Persistent Luminescence Nanoparticles Research Articles

Overcoming surface quenching in persistent luminescence nanoparticles with organic ligand coordination: Implications for enhanced optical imaging

Persistent luminescence nanoparticles (PLNPs) have been considered as excellent luminescent tools for sensitive optical imaging. However, the persistent luminescence (PL) properties of PLNPs are usually suppressed due to severe surface quenching caused by nanoscale size. Despite considerable efforts, the understanding of surface quenching mechanisms remains a challenge. Here we report a surface ligand coordination method to enhance the PL properties of ZnGa2O4:Al,Cr (ZGO:AC) PLNPs. ZGO:AC PLNPs coated with organic ligands containing carboxyl groups show enhanced PL intensity and prolonged decay time. Among the six ligands, the phthalic acid (PA) ligands yielded the largest luminescence enhancement effect, on which the PL intensity and decay time increased 3 and 2 times compared with ligand-free ZGO:AC PLNPs, respectively. Density functional theory (DFT) calculations and detailed characterizations demonstrated that surface quenching is suppressed due to the coordination of non-saturated Ga ions and -COO- of ligands. Finally, ZGO:AC@PA PLNPs were applied in autofluorescence-free bioimaging and exhibited high imaging sensitivity and contrast ratio. These findings provide insights into the surface quenching mechanisms of PLNPs and offer a platform for developing highly emissive PLNPs on nanoscale.

Persistent luminescent nanoparticles with enhanced afterglow through polydopamine modification for separation-free and visual detection of iron ions in water

Fluorescence analysis is one of the most popular methods in metal ions detection, but the background interference is an unavoidable obstacle in the fluorescence analysis of complex samples. In this work, a persistent luminescence nanoprobe was designed to detect iron ions in real samples by avoiding background interference. First, the Sr4Al14O25:Eu2+, Dy3+ persistent luminescent nanoparticles (PLNPs) were prepared by solid-state reaction protocols and polydopamine (PDA) encapsulation. After modification, these PLNPs@PDA showed better afterglow performance. More importantly, the PLNPs@PDA are highly selective toward iron ions, and could serve as an afterglow “turn off” nanoprobe for selective detection of iron ions through a dynamic quenching mechanism, with a detection limit of 2.86 μM. To further realize rapid and on-site detection, a test strip based on PLNPs@PDA was prepared and applied, which also showed good detection performance in real water samples. Compared with other detection methods, this afterglow imaging detection does not depend on expensive instruments, and can effectively shield the interference of background fluorescence from complex water samples, which has a good application prospects in the actual water sample. This work opens a new avenue for developing afterglow probe for the detection of metal ion in water samples without background interference.

Ratiometric temperature sensing with non-thermally coupled levels from Pr–Al co-doped MgGa2O4

Fluorescence intensity ratio (FIR) technique demonstrates significant potential for non-contact temperature sensing with rapid response time, while the design of FIR probes is particularly intriguing. Herein, we report Pr–Al co-doped MgGa2O4 persistent luminescence nanoparticles (PLNPs), as MgAl0.04Ga1.96O4: 0.1 % Pr3+ (MAGP), for ratiometric temperature sensing application. Pr3+ ions function as the emission centers for dual-emission at 612 and 494 nm, while Al3+ ions adjust the lattice environment around Pr3+ ions to enhance the luminescence. Consequently, 274 nm excitation induces the emissions at 494 and 612 nm, as the transitions of Pr3+ for 3P0→3H4 and 1D2→3H4, respectively. The emission mechanism is substantiated by density functional theory calculations, regarding the electronic transitions of Pr3+. Ratiometric temperature sensing is achieved over the temperature range of 303–573 K with the thermally non-coupled mechanism of the 3P0/1D2 energy levels by FIR at 612 and 494 nm, respectively. The maximum relative sensitivity was 0.91 %. The mechanism is corroborated as the non-thermally coupled energy levels through intervalence charge transfer. Thus, the reversible and sensitive response was illustrated for temperature measurement and the non-thermally coupled mechanism is efficient for the design of ratiometric temperature sensors.

