Self‐Assembled Semiconducting Polymer Nanoparticles for Ultrasensitive Near‐Infrared Afterglow Imaging of Metastatic Tumors

Detection of metastatic tumor tissues is crucial for cancer therapy; however, fluorescence agents that allow to do share the disadvantage of low signal‐to‐background ratio due to tissue autofluorescence. The development of amphiphilic poly(p‐phenylenevinylene) derivatives that can self‐assemble into the nanoagent (SPPVN) in biological solutions and emit near‐infrared afterglow luminescence after cessation of light irradiation for ultrasensitive imaging of metastatic tumors in living mice is herein reported. As compared with the counterpart nanoparticle (PPVP) prepared from the hydrophobic PPV derivate, SPPVN has smaller size, higher energy transfer efficiency, and brighter afterglow luminescence. Moreover, due to the higher PEG density of SPPVN relative to PPVP poly(ethylene glycol), SPPVN has a better accumulation in tumor. Such a high sensitivity and ideal biodistribution allow SPPVN to rapidly detect xenograft tumors with the size as small as 1 mm³ and tiny peritoneal metastatic tumors that are almost invisible to naked eye, which is not possible for PPVP. Moreover, the oxygen‐sensitive afterglow makes SPPVN potentially useful for in vivo imaging of oxygen levels. By virtue of enzymatic biodegradability and ideal in vivo clearance, these organic agents can serve as a platform for the construction of advanced afterglow imaging tools.     

Influence of Zn2+ and Si4+ codoping on luminescence properties of CaWO4:Eu3+ phosphor

The red afterglow phosphors of CaWO₄ doped with Eu³⁺, Zn²⁺ or (and) Si⁴⁺ were prepared by solid state reaction. All crystalline phases were identified by the X-ray powder diffraction (XRD). The photoluminescence spectra and decay curves as well as thermoluminecence (TL) curves of all samples were also investigated. In comparison to CaWO₄:Eu³⁺ phosphor, the luminescence and afterglow properties could be improved greatly after being doped with Zn²⁺ or (and) Si⁴⁺ ions.     

Ultralong Phosphorescence of Water‐Soluble Organic Nanoparticles for In Vivo Afterglow Imaging

Afterglow or persistent luminescence eliminates the need for light excitation and thus circumvents the issue of autofluorescence, holding promise for molecular imaging. However, current persistent luminescence agents are rare and limited to inorganic nanoparticles. This study reports the design principle, synthesis, and proof‐of‐concept application of organic semiconducting nanoparticles (OSNs) with ultralong phosphorescence for in vivo afterglow imaging. The design principle leverages the formation of aggregates through a top‐down nanoparticle formulation to greatly stabilize the triplet excited states of a phosphorescent molecule. This prolongs the particle luminesce to the timescale that can be detected by the commercial whole‐animal imaging system after removal of external light source. Such ultralong phosphorescent of OSNs is inert to oxygen and can be repeatedly activated, permitting imaging of lymph nodes in living mice with a high signal‐to‐noise ratio. This study not only introduces the first category of water‐soluble ultralong phosphorescence organic nanoparticles but also reveals a universal design principle to prolong the lifetime of phosphorescent molecules to the level that can be effective for molecular imaging.     

Combustion synthesis and photoluminescence of SrAl2O4:Eu,Dy phosphor nanoparticles

Eu²⁺,Dy³⁺ co-doped strontium aluminate (SrAl₂O₄) phosphor nanoparticles with high brightness and long afterglow were prepared by glycine–nitrate solution combustion synthesis at 500 °C, followed by heating the resultant combustion ash at 1100 °C in a weak reductive atmosphere of active carbon. The average particle size of the SrAl₂O₄:Eu,Dy phosphor nanoparticles ranges from 15 to 45 nm as indicated by transmission electron microscopy (TEM). The broad-band UV-excited luminescence of the SrAl₂O₄:Eu,Dy phosphor nanoparticles was observed at λ_max=513 nm due to transitions from the 4f⁶5d¹ to the 4f⁷ configuration of the Eu²⁺ ion. The results indicated that the main peaks in the emission and excitation spectrum of phosphor nanoparticles shifted to the short wavelength compared with the phosphor obtained by the solid-state reaction synthesis method. The decay speed of the afterglow for phosphor nanoparticles was faster than that obtained by the solid-state reaction method.     

