Eu3+-functionalized covalent organic framework for ratiometric fluorescence detection and adsorption of tetracycline and information steganography.

Functional materials with organic/inorganic composites as the main matrix and rare earth ion complexes as the guest have shown a very broad application prospect for antibiotic sensors. However, Eu3+-complex often relies on a single fluorescence response signal, which is susceptible to changes in the detection environment and cannot simultaneously detect and remove tetracycline (TC). Herein, green fluorescent covalent two-dimensional organic framework (COF-TD) is synthesized, followed by modification of Eu3+ to synthesize COF-TD@Eu3+. In the ratiometric sensor, Eu3+ serves as the recognition site and specific response probe for TC, while COF-TD is the fluorescence reference and carrier for Eu3+. Due to the antenna effect, TC enhances the red fluorescence of Eu3+, while the green fluorescence of COF-TD remains almost stable. Based on the change of fluorescence intensity and fluorescence color from green to red, the efficient ratiometric sensing can be finished in 1 min. The developed method shows high sensitivity with a detection limit of 0.3 µM and high selectivity to TC which makes the method applicable to detect TC in traditional Chinese medicine preparations. In addition, due to the high specific surface area of COFs and specific adsorption sites, COF-TD@Eu3+ also shows good performance for TC removal. The findings show that the maximum adsorption capacity is 137.3 mg g-1 and the adsorption equilibrium is reached in 30 min. Smartphone assisted COF-TD@Eu3+ for both ratiometric fluorescence detection and detecting the absorption of TC is proposed for the first time. The molecular cryptosteganography that transforms the selective response of COF-TD@Eu3+ to binary strings is anticipated to advance utilization of nanomaterials in logic sensing and information safety.

Heterometallic Eu/Zn-MOF-based ratiometric sensing platform: Highly sensitive fluorescence / second-order scattering identification of tetracycline analogs and its molecular informatization applications.

The traditional preparation method of ratiometric probes faces challenges such as cumbersome preparation and low sensitivity. Thus, there is an urgent need to provide a simple method of preparing a highly sensitive ratiometric probe. Here, Eu3+-doped zinc-based organic framework (Eu/Zn-MOF) was prepared through hydrothermal method for the detection of tetracycline analogs (TCs). Under the same excitation conditions, the probe can simultaneously display valuable fluorescence and second-order scattering signals. The developed probe enabled specific identification and fast detection (1 min) of TCs, including tetracycline, oxytetracycline, doxycycline, and chlortetracycline. The linear detection ranges of tetracycline, oxytetracycline, doxycycline and chlortetracycline were respectively 100 nM - 200 µM, 100 nM - 200 µM, 98 nM - 195 µM, and 97 nM - 291 µM, and the corresponding detection limits were respectively 15.79 nM, 20.83 nM, 15.31 nM, and 28.30 nM. The developed sensor was successfully applied to detect TCs in real samples, and the recovery rate was from 92.54 % to 109.69 % and the relative standard deviation was from 0.04 % to 2.97 %. Moreover, the heterometallic Eu/Zn-MOF was designed as a ratiometric neuron for Boolean logic computing and information encryption based on the specific identification of TCs. As a proof of concept, molecular steganography was successfully employed to encode, store, and conceal information by transforming the specific identification patterns of Eu/Zn-MOF into binary strings. This study is anticipated to advance the application of metal-organic frameworks in logic detection and information security, and bridging the gap between molecular sensors and the realm of information.

Multifunctional Janus Membrane for Diabetic Wound Healing and Intelligent Monitoring.