Single-Atom Iridium Nanozyme-Based Persistent Luminescence Nanoparticles for Multimodal Imaging-Guided Combination Tumor Therapy.

Persistent luminescence nanoparticles (PLNPs) can achieve autofluorescence-free afterglow imaging, while near-infrared (NIR) emission realizes deep tissue imaging. Nanozymes integrate the merits of nanomaterials and enzyme-mimicking activities with simple preparation. Here PLNPs are prepared of Zn1.2Ga1.6Ge0.2O4:Cr0.0075 with NIR emission at 700 nm. The PLNPs are then incubated with IrCl3 solution, and the nanoparticles are collected and annealed at 750 °C to obtain iridium@PLNPs. Iridium is observed on the PLNPs at the atomic level as a single-atom nanozyme with peroxidase-like catalytic activity, photothermal conversion, and computed tomography (CT) contrast capability. After coating with exosome membrane (EM), the Ir@PLNPs@EM composite exhibits long-lasting NIR luminescence, peroxidase-like catalytic activity, photothermal conversion, and CT contrast capability, with the targeting capability and biocompatibility from EM. Thus, NIR afterglow/photothermal/CT trimodal imaging-guided photothermal-chemodynamic combination therapy is realized as validated with the in vitro and in vivo inhibition of tumor growth, while toxicity and side effects are avoided as drug-free treatment. This work offers a promising avenue for advanced single-atom nanozyme@PLNPs to promote the development of nanozymes and PLNPs for clinical applications.

Heterogenous Core-Shell Persistent Luminescent Nanoparticles with Enhanced Afterglow Luminescence.

Persistent luminescent nanoparticles (PLNPs) are promising for many bioapplications due to their unique afterglow luminescence following the stoppage of light excitation. However, PLNPs are prone to surface quenching that results in weak afterglow luminescence. Although some efforts have been made to reduce surface quenching through designing homogeneous core-shell PLNPs, the enhancement in afterglow luminescence was insignificant. We hypothesize that the independent absorption and emission of the shell caused less energy to reach the activator ions in the core. Hence, a heterogeneous core-shell PLNP where the shell has a higher band gap than the core would reduce the absorption and emission of the shell. In this work, ZnGa2O4 and Zn2GeO4 were coated on Zn1.2Ga1.6Ge0.2O4:Cr and Zn3Ga2Ge2O10:Eu nanocrystals, respectively, to form heterogeneous core-shell PLNPs and significant luminescence enhancement was achieved compared to their traditional homogeneous core-shell nanostructures.

Persistent ultraviolet luminescence and photocatalytic properties of SiO2-Zn2SiO4:Ga,Pb nanoparticles

Persistent phosphors possess unique afterglow optical properties. In this paper, a class of ultra-violet (UV) persistent luminescence nanoparticles were developed for catalytic photodegradation applications. UV persistent luminescence nanoparticles of SiO2-Zn2SiO4:Ga and SiO2-Zn2SiO4:Ga,Pb were successfully synthesized by using a mesoporous template method. The UV persistent luminescence intensity of SiO2-Zn2SiO4:Ga at 405 nm was enhanced up to ca. 3.5 times by co-doping with Pb2+ (396 nm), along with longer persistent luminescence duration. The photodegradation results indicate that it is useful to introduce UV persistent luminescence property into SiO2-Zn2SiO4:Ga,Pb to obtain enhanced catalytic activity of SiO2-Zn2SiO4 with a bigger catalytic oxidation reaction kinetic constant (up to ∼4 times). This kind of UV persistent catalysis strategy may become a potential feasible method for better catalytic photodegradation activity. The UV persistent photocatalyst has potential applications in the photooxidation of organic molecules in high chroma and/or turbidity aqueous systems.

Synthesis of Persistent Luminescent Nanoparticles for Rewritable Displays and Illumination Applications.

