A Superstable Luminescent Lanthanide Metal Organic Gel Utilized in an Electrochemiluminescence Sensor for Epinephrine Detection with a Narrow Potential Sweep Range

An Encyclopedic Compendium on Chemosensing Supramolecular Metal-Organic Gels

Chemosensing, an interdisciplinary scientific domain, plays a pivotal role ranging from environmental monitoring to healthcare diagnostics and (inter)national security. Metal-organic gels (MOGs) are recognized for their stability, selectivity, and responsiveness, making them valuable for chemosensing applications. Researchers have explored the development of MOGs based on different metal ions and ligands, allowing for tailored properties and sensitivities, and have even demonstrated their applications as portable sensors such as paper-based test strips for practical use. Herein, several studies related to MOGs development and their applications in the chemosensing field via UV-visible or luminance along with electrochemical approach are presented. These papers explored MOGs as versatile materials with their use in sensing bio or environmental analytes. This review provides a foundational understanding of key concepts, methodologies, and recent advancements in this field, fostering the scientific community.

Luminescent Supramolecular Metallogels: Drug Loading and Eu(III) as Structural Probe

Supramolecular metallogels combine the rheological properties of gels with the color, magnetism, and other properties of metal ions. Lanthanide ions such as Eu(III) can be valuable components of metallogels due to their fascinating luminescence. In this work, we combine Eu(III) and iminodiacetic acid (IDA) into luminescent hydrogels. We investigate the tailoring of the rheological properties of these gels by changes in their metal:ligand ratio. Further, we use the highly sensitive Eu(III) luminescence to obtain information about the chemical structure of the materials. In special, we take advantage of computational calculations to employ an indirect method for structural elucidation, in which the simulated luminescent properties of candidate structures are matched to the experimental data. With this strategy, we can propose molecular structures for different EuIDA gels. We also explore the usage of these gels for the loading of bioactive molecules such as OXA, observing that its aldose reductase activity remains present in the gel. We envision that the findings from this work could inspire the development of luminescent hydrogels with tunable rheology for applications such as 3D printing and imaging-guided drug delivery platforms. Finally, Eu(III) emission-based structural elucidation could be a powerful tool in the characterization of advanced materials.

Artificial Intelligence-Guided Gut-Microenvironment-Triggered Imaging Sensor Reveals Potential Indicators of Parkinson's Disease

The gut-brain axis has recently emerged as a crucial link in the development and progression of Parkinson's disease (PD). Dysregulation of the gut microbiota has been implicated in the pathogenesis of this disease, sparking growing interest in the quest for non-invasive biomarkers derived from the gut for early PD diagnosis. Herein, an artificial intelligence-guided gut-microenvironment-triggered imaging sensor (Eu-MOF@Au-Aptmer) to achieve non-invasive, accurate screening for various stages of PD is presented. The sensor works by analyzing α-Syn in the gut using deep learning algorithms. By monitoring changes in α-Syn, the sensor can predict the onset of PD with high accuracy. This work has the potential to revolutionize the diagnosis and treatment of PD by allowing for early intervention and personalized treatment plans. Moreover, it exemplifies the promising prospects of integrating artificial intelligence (AI) and advanced sensors in the monitoring and prediction of a broad spectrum of diseases and health conditions.

Dual-source signal amplification electrochemiluminescence sensor combined with molecularly imprinted polymers for the imidacloprid detection

A novel lanthanide metal-organic-gel (MOG)-derived material/nitrogen-doped graphdiyne (Tb-Ru-MOG/CeO2/N-GDY) composite with a dual-source signal amplification strategy was prepared and used to construct a molecularly imprinted sensor based on bifunctional monomers for the detection of imidacloprid (IMI) using electrochemiluminescence (ECL). In a green reaction environment, terbium (III) (Tb3+) can undergo multiple coordination reactions with 4'-(4-carboxyphenyl)-2,2':6',2″-terpyridine (Hcptpy) and tris(4,4'-dicarboxylicacid-2,2'-bipyridyl) ruthenium (II) dichloride (Ru(dcbpy)32+), and combine with ceria nanoparticles (CeO2 NPs) to form Tb-Ru-MOG/CeO2. Within the Tb-Ru-MOG/CeO2 framework, energy transfer from the double ligands can sensitize the central Tb3+, triggering a distinct antenna effect and energy-transfer, and its polyporous configuration offered a nanoconfined space for Ce3+/Ce4+ to effectively catalyze coreactant radicals (S2O82-), leading to in-situ endogenous activation ECL reactions. The conductive N-GDY accelerated electron movement and increased the loading on the electrode surface, enhancing the exogenous excitation of the ECL signals. Leveraging the synergistic effect of the bifunctional monomer, the synthesized molecularly imprinted polymers (MIPs) ECL sensor demonstrated a wide detection range from 10 nM to 10,000 nM for IMI, with a limit of detection (LOD) of 1.37 nM, showcasing an innovative concept for the dual-source strategy of signal amplification in integrated ECL composites to analyze food and environmental hazards.