The complex microenvironment of diabetic wounds often hinders the healing process, ultimately leading to the formation of diabetic foot ulcers and even death. Dual monitoring and treatment of wounds can significantly reduce the incidence of such cases. Herein, a multifunctional Janus membrane (3D chitosan sponge-ZE/polycaprolactone nanofibers-ZP) was developed by incorporating the zinc metal-organic framework, europium metal-organic framework, and phenol red into nanofibers for diabetic wound monitoring and treatment. The directional water transport capacity of the resulting Janus membrane allows for unidirectional and irreversible drainage of wound exudate, and the multifunctional Janus membrane creates up to a 99% antibacterial environment, both of which can treat wounds. Moreover, the pH (5-8) and H2O2 (0.00-0.80 µM) levels of the wound can be monitored using the color-changing property of phenol red and the fluorescence characteristic of Eu-MOF on the obtained membrane, respectively. The healing stages of the wound can also be monitored by analyzing the RGB values of the targeted membrane images. This design can more accurately reflect the wound state and treat the wound to reduce bacterial infection and accelerate wound healing, which has been demonstrated in in vivo experiments. The results provide an important basis for early intervention in diabetic patients.

Europium-tannic acid nanocomplexes devised for bone regeneration under oxidative or inflammatory environments.

Europium ions (Eu3+) are gaining attention in the field of regenerative medicine due to increasing evidence of their osteogenic properties. However, inflammatory and oxidative environments present in many bone diseases, such as osteoporosis or rheumatoid arthritis, are known to hinder this regenerative process. Herein, we describe a straightforward synthetic procedure to prepare Eu3+-tannic acid nanocomplexes (EuTA NCs) with modulable physicochemical characteristics, as well as antioxidant, anti-inflammatory, and osteogenic properties. EuTA NCs were rationally synthesized to present different contents of Eu3+ on their structure to evaluate the effect of the cation on the biological properties of the formulations. In all the cases, EuTA NCs were stable in distilled water at physiological pH, had a highly negative surface charge (ζ ≈ -25.4 mV), and controllable size (80 < Dh < 160 nm). In vitro antioxidant tests revealed that Eu3+ complexation did not significantly alter the total radical scavenging activity (RSA) of TA but enhanced its ability to scavenge H2O2 and ferrous ions, thus improving its overall antioxidant potential. At the cellular level, EuTA NCs reduced the instantaneous toxicity of high concentrations of free TA, resulting in better antioxidant (13.3% increase of RSA vs. TA) and anti-inflammatory responses (17.6% reduction of nitric oxide production vs. TA) on cultures of H2O2- and LPS-stimulated macrophages, respectively. Furthermore, the short-term treatment of osteoblasts with EuTA NCs was found to increase their alkaline phosphatase activity and their matrix mineralization capacity. Overall, this simple and tunable platform is a potential candidate to promote bone growth in complex environments by simultaneously targeting multiple pathophysiological mechanisms of disease.

Ion coordination and chelation in Eu-MOFs matrices: Ultrafast fluorescence visual quantification monitoring of antibiotic residues.

Rapid monitoring of trace antibiotics in the field in real time is essential for environment forewarning and human health. High sensitivity and real-time on-site quantitative monitoring of antibiotic residues can be accomplished by integrating portable sensors alongside fluorescent optics to construct an intelligent sensing platform that smoothly eliminates the instability of conventional detection methods. In this study, a ratiometric fluorescence sensor for the ultrasensitive detection of pefloxacin was built employing the photoinduced electron transfer (PET) mechanism from red Eu-MOFs to Mn2+-PEF complex. A visual color change results from the photoinduced electron transfer process from manganese ions to pefloxacin weakening the ligand metal charge transfer (LMCT) process in Eu-MOFs. This enables the ultrafast visible detection of pefloxacin and produces a transient shift in visual color with a detection limit as low as 15.4 nM. For the detection of pefloxacin in water, tomato, and raw pork samples, various sensing devices based on the developed fluorescent probes exhibit good practicability and accuracy. With the development of the ratiometric fluorescence sensing probe, it is now possible to quickly and quantitatively identify pefloxacin residues in the environment, offering a new method for ensuring the safety of food and people's health.

Responsive ß-Diketonate-europium(III) Complex-Based Probe for Time-Gated Luminescence Detection and Imaging of Hydrogen Sulfide In Vitro and In Vivo.

