Electrochemiluminescence Enhancement Research Articles

Porphyrin-functionalized glutathione-Ti3C2 MXene quantum dots for enhanced electrochemiluminescence and sensitive detection of copper ions

Ti3C2 MXene quantum dots (MQDs) have recently gained considerable attention as promising emerging nanomaterials for biosensing applications. However, it is still in the infancy of research on the functionalisation of MQDs to improve their properties. This work synthesised glutathione (GSH)-modified MQDs by hydrothermal method and functionalised them with porphyrin (TMPyP4), resulting in porphyrin-functionalised GSH-Ti3C2 MXene quantum dots (MQDs-TMPyP4) nanocomposite with enhanced electrochemiluminescence (ECL) properties. The lack of selectivity of MQDs and the weak luminescence intensity of ECL have been solved, expanding the method for developing materials with enhanced ECL properties. Cu2+ was found to quench the ECL luminescence of MQDs-TMPyP4, which is valuable for detecting copper ions. Consequently, we constructed a sensitive “Signal on–off” biosensor for Cu2+ detection. The biosensor demonstrated a sensitive response to copper ions within the concentration range of 10 nM to 10 μM, with an impressively low detection limit of 3.22 nM. Additionally, the biosensor exhibited good stability and selectivity. The ECL biosensor performed well and provided an efficient and ultra-sensitive method for detecting Cu2+.

Silver Nanoparticles In Situ Enhanced Electrochemiluminescence of the Porphyrin Organic Matrix for Highly Sensitive and Rapid Monitoring of Tetracycline Residues.

Accurate monitoring of tetracycline (TC) residues in the environment is crucial for avoiding contaminant risk. Herein, a novel TC biosensor was facilely designed by integrating silver nanoparticles (Ag NPs) into the porphyrin metal-organic matrix (Ag@AgPOM) as a bifunctional electrochemiluminescence (ECL) probe. Different from the step-by-step synthesis of the co-reaction accelerator and ECL emitter, the co-reaction accelerators Ag NPs were in situ-grown on the surface of 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) via a simple one-pot approach. Symbiotic Ag NPs on Ag@AgPOM formed an intimate interface and increased the collision efficiency of the ECL reaction, achieving the ECL enhancement of TCPP. Under the optimized conditions, the ternary ECL biosensor showed a wide linear detection range toward TC with a low detection limit of 0.14 fmol L-1. Compared with the traditional HPLC and ELISA methods, satisfied analytical adaptability made this sensing strategy feasible to monitor TC in complex environmental samples.

Enhancing electrochemiluminescence for chloramphenicol detection based on the synergistic effect of doped Ti3C2 with ultrasound

Chloramphenicol (CAP) is known to be harmful to the environment and food, posing a threat to human health. Developing an effective and convenient method for detecting CAP is crucial. An electrochemiluminescence (ECL) biosensor has been designed for sensitive detection of CAP. The improved ECL behavior was attributed to the synergistic effect of N and P co-doped Ti3C2-Apt1 (N, P-Ti3C2-Apt1) nanoprobes and high intensity focused ultrasound (HIFU) pretreatment. The doping of N and P could improve the electrochemical performance of Ti3C2. HIFU pretreatment generated more reactive oxygen species (ROS) in the luminol-O2 system. N, P-Ti3C2 could aggregate and catalyze ROS, causing an increase in ECL intensity. Furthermore, N, P-Ti3C2 as a carrier loaded more aptamer, which could recognize CAP with high specificity. The detection limit was 0.01 ng/mL. This biosensor has been successfully applied in milk and environmental water samples, highlighting its potential in the field of food and environmental analysis.

Bimodal Oxidation Electrochemiluminescence Mechanism of Coreactant-Embedded Covalent Organic Frameworks via Postsynthetic Modification.