Ultrasensitive Detection of SARS-CoV-2 Nucleocapsid Protein Based on Porphyrin-Based Metal-Organic Gels with Highly Efficient Electrochemiluminescence at Low Potential

Metal-organic gels (MOGs) are a new type of intelligent soft material, which are bridged by metal ions and organic ligands through noncovalent interactions. In this paper, we prepared highly stable P-MOGs, using the classical organic electrochemiluminescence (ECL) luminescence meso-tetra(4-carboxyphenyl)porphine as the organic ligand and Fe3+ as the metal ion. Surprisingly, P-MOGs can stably output ECL signals at a low potential. We introduced P-MOGs into the ECL resonance energy transfer strategy (ECL-RET) and constructed a quenched ECL immunosensor for the detection of the SARS-CoV-2 nucleocapsid protein (SARS-CoV-2-N). In the ECL-RET system, P-MOGs were used as energy donors, and Au@Cu2O@Fe3O4 were selected as energy acceptors. The ultraviolet-visible spectrum of Au@Cu2O@Fe3O4 partially overlaps with the ECL spectrum of P-MOGs, which can effectively touch off the ECL-RET behavior between the donors and receptors. Under the ideal experimental situation, the linear detection range of the SARS-CoV-2-N concentration was 10 fg/mL to 100 ng/mL, and the limit of detection was 1.5 fg/mL. This work has broad application prospects for porphyrin-MOGs in ECL sensing.

Facile synthesis of dual-ligand europium-metal organic gels for ratiometric electrochemiluminescence detecting I27L gene

Metal organic gels (MOGs) are a new kind of intelligent soft materials with excellent luminescence properties. However, MOGs with dual electrochemiluminescence (ECL) properties have not been reported. In this study, using Eu3+ as metal node, 4'-(4-carboxyphenyl)-2,2':6',2″-terpyridine (Hcptpy) and Luminol as organic ligands, a novel dual-ligand Europium-organic gels (Eu-L-H MOGs) were prepared by simple mixing at room temperature. On the one hand, Eu-L-H MOGs could exhibit strong and stable anodic ECL signals in the phosphate buffered saline (PBS) without the addition of co-reactants, which came from the blue emission of Luminol. On the other hand, using K2S2O8 as a cathodic co-reactant, Eu-L-H MOGs produced cathodic signals, which were derived from the red emission of Eu sensitized by Hcptpy through the antenna effect. Based on the independent dual ECL signals of Eu-L-H MOGs, we selected Alexa Flour 430 as the receptor and anodic ECL emission of Eu-L-H MOGs as the donor to construct the ECL resonance energy transfer (ECL-RET) ratio biosensor, which utilized exonuclease III assisted DNA cycle amplification to achieve ultrasensitive detection of the I27L gene. The detection linearity of I27L ranged from 1 fM to 10 nM, with a detection limit as low as 284 aM. This study developed a straightforward technique for obtaining a single luminescent material with dual signals, and further broadened the analytical application of MOGs in the realm of ECL.

Calix[4]arene-based Supramolecular Gels for Mercury Ion Removal in Water

A calix[4]arene-based gelator 1, with lower-rim mono triazolylpyridine group, capable of spontaneous self-assembly into microspheres in different ethanol/H2 O mixtures, is synthesized. The concentration-dependent 1 H NMR spectra and X-ray single-crystal structure of 1 provided evidence for self-assembly of gelator 1 via cooperative interactions of intermolecular noncovalent forces. Furthermore, metallogels by self-assembly of 1 was found to exhibit remarkable selectivity toward Hg2+ ions. 1 H NMR spectra support that Hg2+ ion was bound to the nitrogen atoms of two coordination sites of 1, which composed of triazole and pyridine. Moreover, the results of field emission scanning electron microscopy and rheology experiments indicated that Hg2+ ions not only enhanced the gelling ability of gelator 1 in ethanol but also led to morphological change of its self-assembly through metal-ligand interactions. Finally, the in situ gelation, triggered by mixing a gelator solution of 1 in ethanol with water samples such as deionized (DI), tap, and lake water, leads to the effective removal of Hg(II) from a water sample which reduced from 400 to 1.6 ppm.

