In this work, a novel near‐infrared (NIR) persistent luminescence (PersL) material Na2CaGe5SiO14 (NCGSO):Cr3+ is designed and prepared. The phase composition and crystal structure are analyzed by X‐ray diffraction (XRD) and Rietveld structural refinement. The band gap of NCGSO is calculated to be 4.245 eV by density functional theory (DFT) and confirmed by diffuse reflection spectroscopy (DRS). It is determined by the photoluminescence (PL) spectra, X‐ray absorption near‐edge spectroscopy (XANES), and time‐resolved emission spectra (TRES) that three Ge4+ sites can be superseded simultaneously when Cr3+ ions are doped. In addition, the PL, photoluminescence excitation (PLE), and PersL performance are analyzed systematically. Under the radiation of 254 nm ultraviolet (UV) lamp, the samples exhibit excellent PL and PersL performance in the range of 600–900 nm, and the optimal afterglow duration lasts for more than 10 h. According to results, a possible mechanism is proposed to explain the PersL phenomenon. In the end, a set of information encrypted digital labels is designed and biological tissue penetration experiments are performed. The results reveal the potential of NCGSO:Cr3+ for information encryption and biological imaging applications.

No abstract

We constructed an empirical energy level scheme of the CaMgGe2O6:Ln2+/Ln3+ phosphors and improved the persistent luminescent properties of the sample, which the persistence duration was three times that of the red commercial phosphor Y2O2S:Eu3+.

Color-tunable long persistent luminescence (LPL) phosphors are more strongly desired for intelligent anti-counterfeiting and information storage compared with single color types.

Near-infrared (NIR) long persistent luminescent (LPL) materials have attracted the interest of many researchers as they have potential applications in many aspects. However, majority of studies on Cr3+ ion-doped LPL materials have focused on Cr3+ in an octahedral site, and the luminescence is limited to the short-wavelength NIR-I region (700–900 nm), which is detrimental to fully explore Cr3+ ion-doped LPL materials with potential applications. In this work, a novel ultra-broadband NIR LPL material, Na2CaGe6O14 (NCGO):x%Cr3+, was successfully designed and synthesized, covering the luminescence range of 600–1200 nm and having the best afterglow duration of more than 10 h. Combining the luminescence lifetime with the low-temperature spectrum, it was concluded that the luminescence of NCGO:Cr3+ consists of the co-emission of Cr3+ in octahedra and tetrahedra. And it was confirmed by electron paramagnetic resonance (EPR) spectrum and X-ray absorption near-edge spectrum (XANES). The application prospects of NCGO:x%Cr3+ in many aspects were investigated in detail. This work could not only give a reference for researchers to study Cr3+ luminescence in multiple coordination but also provide a new strategy for obtaining new ultra-broadband NIR LPL materials.

No abstract

In this work, mixed-valence Eu-doped Ba 2 AlB 4 O 9 Cl (BABOC) was successfully synthesized in an air atmosphere for the first time. The samples were determined to possess a good single phase by Rietveld structure refinement and X-ray powder diffraction (XRD). The luminescence spectra of the samples showed that the characteristic emission and excitation peaks of Eu 2+ and Eu 3+ were both present in the sample, and their emitting color could be adjusted by changing the Eu doping concentration. The band gap of BABOC, calculated by density functional theory (DFT), was found to be 4.70 eV and was confirmed by diffuse reflection spectroscopy (DRS). The relationship between the selfreduction efficiency of the sample and the doping concentration of Eu ions was studied by measuring the decay lifetimes of Eu 2+ and Eu 3+ . The thermal quenching and thermoluminescence spectroscopy of the samples were also studied in detail. All of the results indicated that BABOC:Eu has special self-reduction properties, and the abnormal self-reduction phenomenon was explained by a charge compensation model. Our investigation of BABOC:Eu provides practical evidence and a theoretical basis for the self-reduction phenomenon and a new method to further modify the luminescence properties of phosphors.

In this study, we identified a novel yellow long persistent luminescent phosphor of Pr3+, Li+-doped CaGa2O4 (CGO) in terms of its crystal structure, photoluminescence (PL), long persistent luminescence (LPL), thermoluminescence...