Persistent luminescent nanoparticles (PLNPs) possess the capabilities to maintain extended longevity and robust emission even after the excitation has ceased. PLNPs have been widely used across various domains, including information displays, data encryption, biological imaging, and artistic decoration with sustained and vivid luminosity, providing boundless possibilities for a variety of innovative technology and artistic projects. This protocol focuses on an experimental procedure for the hydrothermal synthesis of PLNPs. The successful synthesis of enduring luminescent nanomaterials with Mn2+ or Cr3+ serving as a luminescent center in Zn2GeO4: Mn (ZGO: Mn) or ZnGa2O4: Cr highlights the universality of this synthetic method. On the other hand, the optical properties of ZGO: Mn can be changed by adjusting the pH of precursor solutions, demonstrating the tunability of the protocol. When charged with ultraviolet (UV) at a wavelength of 365 nm for 3 min and then stopped, PLNPs exhibit the remarkable capacity to generate afterglow efficiently and consistently, which makes them ideal for making two-dimensional rewritable displays and three-dimensional transparent, luminous artworks. This protocol outlined in this paper provides a feasible method for the synthesis of persistent luminescent nanoparticles for further illumination and imaging applications, opening up novel prospects for the fields of science and art.

PH-responsive persistent luminescence nanoprobes biosensor for autofluorescence-free determination of glucose level in human samples and fingerprint encryption.

Glucose level is an important indicator of diabetes, and maintaining an appropriate physiological concentration of glucose is important for human health. However, traditional optical sensors are interfered by the interference of strong background autofluorescence and natural responsive luminescence, which severely limits their application in complex biological samples. Herein, as a novel glucose biosensing probe, green-emitting Zn2GeO4:Mn2+, Eu3+ (ZGME) persistent luminescence nanoparticles (PLNPs) with pH stimulus-responsive was prepared by a facile one-pot hydrothermal method. We also investigated the pH stimulus-responsive luminescence behaviour of ZGME over a range of pH values from 2.8 to 8.0. Taking advantage of the interesting property that ZGME photoluminescence intensity has a pH response, within an extraordinarily narrow pH range of 5.0-6.5 for highly selectivity and sensitive determination of glucose level in human samples by acid-responsive quenching and persistent luminescent performance. The detection results show high accuracy of the measured values of glucose in serum with a wide detection range (2.5μg L-1-10mg L-1) and low detection limit (0.5μg L-1). Finally, the pH-responsive persistent luminescence also makes ZGME promising for high-level fingerprint information encryption. Hence, the established pH stimulation-responsive PLNPs-based biosensing probe offers excellent performance with high selective, accuracy and signal-to-noise ratio for detection of glucose level in human samples.

Persistent Luminescent Nanoparticle-Loaded Filaments for Identification of Fabrics in the Visible and Infrared.

Persistent luminescent materials are those which can store an amount of energy locally and release it slowly in the form of light. In this work, persistent luminescent nanoparticles (PLNPs) were synthesized and incorporated into polypropylene (PP) filaments at various loading percentages. We investigated the optical properties of both the as-prepared PLNPs and the PLNP-loaded filaments, focusing on any changes resulting from the integration into the filaments. Specifically, visible and near-infrared spectroscopy were used to analyze the emission, excitation, and persistent luminescence of the PLNPs and PLNP-loaded filaments. The tensile properties of the extruded filaments were also investigated through breaking tenacity, elongation at break, Young's modulus, and secant modulus. All PLNP-loaded filaments were shown to exhibit persistent luminescence when exposed to ultraviolet light. While there were no significant changes in the elongation at break or Young's modulus for the loading percentages tested, there was a slight increase in breaking tenacity and a decrease in the secant modulus. Finally, the filaments were shown to maintain their optical properties and persistent luminescence even after abrasion testing used to simulate the normal wear and tear that fabric experiences during use. These results show that PLNPs can be successfully incorporated into filaments which can be used in fabrics and will maintain the persistent luminescent properties.

Biodegradable Persistent Luminescence Nanoparticles as Pyroptosis Inducer for High-Efficiency Tumor Immunotherapy.

