Imaging and therapeutic applications of persistent luminescence nanomaterials

The development of probes for biomolecular imaging and diagnostics is a very active research area. Among the different imaging modalities, optics emerged since it is a noninvasive and cheap imaging technique allowing real time imaging. In vitro, this technique is very useful however in vivo, fluorescence suffers from low signal-to-noise ratio due to tissue autofluorescence under constant excitation. To address this limitation, novel types of optical nanoprobes are actually being developed and among them, persistent luminescence nanoparticles (PLNPs), with long lasting near-infrared (NIR) luminescence capability, allows doing optical imaging without constant excitation and so without autofluorescence. This review will begin by introducing the physical phenomenon associated to the long luminescence decay of such nanoprobes, from minutes to hours after ceasing the excitation. Then we will show how this property can be used to develop in vivo imaging probes and also more recently nanotheranostic agents. Finally, preliminary data on their biocompatibility will be mentioned and we will conclude by envisioning on the future applications and improvements of such nanomaterials.

Erythrocyte membrane bioinspired near-infrared persistent luminescence nanocarriers for in vivo long-circulating bioimaging and drug delivery

Combination of biological entities with functional nanostructure would produce the excellent systemic drug-delivery vehicles that possess the ability to cross the biological barriers. Herein, from a biomimetic point of view, erythrocyte membrane bioinspired optical nanocarrier is fabricated by integrating Red blood cell (RBC) membrane vesicle with near-infrared persistent luminescence nanophosphors (PLNPs). The triple-doped zinc gallogermanate nanostructures with super-long near-infrared persistent luminescence (ZGGO) are used as optical emission center, mesoporous silica coated on the PLNPs (ZGGO@mSiO₂) is employed for drug delivery, and the RBC membrane vesicle is introduced for biomimetic functionalization to ensure the developed nanocarriers bypass macrophage uptake and systemic clearance. Owing to the coating of natural erythrocyte membrane along with membrane lipids and associated membrane proteins, the proposed bioinspired nanocarriers have exhibited cell-mimicking property. Retaining the applicability of PLNPs core that favored in vitro excitation, the developed RBC-ZGGO@mSiO₂ biomimetic nanocarriers have demonstrated intense fluorescence, super-long persistent luminescence, monodispersed nanosize, red light renewability, and excellent biocompatibility. In vivo mice bioimaging and biodistribution study demonstrate the erythrocyte membrane bioinspired nanoprobe loaded with doxorubicin as ideal nanocarriers for long-circulating bioimaging, in situ real-time monitoring and drug delivery. We believe the PLNPs-based biomimetic nanocarriers offer a promising nano-platform for diagnostics and therapeutics application.

Near-infrared rechargeable "optical battery" implant for irradiation-free photodynamic therapy

As a minimal or noninvasive therapeutic method for tumors, photodynamic therapy (PDT) induced by the external laser irradiations has attracted great attentions. However, the UV-visible responsive property with low tissue penetration and photothermal effect from the prolonged irradiation impedes their further applications. Herein, a near-infrared (NIR) rechargeable "optical battery" for irradiation-free PDT is fabricated by embedding upconversion materials, persistent luminescence materials, photosensitizer into biocompatible polydimethylsiloxane. After 5 s quickly charged by 980-nm NIR laser, the PDT "optical battery" can generate green persistent luminescence and produce cytotoxic singlet oxygen for continuous irradiation-free PDT (∼30 min) without external irradiation. Due to deep tissue penetration and discontinuous short exposure of NIR light charging source, the "optical battery" can still be charged to continuously generate singlet oxygen in deep tissue (∼4 mm) with low photothermal effect. The PDT implant can be easily optimized in size and shape aiming at different nidus sites and achieved different functions by adding other functional components (e.g. CaO₂ for oxygen envolving to overcome hypoxia tumor). The effective tumor proliferation inhibiting capability of this NIR rechargeable "optical battery" may give rise to next generation of intelligent stimuli-responsive nanomedicine and noninvasive photo bio-stimulation research for future clinical applications.