As a crucial biological gasotransmitter, hydrogen sulfide (H2S) plays important roles in many pathological and physiological processes. Highly selective and sensitive detection of H2S is significant for the precise diagnosis and evaluation of diverse diseases. Nevertheless, challenges remain in view of the interference of autofluorescence in organisms and the stronger reactivity of H2S itself. Herein, we report the design and synthesis of a novel H2S-responsive ß-diketonate-europium(III) complex-based probe, [Eu(DNB-Npketo)3(terpy)], for background-free time-gated luminescence (TGL) detection and imaging of H2S in autofluorescence-rich biological samples. The probe, consisting of a 2,4-dinitrobenzenesulfonyl (DNB) group coupled to a ß-diketonate-europium(III) complex, shows almost no luminescence owing to the existence of intramolecular photoinduced electron transfer. The cleavage of the DNB group by a H2S-triggered reaction results in the recovery of the long-lived luminescence of the Eu3+ complex, allowing the detection of H2S in complicated biological samples to be performed in TGL mode. The probe showed a fast response, high specificity, and high sensitivity toward H2S, which enabled it to be successfully used for the quantitative TGL detection of H2S in tissue homogenates of mouse organs. Additionally, the low cytotoxicity of the probe allowed it to be further used for the TGL imaging of H2S in living cells and mice under different stimuli. All of the results suggested the potential of the probe for the investigation and diagnosis of H2S-related diseases.

Broadband sensitized near-infrared emission in Eu2+-Nd3+ co-doped BaAl2O4 as a potential spectral modulator for silicon solar cells.

The near-infrared (NIR) down-conversion process for broadband sensitization has been studied in Eu2+-Nd3+ co-doped BaAl2O4. This material has a broad absorption band of 200-480 nm and can convert photons in the visible region into NIR photons. The NIR emission at 1064 nm, attributed to the Nd3+:4F3/2 → 4I11/2 transition, matches the bandgap of Si, allowing Si solar cells to utilize the solar spectrum better. The energy transfer (ET) process between Eu2+ and Nd3+ was demonstrated using photoluminescence spectra and luminescence decay curves, and Eu2+ may transfer energy to Nd3+ through the cooperative energy transfer (CET) to achieve the down-conversion process. The energy transfer efficiency (ETE) and theoretical quantum efficiency (QE) were 68.61% and 156.34%, respectively, when 4 mol% Nd3+ was introduced. The results indicate that BaAl2O4:Eu2+-Nd3+ can serve as a potential modulator of the solar spectrum and is expected to be applied to Si solar cells.

Stable Europium(III) Metal-Organic Framework Fluorescence Probe for Intelligent Visualization Detection of Gossypol and Nitrofuran Antibiotics in Real Samples.

Gossypol (Gsp) and antibiotics present in water bodies become organic pollutants that are harmful to human health and the ecological environment. Accurate and effective detection of these pollutants has far-reaching significance in many fields. A new three-dimensional metal-organic framework (MOF), {[Eu3(L)2(HCOO-)(H2O)3]·2H2O·2DMF}n (Eu-MOF), was synthesized from 3,5-bis(2,4-dicarboxylphenyl)nitrobenzene (H4L) ligand and Eu3+ via the solvothermal method in this paper. The Eu-MOF demonstrates strong red fluorescence and can remain stable in different pH solutions. The MOF fluorescence probe could detect organic pollutants through the "shut-off" effect, with a fast response speed and a low detection limit [Gsp, nitrofurantoin (NFT), and nitrofurazone (NFZ) for 0.43, 0.38, and 0.41 µM, respectively]. During the testing process, Eu-MOF exhibited good selectivity and recoverability. Furthermore, the mechanism of fluorescence quenching was investigated, and the recoveries were also good in real samples. This paper introduced a deep learning model to recognize the fluorescence images, a portable intelligent logic detector designed for real-time detection of Gsp by logic gate strategy, and an anticounterfeiting mark prepared based on inkjet printing. Importantly, this work provides a new way of thinking for the detection of organic pollutants in water with high sensitivity and practicality by combining the fluorescence probe with machine learning and logical judgment.

Europium Nanoparticle-Based Lateral Flow Strip Biosensors for the Detection of Quinoxaline Antibiotics and Their Main Metabolites in Fish Feeds and Tissues.