Pyroptosis possesses potent antitumor immune activity, making pyroptosis inducer development a promising direction for tumor immunotherapy. Persistent luminescence nanoparticles (PLNPs) are highly sensitive optical probes extensively employed in tumor diagnosis and therapy. However, a pyroptosis inducer based on PLNPs has not been reported yet. Herein, polyethylene glycol-poly lactic acid-co-glycolic acid (PEG-PLGA: PP) modified biodegradable CaS:Eu2+ (CSE@PP) PLNPs are synthesized as a pyroptosis inducer for tumor immunotherapy for the first time. The synthesized CSE@PP possesses biowindow persistent luminescence (PersL) and pH-responsive degradation properties, allowing it to remain stable under neutral pH but degrade when exposed to weak acid (pH< 6.5). During degradation within the tumor, CSE@PP constantly releases H2S and Ca2+ while its PersL gradually fades away. Thus, the PersL signal can self-monitor H2S and Ca2+ release. Furthermore, the released H2S and Ca2+ result in mitochondrial dysfunction and the inactivation of reactive oxygen species scavenging enzymes, synergistic facilitating intracellular oxidative stress, which induces caspase-1/GSDM-D dependent pyroptosis and subsequent antitumor immune responses. In a word, it is confirmed that CSE@PP can self-monitor H2S and Ca2+ release and pyroptosis-mediated tumor Immunotherapy. This work will facilitate biomedical applications of PLNPs and inspire pyroptosis-induced tumor immunotherapy.

Trimodality applications validation of near-infrared persistent luminescence nanoparticles

Here, we introduced Cr ion, as emission center, to achieve the NIR emission for MgGa2O4, while Zn ion is used to increase oxygen vacancy to improve the emission intensity. Thus, Mg0.9Zn0.1Ga2O4: 0.006 Cr3+ (MZGC) was prepared as the optimal composite with the enhanced NIR emission at 708 nm, while the host, Mg0.9Zn0.1Ga2O4 (MZG), exhibited the afterglow emission at 425 nm under 224 nm excitation. The result from density functional theory confirmed Cr and Zn ions occupied in the octahedral coordination to improve the optical behaviors. The NIR emission of MZGC was applied for bioimaging as confirmed with mice model under both visible and NIR excitation. We proposed MZGC strategy for fingerprint imaging and recognition with their resistance to stray light interference. By applying the mixture of MZGC and MZG, we realized ratiometric temperature sensing at 35–40 °C within body temperature range. The optical mechanism clearly illustrated for tri-modality applications as bioimaging, fingerprint recognition, and temperature sensing. This work provides a reliable method for the improvement of optical properties and thus extend the applications of persistent luminescence nanoparticles.

Retraction of "Extracellular Vesicles Embedded with Persistent Luminescence Nanoparticles Exhibiting Near-Infrared Emission for Long-Term Tracking in Primary Tumors".

[This retracts the article DOI: 10.1021/acsaom.3c00474.].

Heterojunction composites of covalent organic frameworks grown on the surface of persistent luminescent nanoparticles for photocatalytic hydrogen evolution and degradation of organic pollutants

Covalent organic frameworks (COFs) have shown great promise for photocatalytic hydrogen evolution from water and photocatalytic degradation of organic pollutants. However, a single COFs suffers from poor photogenerated charge separation efficiency. In this study, we synthesized persistent luminescent nanoparticles (PLNPs)@COFs composites with core–shell heterostructures by the in situ growth of COFs on the surface of PLNPs. The PLNPs@COFs composites demonstrated better photocatalytic performance than pure PLNPs and COFs. The hydrogen production rate of PLNPs@COFs (1:6) was about 35 mmol h−1 g−1, and the photodegradation efficiency of Rhodamine B by PLNPs@COFs (3:1) reached 100 % in 50 min. Evidently, the combination of COFs with PLNPs to form a core–shell heterostructure with a tight contact interface can effectively improve the photogenerated charge separation efficiency. Our covalent bonding and in situ growth approach is more conducive to the formation of stable core-shell heterostructures. A good match between the persistent luminescence emission spectrum of the PLNPs and the absorption range of the COFs improves the potential of PLNPs@COFs to function as a round-the-clock photocatalyst. This strategy holds excellent promise in the efficient use of solar photocatalytic hydrogen evolution and in environmental purification in the future.