Dendrimer grafted persistent luminescent nanoplatform for aptamer guided tumor imaging and acid-responsive drug delivery

Theranostic nano-drug delivery systems are promising candidates for early diagnosis and treatment of tumors. However, it is a great challenge to achieve accurate intracellular delivery and stimuli-responsive drug release with the enhanced anti-tumor effects and reduced side effects. Herein we report the fabrication of polyamide-amine (PAMAM) dendrimer grafted persistent luminescence nanoparticles (PLNPs) via in situ growth of PAMAM on the surface of PLNPs and its application in targeted bioimaging and drug delivery. The developed PLNPs-PAMAM possesses strong renewable near-infrared persistent luminescence for imaging and gives abundant terminal groups for further functionalization. Aptamer AS1411 coupled to the PLNPs-PAMAM surface can specifically bind to the over-expressed nucleolin on the membrane of tumor cells and improve the intracellular accumulation of the nanoparticles. Doxorubicin (DOX) is loaded on PLNPs-PAMAM by a pH-sensitive hydrazine, can be specifically released in the intracellular acid environment, leading to apoptosis of HeLa tumor cells and inhibition of tumor growth. The as-prepared smart drug delivery nanoplatform with persistent luminescence, PLNPs-PAMAM-AS1411/DOX, shows a good application prospect for precise cancer theranostics.

Turning solid into gel for high-efficient persistent luminescence-sensitized photodynamic therapy

Bioavailable persistent luminescence material is an ideal internal light source for long-term photodynamic therapy, but inevitably suffers from low utilization efficiency and weak persistent luminescence due to corrosion and screening processes. Herein, we show a facile and smart "turning solid into gel" strategy to fabricate persistent luminescence hydrogel for high-efficient persistent luminescence-sensitized photodynamic therapy. The homogeneous persistent luminescence hydrogel was synthesized via dispersing high-temperature calcined persistent luminescence material without corrosion and screening into a biocompatible alginate-Ca²⁺ hydrogel. The simple synthesis strategy allows 100% of utilization efficiency and intact persistent luminescence of persistent luminescence material. The persistent luminescence hydrogel possesses favorable biocompatibility, bright persistent luminescence, red light renewability, good syringeability, and strong fixing ability in tumors. The persistent luminescence hydrogel can be easily injected in vivo as a powerful localized light source for superior persistent luminescence-sensitized photodynamic therapy of tumors. The "turning solid into gel" strategy enables taking full advantages of persistent luminescence for biological applications, and shows great potential in utilizing diverse theranostic agents regardless of hydrophilicity and hydrophobicity.

Persistent luminescence phosphor as in-vivo light source for tumoral cyanobacterial photosynthetic oxygenation and photodynamic therapy

Tumor oxygenation level has been regarded as an attractive target to elevate the efficiency of photodynamic therapy (PDT). Cyanobacterial photosynthesis-mediated reversal of tumor hypoxia could enable an oxygen-boosted PDT, but is limited by scant penetration depth and efficiency of external light. Herein, aiming at the dual purposes of reducing biological toxicity induced by long-term light irradiation and alleviating hypoxia, we here introduce a novel-designed CaAl₂O₄:Eu,Nd blue persistent luminescence material (PLM) as the in vivo light source after pre-excited in vitro. The ingenious construction of blue-emitting PLM with “optical battery” characteristics activates cyanobacterial cells and verteporfin simultaneously, which performs the successive oxygen supply and singlet oxygen generation without the long-term external excitation, resulting in the modulated tumor hypoxic microenvironment and enhanced photodynamic tumor proliferation inhibition efficiency. Both in vitro cellular assessment and in vivo tumor evaluation results affirm the advantages of self-produced oxygen PDT system and evidence the notable antineoplastic outcome. This work develops an irradiation-free photosynthetic bacteria-based PDT platform for the optimization of both oxygen production capacity and light utilization efficiency in cancer treatment, which is expected to promote the clinical progress of microbial-based photonic therapy.

