Near-infrared (NIR) light has wide applications in various fields such as non-destructive testing, food analysis, plant growth lighting, and night vision. However, developing integrated and portable high-performance NIR light sources remains a significant challenge. Currently, most research focuses on Cr³⁺-doped phosphors as the preferred choice for broadband NIR emission. These materials are sensitive to crystal field strength and coordination environment, allowing for a broad emission range of 650-1200 nm in a weak octahedral crystal field. However, Cr³⁺ may be oxidized to Cr⁴⁺, Cr⁵⁺, or Cr⁶⁺ during phosphor preparation, leading to unavoidable non-radiative energy loss through inter-ion energy transfer and ultimately reducing luminous efficiency. Furthermore, the toxicity of Cr³⁺ limits its application in the biomedical field. Therefore, there is an urgent need to explore new ions for NIR phosphors to achieve high emission performance.
Methods
Prof. Jia-Song Zhong's team from Hangzhou Dianzi University proposes a vacancy repair engineering strategy to enhance NIR emission by F⁻ substitution in MgGa₂O₄:Fe³⁺ (MGO:Fe³⁺). F⁻ substitution can effectively repair the intrinsic O vacancy defects of MGO, thereby suppressing the detrimental electron capture effect. Meanwhile, the introduction of F⁻ leads to MGO lattice distortion, breaking the forbidden transition of Fe³⁺. A series of MGO:0.002Fe³⁺ phosphors with different F⁻ doping ratios were synthesized via a high-temperature solid-state method. The samples were characterized and analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) spectroscopy, diffuse reflectance spectroscopy, photoluminescence excitation (PLE) spectroscopy, and density functional theory (DFT) calculations.
Highlights
Compared with the original MGO:Fe³⁺, the NIR emission intensity of F⁻ repaired MGO:Fe³⁺ (MGOF:Fe³⁺) is increased by 16 times.
MGOF:Fe³⁺ still maintains 91.17% and 85.10% of the luminescence intensity at 363 K and 423 K, respectively, exhibiting excellent thermal stability. The NIR emission of MGOF:Fe³⁺ can be used for night vision, non-destructive biological tissue detection, and food analysis.
This work not only demonstrates a new type of NIR phosphor with high emission performance but also provides a new perspective for Fe³⁺-doped phosphors in multifunctional applications. The proposed vacancy repair strategy for enhancing NIR emission can inspire new ideas and concepts for fabricating high-performance phosphors for broader applications.
Fig. 1. a) Fitted PersL peak of MGO sample. b) PersL decay curves of MGO and MGOF samples. c) Electron paramagnetic resonance spectra of MGO and MGOF samples. d) High-resolution XPS spectra and e) the corresponding fitting peaks of the O1s for the MGO: Fe³⁺ and MGOF: Fe³⁺ samples. f,g) Contour plot of thermoluminescence spectra for MGO: Fe³⁺ and MGOF: Fe³⁺ samples.
Authors
The first author of this work is Yu-Long Ye, a master student at Hangzhou Dianzi University. Prof. Jia-Song Zhong from Hangzhou Dianzi University is the corresponding author of this paper.
Y. Ye, Y. Ding, H. Yang, Q. Mao, L. Pei, M. Liu, J. Zhong, Boosting Near-Infrared Emission in Spinel-Type Phosphor via Oxygen Vacancy Engineering for Versatile Application, Advanced Functional Materials 34(42) (2024) 2405048. DOI: https://doi.org/10.1002/adfm.202405048