Detection of ascorbic acid by persistent luminescent nanoparticles based on CoOOH nanosheets modification.

Persistent luminescent nanomaterials (PLNPs) Zn0.8Ga2O4: Cr3+, Zr3+ with high brightness and good dispersion were prepared by hydrothermal method. The PLNPs were used as luminescent units, and CoOOH nanosheets were used as quenching agents. Based on the fluorescence internal filtering effect, the luminescence of PLNPs were effectively quenched by CoOOH modification on the surface of PLNPs. However, the introduction of ascorbic acid (AA) restored the luminescence of PLNPs and successfully achieved highly sensitive and selective detection of AA. This was due to a selective redox reaction between CoOOH and AA, in which CoOOH was reduced to Co2+. The degree of luminescence recovery of PLNPs showed a good linear relationship with AA concentration in the range 5-250 µM, with a detection limit of 0.72 µM. Therecovery of actualspikedsamples were 97.9-102.2%. This method isexpected to provide reference for the study of other redox substances in biological systems.

Persistent Luminescence Nanoplatform for Autofluorescence-Free Tracking of Submicrometer Plastic Particles in Plant.

The uptake of plastic particles by plants and their transport through the food chain make great risks to biota and human health. Therefore, it is important to trace plastic particles in the plant. Traditional fluorescence imaging in plants usually suffers significant autofluorescence background. Here, we report a persistent luminescence nanoplatform for autofluorescence-free imaging and quantitation of submicrometer plastic particles in plant. The nanoplatform was fabricated by doping persistent luminescence nanoparticles (PLNPs) onto polystyrene (PS) nanoparticles. Cr3+-doped zinc gallate PLNP was employed as the dopant for autofluorescence-free imaging due to its persistent luminescence nature. In addition, the Ga element in PLNP was used as a proxy to quantify the PS in the plant by inductively coupled plasma mass spectrometry (ICP-MS). Thus, the developed nanoplatform allows not only dual-mode autofluorescence-free imaging (persistent luminescence and laser-ablation ICP-MS) but also ICP-MS quantitation for tracking PS in plant. Application of this nanoplatform in a typical plant model Arabidopsis thaliana revealed that PS mainly distributed in the root (>99.45%) and translocated very limited (<0.55%) to the shoot. The developed nanoplatform has great potential for quantitative tracing of submicrometer plastic particles to investigate the environmental process and impact of plastic particles.

Persistent Luminescence Nanosensors: A Generalized Optode-Based Platform for Autofluorescence-Free Sensing in Biological Systems.

Fluorescent nanosensors have revolutionized diagnostics and our ability to monitor cellular dynamics. Yet, distinguishing sensor signals from autofluorescence remains a challenge. Here, we merged optode-based sensing with near-infrared-emitting ZnGa2O4:Cr3+ persistent luminescence nanoparticles (PLNPs) to create nanocomposites for autofluorescence-free "glow-in-the-dark" sensing. Hydrophobic modification and incorporation of the persistent luminescence nanoparticles into an optode-based nanoparticle core yielded persistent luminescence nanosensors (PLNs) for five analytes (K+, Na+, Ca2+, pH, and O2) via two distinct mechanisms. We demonstrated the viability of the PLNs by quantifying K+ in fetal bovine serum, calibrating the pH PLNs in the same, and ratiometrically monitoring O2 metabolism in cultures of Saccharomyces cerevisiae, all the while overcoming their respective autofluorescence signatures. This highly modular platform allows for facile tuning of the sensing functionality, optical properties, and surface chemistry and promises high signal-to-noise ratios in complex optical environments.