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Construction of CaAl₂O₄:Eu,Nd PLM to generate ¹O₂ without the aid of exogenous light excitation.

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Cyanobacteria with light-triggered oxygenation effect were employed for the normalization of tumor microenvironment.

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A distinct exogenous “irradiation-free” cyanobacteria-based PDT platform was rationally engineered.

A persistent luminescence-based label-free probe for the ultrasensitive detection of hemoglobin in human serum

Hemoglobin (Hb) plays an important role in oxygen carriage for mammals, which is also a typical biomarker for certain diseases. Although numerous methods had been developed for the detection of Hb in red blood cells, analytical technology for the monitoring of low-abundance Hb in serum or plasma is still a challenge. Herein, persistent luminescence nanoparticles (PLNPs) with strong near-infrared (NIR) emission character behaving as a label-free probe for the highly sensitive and selective detection of Hb were developed. Further studies revealed that the sensing mechanism should be attributed to the Hb-induced dynamic quenching process. Moreover, the nanoprobe showed high selectivity to Hb against the common existing substances in human serum and a linear response to Hb ranging from 1 to 50 nM with an extremely high limit of detection (LOD) of 0.13 nM. Finally, applicability of the proposed probe for the detection of Hb in human serum samples was validated.

Persistent luminescence nanorod based luminescence resonance energy transfer aptasensor for autofluorescence-free detection of mycotoxin

Serious ochratoxin A (OTA) contamination necessitates the development of rapid, sensitive and selective analytical methods for its determination in food safety. Herein, we report a persistent luminescence resonance energy transfer (LRET) based aptasensor for the autofluorescence-free detection of OTA. OTA aptamer functionalized persistent luminescence nanorod (PLNR) Zn₂GeO₄:Mn²⁺ and the aptamer complementary DNA modified gold nanoparticle (AuNP) were used as the donor and the acceptor, respectively. The developed LRET aptasensor integrated the advantages of the long-lasting persistent luminescence of PLNR, the high selectivity of aptamer and the low probe background of LRET sensors, allowing autofluorescence-free detection of OTA in biological samples with high sensitivity and selectivity. The developed LRET aptasensor gave an excellent linearity in the range of 0.01-10 ng mL^-1, the detection limit of 3 pg mL^-1 and the precision of 2.7% (RSD, n = 11) at 1 ng mL^-1 level. The applicability of the developed aptasensor was demonstrated by analyzing beer samples for OTA with the recoveries of 92.3%-104%.

A novel differential display material: K3LuSi2O7: Tb3+/Bi3+ phosphor with thermal response, time resolution and luminescence color for optical anti-counterfeiting

Optical anti-counterfeiting and encryption have become a hotspot in information security. However, the advanced optical anti-counterfeiting technology still suffers from low security by single-luminescent mode. Herein, we present a novel multi-mode anti-counterfeiting strategy based on K₃LuSi₂O₇: Tb³⁺/Bi³⁺ (KLSO: Tb³⁺/Bi³⁺) phosphors for the first time. KLSO not only provides various lattice sites for Bi³⁺ ions occupying to achieve tunable luminescence but can also be non-equivalently substituted by Tb³⁺ ions to produce persistent or thermo-luminescence. Furthermore, in the pattern "8888" constructed by the mixture of polyacrylic acid (PAA) with KLSO: Tb³⁺/Bi³⁺ phosphors, we selectively trigger the three luminescent modes of Bi³⁺ and Tb³⁺ ions to realize the design of differential display in the fields of thermal response, time resolution, and luminescence color for optical anti-counterfeiting. The differentiated display can only be presented under specific multi-stimuli response, which further improves the security of information. Our work provides a new insight for designing advanced materials and can be expected to inspire future studies to explore optical anti-counterfeiting technology.