Nanoagents Based on Poly(ethylene glycol)‐b‐Poly(l‐thyroxine) Block Copolypeptide for Enhanced Dual‐Modality Imaging and Targeted Tumor Radiotherapy

Future healthcare requires development of novel theranostic agents that are capable of not only enhancing diagnosis and monitoring therapeutic responses but also augmenting therapeutic outcomes. Here, a versatile and stable nanoagent is reported based on poly(ethylene glycol)‐b‐poly(l ‐thyroxine) (PEG‐PThy) block copolypeptide for enhanced single photon emission computed tomography/computed tomography (SPECT/CT) dual‐modality imaging and targeted tumor radiotherapy in vivo. PEG‐PThy acquired by polymerization of l ‐thyroxine‐N‐carboxyanhydride (Thy‐NCA) displays a controlled M_n, high iodine content of ≈49.2 wt%, and can spontaneously form 65 nm‐sized nanoparticles (PThyN). In contrast to clinically used contrast agents like iohexol and iodixanol, PThyN reveals iso‐osmolality, low viscosity, and long circulation time. While PThyN exhibits comparable in vitro CT attenuation efficacy to iohexol, it greatly enhances in vivo CT imaging of vascular systems and soft tissues. PThyN allows for surface decoration with the cRGD peptide achieving enhanced CT imaging of subcutaneous B16F10 melanoma and orthotopic A549 lung tumor. Taking advantages of a facile iodine exchange reaction, ¹²⁵I‐labeled PThyN enables SPECT/CT imaging of tumors and monitoring of PThyN biodistribution in vivo. Besides, ¹³¹I‐labeled and cRGD‐functionalized PThyN displays remarkable growth inhibition of the B16F10 tumor in mice (tumor inhibition rate > 89%). These poly(l ‐thyroxine) nanoparticles provide a unique and versatile theranostic platform for varying diseases.     

Molecular Imaging Using Nanoparticle Quenchers of Cerenkov Luminescence

Cerenkov luminescence (CL) imaging is an emerging technique that collects the visible photons produced by radioisotopes. Here, molecular imaging strategies are investigated that switch the CL signal off. The noninvasive molecularly specific detection of cancer is demonstrated utilizing a combination of clinically approved agents, and their analogues. CL is modulated in vitro in a dose dependent manner using approved small molecules (Lymphazurin), as well as the clinically approved Feraheme and other preclinical superparamagnetic iron oxide nanoparticles (SPIO). To evaluate the quenching of CL in vivo, two strategies are pursued. [¹⁸F]‐FDG is imaged by PET and CL in tumors prior to and following accumulation of nanoparticles. Initially, non‐targeted particles are administered to mice bearing tumors in order to attenuate CL. For targeted imaging, a dual tumor model (expressing the human somatostatin receptor subtype‐2 (hSSTr2) and a control negative cell line) is used. Targeting hSSTr2 with octreotate‐conjugated SPIO, quenched CL enabling non‐invasive distinction between tumors' molecular expression profiles is demonstrated. In this work, the quenching of Cerenkov emissions is demonstrated in several proof of principle models using a combination of approved agents and nanoparticle platforms to provide disease relevant information including tumor vascularity and specific antigen expression.     

Glutathione Mediated Size‐Tunable UCNPs‐Pt(IV)‐ZnFe2O4 Nanocomposite for Multiple Bioimaging Guided Synergetic Therapy

Here a multifunctional nanoplatform (upconversion nanoparticles (UCNPs)‐platinum(IV) (Pt(IV))?ZnFe₂O₄, denoted as UCPZ) is designed for collaborative cancer treatment, including photodynamic therapy (PDT), chemotherapy, and Fenton reaction. In the system, the UCNPs triggered by near‐infrared light can convert low energy photons to high energy ones, which act as the UV–vis source to simultaneously mediate the PDT effect and Fenton's reaction of ZnFe₂O₄ nanoparticles. Meanwhile, the Pt(IV) prodrugs can be reduced to high virulent Pt(II) by glutathione in the cancer cells, which can bond to DNA and inhibit the copy of DNA. The synergistic therapeutic effect is verified in vitro and in vivo results. The cleavage of Pt(IV) from UCNPs during the reduction process can shift the larger UCPZ nanoparticles (NPs) to the smaller ones, which promotes the enhanced permeability and retention (EPR) and deep tumor penetration. In addition, due to the inherent upconversion luminescence (UCL) and the doped Yb³⁺ and Fe³⁺ in UCPZ, this system can serve as a multimodality bioimaging contrast agent, covering UCL, X‐ray computed tomography, magnetic resonance imaging, and photoacoustic. A smart all‐in‐one imaging‐guided diagnosis and treatment system is realized, which should have a potential value in the treatment of tumor.     

