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

AbstractRecently, 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:0.3Cr3+ and LZG:0.3Cr3+,0.01Ni2+ 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:0.3Cr3+,0.01Ni2+ 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 (Sr) 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:0.3Cr3+,0.01Ni2+ to become a candidate for NIR optical thermometers in biotechnological applications.