Olaquindox (OLA) and quinocetone (QCT) have been prohibited in aquatic products due to their significant toxicity and side effects. In this study, rapid and visual europium nanoparticle (EuNP)-based lateral flow strip biosensors (LFSBs) were developed for the simultaneous quantitative detection of OLA, QCT, and 3-methyl-quinoxaline-2-carboxylic acid (MQCA) in fish feed and tissue. The EuNP-LFSBs enabled sensitive detection for OLA, QCT, and MQCA with a limit of detection of 0.067, 0.017, and 0.099 ng/mL (R2 ≥ 0.9776) within 10 min. The average recovery of the EuNP-LFSBs was 95.13%, and relative standard deviations were below 9.38%. The method was verified by high-performance liquid chromatography (HPLC), and the test results were consistent. Therefore, the proposed LFSBs serve as a powerful tool to monitor quinoxalines in fish feeds and their residues in fish tissues.

Europium insertion into MgAl hydrotalcite-like compound to promote the photocatalytic oxidation of nitrogen oxides.

Easy synthesis of efficient, non-toxic photocatalysts is a target to expand their potential applications. In this research, the role of Eu3+ doping in the non-toxic, affordable, and easily prepared MgAl hydrotalcite-like compounds (HTlcs) was explored in order to prepare visible light semiconductors. Eu doped MgAl-HTlcs (MA-xEu) samples were prepared using a simple coprecipitation method (water, room temperature and atmospheric pressure) and europium was successfully incorporated into MgAl HTlc frameworks at various concentrations, with x (Eu3+/M3+ percentage) ranging from 2 to 15. Due to the higher ionic radius and lower polarizability of Eu3+ cation, its presence in the metal hydroxide layer induces slight structural distortions, which eventually affect the growth of the particles. The specific surface area also increases with the Eu content. Moreover, the presence of Eu3+ 4f energy levels in the electronic structure enables the absorption of visible light in the doped MA-xEu samples and contributes to efficient electron-hole separation. The microstructural and electronic changes induced by the insertion of Eu enable the preparation of visible light MgAl-based HTlcs photocatalysts for air purification purposes. Specifically, the optimal HTlc photocatalyst showed improved NOx removal efficiency, ∼ 51% (UV-Vis) and 39% (visible light irradiation, 420 nm), with excellent selectivity (> 96 %), stability (> 7 h), and enhanced release of •O2- radicals. Such results demonstrate a simple way to design photocatalytic HTlcs suitable for air purification technologies.

Site occupancy and tunable luminescence of Eu2+ and Eu3+ coactivated KCaY (PO4)2:Eu phosphors.

Utilizing the structure characteristic of KCaY (PO4)2 crystal, the site distribution of Eu2+ in KCaY (PO4)2:Eu phosphor coactivated with Eu2+ and Eu3+ ions is tuned. Upon 393-nm excitation, the as-prepared phosphor exhibits a broadband emission of Eu2+ peaked at ~ 475 nm and a typical red emission of Eu3+ with a strong 5D0-7F1 emission at ~ 591 nm. The luminescence color of the phosphor can be adjusted from blue to green, white, yellow, and red. The increasing concentration of Sr2+ and Eu2+ results in a blue shifting of Eu2+ emission. The increasing concentration of Eu3+ results in a red shifting of Eu2+ emission and an enhanced red emission of Eu3+. The luminescence behaviors of the phosphors are analyzed in terms of the site distribution of Eu2+ and Eu3+. A single-phase white light emitting was achieved in KCaY (PO4)2:Eu phosphor upon UV and NUV light excitation, indicating that the phosphor has potential application in white lighting.

Integrated Eu3+ loaded covalent organic framework with smartphone for ratiometric fluorescence detection of tetracycline.

