Ultrabroadband Long-Wavelength Near-Infrared MgIn 2 O 4 :Ni 2+ Phosphor Synthesized via Sol-gel Combustion Method as a Light Source for Night Vision Imaging, Nonvisual Detection, and Anticounterfeiting Display.

Long-wavelength near-infrared (LWNIR) imaging technology has exciting application potential across various fields due to its ability of deeper penetration and unique properties related to its emission wavelength, when compared to short-wavelength near-infrared imaging. However, the limited availability of materials for LWNIR light sources, due to the lack of suitable host materials that constitute luminescence centers, has been a major challenge and technical obstacle in realizing such applications. Here, we developed MgIn 2 O 4 :Ni 2+ phosphors with an antispinel structure and LWNIR luminescence properties through a sol-gel combustion method. Under excitation at 365 nm, its emission wavelength covers the range of 1000-2000 nm, with a peak emission at approximately 1520 nm, a full width at half-maximum of ∼340 nm, and an optimized photoluminescence quantum yield of ∼21.22%, when an optimal Ni 2+ doping content of 1 mol % was used. Studies on the crystal structure of MgIn 2 O 4 have shown that Ni 2+ ions preferentially replace the lattice position occupied by Mg 2+ ions in the [MgO 6 ] octahedrons, which provides a crystal field microenvironment of weak strength to the Ni 2+ luminescence centers and promotes their LWNIR emission with a large Stokes shift. A LWNIR pc-LED device was assembled using the optimized MgIn 2 O 4 :Ni 2+ phosphor and a near-ultraviolet LED chip (@ 365 nm), and its potential applications, including NIR night vision imaging, nonvisual detection, and anticounterfeiting displays, were demonstrated. Our results show that the antispinel MgIn 2 O 4 :Ni 2+ phosphor prepared by the sol-gel combustion method is a promising LWNIR luminescence material.