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X‐ray absorption near‐edge spectroscopy (XANES), and time‐resolved emission spectra (TRES) that three Ge4+ sites can be superseded simultaneously when Cr3+ ions are doped.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.

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+.

A series of cyan emission (Ba, Li) (Si, Ge, P)2O5:Eu2+, Pr3+ long persistent phosphors (LPP) were designed by solid solution strategy and synthesized by solid-state reaction; the crystal structure and photoluminescence of this long persistent phosphor have been analyzed systematically. Under 256 nm light excitation, the as-prepared (Ba, Li) (Si, Ge, P)2O5:Eu2+, Pr3+ presents a strong cyan emission located at 514 nm, and the decay time of samples can be extended to about 38 h (BaSi2O5:0.008Eu2+, 0.01Pr3+), 47 h (BaSi1.5Ge0.5O5:0.008Eu2+, 0.01Pr3+), and 56 h (Ba0.92Li0.08 Si1.92 P0.08O5:0.008Eu2+, 0.01Pr3+) after ceasing the excitation source. A number of excitation duration (1 s ≤ t ≤ 30 s)-, decay duration (10 min ≤ t ≤ 10 h)-, and temperature-dependent thermoluminescence experiments of (Ba, Li) (Si, Ge, P)2O5:0.008Eu2+, 0.01Pr3+ were conducted, revealing that the existence of shallow and deep traps caused by Eu2+ and Pr3+ ions in samples gives rise to the excellent LPP property. According to the experimental results, a feasible mechanism of persistent luminescence of (Ba, Li) (Si, Ge, P)2O5:0.008Eu2+, 0.01Pr3+ was proposed and illustrated in detail.

The appropriate electronic traps and energy gaps between the bottom of the conduction band (CB) and the excited state of the luminescence center are crucial factors for excellent persistent luminescence (PersL) performance. In this article, the possibilities of regulating electronic traps and the energy gap mentioned above are investigated via partial substitution of the host lattice cation Zr4+ by Hf4+. A comprehensive study on the structural transformation, luminescent properties, and PersL decay curves was carried out to unearth the influence of partially substituting Zr4+ ions by Hf4+ ions. The broader band gap was revealed by diffuse reflectance spectra and density functional theory calculations, which ascribed to the relatively higher energy levels of the Hf 5d state compared with those of the Zr 4d state, whereas the thermoluminescence spectra showed a successive red shift because of the broader band gap and the deeper trap depth from the bottom of the CB to the trap energy levels. Guided by regulating the composition of matrix elements through partially substituting Zr4+ ions by Hf4+ ions, the band gap is modified from 5.12 to 5.46 eV and the trap depth varies from 0.66 to 0.75 eV, and the PersL decay time is extended from 25 to 31 h above the recognizable intensity level (≥0.32 mcd/m2).