Electrochemiluminescence (ECL) efficiency is determined by charge transfer between coreactants and emitters in coreactant systems, which are usually limited by their slow intermolecular charge transfer. In this study, a covalent organic framework (COF) with aldehyde residue was synthesized, and then coreactants were covalently integrated into the skeleton through the postsynthetic modification strategy, resulting in a crystalline coreactant-embedded COF nanoemitter (C-COF). Compared to the pristine COF with an equivalent external coreactant, C-COF exhibited an extraordinary 1008-fold enhancement of ECL intensity due to the rapid intrareticular charge transfer. Significantly, with the pH increase, C-COF shows protonation-induced ECL enhancement for the first ECL peaked at +1.1 V and an opposite trend for the second ECL at +1.4 V, which were attributed to the antedating oxidation of coreactant in framework and COF self-oxidation, respectively. The resulting bimodal oxidation ECL mechanism was rationalized by spectral characterization and density functional theory calculations. The postsynthetic coreactant-embedded nanoemitters present innovative and universal avenues for advancing ECL systems.

Bimodal Oxidation Electrochemiluminescence Mechanism of Coreactant‐Embedded Covalent Organic Frameworks via Postsynthetic Modification

AbstractElectrochemiluminescence (ECL) efficiency is determined by charge transfer between coreactants and emitters in coreactant systems, which are usually limited by their slow intermolecular charge transfer. In this study, a covalent organic framework (COF) with aldehyde residue was synthesized, and then coreactants were covalently integrated into the skeleton through the postsynthetic modification strategy, resulting in a crystalline coreactant‐embedded COF nanoemitter (C–COF). Compared to the pristine COF with an equivalent external coreactant, C–COF exhibited an extraordinary 1008‐fold enhancement of ECL intensity due to the rapid intrareticular charge transfer. Significantly, with the pH increase, C–COF shows protonation‐induced ECL enhancement for the first ECL peaked at +1.1 V and an opposite trend for the second ECL at +1.4 V, which were attributed to the antedating oxidation of coreactant in framework and COF self‐oxidation, respectively. The resulting bimodal oxidation ECL mechanism was rationalized by spectral characterization and density functional theory calculations. The postsynthetic coreactant‐embedded nanoemitters present innovative and universal avenues for advancing ECL systems.

Fine tuning of porphyrin based-paddlewheel framework by imidazole derivative to boost electrochemiluminescence performance

Precise tuning the structure of catalytic center is of great importance for the construction of enhanced electrochemiluminescence (ECL) emitters and the development of ECL amplification strategies, which is a key factor in improving the sensitivity of biosensors. In this work, we report the enhanced ECL emitters based on the porphyrin-based paddlewheel framework (PPF) with axial coordinated imidazole-like ligands (PPF/X, X = 2-methylimidazole (MeIm), imidazole (Im), benzimidazole (BIM)). In this system, the electron-donating ability of the axial ligands is positively correlated to its coordination ability to the paddlewheel units and the catalytic ability of the axially coordinated paddlewheel units. In addition, the electrochemical and ECL behavior of PPF/X (X = MeIm, Im, BIM) with different axial coordinated ligands are explored.

Rigidifying AIEgens in covalent organic framework nanosheets for electrochemiluminescence enhancement: TABE-PZ-CON as a novel emitter for microRNA-21 detection

Enhancing electrochemiluminescence (ECL) properties of luminophores is a hot direction in the current ECL field. Herein, we found that covalent rigidification of the aggregation-induced emission luminogens (AIEgens) TABE (TABE = tetra-(4-aldehyde-(1,1-biphenyl))ethylene) into covalent organic framework nanosheets (TABE-PZ-CON, PZ = piperazine) could result in stronger ECL emission than those of TABE aggregates and TABE monomers. We termed the interesting phenomenon “covalent rigidification-triggered electrochemiluminescence (CRT-ECL) enhancement”. The superior ECL performance of TABE-PZ-CON not only because massive TABE luminogens were covalently assembled into the rigid TABE-PZ-CON network, which limited the intramolecular motions of TABE and hampered the radiationless transition, but also because the ultrathin porous TABE-PZ-CON significantly reduced the transportation distance of ions, electrons, and coreactants, which enabled the electrochemical excitation of more TABE luminogens and thus enhanced the ECL efficiency. Bearing in mind the exceptional ECL performance of TABE-PZ-CON, it was utilized as a high-efficient ECL indicator in combination with the DNA walker and duplex-specific nuclease-assisted target recycling amplification strategies to design an “off-on” ECL biosensor for the ultrasensitive assay of microRNA-21, exhibiting a favorable response range (100 aM–1 nM) with an ultralow detection limit of 17.9 aM. Overall, this work offers a valid way to inhibit the intramolecular motions of AIEgens for ECL enhancement, which gives a new vision for building high-performance AIEgen-based ECL materials, thus offering more chances for assembling hypersensitive ECL biosensors.