Emitting/Sensitizing Ions Spatially Separated Lanthanide Nanocrystals for Visualizing Tumors Simultaneously through Up‐ and Down‐Conversion Near‐Infrared II Luminescence In Vivo

Near‐infrared lights have received increasing attention regarding imaging applications owing to their large tissue penetration depth, high spatial resolution, and outstanding signal‐to‐noise ratio, particularly those falling in the second near‐infrared window (NIR II) of biological tissues. Rare earth nanoparticles containing Er³⁺ ions are promising candidates to show up‐conversion luminescence in the first near‐infrared window (NIR I) and down‐conversion luminescence in NIR II as well. However, synthesizing particles with small size and high NIR II luminescence quantum yield (QY) remains challenging. Er³⁺ ions are herein innovatively combined with Yb³⁺ ions in a NaErF₄@NaYbF₄ core/shell manner instead of being codoped into NaLnF₄ matrices, to maximize the concentration of Er³⁺ in the emitting core. After further surface coating, NaErF₄@NaYbF₄@NaYF₄ core/shell/shell particles are obtained. Spectroscopy studies are carried out to show the synergistic impacts of the intermediate NaYbF₄ layer and the outer NaYF₄ shell. Finally, NaErF₄@NaYbF₄@NaYF₄ nanoparticles of 30 nm with NIR II luminescence QY up to 18.7% at room temperature are obtained. After covalently attaching folic acid on the particle surface, tumor‐specific nanoprobes are obtained for simultaneously visualizing both subcutaneous and intraperitoneal tumor xenografts in vivo. The ultrahigh QY of down‐conversion emission also allows for visualization of the biodistribution of folate receptors.     

Albumin‐Templated Manganese Dioxide Nanoparticles for Enhanced Radioisotope Therapy

Although nanoparticle‐based drug delivery systems have been widely explored for tumor‐targeted delivery of radioisotope therapy (RIT), the hypoxia zones of tumors on one hand can hardly be reached by nanoparticles with relatively large sizes due to their limited intratumoral diffusion ability, on the other hand often exhibit hypoxia‐associated resistance to radiation‐induced cell damage. To improve RIT treatment of solid tumors, herein, radionuclide ¹³¹I labeled human serum albumin (HSA)‐bound manganese dioxide nanoparticles (¹³¹I‐HSA‐MnO₂) are developed as a novel RIT nanomedicine platform that is responsive to the tumor microenvironment (TME). Such ¹³¹I‐HSA‐MnO₂ nanoparticles with suitable sizes during blood circulation show rather efficient tumor passive uptake owing to the enhanced permeability and retention effect, as well as little retention in other normal organs to minimize radiotoxicity. The acidic TME can trigger gradual degradation of MnO₂ and thus decomposition of ¹³¹I‐HSA‐MnO₂ nanoparticles into individual ¹³¹I‐HSA with sub‐10 nm sizes and greatly improves intratumoral diffusion. Furthermore, oxygen produced by MnO₂‐triggered decomposition of tumor endogenous H₂O₂ would be helpful to relieve hypoxia‐associated RIT resistant for those tumors. As the results, the ¹³¹I‐HSA‐MnO₂ nanoparticles appear to be a highly effective RIT agent showing great efficacy in tumor treatment upon systemic administration.     