N-doped carbon Co/CoOx with laccase-like activity for detection of epinephrine

N-doped carbon Co/CoOx with laccase-like activity was directionally designed by pyrolyzing Co-coordination polymer and applied to detect epinephrine, which revealed a new preparation strategy for laccase mimics. The formation mechanism of the N-doped carbon Co/CoOx nanozyme was reconnoitered by a thermogravimetric-mass spectrometry system (TG-MS). N-doped carbon Co/CoOx exhibited outstanding laccase-like activity, and the Michaelis-Menten constant and maximum initial velocity were calculated to be 0.087 mM and 0.0089 μM s-1, respectively. Based on this principle, a simple colorimetric sensing platform was developed for the quantitative detection of epinephrine, which can be used to diagnose pheochromocytoma. In addition, the visual platform for detecting epinephrine exhibited a linear range of 3 to 20 μg mL-1 and a calculated detection limit of 0.42 μg mL-1. Therefore, the proposed colorimetric sensing platform is a promising candidate to be applied in precise early pheochromocytoma diagnosis.

Competitive substitution in europium metal-organic gel for signal-on electrochemiluminescence detection of dipicolinic acid

Metal-organic gels (MOGs) emerged as an attractive luminescent soft material for electrochemiluminescence (ECL). In this work, a cathodic ECL-activated europium metal-organic gel (Eu-MOG) has been synthesized by a facile mixing of Eu3+ with 4'-(4-carboxyphenyl)-2,2':6',2''-terpyridine (Hcptpy) under mild conditions. The prepared Eu-MOG is highly mesoporous for co-reactant permeation to produce an ultra-stable and high-efficient ECL, based on the antenna effect of Eu3+ coordinating with Hcptpy. Moreover, dipicolinic acid (DPA) can competitively coordinate with Eu3+ instead of water molecules, producing an enhanced ECL signal. Therefore, an ECL enhancement assay was developed for DPA detection. There was a linear relationship between the ECL intensity and the logarithmic concentration of DPA in the 0.01-1 μM range, and the detection limit is 7.35 nM. This work displays the promising application of Eu-MOG in the ECL field, opening a broad inspection for seeking a new generation of ECL luminophores.

Current Trends in Nanomaterials-Based Electrochemiluminescence Aptasensors for the Determination of Antibiotic Residues in Foodstuffs: A Comprehensive Review

Veterinary pharmaceuticals have been recently recognized as newly emerging environmental contaminants. Indeed, because of their uncontrolled or overused disposal, we are now facing undesirable amounts of these constituents in foodstuff and its related human health concerns. In this context, developing a well-organized environmental and foodstuff screening toward antibiotic levels is of paramount importance to ensure the safety of food products as well as human health. In this case, with the development and progress of electric/photo detecting, nanomaterials, and nucleic acid aptamer technology, their incorporation-driven evolving electrochemiluminescence aptasensing strategy has presented the hopeful potentials in identifying the residual amounts of different antibiotics toward sensitivity, economy, and practicality. In this context, we reviewed the up-to-date development of ECL aptasensors with aptamers as recognition elements and nanomaterials as the active elements for quantitative sensing the residual antibiotics in foodstuff and agriculture-related matrices, dissected the unavoidable challenges, and debated the upcoming prospects.

Progress in Research and Application of Metal-Organic Gels: A Review

In recent years, metal-organic gels (MOGs) have attracted much attention due to their hierarchical porous structure, large specific surface area, and good surface modifiability. Compared with MOFs, the synthesis conditions of MOGs are gentler and more stable. At present, MOGs are widely used in the fields of catalysis, adsorption, energy storage, electrochromic devices, sensing, analysis, and detection. In this paper, literature metrology and knowledge graph visualization analysis are adopted to analyze and summarize the literature data in the field of MOGs. The visualization maps of the temporal distribution, spatial distribution, authors and institutions' distribution, influence of highly cited literature and journals, keyword clustering, and research trends are helpful to clearly grasp the content and development trend of MOG materials research, point out the future research direction for scholars, and promote the practical application of MOGs. At the same time, the paper reviews the research and application progress of MOGs in recent years by combining keyword clustering, time lines, and emergence maps, and looks forward to their challenges, future development trend, and application prospects.

