Optical Thermometer Based on Efficient Near-Infrared Dual-Emission of Cr3+ and Ni2+ in Magnetoplumbite Structure

Recently, an optical thermometer based on the dual-emitting fluorescent intensity ratio (FIR) in the visible light (VIS) region has achieved great development. However, there is very little progress in thermometers from NIR light. In this work, a novel optical thermometer based on highly efficient NIR dual-emission of Cr3+ and Ni2+ in LaZnGa11O19 (LZG) with a magnetoplumbite structure is designed. Utilizing energy transfer from Cr3+ to Ni2+, the dual-emission shows a wide coverage in the 650-1600 nm region, covering the NIR I and II windows, respectively. The as-reported LZG:0.3Cr(3+) and LZG:0.3Cr(3+),0.01Ni(2+) phosphors can reach internal/external quantum efficiency (IQE/EQE) of 94%/64% and 77%/53%, respectively. The electroluminescence property and potential applications in spectroscopic analysis, night-vision, and bioimaging of fabricated NIR-LED with LZG:0.3Cr(3+),0.01Ni(2+) have also been investigated. In addition, the designed ratiometric optical thermometer responds to wide temperature ranges (100-175 K, 200-475 K) and shows a maximum relative sensitivity value (S-r) of 2.4% K-1 at 475 K. The optical performance of absorption in the red region and emission in the NIR region enables the LZG:0.3Cr(3+),0.01Ni(2+) to become a candidate for NIR optical thermometers in biotechnological applications.