Schiff Base Complexes with Covalently Anchored Luminophores: Self-Enhanced Electrochemiluminescence Detection of Neomycin

Signal Enhancement of Luminol-Based Electrochemiluminescence Systems and Their Applications

Electrochemiluminescence (ECL) has emerged as a powerful analytical tool owing to its low background, high sensitivity, and wide dynamic range. Luminol, a commonly used ECL emitter, is widely applied in ECL-based analysis due to its low triggering potential, cost-effectiveness, and low toxicity. Despite the significant advantages of the luminol ECL system, its relatively low luminescence efficiency limits its application in high-sensitivity detection. As a result, numerous strategies have been proposed to enhance the luminol ECL signal intensity. This review summarizes four typical ECL signal amplification strategies and analyzes their roles in improving the effectiveness of luminol-based ECL signals. Furthermore, the applications of luminol ECL in fields such as sensing, imaging analysis, and material characterization are discussed. Finally, the future research directions and potential applications of the luminol ECL system are highlighted.

Efficient Separation-Free and Wash-Free Immunoassay for Sensitive Detection of Biomarkers Based on the Distance-Driven Chemiluminescent Technique

The wash-free method represents a promising strategy for enhancing the detection efficiency of automated chemiluminescent (CL) immunoassay analyzers. Herein, a novel separation-free and wash-free immunoassay was developed for the first time based on the distance-driven CL technique. In the CL immunoassay, the well-designed Au-Co metal nanoclusters (NCs) exhibited excellent peroxidase-like activity and good stability, allowing for efficient catalysis of luminol or its analogue (ABEI)-H2O2 system even at low concentrations. Furthermore, the large specific surface area of Au-Co NCs facilitated the accommodation of a greater number of antibodies, thereby enhancing the capture of antigens and achieving dual amplification of the CL signal. The distance-driven CL technique relied on the formation of sandwich-type immunocomplexes. Upon the generation of hydroxyl radicals and superoxide anion radicals through the catalytic decomposition of H2O2 by Au-Co NCs, the ABEI within sandwich-type immunocomplexes could efficiently react with these radicals, leading to a significant enhancement in CL signals. Furthermore, C-reactive protein (CRP) was chosen as the model analyte to evaluate the practicability of the proposed immunoassay. Notably, the proposed immunoassay presented high sensitivity, selectivity, reproducibility, and stability, successfully determining CRP in serum samples with recoveries of 96.55-106.29%. Accordingly, the proposed strategy with the advantage of separation-free, wash-free, and reliable characteristics could drastically simplify the detection operation steps and enhance the detection efficiency, which would make significant advances in the revolution of traditional CL immunoassay.

Electron effect regulation: A study on the influence of electron-donating and withdrawing group modification on the performance of metal-coordinated catalysts for electrochemical carbon dioxide reduction

Electron effect regulation is a crucial factor influencing the activity and selectivity of Cu-based coordination compound catalysts in the electrochemical carbon dioxide reduction reaction (CO2RR). Despite significant progress, the structure-activity relationship and the underlying regulatory mechanisms warrant further in-depth investigation. In this study, three types of Cu-[ONNO] tetradentate coordination molecular catalysts with varying electron densities, namely Cu-N2O2, methoxy-modified Cu-N2O2 (Cu-EDG-N2O2), and nitro-modified Cu-N2O2 (Cu-EWG-N2O2), were prepared using a substituent regulation strategy. The prepared catalyst's micromorphology and structural characteristics were analyzed using various characterization methods. Systematic electrocatalytic CO2RR experiments were conducted to evaluate the performance of these catalysts. Compared to the unmodified Cu-N2O2, the Cu-EDG-N2O2 catalyst exhibited superior reduction performance for CH4 and C2H4 products. At an applied potential of -1.7 V vs. the reversible hydrogen electrode, the Faradaic efficiencies for CH4 and C2H4 of Cu-EDG-N2O2 were 37.8 ± 2.2 % and 25.0 ± 0.5 %, respectively. In contrast, the Cu-EWG-N2O2 catalyst demonstrated higher activity towards the production of H2 as a by-product. The effects of electronic properties of substitutions on catalyst performance were revealed by combining experimental characterization and theoretical simulation. The results showed that the conjugation effect of the -OCH3 group facilitates faster electron transfer between Cu and CO2, thereby enhancing CO2RR activity. Additionally, the introduction of different substituents modulates the local microenvironment around the Cu active centers, significantly influencing the catalytic performance. This study provides valuable theoretical and experimental insights into the design of efficient Cu-N2O2-type metal coordination electrocatalysts for CO2RR processes.

