their toxic nature 1,50–54 .…”