Improvement of Hydrogen Peroxide and Glucose Detection in Serum using Persistent Luminescent Nanoparticles: Impact of Synthesis Parameters and Particle Size

AbstractPersistent Luminescent Nanoparticles (PLNPs) emit prolonged light after excitation, allowing getting images with high signal‐to‐noise ratio, making them particularly beneficial for in vitro biodetection. In this study, we report the preparation of a library of gallium and zinc‐based Persistent Luminescent Nanoparticles doped with chromium (ZnGa2O4:Cr3+) through two distinct syntheses conducted at 120 °C for 12 hours or 24 hours, followed by a calcination at 500 °C or 750 °C. Using centrifugation, and starting from polydisperse samples, we demonstrated the ability to achieve different sizes in a monodisperse manner. Furthermore, our research revealed that ZnGa2O4:Cr3+ (ZGO) nanoparticles react differently with hydrogen peroxide (H2O2) based on their size, synthesis duration, and calcination temperature. We observed the most significant amplification of persistent luminescence for ZGO particles prepared at 120 °C for 12 hours and calcinated at 500 °C, with a size of approximately 100 nm, in the presence of 100 mM H2O2 (later named ZGO‐2). This study enabled the detection of H2O2 in serum without autofluorescence using the developed PLNPs, with a detection limit of up to 2.1 μM and a recovery rate of around 99 %. Additionally, we designed a glucose test for based on the responsiveness of ZGO PLNPs to H2O2. Using glucose oxidase, the glucose detection limit in serum was established around 0.13 μM, with a detection range between 0–5 μM. These findings could open new avenues to further control the size, synthesis, calcination temperature, and persistent luminescence of PLNPs, thus enhancing their utility in the development of new in vitro biosensors.

Biological window excited up-conversion persistent luminescence nanoparticles for bioimaging and photodynamic therapy

Near-infrared (NIR) persistent luminescence nanoparticles (PLNPs) have inherent advantages for high-sensitivity bioimaging due to the separation of excitation and emission light. However, the single-wavelength emission of NIR PLNPs for bioimaging limits their use in photodynamic therapy (PDT). Herein, a biological window excited up-conversion (UC) PLNPs, Zn3Ga2SnO8:Cr3+,Yb3+,Ho3+ (ZGS), was reported for bioimaging and PDT. ZGS exhibits NIR persistent luminescence (PersL) after red LED excitation and visible UCL under 980 nm excitation. The NIR PersL is designed for in vivo bioimaging; the visible UCL is used to activate photosensitizer (PS) to generate reactive oxygen species (ROS) for PDT. The dual-functional ZGS with UCL and PersL provides an effective method for bioimaging and PDT, which is expected to further promote the application of PLNPs in the integration of efficient diagnosis and treatment.

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.

Chromium-doped zinc gallate: Impact of Sn4+ co-doping on the persistent luminescence properties at the nanoscale applied to bio-imaging

Persistent luminescence (PersL) nanoparticles emit a signal that lasts long after the excitation has ended, enabling highly sensitive bioimaging without background noise. By using UV light as the excitation source prior to injection, a strong PersL signal can be detected in vivo before disappearing within a few hours. For long-term imaging, we have shown in the past that visible LED can be used to re-excite ZnGa1.995Cr0.005O4 (ZGO:Cr3+) nanoparticles in vivo, producing a signal intensity that is, however, much lower compared to the signal obtained after the UV pre-excitation method. This lower signal intensity of the nanoprobe when using a visible LED may prevent its detection in some cases. Herein, we report an improvement in visible LED excitation efficiency using PersL Zn1.33Ga1.335Cr0.005Sn0.33O4 (ZGSO:Cr3+) nanoparticles. We fully compared ZGSO:Cr3+ and the original ZGO:Cr nanoparticles in terms of structure, optical properties and bio-imaging potential. Co-doping with tin strongly increases persistent luminescence, even at the nanoscale. In vivo imaging results showed that ZGSO:Cr3+ exhibited an approximately 3-fold signal enhancement over ZGO:Cr3+ using UV pre-excitation. More interestingly, when using LED excitation, the signal intensity of ZGSO: Cr3+ is more than 10 times higher than that of ZGO:Cr3+, making ZGSO nanoparticles much easier to detect. ZGSO:Cr nanoparticles can be surface-modified with PEG to produce nanoprobes with much longer residence time in blood. This unique comparison between the two compositions makes ZGSO:Cr3+ a more effective imaging diagnostic probe than the original ZGO:Cr3+ nanoparticles, opening up new applications for in vivo diagnostics.