Boron Ligands Boosting the Electrochemiluminescence Performance of Europium Metal-Organic Frameworks by Facilitating the Electronic Bridging

For optimal energy transfer in self-luminous lanthanide metal-organic frameworks (Ln-MOFs), the energy of the lowest triplet excited state must align with ideal energy levels. Failure to meet this condition can lead to reverse energy transfer, reducing luminous efficiency. In this study, we developed a mixed-ligand MOF, Eu-TCPP-BOP, which exists as an ECL self-enhancing luminophore. We used SPECM to study the role of boron ligands as a bridge for electron transport in improving the ECL performance of Eu-TCPP. The ligands H4TCPP and 5-BOP act as electron donor and shuttle, facilitating electron transport during the synthesis of Eu-TCPP-BOP and promoting energy transfer to the excited state of the acceptor Ln3+, thus enhancing overall energy transfer in Ln-MOF. The results indicate that the introduction of boron ligands enhances the ECL intensity of Eu-TCPP by a factor of 1.4 under voltage excitation. As an ECL sensing platform, it demonstrates high sensitivity and selectivity for the detection of catechol, with a concentration range of 1∼70 μM and a detection limit of 0.35 μM.

Oxygen Activation Biocatalytic Precipitation Strategy Based on a Bimetallic Single-Atom Catalyst for Photoelectrochemical Biosensing

The traditional biocatalytic precipitation (BCP) strategy often required the participation of H2O2, but H2O2 had the problem of self-decomposition, which prevented its application in quantitative analysis. This work first found that a bimetallic single-atom catalyst (Co/Zn-N-C SAC) could effectively activate dissolved O2 to produce reactive oxygen species (ROS) due to its superior oxidase (OXD)-like activity. Experimental investigations demonstrated that Co/Zn-N-C SAC preferred to produce highly active hydroxyl radicals (•OH), which oxidized 3-amino-9-ethyl carbazole (AEC) to produce reddish-brown insoluble precipitates. Based on this property, a unique oxygen-activated photoelectrochemical (PEC) biosensor was developed for chloramphenicol (CAP) detection. Cesium platinum bromide nanocrystals (Cs2PtBr6 NCs) were a new type of halide perovskite with lead-free, narrow band gaps, and water-oxygen resistance. Cs2PtBr6 NCs showed excellent cathodal PEC performance without an exogenous coreactant and were first used for PEC detection. As a "proof-of-concept application", Co/Zn-N-C SAC was introduced onto the surface of Cs2PtBr6 NCs by using the CAP dual-aptamer sandwich strategy. Co/Zn-N-C SAC activated dissolved O2 to produce ROS, which oxidized AEC to produce precipitates, quenching the cathodal PEC signal of Cs2PtBr6 NCs for CAP detection. In summary, this work first used SAC to overcome the restriction of the traditional enzymatic BCP strategy requiring H2O2, improved the stability and accuracy of quantitative analysis, and also broadened the application range of coreactant-free perovskite-type PEC biosensors.

Novel Dual-Potential Color-Resolved Luminophore Ru(bpy)32+-Doped CdSe QDs for Bipolar Electrode Electrochemiluminescence Biosensing

The classical electrochemiluminescence (ECL) reagent Ru(bpy)32+ was first doped into CdSe QDs to prepare novel dual-potential color-resolved luminophore Ru-CdSe QDs. Ru-CdSe QDs emitted a strong red ECL signal at a positive potential with coreactant TPrA and a strong green ECL signal at a negative potential with coreactant K2S2O8. As a proof-of-concept application, this work introduced Ru-CdSe QDs into a dual-channel closed bipolar electrode (CBPE) system to construct an ECL biosensor for simultaneous detection of chloramphenicol (CAP) and kanamycin (KAN). Ru-CdSe QDs were dropped on BPE holes A and B for ECL emission. Cobalt single-atom catalysts (Co-N-C SACs) had superior electric double layer (EDL) performance and conductivity. It could greatly promote the electron transfer of the CBPE system and realize ECL signal amplification. Based on this characteristic, Co-N-C SACs were introduced into BPE hole C and driving electrode hole D, respectively, using the CAP and KAN split dual-aptamer sandwich strategy. During positive potential scanning, the polarity of BPE hole A was anode, and Ru-CdSe QDs emitted a red ECL signal. With the increase of CAP concentration, abundant Co-N-C SACs were introduced to the electrode surface. The positive potential ECL signal was increased for CAP detection. During negative potential scanning, the polarity of the BPE hole B was cathode, and Ru-CdSe QDs emitted a green ECL signal for KAN detection. Finally, a zero-background spatial-potential color-resolved CBPE-ECL biosensor was developed for dual-mode detection of CAP and KAN. This work explored a novel ECL luminophore to construct a CBPE-ECL sensor, which greatly facilitated the development of the ECL assay.