Facile synthesis of Pt/polyoxometalate/hollow carbon sphere tri-component nanoparticles via a "double gain strategy" for high-performance electrochemical sensing of adrenaline

In this study, we designed and successfully synthesized the Pt/polyoxometalate/hollow carbon sphere (Pt/POM/HCS) tri-component nanoparticles (NPs) by a pollution-free, efficient, and convenient method. HCSs with outstanding chemical stability and conductivity are self-generated by acid etching and calcination of silica spheres synthesized by a hard template method. HCSs have a hollow internal structure that provides specific three-dimensional storage space, and can increase the surface area. The mesoporous system is beneficial to providing numerous mass transfer passageways and immobilizing NPs. In addition, we introduced a "double gain strategy", by taking advantage of POMs as reducing and bridging agents, to achieve the loading of ultrafine Pt NPs on the surface of HCSs. Pt NPs have excellent stability and unique electrocatalytic activity. As a result of the synergistic effect of HCSs and ultrafine Pt NPs, the electrochemical sensing of adrenaline exhibits high-performance catalytic activity, sensitivity, suitable linearity range (0.16 μM-1.195 mM), and low limit of detection (57.5 nM, S/N = 3), excellent stability, and reproducibility. The developed platform is a sensitive and effective adrenaline electrical sensing platform with broad practical application prospects.

Recent advances in the development of europium(III) and terbium(III)-based luminescent supramolecular metallogels

In the recent past, special attention has been paid to the development of metallogels as novel luminescent materials from rationally designed gelators with lanthanide ions, especially europium (Eu(III)) and terbium (Tb(III)) metal ions. Lanthanide (Ln(III)) based metallogels possess various useful properties with an extensive range of applications in the field of advanced materials, and electronic and bio-technologies. Lanthanide ions in coordination with appropriate sensitizer ligands can reproduce metal-based optical, redox, and electronic properties in soft gel materials. The optical properties of the luminescent Ln(III) based metallogels can be tuned over the complete visible spectrum (400-750 nm) including the generation of white light by mixing both Eu(III) and Tb(III) with the ligand in various stoichiometric ratios. Additionally, the dynamic nature of the lanthanide-ligand (Ln-N) coordination bond allows the Ln(III) based metallogels to respond to various external stimuli. Luminescent self-healing supramolecular gels using organic ligands as 'hosts' and Ln(III) ions as 'guests' are also a current topic of research interest. In this review, we discuss and summarize some selected recent examples of newly developed luminescent Eu(III) and Tb(III) based supramolecular metallogels with potential applications in the fields of optoelectronic devices, stimuli responsiveness, self-healing, luminescent films, and sensors.

Schottky-functionalized Z-scheme heterojunction: Improved photoelectric conversion efficiency and immunosensing

Designing photovoltaic materials with good photoelectric activity is the crucial to boost the sensitivity of photoelectrochemical (PEC) biosensors. To meet this concern, a Schottky-functionalized direct Z-scheme heterojunction photovoltaic material was proposed by electrodeposition of gold nanoparticles on two kinds of bismuth oxyhalide composites surface (bismuth oxybromide and bismuth oxyiodide with different but matched band gaps) (depAu/BiOI/BiOBr). Specifically, synergistic effect was achieved through the direct Z-scheme heterojunction formed by BiOBr and BiOI as well as the gold Schottky junction, resulting in the enhanced light harvest and photoelectric conversion efficiency. Meanwhile, combined with sandwich immunotechnology, a "signal-off" PEC biosensor was fabricated for highly sensitive detection of carcinoembryonic antigen (CEA). In which, using depAu/BiOI/BiOBr modified glassy carbon electrodes both as the photoactive sensing interface and capture antibody loading matrix, polyethyleneimine copper complex encapsulated gold nanoclusters labeled detection antibody (Ab₂-Au@PEI-Cu) as the quencher, the photocurrent decreased with the increasing target CEA introduced by sandwich immune reaction. The proposed smart PEC immunoassay platform exhibited a wide detection range (1.0 fg/mL-2.0 ng/mL) and a detection limit as low as 0.11 fg/mL with favorable selectivity and stability. In addition, this PEC sensing strategy can be easily extended for other tumor marker analysis, which offers a new perspective of using multiple bismuth oxyhalide as photoactive materials for early diseases diagnosis.