Ultrasound-Chargeable Persistent Luminescence Nanoparticles to Generate Self-Propelled Motion and Photothermal/NO Therapy for Synergistic Tumor Treatment

Cancer phototherapy indicates advantages in ease of manipulation, negligible drug resistance, and spatiotemporal control but is confronted with challenges in tumor cell accessibility and intermittent light excitation. Herein, we propose a strategy with persistent luminescence (PL)-excited photothermal therapy (PTT), concurrent thermophoresis-propelled motion, and PL-triggered NO release, where PL emission is chargeable by ultrasonication for readily applicable to deep tumors. Mechanoluminescent (ML) nanodots of SrAl2O4:Eu2+ (SAOE) and PL nanodots of ZnGa2O4:Cr3+ (ZGC) were deposited on mesoporous silicates to obtain mSZ nanoparticles (NPs), followed by partially coating with polydopamine (PDA) caps and loading NO donors to prepare Janus mSZ@PDA-NO NPs. The ML emission bands of SAOE nanodots overlap with the excitation band of ZGC, and the persistent near-infrared (NIR) emission could be repeatedly activated by ultrasonication. The PL emission acts as an internal NIR source to produce a thermophoretic force and NO gas propellers to drive the motion of Janus NPs. Compared with the commonly used intermittent NIR illumination at both 660 and 808 nm, the persistent motion of ultrasound-activated NPs enhances cellular uptake and long-lasting PTT and intracellular NO levels to combat tumor cells without the use of any chemotherapeutic drugs. The ultrasound-activated persistent motion promotes intratumoral accumulation and tumor distribution of PTT/NO therapeutics and exhibits significantly higher tumor growth inhibition, longer animal survival, and larger intratumoral NO levels than those who experience external NIR illumination. Thus, this study demonstrates a strategy to activate PL emissions and construct PL-excited nanomotors for phototherapy in deep tissues.

Up-conversion Persistent Luminescence of a 980 nm Laser Activated Zn3Ga2(GexSn1-x)O8:Yb,Er,Cr Phosphors

Zn₃Ga₂(Ge_xSn_1-x)O₈:Yb,Er,Cr phosphors with different doping ratio of Ge/Sn were prepared by high temperature solid-state method. After excited at 270 nm with a xenon lamp for 15 min, the persistent luminescence (PL) of Zn₃Ga₂(Ge_xSn_1-x)O₈:Yb,Er,Cr phosphor can last more than 60 min. Under the excitation at 980 nm, Zn₃Ga₂(Ge_xSn_1-x)O₈:Yb,Er,Cr phosphors can generate effective up-conversion emissions from Er³⁺ ions at 410 nm, 525 nm, 550 nm, 660 nm and Cr³⁺ ions around 700 nm. Besides, after ceasing irradiation, Zn₃Ga₂(Ge_xSn_1-x)O₈:Yb,Er,Cr phosphors show up-conversion persistent luminescence (UCPL) from Cr³⁺ ions around 700 nm. Moreover, Zn₃Ga_1.995(Ge_0.3Sn_0.7) O₈:Yb³⁺,Er³⁺,Cr³⁺ phosphor is optimal with the best persistent luminescent and up-conversion persistent luminescent properties. In short, owing to the long afterglow time, strong up-conversion emissions and novel up-conversion persistent luminescence, the as-prepared Zn₃Ga₂(Ge_xSn_1-x)O₈:Yb,Er,Cr phosphors can be potentially applied in a wide range of fields, such as security materials, coating materials, infrared detection, fluorescent label, tracer and testing.

Persistent luminescence dosimetry performance of solid state synthesized BaZrO3 phosphors

This work reports for the first time on the thermoluminescence (TL) and persistent luminescence (PLu) characterization of BaZrO₃ synthesized through solid state reaction. X-Ray diffraction confirmed the crystalline structure of the synthesized phosphors. The characteristic glow curves of the synthesized samples exhibit TL maxima located at 85 and 165 °C, whose fading after radiation exposure gives rise to intense PLu. PLu decay curves were recorded after beta particle irradiation in the dose range from 1.0 up to 1024 Gy. Both TL and PLu exhibit remarkable reproducibility. The integrated persistent luminescence (IPLu) as a function of the irradiation dose exhibits a linear dependence in the 1.0-16 Gy dose range, followed by a sublinear behavior from 16 to 128 Gy. From the experimental evidence here presented, it is concluded that solid state synthesized BaZrO₃ is an interesting phosphor material to be implemented as a PLu-based detector and dosimeter.