Self-Powered Electrochemiluminescence for Imaging the Corrosion of Protective Coating of Metal and Quantitative Analysis

In almost all electrochemical systems for electrochemiluminescence (ECL) analysis, electrodes are connected with an external power source, either directly or via wireless energy transfer circuit. That is inconvenient and makes some applications impossible. Herein, we use galvanized iron with two different metals as both power source and electrodes to achieve a self-powered ECL and exploit ECL for the imaging of the corrosion of protective coating of widely used metal (e.g. galvanized iron) for the first time. The self-powered ECL enables the visualization of the deterioration of galvanic coating on iron using a smartphone and the detection of ascorbic acid with a linear range of 0.5-100 μM and a limit of detection of 0.31 μM. The devices based on self-powered approach do not require external power supply, thus effectively reducing their volume and cost. The self-powered ECL holds great promise for metal corrosion imaging and analytical applications.

Study on the Electrochemiluminescence Emission Mechanism of HOF-14 and Its Multimode Sensing and Imaging Application

A novel hydrogen-bonded organic framework (HOF-14) has attracted much attention due to its excellent biocompatibility and low toxicity, but its research in the electrochemiluminescence (ECL) field has not been reported. In this work, the annihilation-type and coreactant-type ECL emission mechanisms of HOF-14 were studied systematically for the first time. It was found that the ECL quantum efficiency of HOF-14/TEA coreactant system was the highest, which was 1.82 times that of Ru(bpy)32+/TEA. Further, the ECL emission intensity of HOF-14/TEA system could achieve colorimetric (CL) imaging of mobile phone. We also discovered that HOF-14 had superior photoelectrochemical (PEC) performance. Based on the above research results, a unique HOF-14-based multimode sensing and imaging platform was constructed. The antibiotic Enrofloxacin (ENR) was selected as the detection target, and the Cu-Zn bimetallic single-atom nanozyme (Cu-Zn/SAzyme) with excellent peroxidase (POD)-like activity was used to prepare quenching probes. When the target ENR was present, Cu-Zn/SAzyme quenching probes were introduced to the surface of HOF-14 by the dual-aptamer sandwich method. Cu-Zn/SAzyme could catalyze diaminobenzidine (DAB) to produce brown precipitations to quench the ECL, PEC, and CL signals of HOF-14, realizing multimode detection of ENR. This work not only discovered excellent ECL and PEC property of new HOF-14 material but also systematically studied the ECL emission mechanism of HOF-14, and proposed a novel multimode sensing and imaging platform, which greatly improved the detection accuracy of target and showed great contributions to the field of ECL analysis.

Metal-organic framework-based aptasensor utilizing a novel electrochemiluminescence system for detecting acetamiprid residues in vegetables

The work was based on N-(4-Aminobutyl)-N-ethylisoluminol (ABEI)-functionalized Fe-MIL-101 and gold nanoparticles (AuNPs) as sensing materials, and an electrochemiluminescence (ECL) aptasensor was constructed for detecting acetamiprid. As a metal-organic framework (MOF) material, Fe-MIL-101, was renowned for its unique three-dimensional network structure and efficient catalytic capability. ABEI, a common ECL reagent, was widely applied. ABEI was introduced into the Fe-MIL-101 structure as a luminescence functionalization reagent to form Fe-MIL-101@ABEI. This approach avoided limitations on the loading capacity of luminescent reagents imposed by modification and encapsulation methods. With character of excellent catalytic activity and ease of bioconjugation, AuNPs offered significant advantages in biosensing. Leveraging the reductive properties of ABEI, AuNPs were reduced around Fe-MIL-101@ABEI, resulting in the modified luminescent functionalized material denoted as Fe-MIL-101@ABEI@AuNPs. An aptamer was employed as a recognition element and was modified accordingly. The aptamer was immobilized on Fe-MIL-101@ABEI@AuNPs through gold-sulfur (Au-S) bonds. After capturing acetamiprid, the aptamer induced a decrease in the ECL signal intensity within the ABEI-hydrogen peroxide (H2O2) system, enabling the quantitative detection of acetamiprid. The aptasensor displayed remarkable stability and repeatability, featured a detection range of 1×10-3-1×102 nM, and had a limit of detection (LOD) of 0.3 pM (S/N=3), which underscored its substantial practical application potential.