Electrochemiluminescence nanoemitters for immunoassay of protein biomarkers

The family of electrochemiluminescent luminophores has witnessed quick development since the electrochemiluminescence (ECL) phenomenon of silicon nanoparticles was first reported in 2002. Moreover, these developed ECL nanoemitters have extensively been applied in sensitive detection of protein biomarker by combining with immunological recognition. This review firstly summarized the origin and development of various ECL nanoemitters including inorganic and organic nanomaterials, with an emphasis on metal-organic frameworks (MOFs)-based ECL nanoemitters. Several effective strategies to amplify the ECL response of nanoemitters and improve the sensitivity of immunosensing were discussed. The application of ECL nanoemitters in immunoassay of protein biomarkers for diagnosis of cancers and other diseases, especially lung cancer and heart diseases, was comprehensively presented. The recent development of ECL imaging with the nanoemitters as ECL tags for detection of multiplex protein biomarkers on single cell membrane also attracted attention. Finally, the future opportunities and challenges in the ECL biosensing field were highlighted.

Advanced Nanomaterials-Based Electrochemical Biosensors for Catecholamines Detection: Challenges and Trends

Catecholamines, including dopamine, epinephrine, and norepinephrine, are considered one of the most crucial subgroups of neurotransmitters in the central nervous system (CNS), in which they act at the brain's highest levels of mental function and play key roles in neurological disorders. Accordingly, the analysis of such catecholamines in biological samples has shown a great interest in clinical and pharmaceutical importance toward the early diagnosis of neurological diseases such as Epilepsy, Parkinson, and Alzheimer diseases. As promising routes for the real-time monitoring of catecholamine neurotransmitters, optical and electrochemical biosensors have been widely adopted and perceived as a dramatically accelerating development in the last decade. Therefore, this review aims to provide a comprehensive overview on the recent advances and main challenges in catecholamines biosensors. Particular emphasis is given to electrochemical biosensors, reviewing their sensing mechanism and the unique characteristics brought by the emergence of nanotechnology. Based on specific biosensors' performance metrics, multiple perspectives on the therapeutic use of nanomaterial for catecholamines analysis and future development trends are also summarized.

Highly Efficient PTCA/Co3O4/CuO/S2O82- Ternary Electrochemiluminescence System Combined with a Portable Chip for Bioanalysis

Herein, we reported an efficient electrochemiluminescence (ECL) biosensor chip for sensitive detection of neuron-specific enolase (NSE). First, 3,4,9,10-perylenetetracarboxylic acid with good luminescence characteristics was used as a luminophore to obtain a stable ECL signal. Subsequently, hollow porous Co₃O₄/CuO concave polyhedron nanocages (CPNCs) were designed as co-reaction promoters to amplify the luminescence signals for highly sensitive trace detection of NSE. In brief, the rapid cyclic conversion of Co³⁺/Co²⁺ and Cu²⁺/Cu⁺ redox pairs could continuously catalyze the reduction of persulfate (S₂O₈^2-), thus providing a large number of essential active intermediates (SO₄^•-) for ECL emission. Meanwhile, the unique structure of Co₃O₄/CuO CPNCs possessed a large specific surface area, which greatly improved its catalytic efficiency. Third, NKFRGKYKC was developed as an affinity ligand for specific antibody fixation, which improved incubation efficiency and protected bioactivity of antibodies. Finally, we independently designed a microchip and applied it for ECL detection to improve the practical application ability of the sensor. The developed biosensor exhibited good sensitivity with a wide linear range (10 fg/mL to 100 ng/mL) and a low detection limit (3.42 fg/mL), which played an active role in the clinical application of sensing analysis.