Developing rapid tetracycline sensing system is of great significance to monitor the illegal addition to drugs and pollution to food and ecosystem. By loading covalent organic frameworks (COFs) with Eu3+, a new hybridized material (COF@Eu3+) was prepared for tetracycline determination. Based on the Schiff base reaction, the COFs were by synthesized through solvent evaporation in 30 min at room temperature. Thereafter, Eu3+ was modified into COFs to develop the COF@Eu3+ sensing platform by adsorption and coordination. In presence of tetracycline, tetracycline can displace water molecules and coordinate with Eu3+ through the antenna effect. As a result, the red fluorescence of Eu3+ was enhanced by tetracycline with green fluorescence of COF as a reference. The developed ratiometric fluorescence sensor exhibits a linear range of 0.1-20 µM for detecting tetracycline with a detection limit of 30 nM. Integrated with a smartphone, the rapid tetracycline detection can be realized in situ, which is potential for high-throughput screening of tetracycline contaminated samples. Furthermore, the COF@Eu3+ fluorescence sensor has been successfully applied to the detection of tetracycline in traditional Chinese medicine compound preparation with satisfied recoveries. Therefore, a smartphone-assisted device was successfully developed based on Eu3+-functionalized COF, which is an attractive candidate for further applications of fluorescence sensing and visual detection.

Luminol-Eu3+-Gd3+-functionalized mesoporous silica for ultrasensitive detection of tetracycline antibiotics and smartphone-assisted sensing analysis.

An organic-inorganic hybrid nanoprobe, namely LML-D-SBA@Eu3+-Gd3+, was constructed, with SBA-15 acting as the carrier material, and luminol and Eu3+ acting as fluorescence channels to achieve ratiometric signals that eliminate external interference (accurate detection). Gd3+ was used as a sensitizer to amplify the red emission of Eu3+ (ultrasensitive detection). In TCs detection, the luminol emission at 428 nm was quenched due to the photoinduced electron transfer mechanism, and the Eu3+ emission at 617 nm was sensitized due to the synergistic energy transfer from TCs and Gd3+ to Eu3+. The fluorescence intensity at 617 and 428 nm showed ratiometric changes as indicated by notable color changes from blue to red. The detection limits for TC and OTC were 0.21 and 0.08 ng/mL, respectively. To realize a facile, rapid, and cost-effective detection, we constructed a portable intelligent sensing platform based on smartphones, and it demonstrated great potential for on-site detection of TCs.

A dual-response ratiometric fluorescent sensor by europium-doped silicon nanoparticles for fluorescent and smartphone imaging detection of tetracycline.

Given the threat to human health posed by the abuse of tetracycline (TC), the development of a portable, on-site methods for highly sensitive and rapid TC detection is crucial. In this work, we initially synthesized europium-doped silicon nanoparticles (SiEuNPs) through a facile one-pot microwave-assisted method. Due to its blue-red dual fluorescence emission (465 nm/621 nm), which was respectively attributed to the silicon nanoparticles and Eu3+, SiEuNPs were designed as a ratiometric fluorescent sensor for TC detection. For the dual-signal reverse response mechanism: TC quenched the blue emission from silicon nanoparticles through inner filter effect (IFE), and enhanced the red emission through "antenna effect" (AE) between TC and Eu3+, the nanoprobe was able to detect TC within a range of 0.2-10 µM with a limit of detection (LOD) of 10.7 nM. Notably, the equilibrium detection time was only 1 min, achieving rapid TC detection. Furthermore, TC was also measured in real samples (tap water, milk and honey) with recoveries ranging from 95.7 % to 117.0 %. More importantly, a portable smartphone-assisted on-site detection platform was developed, enabling real-time qualitative identification and semi-quantitative analysis of TC based on fluorescence color changes. This work not only provided a novel doped silicon nanoparticles strategy, but also constructed a ratiometric sensing platform with dual-signal reverse response for intuitive and real-time TC detection.

A dual-response ratiometric fluorescent sensor for oxytetracycline determination in milk and mutton samples.