Synergistic Multieffect Catalytic Amplified Cathodic Electrochemiluminescence Biosensor via Target Binding-Induced Aptamer Conformational Changes for the Ultrasensitive Detection of Synthetic Cathinone.

Signal amplification is a powerful approach to increasing the detection sensitivity of electrochemiluminescence (ECL). Here, we developed synergistic multieffect catalytic strategies based on CuCo2O4 nanorod combination of Ag NPs as coreaction accelerators to fabricate an efficient covalent organic framework (PTCA-COF)-based ternary ECL biosensor. Concretely, the high redox reversibility of Co3+/Co2+ and Cu2+/Cu+ would constantly promote the decomposition of S2O82- for ECL emission. Meanwhile, the introduction of Ag NPs with excellent electrocatalytic activity further realized multiple amplification of the ECL signal. Furthermore, the good hydrogen evolution reaction (HER) ability of Ag@CuCo2O4 nanorods could accelerate the proton transmission rate of the system to amplify ECL behavior. In the presence of the target synthetic cathinone 4-chloroethcathinone (4-CEC) as the quenching ECL signal-response probe, the Ferrocene (Fc)-labeled aptamer folded into the conformationally limited stem-loop structure, bringing Fc near the ECL luminophore and resulting in quenched ECL emission. The quenching effect was connected with target-induced aptamer conformational changes and consequently reflected the target concentration. Under optimum conditions, the proposed biosensor realized a highly sensitive assay for 4-CEC with a large dynamic range from 1.0 × 10-12 to 1.0 × 10-6 g/L and a detection limit as low as 2.5 × 10-13 g/L. This study integrated multiple amplification strategies for efficient ECL enhancement, which provided a novel approach to constructing highly bioactive and sensitive sensors.

Novel Cu nanocluster superlattice/MBene-induced ECL enhancement strategy for miRNA-221 detection

In this paper, copper nanoclusters with superlative structure (Cu NCSL) were developed as luminescence probe for miRNA-221 detection. The tightly aligned superlattice structure of Cu NCSL effectively reduced the disordered and chaotic accumulation of nanoparticles, which further limited the intramolecular vibration and internal rotation of Cu NCs. Meanwhile, the compact particle stacking in the superlattice structure greatly improved the electron transport efficiency. As a result, the luminescence of Cu NCSL was enhanced greatly with the increase of radiation energy transfer rate. Furthermore, the two-dimensional MBene with good electrical conductivity and high electrochemical performance has been prepared as electrode modification material. In the constructed electrochemiluminescence (ECL) sensor for miRNA-221 detection, the ECL signal of Cu NCSL was amplified by the MBene nanosheets effectively. Finally, the results in the actual tumor tissues showed that the Cu NCSL/MBene-based biosensor has high selectivity, stability and low detection limit in the clinical cancer detection.

Near-infrared electrochemiluminescence of defect-rich molybdenum disulfide quantum dots for sensitive bioanalysis