Facile synthesis of dual-ligand terbium-organic gels as ratiometric fluorescence probes for efficient mercury detection

Mercury (Hg) pollution can negatively impact ecosystems, and there is a need for simple Hg²⁺ monitoring platforms. Here, a dual-ligand fluorescence probe based on terbium-organic gels (Tb-L_0.2P_0.8 MOGs) was constructed for efficient Hg²⁺ detection. Tb-L_0.2P_0.8 MOGs were developed through a facile room-temperature gelation method, showing two emission peaks derived from luminol and Tb³⁺ at 424 nm and 544 nm, respectively. The aggregation-induced emission (AIE) effect between luminol and Tb³⁺ led to luminol with blue fluorescence. However, Hg²⁺ could dramatically quench the fluorescence signal of luminol at 424 nm because of the intense coordination interaction of Hg²⁺ with luminol and photo-induced electron transfer (PET). The Phen ligand could sensitize the luminescence of Tb³⁺ and offer a reference fluorescence, thus resulting in a unique ratiometric fluorescence response toward Hg²⁺. This novel nanoprobe had excellent linearity with Hg²⁺ concentrations range of 0.1-30 μM; the detection limit was 3.6 nM. The analysis of real samples showed the potential application of MOGs for measuring Hg²⁺ in porphyra and tap water. Mixed ligands were introduced for high-efficiency strategies to improve the analytical performance by regulating the emission behavior of MOGs.

Lanthanide Ce(III)/Tb(III) bimetallic coordination polymer as an advanced electrochemiluminescence emitter for epinephrine sensing application

By rationally introducing Ce(III) and Tb(III) into a coordination polymer (CP), a series of lanthanide bimetallic coordination polymers (Tb:Ce-BCPs) has been prepared in this work. Compared with pure Tb-CP and Ce-CP, bimetallic Tb:Ce-BCPs show stronger and more stable ECL intensity, which is mainly attributed to the "dual sensitization effect" combined with the energy transfer from Ce(III) to Tb(III) and the antenna effect from the ligand to the center atoms of Ce(III) and Tb(III). In the meantime, after explore the ECL intensity and morphologies of all these Tb:Ce-BCPs, the results show that the morphologies and ECL intensities of Tb:Ce-BCPs can be adjusted by doping different molar ratios of Ce(III) in Tb:Ce-BCP. Excitingly, Ce(III) can also act as a co-reaction accelerator, effectively promoting S₂O₈^2- to generate more SO₄^•-, thereby enhancing the ECL intensity of Tb:Ce-BCP. That is to say, Ce(III) plays a triple role in Tb:Ce-BCP. Furthermore, the ECL strength of Tb:Ce-BCP decreased by only 1.8% and 3.5%, respectively after the modified electrode was scanned for 800 s and stored for one month. Enlightened by the excellent ECL properties of Tb:Ce-BCP, we modified Tb:Ce-BCP directly on the surface of electrode, and explored its application in electroanalytical chemistry through the detection of epinephrine (EP) and the detection limit is 33 fmol L^-1. Significantly, our ECL sensing strategy promotes the application of lanthanides in ECL sensor and opens vast possibilities for the synthesis of a new generation of ECL emitter in electroanalytical fields.

Regulation of Ru(bpy)32+ Electrochemiluminescence Based on Distance-Dependent Electron Transfer of Ferrocene for Dual-Signal Readout Detection of Aflatoxin B1 with High Sensitivity

Ferrocene (Fc) is a common quencher of Ru(bpy)₃²⁺ luminescence. However, interactions between Fc and Ru(bpy)₃²⁺ can be extremely complicated. In this work, we reported the first use of Fc to regulate the electrochemiluminescence (ECL) of Ru(bpy)₃²⁺ by tuning the length of the DNA sequence between Fc and the luminophore of nitrogen-doped graphene quantum dots-Ru(bpy)₃²⁺-doped silica nanoparticles (SiO₂@Ru-NGQDs). The ECL of SiO₂@Ru-NGQDs was depressed when the distance between Ru(bpy)₃²⁺ and Fc was less than 8 nm; a stronger ECL was observed when the distance was more than 12 nm. The switching of the ECL of Ru(bpy)₃²⁺ by Fc was attributed to the electron transfer mechanism, in which Fc participated in the redox of Ru(bpy)₃²⁺ for "signal-off" ECL; this favored electron transfer at the electrode fabricated with an Fc-labeled aptamer (Fc-apt) and SiO₂@Ru-NGQDs for "signal-on" ECL depending on the length of the DNA sequence. Here, a dual-signal readout aptasensor for aflatoxin B1 (AFB1) detection was developed via the enhanced ECL of SiO₂@Ru-NGQDs by Fc-apt. The redox currents of Fc and the ECL of Ru(bpy)₃²⁺ were simultaneously collected as yardsticks, and both decreased with higher concentrations of AFB1. The aptasensor allowed linear ranges of 3 × 10^-5 to 1 × 10² ng mL^-1 for ECL mode and 1 × 10^-3 to 3 × 10³ ng mL^-1 for electrochemical mode. Our work provides insight into the interactions between Fc and Ru(bpy)₃²⁺. The dual-signal readout strategy is a potential platform for the versatile design of aptasensors.

