Abstract
Accurate and reliable non-contact temperature sensors are imperative for industrial production and scientific research. Here, Er3+/Tm3+/Yb3+ co-doped NaYF4 phosphors were studied as an optical thermometry material. The typical hydrothermal method was used to synthesize hexagonal Er3+/Tm3+/Yb3+ co-doped NaYF4 phosphors and the morphology was approximately rod-like. The up-conversion emissions of the samples were located at 475, 520, 550, 650, 692 and 800 nm. Thermo-responsive emissions from the samples were monitored to evaluate the relative sensing sensitivity. The thermal coupled energy level- and non-thermal coupled energy level-based luminescence intensity ratio thermometry of the sample demonstrated that these two methods can be used to test temperature. Two green emissions (520 and 550 nm), radiated from 2H11/2/4S3/2 levels, were monitored, and the maximum relative sensing sensitivities reached to 0.013 K−1 at 297 K. The emissions located in the first biological window (650, 692 and 800 nm) were monitored and the maximum relative sensing sensitivities reached to 0.027 (R692/650) and 0.028 K−1 (R692/800) at 297 K, respectively. These results indicate that Er3+/Tm3+/Yb3+ co-doped NaYF4 phosphors have potential applications for temperature determination in the visible and the first biological window ranges.
Highlights
Temperature (T) is an important physical parameter in many fields, like scientific research, industrial production and biotherapy
For lanthanide ion-doped materials, their luminescence intensity, peak position, emission band width, emission lifetime and luminescence intensity ratio (LIR) have been extensive researched for non-contact optical thermometry [7,8,9,10,11]
NaYF4 : Er3+, Tm3+, Yb3+ phosphors were prepared through the typical hydrothermal method
Summary
Temperature (T) is an important physical parameter in many fields, like scientific research, industrial production and biotherapy. Er3+ doped nanomaterials are promising in LIR-based temperature sensing for their evident green emissions from 2 H11/2 /4 S3/2 and excellent thermal coupling properties [13,14,15,16]. The non-thermal coupled levels have been used in LIR thermometry because of their high sensing sensitivity [20,21,22]. High relative sensing sensitivity (0.0034 K−1 ) was obtained in NaLuF4 :Yb/Er/Ho nano-rods at 503 K, which is based on the emissions at 659 and 547 nm [23]. LIR thermometry is an excellent method for temperature measuring, which can promote relative sensing sensitivity and select suitable wavebands. We can take advantages of this multi-band noninvasive thermometry in harsh environments or biological tissues
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