Biocompatible zinc gallogermanate persistent luminescent nanoparticles for fast tumor drainage lymph node imaging in vivo

Tumor drainage lymph node identification and dissection are crucial for the oncological surgery to prevent/delay the recurrence. However, commercial imaging reagents distinguish the lymph nodes by staining them dark, which would be seriously interfered by blood and surrounding tissues. In this study, we reported the Cr³⁺/Pr³⁺-doped zinc gallogermanate persistent luminescent nanoparticles (PLNPs) for fast tumor drainage lymph node imaging with high contrast. PLNPs were synthesized by citrate sol-gel method and dispersed in Tween 80 for in vivo applications. PLNPs were well dispersed in water with hydrodynamic radii of 5 nm and emitted strong persistent luminescence at 696 nm upon the irradiation of UV light. The advantage of afterglow imaging over fluorescent imaging of PLNPs was first established after subcutaneous injection to mice with much higher contrast and less interference of autofluorescence. PLNPs quickly migrated to sentinel lymph nodes after the interdermal injection to extremity of mice. The tumor drainage lymph node imaging was achieved within 5 min upon the intratumoral injection to H460 tumor bearing mice and the signal to noise ratio was 462. Due to the lack of targeting moieties, the intravenous injected PLNPs mainly accumulated in liver. There were no statistical changes in serum biochemistry and abnormal histopathological characteristic, indicating the low toxicity of PLNPs. These findings highlighted the great potential of PLNPs as high-performance imaging reagent for lymph node identification.

Rechargeable Afterglow Superclusters for NIR-Excitable Repetitive Phototherapy

Afterglow luminescence has attracted increasing attention due to its prolonged emission, reduced autofluorescence, and minimized photodamage. However, persistent luminescence typically requires high-energy excitation (e.g., ultraviolet and visible light), which has limited tissue penetration. Herein, we have developed a one-pot surface segregation strategy to construct NIR-excitable afterglow superclusters (UCZG-SCs) by modularly assembling spinel-phase afterglow nanoparticles (Zn1.1Ga1.8Ge0.1O4:Cr3+) and hexagonal-phase upconversion nanoparticles (NaYF4:Yb,Tm@NaLuF4:Y). Since the proposed methodology does not require crystal lattice similarity, it enables fabrication of various NIR-excitable persistent superclusters with great flexibility in size, composition, and luminescent profiles. As a proof of concept, an injectable persistent implant is established by embedding UCZG-SCs in the oleosol of poly(lactic-co-glycolic acid)/N-methylpyrrolidone, which serves as an inner-body lamp to excite photosensitizers for photodynamic therapy. With its excellent charging-recharging stability, a repetitive phototherapy under periodic 980 nm light illumination is accomplished, which significantly improves phototherapeutic efficiency and restrains tumor growth.

Persistent luminescent nanophosphors for applications in cancer theranostics, biomedical, imaging and security