Developing high-efficiency near-infrared (NIR) electrochemiluminescence (ECL) active transition metal dichalcogenides quantum dots (TMDs QDs) for spectroscopic multiplex analysis and biological imaging poses a significant challenge in versatile bioanalysis. In this work, we report a facile one-step hydrothermal method for the synthesis of defect-rich molybdenum disulfide quantum dots (MoS2 QDs). Because of the defect effect on the nanocrystalline surface, the MoS2 QDs exhibit enhanced fluorescence (quantum yield is 7.7%) in comparison with those from top-down physical approaches. Moreover, the defect-rich MoS2 QDs exhibit remarkable ECL performance using K2S2O8 as a coreactant, with a maximum emission at ∼810 nm. The ECL mechanisms of potential-dependent emission from MoS2 QDs were elucidated based on electrochemistry, photoluminescence, and spooling ECL spectroscopy. Leveraging the good biocompatibility and defect-induced ECL enhancement of MoS2 QDs, a sandwich ECL immunosensor was developed for carcinoembryonic antigen (CEA) detection. Without any signal amplification techniques, the proposed biosensor demonstrated a detection limit of 0.005 ng/mL CEA with a linear range from 0.005 ng/mL to 400 ng/mL, and a good selectivity and potential for real human serum analysis. The defect engineering of MoS2 QDs in this study provides guidance for regulating their optical properties and exploring new bioanalysis applications.

Enhancing electrochemiluminescence by modifying Fe3CuO4 and CdS@ZnS: A novel ECL sensor for highly sensitive detection of permethrin

A novel electrochemiluminescence (ECL) sensor was constructed for the detection of permethrin by modifying Fe3CuO4–Ru(bpy)32+ and GO-CdS@ZnS on the electrode. Fe3CuO4 was used as a carrier to adsorb more luminous reagent Ru(bpy)32+ to promote luminescence. Meanwhile, it also can be used as a co-reaction promoter to amplify the initial signal of Ru(bpy)32+-tri-n-propylamine (TPrA) system. When GO-CdS@ZnS was introduced into this system, the ECL signal was further enhanced. The porous nature of graphene oxide (GO) was utilized to load a large amount of CdS@ZnS, in which CdS@ZnS acted as the co-reactant to amplify the ECL signal. The amount of permethrin (PMT) increased and the ECL signal decreased. Under the optimum conditions, the ECL response was linearly related to the logarithm of PMT concentration. The developed ECL sensor allowed for sensitive determination of PMT and exhibited a wide linear range from 1.0 × 10−11 mol L−1 to 1.0 × 10−7 mol L−1. The limit of detection was 3.3 × 10−12 mol L−1 (S/N = 3). It can be used for the detection of PMT in vegetable samples.

T4PPVB-COP composite-driven innovative electrochemiluminescence aptasensor for ultra-sensitive detection of chlorpyrifos.

Herein, an enhanced electrochemiluminescence (ECL) aptasensor driven by a complex (T4PPVB-COP@CdS QDs) with large specific surface area and high stability was constructed for highly sensitive detection of chlorpyrifos (CPF), using electrostatic interactions and signal amplification techniques. In the presence of CPF, the specific binding between the aptamer and CPF caused partial detachment of the aptamer from the sensor, thus restoring the ECL signal. Notably, gold nanoparticles functionalized with streptavidin (SA) as signal enhancers further amplified the ECL signal in specific interactions with aptamers, thereby improving the sensitivity of the assay. Based on this, the proposed ECL aptasensor demonstrated significant detection performance for CPF with a linear range of 1-107pg/mL and a LOD of 0.34pg/mL. Furthermore, the feasibility of the ECL aptasensor was validated by the detection and analysis of CPF in real samples, which also provided a broad reference value for bioanalysis.

An electrochemiluminescence sensor based on CsPbBr3 -zquantum dots and poly (3-thiophene acetic acid) cross-linked nanogold imprinted layer for the determination of benzo(a)pyrene in edible oils.

A novel quench molecularly imprinted electrochemiluminescence sensor (MIECLS) based on a covalent organic framework composite (COF-300-Au) with enhanced electrochemiluminescence (ECL) signal from CsPbBr3 quantum dots and cross-linked 3-thiopheneacetic acid functionalized AuNPs (3-TAA@AuNPs) was developed for the detection of the environmental pollutant benzo(a)pyrene (BaP). A composite material constructed of COF-300-Au with a large specific surface area served as the sensor's support substrate, providing more CsPbBr3 and imprint recognition sites. Electropolymerization was then employed to form an AuNPs three-dimensional imprinting layer with polythiophene cross-linked using BaP as a template and 3-TAA@AuNPs as a functional monomer. A specific cross-linked imprinting recognition effect was recorded on BaP along with the quenching effect of quinones. The density functional theory (DFT) evaluation of the binding mechanism between 3-TAA@AuNPs and BaP revealed powerful MIECLS toward the detection of BaP at concentrations ranging from 10-14 to 10-5M, with a detection limit of as low as 4.1×10-15 M.