Owing to the adverse effects of oxytetracycline (OTC) residues on human health, it is of great importance to construct a rapid and effective strategy for OTC detection. Herein, we developed a dual-response fluorescence sensing platform based on molybdenum sulfide quantum dots (MoS2 QDs) and europium ions (Eu3+) for ratiometric detection of OTC. The MoS2 QDs, synthesized through an uncomplicated one-step hydrothermal approach, upon OTC integration into the MoS2 QDs/Eu3+ sensing system, exhibit a significant quenching of blue fluorescence due to the inner filter effect (IFE), simultaneously enhancing the distinct red emission of Eu3+ at 624 nm, a phenomenon attributed to the antenna effect (AE). This sensor demonstrates exceptional selectivity and sensitivity towards OTC, characterized by a linear detection range of 0.2-10 µM and a notably low detection limit of 2.21 nM. Furthermore, we achieved a visual semi-quantitative assessment of OTC through the discernible fluorescence color transition from blue to red under a 365 nm ultraviolet lamp. The practical applicability of this sensor was validated through the successful detection of OTC in milk and mutton samples, underscoring its potential as a robust tool for OTC monitoring in foodstuffs to safeguard food safety.

Synthesis and evaluation of fluorescent resins with europium-ß-diketonate complex for orthodontic use.

No effective technique exists for removing adhesive remnants following bracket debonding. We propose that fluorescence imaging using europium ions (Eu3+) offers an effective solution for minimizing iatrogenic enamel damage. This study aimed to assess the impact of different mixing ratios of monomer mixtures on the photoluminescence and flexural properties of a newly developed fluorescent adhesive. Four monomer blends with varying urethane dimethacrylate (UDMA) to triethylene glycol dimethacrylate (TEGDMA) ratios were prepared and polymerized. The blends contained 0.1 wt% of tris(1,3-diphenyl-1,3-propanedionato)(1,10-phenanthroline) Eu(III), [Eu(DBM)3Phen], as the phosphor. Optical measurements and flexural tests were conducted for each resin specimen. The emission spectra exhibited narrow bands corresponding to the 4f-4f transitions of the Eu3+ ions. The photoluminescence properties remained unaffected by the mixing ratio, whereas the mechanical properties tended to improve with higher UDMA content. We conclude that the Eu(DBM)3Phen-containing resin shows promise as a fluorescent orthodontic adhesive that contributes to preserving enamel health.

Integration of beta counting system with ORION-DSP coupled to NaI(Tl) detector-a comparative study with an HPGe detector.

The integration of the ORION digital signal processing-based MCA system coupled with a 3″ × 3″ NaI(Tl) detector assembly with a GM detector for counting beta (ß) has eliminated the need for a standalone ß-γ method in which U3O8 is determined by gross ß and gross γ counting. Uraniferous and mixed U-Th samples were taken up for study and compared with the results obtained from Canberra p-type coaxial high resolution gamma ray spectrometry detector. In uraniferous samples, U3O8 values obtained are within ±10%, whereas in the case of mixed U-Th samples, U3O8 values are within ±15%. Regression graphs drawn between the outcomes from the two analytical systems indicate R2 > 0.95 for Ra(eU3O8) and ThO2. In uraniferous samples, the R2 value for U3O8 was found to be > 0.99, but in mixed U-Th samples, it is 0.92. The closeness of agreement between the results obtained from two methods at various concentrations over the analytical range shows that the integrated system is suitable for the quantitative determination of eU3O8, U3O8, Ra(eU3O8), ThO2 and K in geological rock samples.

Novel pyrochlore type europium stannate - tungsten disulfide heterostructure for light driven carbon dioxide reduction and nitrogen fixation.