Metal-Organic Framework-Derived High-Entropy Oxides as Coreaction Accelerators for an Efficient Luminol/Dissolved Oxygen Electrochemiluminescence System for Ultrasensitive Mercury Detection

The development of luminol-dissolved O2 (luminol-DO) electrochemiluminescence (ECL) systems is crucial for real-world applications. Despite its stability and low biotoxicity, luminol-DO ECL systems struggle with low ECL performance due to their low reactivity. Investigating new materials like coreactant accelerators increases reactive oxygen species (ROS) formation and enhances luminol-DO ECL intensity. Motivated by the ROS-mediated ECL process, for the first time, we designed oxygen vacancy (OV)-rich high-entropy oxides (HEO) with five metal components [(FeCoNiCuZn)O] derived from metal-organic frameworks (MOFs) as coreaction accelerators to establish efficient luminol-DO ECL systems. High entropy (HE) MOFs were annealed at four different temperatures (600, 700, 800, and 900 °C). Indeed, the HE MOFs annealed at 800 °C (HEO-800) showed a 120-fold stronger ECL intensity compared to the bare glassy carbon electrode in the luminol-DO ECL system. The enhanced ECL performance can be attributed to the porous structure, unique morphology, heterostructures, high-density active sites, rich OV, unsaturated metals, and synergistic impact, which act as catalysts to accelerate the conversion of DO to ROS. The developed HEO-800-based luminol-DO ECL system can be effectively used for the high-sensitivity detection of mercury ions (Hg2+). The system detected Hg2+ over a wide concentration range from 0.1 nM to 100 μM, with a detection limit of 0.02 nM. The sensing mechanism relied on high-affinity metallophilic Hg2+-HEO-800 interactions, effectively quenching the ECL intensity of the luminol-DO/HEO-800 ECL system. The ECL sensing platform, developed without H2O2, offers a novel method for detecting substances, demonstrating significant potential for clinical diagnosis and biomarker analysis.

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.

A novel self-enhanced ECL-RET aptasensor based on the bimetallic MOFs with homogeneous catalytic sites for kanamycin detection

The inappropriate use of antibiotics undoubtedly poses a potential threat to public health, creating an increasing need to develop highly sensitive tests. In this study, we designed a new type of porphyrin metal-organic frameworks (Fe TCPP(Zn) MOFs) with homogeneous catalytic sites. The ferric-based metal ligands of Fe TCPP(Zn) MOFs acted as co-reaction accelerators, which effectively improved the conversion efficiency of H2O2 on the surface of MOFs, then increased the concentration of •OH surrounding porphyrin molecules to achieve self-enhanced electrochemiluminescence (ECL). Based on this, an aptasensor for the specific detection of kanamycin (KAN) in food and environmental water samples was constructed in combination with resonance energy transform (RET), in which Fe TCPP(Zn) MOFs were used as luminescence donor and AuNPs were used as acceptor. Under the best conditions, there was a good linear relationship between the ECL intensity and the logarithm of KAN concentration with a detection limit of 0.28 fM in the range of 1.0 × 10-7-1.0 × 10-13 M, demonstrating satisfactory selectivity and stability. At the same time, the complexity of the detection environment was reduced, which further realized the reliable analysis of KAN in milk, honey and pond water. Overall, this innovative self-enhanced ECL strategy provides a novel approach for constructing efficient ECL systems in MOFs, and also extends the application of MOFs to the analysis and detection of trace antibiotics in food and the environment.

