Upadhyay Madan M, Kumar Kaushal
Optical Materials & Bio-imaging Research Laboratory, Department of Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad, 826004, India.
Heliyon. 2024 Oct 9;10(20):e39081. doi: 10.1016/j.heliyon.2024.e39081. eCollection 2024 Oct 30.
The GdPO:Tm/Yb phosphor codoped with various concentrations of Li ions were synthesized for upconversion emission and optical thermometry studies. Excitation using 980 nm laser diode results in three upconversion (UC) emission bands with centre wavelengths of 478, 648 and 692 nm. These bands are originated from G→H, G→F, and F→H transitions of the Tm ion, respectively. Li ions modified the local crystal symmetry around dopant ions, resulting enhanced UC emissions. The lifetime of the G level of Tm ion was studied using a 980 nm laser excitation. The temperature sensing performances of GdPO:Tm/Yb and GdPO:Tm/Yb/Li based on fluorescence intensity ratio (FIR) technique were evaluated in the temperature range 301-713 K under 980 nm excitation. Non-thermally coupled levels F (692 nm) and G (478, 648 nm) were utilized for FIR estimation. A maximum absolute sensitivity of 6.28 × 10 K at 653 K and 18.71 × 10 K at 713 K were observed for Li undoped and codoped phosphors respectively. The result indicates that codoping of Li ions improved the UC emission as well as optical thermometry. Moreover, CIE colour coordinates and anti-counterfeiting application were also exhibited.
合成了不同锂离子浓度共掺杂的GdPO₄:Tm/Yb荧光粉，用于上转换发光和光学测温研究。使用980 nm激光二极管激发产生三个中心波长分别为478、648和692 nm的上转换（UC）发射带。这些发射带分别源于Tm离子的G→H、G→F和F→H跃迁。锂离子改变了掺杂离子周围的局部晶体对称性，从而增强了UC发射。利用980 nm激光激发研究了Tm离子G能级的寿命。在980 nm激发下，在301 - 713 K温度范围内评估了基于荧光强度比（FIR）技术的GdPO₄:Tm/Yb和GdPO₄:Tm/Yb/Li的温度传感性能。利用非热耦合能级F（692 nm）和G（478、648 nm）进行FIR估计。未掺杂和共掺杂锂离子的荧光粉在653 K时的最大绝对灵敏度分别为6.28×10⁻³ K⁻¹和在713 K时为18.71×10⁻³ K⁻¹。结果表明，锂离子共掺杂改善了UC发射以及光学测温性能。此外，还展示了CIE色坐标和防伪应用。