Aggregation-induced electrochemiluminescence enhancement of Ag-MOG for amyloid β 42 sensing

This study aimed to introduce an immunosensor for measuring amyloid β 42 (Aβ42) levels by aggregation-induced enhanced electrochemiluminescence (ECL). Metal–organic gels (MOGs) are novel soft materials with advantages such as high gel stability, good light-emitting properties, and easy preparation. This study used silver nanoparticle metal–organic gel (Ag-MOG) as a substrate to connect Aβ42-Ab2 and the cathodoluminescent probe. Potassium persulfate was used as a co-reactant that could emit a high ECL signal. CuS@Au had the benefits of a relatively large surface area with excellent carrier function; therefore, it was used as a substrate to load a large amount of Aβ42-Ab1, significantly improving the immunosensor sensitivity. The ECL intensity of Aβ42 was linear in the range of 0.01 pg/mL to 250 ng/mL with a detection limit of 2.2 fg/mL (S/N = 3) under optimized detection conditions. This ECL immunosensor has been successfully applied to detect Aβ42 in human serum with the advantages of excellent stability and high selectivity. This method not only expands the potential applications of ECL immunosensors based on biological testing and clinical diagnosis but also provides a viable approach to basic clinical testing.

Electrocatalytic regulation of electrochemiluminescence: Mechanisms and sensing strategies

Electrocatalysis (EC) can reduce the overpotential and promote electrochemical reactions, leading to improved energy conversion, and electrochemiluminescence (ECL) is a convenient energy output. However, fundamental understanding of the relationship between EC and ECL performance has been very limited, hindering rational improvement and effective applications. Herein, as a proof of concept, we developed a model system composed of multi-walled carbon nanotubes (MWCNTs) as a catalyst, 6-aza-2-thiothymine protected gold nanoclusters (ATT-AuNCs) as luminophore, and tripropylamine (TPA) as coreactant, to evaluate the electrocatalytic effect on ECL by kinetic analysis of electrocatalytic reactions. A dual EC-mediated ECL enhancement was demonstrated in this system. The catalytically active sites were identified to be the carboxyl groups in the MWCNTs. We also discovered that EC could be tuned by other factors, such as wettability. Our findings were supported by density functional theory and molecular dynamics calculations as well. After understanding the EC mechanism, EC was then used to rationally regulate ECL for biosensor development for the first time. The detection of arginase with a record low limit of detection of 1.6 × 10−7 U mL−1 was achieved. This work not only enriches ECL regulation strategies, but also paves a new avenue for engineering EC guided ECL and devices.

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 0.01-1μM range, and the detection limit is 7.35nM. 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.

Aggregation-Induced Enhanced Electrochemiluminescence from Tris(bipyridine)ruthenium(II) Derivative Nanosheets for the Ultrasensitive Detection of Human Telomerase RNA.

The traditional tris(bipyridine)ruthenium(II) complex suffers from the notorious aggregation-caused quenching effect, which greatly compromises its electrochemiluminescence (ECL) efficiency, thus hindering further applications in biosensing and clinical diagnosis. Here, the ultrathin tetraphenylethylene-active tris(bipyridine)ruthenium(II) derivative nanosheets (abbreviated as Ru-TPE NSs) are synthesized through a protein-assisted self-assembly strategy for ultrasensitive ECL detection of human telomerase RNA (hTR) for the first time. The synthesized Ru-TPE NSs exhibit the aggregation-induced enhanced ECL behavior and excellent water-dispersion. Surprisingly, up to a 106.5-fold increase in the ECL efficiency of Ru-TPE NSs is demonstrated compared with the dispersed molecules in an organic solution. The restriction of intramolecular motions is confirmed to be responsible for the significant ECL enhancement. Therefore, this proposed ECL biosensor shows high sensitivity and excellent selectivity for hTR based on Ru-TPE NSs as efficient ECL beacons and the catalytic hairpin assembly as signal amplification, whose detection limit is as low as 8.0fm, which is far superior to the previously reported works. Here, a promising analytical method is provided for early clinical diagnosis and a new type of efficient ECL emitters with great application prospects is represented.