ZnO Film UV Photodetector with Enhanced Performance: Heterojunction with CdMoO4 Microplates and the Hot Electron Injection Effect of Au Nanoparticles

A novel CdMoO₄–ZnO composite film is prepared by spin‐coating CdMoO₄ microplates on ZnO film and is constructed as a heterojunction photodetector (PD). With an optimized loading amount of CdMoO₄ microplates, this composite film PD achieves a ≈18‐fold higher responsivity than pure ZnO film PD at 5 V bias under 350 nm (0.15 mW cm⁻²) UV light illumination, and its decay time shortens to half of the original value. Furthermore, Au nanoparticles are then deposited to modify the CdMoO₄–ZnO composite film, and the as‐constructed photodetector with an optimized deposition time of Au nanoparticles yields an approximately two‐fold higher photocurrent under the same condition, and the decay time reduces by half. The introduced CdMoO₄ microplates form type‐II heterojunctions with ZnO film and improve the photoelectric performance. The hot electrons from Au nanoparticles are injected into the CdMoO₄–ZnO composite film, leading to the increased photocurrent. When the light is off, the Schottky barriers formed between Au nanoparticles and CdMoO₄–ZnO composite film block the carrier transportation and accelerate the decay process of current. The study on Au‐nanoparticle‐modified CdMoO₄–ZnO composite film provides a facile method to construct ZnO film based PD with novel structure and high photoelectric performance.     

Experiments on high excitation density, quenching, and radiative kinetics in CsI:Tl scintillator

Information on quenching as a function of electron-hole density through the range of 10¹⁹ to 2×10²⁰ e-h/cm³ typically deposited towards the end of an electron track has been acquired using 0.5 ps pulses of 5.9 eV light to excite in the band-to-band or high-exciton region of CsI and CsI:Tl. A streak camera records partially quenched luminescence from self-trapped excitons (STE) and excited activators (Tl^+?). Both the Tl^+? and STE luminescence exhibit decreasing light yield versus excitation density N_max, but it is only the 302 nm STE luminescence that exhibits decay time quenching dependent on N_max. Fitting the STE decay time data to a model of dipole-dipole quenching yields the time-dependent bimolecular rate constant for quenching of STEs (and Tl^+? light yield) in CsI at room temperature: k₂(t)=2.4×10⁻¹⁵ cm³ s^−1/2 (t^−1/2).     

An Organic Afterglow Protheranostic Nanoassembly

Cancer theranostics holds potential promise for precision medicine; however, most existing theranostic nanoagents are simply developed by doping both therapeutic agents and imaging agent into one particle entity, and thus have an “always‐on” pharmaceutical effect and imaging signals regardless of their in vivo location. Herein, the development of an organic afterglow protheranostic nanoassembly (APtN) that specifically activates both the pharmaceutical effect and diagnostic signals in response to a tumor‐associated chemical mediator (hydrogen peroxide, H₂O₂) is reported. APtN comprises an amphiphilic macromolecule and a near‐infrared (NIR) dye acting as the H₂O₂‐responsive afterglow prodrug and the afterglow initiator, respectively. Such a molecular architecture allows APtN to passively target tumors in living mice, specifically release the anticancer drug in the tumor, and spontaneously generate the uncaged afterglow substrate. Upon NIR light preirradiation, the afterglow initiator generates singlet oxygen to react and subsequently transform the uncaged afterglow substrate into an active self‐luminescent form. Thus, the intensity of generated afterglow luminescence is correlated with the drug release status, permitting real‐time in vivo monitoring of prodrug activation. This study proposes a background‐free design strategy toward activatable cancer theranostics.     

Recent Progress in Time‐Resolved Biosensing and Bioimaging Based on Lanthanide‐Doped Nanoparticles

Luminescent nanomaterials have attracted great attention in luminescence‐based bioanalysis due to their abundant optical and tunable surface physicochemical properties. However, luminescent nanomaterials often suffer from serious autofluorescence and light scattering interference when applied to complex biological samples. Time‐resolved luminescence methodology can efficiently eliminate autofluorescence and light scattering interference by collecting the luminescence signal of a long‐lived probe after the background signals decays completely. Lanthanides have a unique [Xe]4f^N electronic configuration and ladder‐like energy states, which endow lanthanide‐doped nanoparticles with many desirable optical properties, such as long luminescence lifetimes, large Stokes/anti‐Stokes shifts, and sharp emission bands. Due to their long luminescence lifetimes, lanthanide‐doped nanoparticles are widely used for high‐sensitive biosensing and high‐contrast bioimaging via time‐resolved luminescence methodology. In this review, recent progress in the development of lanthanide‐doped nanoparticles and their application in time‐resolved biosensing and bioimaging are summarized. At the end of this review, the current challenges and perspectives of lanthanide‐doped nanoparticles for time‐resolved bioapplications are discussed.     