Spatial-Potential-Color-Resolved Bipolar Electrode Electrochemiluminescence Biosensor Using a CuMoOx Electrocatalyst for the Simultaneous Detection and Imaging of Tetracycline and Lincomycin

A spatial-potential-color-resolved bipolar electrode electrochemiluminescence biosensor (BPE-ECL) using a CuMoOx electrocatalyst was constructed for the simultaneous detection and imaging of tetracycline (TET) and lincomycin (LIN). HOF-101 emitted peacock blue light under positive potential scanning, and CdSe quantum dots (QDs) emitted green light under negative potential scanning. CuMoOx could catalyze the electrochemical reduction of H2O2 to greatly increase the Faradic current of BPE and realize the ECL signal amplification. In channel 1, CuMoOx-Aptamer II (TET) probes were introduced into the BPE hole (left groove A) by the dual aptamer sandwich method of TET. During positive potential scanning, the polarity of BPE (left groove A) was negative, resulting in the electrochemical reduction of H2O2 catalyzed by CuMoOx, and the ECL signal of HOF-101 was enhanced for detecting TET. In channel 2, CuMoOx-Aptamer (LIN) probes were adsorbed on the MXene of the driving electrode (DVE) hole (left groove B) by hydrogen-bonding and metal-chelating interactions. LIN bound with its aptamers, causing CuMoOx to fall off. During negative potential scanning, the polarity of DVE (left groove B) was negative and the Faradic current decreased. The ECL signal of CdSe QDs was reduced for detecting LIN. Furthermore, a portable mobile phone imaging platform was built for the colorimetric (CL) detection of TET and LIN. Thus, the multiple mode-resolved detection of TET and LIN could be realized simultaneously with only one potential scan, which greatly improved detection accuracy and efficiency. This study opened a new technology of BPE-ECL sensor application and is expected to shine in microchips and point-of-care testing (POCT).

Ternary electrochemiluminescence quenching effects of CuFe2O4@PDA-MB towards self-enhanced Ru(dcbpy)32+ functionalized 2D metal-organic layer and application in carcinoembryonic antigen immunosensing

BACKGROUND

Carcinoembryonic antigen (CEA) is a significant glycosylated protein, and the unusual expression of CEA in human serum is used as a tumor marker in the clinical diagnosis of many cancers. Although scientists have reported many ways to detect CEA in recent years, such as electrochemistry, photoelectrochemistry, and fluorescence, their operation is complex and sensitivity is average. Therefore, finding a convenient method to accurately detect CEA is significance for the prevention of malignant tumors. With high sensitivity, quick reaction, and low background, electrochemiluminescence (ECL) has emerged as an essential method for the detection of tumor markers in blood.

RESULTS

In this work, a "signal on-off" ECL immunosensor for sensitive analysis of CEA ground on the ternary extinction effects of CuFe2O4@PDA-MB towards a self-enhanced Ru(dcbpy)32+ functionalized metal-organic layer [(Hf)MOL-Ru-PEI-Pd] was prepared. The high ECL efficiency of (Hf)MOL-Ru-PEI-Pd originated from the dual intramolecular self-catalysis, including intramolecular co-reaction between polyethylenimine (PEI) and Ru(dcbpy)32+. At the same time, loading Pd NPs onto (Hf)MOL-Ru-PEI could not only improve the electron transfer ability of (Hf)MOL-Ru-PEI, but also provide more active sites for the reaction of Ru(dcbpy)32+ and PEI. In the presence of CEA, CuFe2O4@PDA-MB-Ab2 efficiently quenches the excited states of (Hf)MOL-Ru-PEI-Pd by PDA, Cu2+, and methylene blue (MB) via energy and electron transfer, leading to an ECL signal decrease. Under optimal conditions, the proposed CEA sensing strategy showed satisfactory properties ranging from 0.1 pg mL-1 to 100 ng mL-1 with a detection limit of 20 fg mL-1.

SIGNIFICANCE

The (Hf)MOL-Ru-PEI-Pd and CuFe2O4@PDA-MB were prepared in this work might open up innovative directions to synthesize luminescence-functionalized MOLs and effective quencher. Besides, the ECL quenching mechanism of Ru(dcbpy)32+ by MB was successfully explained by the inner filter effect (ECL-IFE). At last, the proposed immunosensor exhibits excellent repeatability, stability, and selectivity, and may provide an attractive way for CEA and other disease markers determination.