Synergistic enhancement of electrochemiluminescence through hybridization of α-Ge nanolayers and gold nanoparticles for highly sensitive detection of tyramine

This work presents a novel approach for detecting biogenic amine tyramine using a sensitive and disposable electrochemiluminescent sensor. The sensor is fabricated by modifying a screen-printed carbon electrode surface with two nanomaterials, α-Ge nanolayers and AuNP, which synergistically enhance the electrochemiluminescence response. The sensor was characterized using various techniques such as SEM-EDX, EIS, Raman, and AFM. The principle of the biosensor relays on the fact that tyramine molecule acts as an analyte and co-reactant, which interacts with the luminophore [Ru(bpy)3]2+ on the sensor surface. The proposed sensor shows a linear response to tyramine concentration, with a detection limit of 2.28 µM. The sensor successfully detected tyramine in avocado samples, demonstrating its potential for practical applications.

Bright dual‐color electrochemiluminescence of a structurally determined Pt1Ag18 nanocluster

AbstractMetal nanoclusters possess excellent electrochemical, optical, and catalytic properties, but correlating these properties remains challenging, which is the foundation to generate electrochemiluminescence (ECL). Herein, we report for the first time that a structurally determined Pt1Ag18 nanocluster generates intense ECL and simultaneously enhances the ECL of carbon dots (CDs) via an electrocatalytic effect. Pt1Ag18 nanocluster show aggregation‐induced emission enhancement and aggregation‐induced ECL enhancement under light and electrochemical stimulation, respectively. In the presence of tripropylamine (TPrA) as a coreactant, solid Pt1Ag18 shows unprecedented ECL efficiency, which is more than nine times higher than that of 1 mM Ru(bpy)32+ with the same TPrA concentration. Potential‐resolved ECL spectra reveal two ECL emission bands in the presence of TPrA. The ECL emission centered at 650 nm is assigned to the solid Pt1Ag18 nanocluster, consistent with the peak wavelength in self‐annihilation ECL and photoluminescence of the solid state. The ECL emission centered at 820 nm is assigned to the CDs on the glassy carbon electrode. The electrocatalytic effect of the nanoclusters enhanced the ECL of the CDs by a factor of more than 180 in comparison to that without nanoclusters. Based on the combined optical and electrochemical results, the ECL generation pathways and mechanisms of Pt1Ag18 and CDs are proposed. These findings are extremely promising for designing multifunctional nanocluster luminophores with strong emissions and developing ratiometric sensing devices.

Framework-Enhanced Electrochemiluminescence in Biosensing

Electrochemiluminescence (ECL) has attracted increasing attention owing to its intrinsic advantages of high sensitivity, good stability, and low background. Considering the fact that framework nanocrystals such as metal–organic frameworks and covalent organic frameworks have accurate molecular structures, a series of framework-based ECL platforms are developed for decoding emission fundamentals. The integration of fluorescent ligands into frameworks significantly improves the ECL properties due to the arrangement of molecules and intramolecular electron transfer. Moreover, the various framework topologies can be easily functionalized with the recognition elements to trace the targets for signal readout. These ECL enhancement strategies lead to a series of sensitive analytical methods for protein biomarkers, DNA, small biomolecules, and cells. In this review, we summarize recent advances in various functions of frameworks during the ECL process, and constructions of framework-based ECL platforms for biosensing. The framework-based ECL nanoemitters and enhancement mechanisms show both theoretical innovation and potential applications in designing ECL biosensing systems. Perspectives are also discussed, which may give a guideline for researchers in the fields of ECL biosensing and reticular materials.