915 nm Light‐Triggered Photodynamic Therapy and MR/CT Dual‐Modal Imaging of Tumor Based on the Nonstoichiometric Na0.52YbF3.52:Er Upconversion Nanoprobes

Lanthanide (Ln³⁺)‐doped upconversion nanoparticles (UCNPs) as a new generation of multimodal bioprobes have attracted great interest for theranostic purpose. Herein, red emitting nonstoichiometric Na_0.52YbF_3.52:Er UCNPs of high luminescence intensity and color purity are synthesized via a facile solvothermal method. The red UC emission from the present nanophosphors is three times more intense than the well‐known green emission from the ≈30 nm sized hexagonal‐phase NaYF₄:Yb,Er UCNPs. By utilizing Na_0.52YbF_3.52:Er@SrF₂ UCNPs as multifunctional nanoplatforms, highly efficient in vitro and in vivo 915 nm light‐triggered photodynamic therapies are realized for the first time, with dramatically diminished overheating yet similar therapeutic effects in comparison to those triggered by 980 nm light. Moreover, by virtue of the high transverse relaxivity (r ₂) and the strong X‐ray attenuation ability of Yb³⁺ ions, these UCNPs also demonstrate good performances as contrast agents for high contrast magnetic resonance and X‐ray computed tomography dual‐modal imaging. Our research shows the great potential of the red emitting Na_0.52YbF_3.52:Er UCNPs for multimodal imaging‐guided photodynamic therapy of tumors.     

Integrating Fluorinated Polymer and Manganese‐Layered Double Hydroxide Nanoparticles as pH‐activated 19F MRI Agents for Specific and Sensitive Detection of Breast Cancer

¹⁹F magnetic resonance imaging (¹⁹F MRI) agents capable of being activated upon interactions with cancer triggers are attracting increasing attention, although challenges still remain for precise and specific detection of cancer tissues. In this study, a novel hybrid ¹⁹F MRI agent for pH‐sensitive detection of breast cancer tissues is reported, a composite system designed by conjugating a perfluoropolyether onto the surface of manganese‐incorporated layered double hydroxide (Mn‐LDH@PFPE) nanoparticles. The ¹⁹F NMR/MRI signals from aqueous solutions of Mn‐LDH@PFPE nanoparticles are quenched at pH 7.4, but “turned on” following a reduction in pH to below 6.5. This is due to partial dissolution of Mn²⁺ from the Mn‐LDH nanoparticles and subsequent reduction in the effect of paramagnetic relaxation. Significantly, in vivo experiments reveal that an intense ¹⁹F MR signal can be detected only in the breast tumor tissue after intravenous injection of Mn‐LDH@PFPE nanoparticles due to such a specific activation. Thus pH‐activated Mn‐LDH@PFPE nanoparticles are a potential “smart” ¹⁹F MRI agent for precise and specific detection of cancer diseases.     

Synthesis and laser-excited IR luminescence of Y<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Yb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>PO<Subscript>4</Subscript> solid solutions

We have determined the composition range of solid solutions in the binary system YPO₄-YbPO₄ and identified the key trends in the composition dependence of their IR Stokes luminescence intensity and decay time in the range 0.96–1.1 μm. The results were used to develop a new narrow-band IR phosphor, YPO₄:Yb³⁺. Under 0.940-μm laser excitation, this phosphor offers an increased IR Stokes luminescence intensity in the range 0.96–1.1 μm (about twice as high as that of the well-known commercially available phosphors L-54 and FSD-546-2), with an afterglow time of 1700–1800 μs.     

Nanoparticle‐Enhanced Radiotherapy to Trigger Robust Cancer Immunotherapy

External radiotherapy is extensively used in clinic to destruct tumors by locally applied ionizing‐radiation beams. However, the efficacy of radiotherapy is usually limited by tumor hypoxia‐associated radiation resistance. Moreover, as a local treatment technique, radiotherapy can hardly control tumor metastases, the major cause of cancer death. Herein, core–shell nanoparticles based poly(lactic‐co‐glycolic) acid (PLGA) are fabricate, by encapsulating water‐soluble catalase (Cat), an enzyme that can decompose H₂O₂ to generate O₂, inside the inner core, and loading hydrophobic imiquimod (R837), a Toll‐like‐receptor‐7 agonist, within the PLGA shell. The formed PLGA‐R837@Cat nanoparticles can greatly enhance radiotherapy efficacy by relieving the tumor hypoxia and modulating the immune‐suppressive tumor microenvironment. The tumor‐associated antigens generated postradiotherapy‐induced immunogenic cell death in the presence of such R837‐loaded adjuvant nanoparticles will induce strong antitumor immune responses, which together with cytotoxic T‐lymphocyte associated protein 4 (CTLA‐4) checkpoint blockade will be able to effectively inhibit tumor metastases by a strong abscopal effect. Moreover, a long term immunological memory effect to protect mice from tumor rechallenging is observed post such treatment. This work thus presents a unique nanomedicine approach as a next‐generation radiotherapy strategy to enable synergistic whole‐body therapeutic responses after local treatment, greatly promising for clinical translation.     