High-Density N-Vacancy-Induced Multipath Electrochemiluminescence Improvement of 3D g-C3N4 for Ultrasensitive MiRNA-222 Analysis

Using dissolved O₂ as the cathodic co-reactant of three-dimensional (3D) g-C₃N₄ is a convenient method to improve the electrochemiluminescence (ECL) signal, but it still suffers the disadvantages of limited luminous efficiency of 3D g-C₃N₄ and low content, low reactivity, and instability of dissolved O₂. Here, N vacancy with high density was first introduced into the structure of 3D g-C₃N₄ (3D g-C₃N₄-NV), which could conveniently realize multipath ECL improvement by simultaneously solving the above shortcomings effectively. Specifically, N vacancy could change the electronic structure of 3D g-C₃N₄ to broaden its band gap, increase fluorescence (FL) lifetime, and accelerate electron transfer rate, obviously improving the luminous efficiency of 3D g-C₃N₄. Meanwhile, N vacancy made the excitation potential of 3D g-C₃N₄-NV to shift from -1.3 to -0.6 V, effectively weakening the electrode passivation. Moreover, the adsorption capacity of 3D g-C₃N₄-NV was obviously enhanced, which could make the dissolved O₂ enrich around 3D g-C₃N₄-NV. And massive active NV sites of 3D g-C₃N₄-NV could promote O₂ to more efficiently convert to reactive oxygen species (ROS) that were key intermediates in ECL generation. Using the newly proposed 3D g-C₃N₄-NV-dissolved O₂ system as an ECL emitter, an ultrasensitive target conversion biosensor was constructed for miRNA-222 detection. The fabricated ECL biosensor exhibited satisfactory analytical performance for miRNA-222 with a detection limit of 16.6 aM. The strategy achieved multipath ECL improvement by introducing high-density N vacancy simply in the 3D structure of g-C₃N₄ and could open a new horizon for developing a high-performance ECL system.

Machine learning-assisted Te-CdS@Mn3O4 nano-enzyme induced self-enhanced molecularly imprinted ratiometric electrochemiluminescence sensor with smartphone for portable and visual monitoring of 2,4-D

Here, a novel and portable machine learning-assisted smartphone-based visual molecularly imprinted ratiometric electrochemiluminescence (MIRECL) sensing platform was constructed for highly selective sensitive detection of 2,4-Dichlorophenoxyacetic acid (2,4-D) for the first time. Te doped CdS-coated Mn₃O₄ (Te-CdS@Mn₃O₄) with catalase-like activity served as cathode-emitter, while luminol as anode luminophore accompanied H₂O₂ as co-reactant, and Te-CdS@Mn₃O₄ decorated molecularly imprinted polymers (MIPs) as recognition unit, respectively. Molecular models were constructed and MIP band and binding energies were calculated to elucidate the luminescence mechanism and select the best functional monomers. The peroxidase activity and the large specific surface area of Mn₃O₄ and the electrochemical effect can significantly improve the ECL intensity and analytical sensitivity of Te-CdS@Mn₃O₄. 2,4-D-MIPs were fabricated by in-situ electrochemical polymerization, and the rebinding of 2,4-D inhibits the binding of H₂O₂ to the anode emitter, and with the increase of the cathode impedance, the ECL response of Te-CdS@Mn₃O₄ decreases significantly. However, the blocked reaction of luminol on the anode surface also reduces the ECL response. Thus, a double-reduced MIRECL sensing system was designed and exhibited remarkable performance in sensitivity and selectivity due to the specific recognition of MIPs and the inherent ratio correction effect. Wider linear range in the range of 1 nM-100 μM with a detection limit of 0.63 nM for 2,4-D detection. Interestingly, a portable and visual smartphone-based MIRECL analysis system was established based on the capture of luminescence images by smartphones, classification and recognition by convolutional neural networks, and color analysis by self-developed software. Therefore, the developed MIRECL sensor is suitable for integration with portable devices for intelligent, convenient, and fast detection of 2,4-D in real samples.

Artificial Light-Harvesting System Based on Zinc Porphyrin and Benzimidazole: Construction, Resonance Energy Transfer, and Amplification Strategy for Electrochemiluminescence

Constructing robust and efficient luminophores is of significant importance in the development of electrochemiluminescence (ECL) amplification strategies. Inspired by the resonance energy transfer in natural light-harvesting systems, we propose a novel ECL amplification system based on ECL resonance energy transfer (ECL-RET), which integrates two luminophores, benzimidazole (BIM) and zinc(II) tetrakis(4-carboxyphenyl)porphine (ZnTCPP), into one framework. Through disassembling and reconstruction processes, numerous BIM surround ZnTCPP in the constructed ZIF-9-ZnTCPP. Combined with the overlapped spectra between the emission of BIM and the absorption of ZnTCPP, the energy of multiple BIM (donor) can be concentrated to a single ZnTCPP (acceptor) to amplify the ECL emission of the acceptor. This work provides a convenient way to design an efficient ECL-RET system, which initiates a brand-new chapter in the development of ECL amplification strategies.