The extraordinary and unique properties of persistent luminescent (PerLum) nanostructures like storage of charge carriers, extended afterglow, and some other fascinating characteristics like no need for in-situ excitation, and rechargeable luminescence make such materials a primary candidate in the fields of bio-imaging and therapeutics. Apart from this, due to their extraordinary properties they have also found their place in the fields of anti-counterfeiting, latent fingerprinting (LPF), luminescent markings, photocatalysis, solid-state lighting devices, glow-in-dark toys, etc. Over the past few years, persistent luminescent nanoparticles (PLNPs) have been extensively used for targeted drug delivery, bio-imaging guided photodynamic and photo-thermal therapy, biosensing for cancer detection and subsequent treatment, latent fingerprinting, and anti-counterfeiting owing to their enhanced charge storage ability, in-vitro excitation, increased duration of time between excitation and emission, low tissue absorption, high signal-to-noise ratio, etc. In this review, we have focused on most of the key aspects related to PLNPs, including the different mechanisms leading to such phenomena, key fabrication techniques, properties of hosts and different activators, emission, and excitation characteristics, and important properties of trap states. This review article focuses on recent advances in cancer theranostics with the help of PLNPs. Recent advances in using PLNPs for anti-counterfeiting and latent fingerprinting are also discussed in this review.

Energy-storing DNA-based hydrogel remodels tumor microenvironments for laser-free photodynamic immunotherapy

Photodynamic therapy (PDT) is a promising modality for cancer treatment. However, limited tissue penetration of external radiation and complicated tumor microenvironments (TMEs) restrict the antitumor efficiency of PDT. Herein, we report an energy-storing DNA-based hydrogel, which enables tumor-selective PDT without external radiation and regulates TMEs to achieve boosted PDT-mediated tumor immunotherapy. The system is constructed with two ultralong single-stranded DNA chains, which programmed partial complementary sequences and repeated G-quadruplex forming AS1411 aptamer for photosensitizer loading via hydrophobic interactions and π-π stacking. Then, energy-storing persistent luminescent nanoparticles are incorporated to sensitize PDT selectively at tumor site without external irradiation, generating tumor antigen to agitate antitumor immune response. The system catalytically generates O2 to alleviate hypoxia and releases inhibitors to reverse the IDO-related immunosuppression, synergistically remodeling the TMEs. In the mouse model of breast cancer, this hydrogel shows a remarkable tumor suppression rate of 78.3 %. Our study represents a new paradigm of photodynamic immunotherapy against cancer by combining laser-free fashion and TMEs remodeling.

Improving preparation and luminescence properties of Eu and dy doped Sr2MgSi2O7 phosphors by adding excess silica

Solid state reaction method is most commonly used to synthesize Sr2MgSi2O7: Eu2+, Dy3+ phosphors. In order to avoid the energy waste caused by high sintering temperature, we systematically studied and optimized the preparation process of Sr2MgSi2O7: Eu2+, Dy3+ long afterglow phosphors by increasing the Si/Sr ratio in the raw materials. The appropriate addition of silica not only facilitates the preparation of single phase Sr2MgSi2O7: Eu2+, Dy3+ phosphor but also enhances the rate of solid state reaction, so as to achieve the purpose of reducing the sintering temperature. The photoluminescence performance of the sample with a Si/Sr ratio of 1.1 sintered at 1350 °C is the highest, followed by that of the sample sintered at 1400 °C with a Si/Sr ratio of 1.0. Notably, the photoluminescence properties of the Si/Sr ratio of 1.3 sample sintered at 1300 °C are comparable to those of the Si/Sr ratio of 1.0 sample sintered at 1400 °C. However, in terms of afterglow properties, the former exhibits an enhancement by a factor of 3.5 compared to the latter. This finding suggests that strategically increasing the Si/Sr ratio can reduce the sintering temperature by 100 °C while maintaining or even enhancing the luminescence and afterglow properties of the samples. Additionally, the electronic structures of the Sr2MgSi2O7 host, the doped luminescence center Eu, the oxygen vacancies and the co-doped activator Dy have been methodically investigated through first-principles calculations. By integrating the findings on the distribution of the dopants and defects levels, we predict and propose the photoluminescence and afterglow mechanisms of Sr2MgSi2O7: Eu2+, Dy3+. These studies suggest an efficient, cheap and energy-saving strategy for the preparation of Sr2MgSi2O7: Eu2+, Dy3+ long afterglow phosphor, and reveal the roles of oxygen vacancies and co-doped Dy in the afterglow luminescence.