Luminescence enhancement of CaZnGe2O6:Tb afterglow phosphors synthesized using ZnO nanopowders

CaZnGe₂O₆:Tb³⁺ afterglow phosphors were prepared by solid state reaction using organic coated ZnO nanopowders and their photoluminescence, X-ray luminescence and afterglow properties were investigated. The CaZnGe₂O₆:Tb³⁺ samples emit a green luminescence at 548 nm attributed to the ⁵D₄-⁷F₅ transition of Tb³⁺. It was observed that the replacement of bulk ZnO by ZnO nanopowder in the sample synthesis increases the luminescence intensity. By adjusting the mass ratio of bulk ZnO to nanopowder ZnO, the photoluminescence intensity, X-ray luminescence intensity, and afterglow efficiency are improved. The optimized sample made with a 0.71 ratio of nano ZnO to bulk ZnO has a factor of four enhancement in X-ray luminescence, photoluminescence and afterglow intensities in comparison with the sample made with 100% bulk ZnO.     

Fluorescent Magnetic Fe3O4/Rare Earth Colloidal Nanoparticles for Dual‐Modality Imaging

Fluorescent magnetic colloidal nanoparticles (FMCNPs) are produced by a two‐step, seed emulsifier‐free emulsion polymerization in the presence of oleic acid and sodium undecylenate‐modified Fe₃O₄ nanoparticles (NPs). The Fe₃O₄/poly(St‐co‐GMA) nanoparticles are first synthesized as the seed and Eu(AA)₃Phen is copolymerized with the remaining St and GMA to form the fluorescent polymer shell in the second step. The uniform core–shell structured FMCNPs with a mean diameter of 120 nm exhibit superparamagnetism with saturation magnetization of 1.92 emu/g. Red luminescence from the FMCNPs is confirmed by the salient fluorescence emission peaks of europium ions at 594 and 619 nm as well as 2‐photon confocal scanning laser microscopy. The in vitro cytotoxicity test conducted using the MTT assay shows good cytocompatibility and the T₂ relaxivity of the FMCNPs is 353.86 mM^?1S^?1 suggesting its potential in magnetic resonance imaging (MRI). In vivo MRI studies based on a rat model show significantly enhanced T₂‐weighted images of the liver after administration and prussian blue staining of the liver tissue slice reveals accumulation of FMCNPs in the organ. The cytocompatibility, superparamagnetism, and excellent fluorescent properties of FMCNPs make them suitable for biological imaging probes in MRI and optical imaging.     

Cr<Superscript>3+</Superscript> activated Zn<Subscript>3</Subscript>Al<Subscript>2</Subscript>Ge<Subscript>3</Subscript>O<Subscript>12</Subscript>: a novel near-infrared long persistent phosphor

The near-infrared (NIR) long persistent phosphors have gained considerable attention owing to the potential applications in in vivo imaging. A novel NIR long-persistent phosphors Zn₃Al₂Ge₃O₁₂:Cr³⁺ was successfully synthesized by a high temperature solid-state reaction. The luminescent properties and the afterglow behaviors of the Zn₃Al₂Ge₃O₁₂:Cr³⁺ were investigated in detail. On the basis of thermoluminescence analyses, the mechanism of the persistent afterglow of the phosphors was also discussed briefly. The afterglow duration of this phosphor can last more than 12 h with the 650–750 nm emission range after stoppage of 254 nm ultraviolet light irradiation. Specifically, the persistent luminescence intensity and duration were regulated by changing Cr³⁺ doping concentration. All the results indicate that the Cr³⁺ activated Zn₃Al₂Ge₃O₁₂ has promising potential of practical applications.