An imine-linked covalent organic framework for renewable and sensitive determination of antibiotic

Lanthanide-functionalized porous organic materials have been the promising candidates in the chemical and biological sensing. Considering the superior thermal and solvent stability of covalent organic frameworks (COFs), the development of lanthanide ions-functionalized COFs based sensing platform is meaningful, while remains to be a challenge. In this work, a new imine-linked COF which provides suitable coordination sites for Tb³⁺ was constructed via the Schiff base reaction between P-phenylenediamine (Pda) and 2,6-Diformylpyridine (Dfp). Benefiting from its high signal-to-noise, the COF@Tb shows excellent ability to determinate ciprofloxacin (CIP) with a detection limit of 3.01 nM. The measurement can maintain good stability in the presence of potential interference or in actual sample. Being washed with ethanol after each measurement, COF@Tb can be recycled for five times. This work provides a novel alternative strategy for efficient construction of lanthanide-grafted COFs and may promote the development of porous organic materials based chemical sensing.

Gel-Based Luminescent Conductive Materials and Their Applications in Biosensors and Bioelectronics

The gel is an ideal platform for fabricating materials for bio-related applications due to its good biocompatibility, adjustable mechanical strength, and flexible and diversified functionalization. In recent decades, gel-based luminescent conductive materials that possess additional luminescence and conductivity simultaneously advanced applications in biosensors and bioelectronics. Herein, a comprehensive overview of gel-based luminescent conductive materials is summarized in this review. Gel-based luminescent conductive materials are firstly outlined, highlighting their fabrication methods, network structures, and functions. Then, their applications in biosensors and bioelectronics fields are illustrated. Finally, challenges and future perspectives of this emerging field are discussed with the hope of inspire additional ideas.

Construction of self-enhanced photoelectrochemical platform for L-cysteine detection via electron donor-acceptor type coumarin 545 aggregates

Self-enhanced electron donor-acceptor type coumarin 545 aggregates prepared via an anionic surfactant-assisted reprecipitation method provide an underlying approach for the photoelectrochemical detection of L-cysteine, which can be employed in aqueous solution without the addition of electron donors.

Novel Enhanced Lanthanide Electrochemiluminescence Luminophores: Ce3+-Doped TbPO4 Facile Synthesis and Detection for Mucin1

Despite the upsurging interest in electrochemiluminescence (ECL) of lanthanides, the research in this field is still in its infancy due to the low intensity. In this work, a series of Ce³⁺-doped terbium orthophosphates (TbPO₄:Ce) in different proportions have been synthesized through the co-precipitation method at room temperature. Meanwhile, through the investigation of morphologies and ECL properties of these TbPO₄:Ce, it is concluded that the ECL intensity reaches the maximum when the molar ratio of Tb/Ce is 9:1 and the material is nanorod-shaped. The ECL intensity of TbPO₄:Ce is significantly improved by doping with Ce³⁺ due to the dual sensitization strategy of the antenna effect from PO₄^3- to Tb³⁺ and the energy transfer from Ce³⁺ to Tb³⁺. Interestingly, doping with Ce³⁺ can not only adjust morphology of TbPO₄:Ce but also improve the ECL intensity. In addition, to verify the application of TbPO₄:Ce, two single mucin1 (MUC1) aptamers are linked together to form a dual MUC1 aptamer chain. Then, a simple and sensitive ECL biosensor is constructed for the detection of MUC1, which can recognize the double amount of MUC1 and quench the ECL signal. As expected, the proposed biosensor shows good stability and acceptable selectivity and achieves sensitive detection of MUC1 with a dynamic range from 1 fg·mL^-1 to 10 ng·mL^-1 and a limit of detection of 0.5 fg·mL^-1. This work may pave a new avenue for the study of direct ECL emission of lanthanides and prove to be ideal for the research of new ECL luminophores in electrochemical analysis.

Electrochemiluminescence properties and luminescence sensing of four novel polymers derived from 3-(pyrazin-2-yl)-1H-pyrazole-5-carboxylic acid

Four novel pyrazolate polymers with high efficiency electrochemiluminescence properties and potential cationic fluorescence sensoring property.