Ultralong luminescence lifetime imaging of edible plant tissue for humidity sensing in food packaging by a smartphone

The safety of luminescence sensors and probes used in food packaging should be seriously considered, while most luminescence sensors were artificially synthesized with unclear toxicity, and cannot be directly used as indicators that were in contact with food. To overcome this problem, a humidity indicator based on an edible plant tissue was developed without any chemical processing. We found that garlic bulbs could emit significant persistent luminescence after drying at room temperature. The luminescence lifetime decreases from hundreds of milliseconds to tens of milliseconds as humidity increases. The long-lived luminescence could easily be detected through smartphones without any sophisticated instruments. The edible garlic is expected to be used as a humidity indicator in food packaging without worrying about food safety. Furthermore, the interference of scattered light and short-lived fluorescence from foods and packages can be eliminated in time-resolved luminescence imaging, greatly increasing the signal-to-noise ratio.

Bimodal persistent luminescence for autofluorescence-free ratiometric biosensing

In optical biosensing, analyte-independent factors such as autofluorescence interference and excitation source fluctuation decrease the sensitivity and accuracy. Herein, we reported a bimodal persistent luminescence strategy to design dual-emissive persistent luminescence nanoparticles (PLNPs) with built-in self-calibration to preclude interference from analyte-independent factors in biosensing. As a proof of concept, ZnGa2O4:Cr PLNPs with emissions at both 490 nm and 695 nm were designed. The I490/I695 ratio of ZnGa2O4:Cr was readily adjusted by simply changing the doping concentration of Cr3+. The ZnGa2O4:Cr PLNPs were employed for the ratiometric detection of urinary mesna. A good linear relationship between the I490/I695 ratio of ZnGa2O4:Cr-based nanoprobe and the concentration of mesna was obtained in the range of 0-40 μM. The limit of detection was about 0.40 μM. Results showed that autofluorescence interference from urine was totally eliminated by collecting the persistent luminescence signal of ZnGa2O4:Cr after excitation ceased. Moreover, the built-in self-calibration feature of the ratiometric ZnGa2O4:Cr PLNPs efficiently suppressed the interference from fluctuations in instrumental parameters during urinary mesna detection. The recovery rates of mesna in the spiked urine samples are in the range of 99.1~109.0%, showing the reliability of the ratiometric ZnGa2O4:Cr PLNPs in urinary mesna detection. ZnGa2O4:Cr can further be expanded to the detection of other analytes in complex matrices. This study may open new opportunities for the design of dual-emissive PLNPs with tunable ratios of emission intensity, and it can further promote the applications of optical biosensing in disease diagnosis, food safety, and environmental monitoring.

Temperature-dependent color-tunable persistent luminescence in Ba0.95Sr0.05Ga2-yGdyO4:Bi3+ phosphor for advanced anti-counterfeiting

As emerging anti-counterfeiting materials, persistent luminescence (PersL) materials have attracted much attention owing to their particular luminescent properties, including durable luminescence, facile identification, high security and environment-friendly. Especially, exploiting color-tunable dynamic afterglow materials that facilitate the use of advanced technology such as multi-mode dynamic anti-counterfeiting remains of great realistic significance. Herein, a series of Ba0.95Sr0.05Ga2-yGdyO4:Bi3+ phosphors with tunable photoluminescence and PersL were synthesized by the cationic substitution strategy. The displacement of Ga3+ by Gd3+ induces an additional blue emission owing to the generation of a new Bi3+ luminescence center. The pure white light is realized in Ba0.942Sr0.05Ga1.9Gd0.1O4:0.8 %Bi3+,0.25 %K+ when excited by 325 nm light. Besides, color-tunable emission is triggered by changing the excitation wavelength or temperature. Significantly, excellent room-temperature PersL and dramatically intensified PersL with tunable color output under thermal stimulation are clearly discernible. Such properties result from the existence of multiple Bi3+ luminescent centers and traps. These findings open up new ideas to produce color-tunable dynamic PersL materials for advanced anti-counterfeiting, information storage and encryption.