The reduction of carbon dioxide (CO2) and nitrogen (N2) to value-added products is a substantial area of research in the fields of sustainable chemistry and renewable energy that aims at reducing greenhouse gas emissions and the production of alternative fuels and chemicals. The current work deals with the synthesis of pyrochlore-type europium stannate (Eu2Sn2O7: EuSnO), tungsten disulfide (WS2:WS), and novel EuSnO/WS heterostructure by a simple and facile co-precipitation-aided hydrothermal method. Using different methods, the morphological and structural analyses of the prepared samples were characterized. It was confirmed that a heterostructure was formed between the cubic EuSnO and the layered WS. Synthesized materials were used for photocatalytic CO2 and N2 reduction under UV and visible light. The amount of CO and CH4 evolved due to CO2 reduction is high in EuSnO/WS (CO = 104, CH4 = 64 µmol h-1 g-1) compared to pure EuSnO (CO = 36, CH4 = 70 µmol h-1 g-1) and WS (CO = 22, CH4 = 1.8 µmol h-1 g-1) under visible light. The same trend was observed even in the N2 fixation reaction under visible light, and the amount of NH4+ produced was found to be 13, 26, and 41 µmol h-1 g-1 in the presence of WS, EuSnO and EuSnO/WS, respectively. Enhanced light-driven activity towards CO2 and N2 reduction reactions in EuSnO/WS is due to the efficient charge separation through the formation of type-II heterostructure, which is in part associated with photocurrent response, photoluminescence, and electrochemical impedence spectroscopic (EIS) results. The EuSnO/WS heterostructure's exceptional stability and reusability may pique the attention of pyrochlore-based composite materials in photocatalytic energy and environmental applications.

Dual-Ligand Europium-Organic Gels as a Highly Efficient Anodic Annihilation Electrochemiluminescence Emitter for Ultrasensitive Detection of MicroRNA.

In this study, a novel europium dual-ligand metal-organic gel (Eu-D-MOGs) with high-efficient anodic annihilation electrochemiluminescence (ECL) was synthesized as an ECL emitter to construct a biosensor for ultrasensitive detection of microRNA-221 (miR-221). Impressively, compared to the ECL signal of europium single-ligand metal-organic gels (Eu-S-MOGs), the ECL signal of Eu-D-MOGs was significantly improved since the two organic ligands could jointly replace the H2O and coordinate with Eu3+, which could remarkably reduce the nonradiative vibrational energy transfer caused by the coordination between H2O and Eu3+ with a high coordination demand. In addition, Eu-D-MOGs could be electrochemically oxidized to Eu-D-MOGs•+ at 1.45 V and reduced to Eu-D-MOGs•- at 0.65 V to achieve effective annihilation of ECL, which overcame the side reaction brought by the remaining emitters at negative potential. This benefited from the annihilation ECL performance of the central ion Eu3+ caused by its redox in the electrochemical process. Furthermore, the annihilation ECL signal of Eu3+ could be improved by sensitizing Eu3+ via the antenna effect. In addition, combined with the improved rolling circle amplification-assisted strand displacement amplification strategy (RCA-SDA), a sensitive biosensor was constructed for the sensitive detection of miR-221 with a low detection limit of 5.12 aM and could be successfully applied for the detection of miR-221 in the lysate of cancer cells. This strategy offered a unique approach to synthesizing metal-organic gels as ECL emitters without a coreactant for the construction of ECL biosensing platforms in biomarker detection and disease diagnosis.

Extraction of rare earth Eu from waste blue phosphor strengthened by microwave alkali roasting.

Spent phosphor is an important secondary resource for extracting rare earth elements. Microwave absorption properties and enhanced extraction of Eu from blue phosphor by microwave alkali roasting were studied. Dielectric properties of alkali roasting system were measured by resonator perturbation method. Dielectric constant increases linearly from 250 °C until it reaches a peak at 400 °C. The dielectric loss reaches a higher value at 400-550 °C, due to the strong microwave absorption properties of molten alkali and roasted products. Effects of roasting temperature, roasting time and alkali addition amount on Eu leaching were investigated. The phosphor was completely decomposed into Eu2O3, BaCO3 and MgO at 400 °C. The alkaline decomposition process of phosphor is more consistent with diffusion control model with Eα being 28.9 kJ/mol. Effects of the main leaching conditions on Eu leaching were investigated. The leaching kinetic of Eu was in line with diffusion control model with Eα being 5.74 kJ/mol. The leaching rules of rare earths in the mixed phosphor were studied. The results showed that the presence of red and green phosphor affected the recovery of blue phosphor. The optimum process parameters of rare earth recovery in single blue phosphor and mixed phosphor were obtained, and the recovery of Eu were 97.81% and 94.80%, respectively. Microwave alkali roasting promoted the dissociation of phosphor and leaching of rare earths. The results can provide reference for the efficient and selective recovery of rare earths in phosphors.