Electrochemiluminescence Emission Research Articles

Electrochemiluminescence aptasensor toward femtomolar detection of alpha synuclein oligomer as parkinson's disease marker using CdTe@ZnS quantum dots as luminescent label and graphdiyne@polyaniline as novel co‐reactant

AbstractParkinson's disease (PD) as a progressive health issue effects on the central nervous system. It is well established that soluble ‐synuclein (−syn) oligomers cause neuronal death in the earliest stages of PD. So, development of sensitive and selective method for a‐syn analysis is a challenge. Here an electrochemiluminescence (ECL) aptasensor designed for selective and ultrasensitive detection of α‐syn oligomer using graphdiyne@polyaniline with N‐doped active sites (GDY@PANI) as novel coreactant agent combined with CdTe@ZnS QD as luminescent lable for amplified self‐enhanced electrochemiluminescence (ECL) response. For the first time a novel ECL sensing platform based on GDY@PANI/CdTe@ZnS QD composite was designed using new co‐reactant based on GDY. Compared to CdTe@ZnS QD, GDY/CdTe@ZnS QD, CdTe@ZnS QD/tri‐propylamine and PANI/CdTe@ZnS QD, the GDY@PANI/CdTe@ZnS QD composite exhibited amplified ECL emissions and ECL efficiency of the proposed system also increased compared to more QDs based ECL systems. Under the optimal conditions, the proposed ECL aptasensor exhibited a wide linear range of 0.2 fM to 8 nM for α‐syn oligomer determination with a low detection limit of 0.02 fM (S/N=3). The fabricated sensor has advantages of good reproducibility, high sensitivity and stability and being capable of detecting α‐syn oligomer in human blood serum and also lysate of dopaminergic nerve cells. The obtained results confirmed that the GDY@PANI can be used as a novel co‐reactant in development of the ECL based bio devices with great potential applicability for biomarkers analysis, diagnosis and management of Parkinson or other diseases.

Electrochemiluminescence quenching effect of Cu2O towards flower-like ferric ion-doped g-C3N4 and its application for Cyfra21-1 immunosensing

In this article, ferric ion-doped floral graphite carbon nitride (Fe–CN-3, energy donor) was used to construct the substrate of the immunosensor and copper oxide nanocubes (Cu2O, energy acceptor) were taken as an efficient ECL quenching probe. A sandwich quench electrochemiluminescence (ECL) immunosensor for soluble cytokeratin 19 fragment (Cyfra21-1) detection was preliminarily developed based on a novel resonant energy transfer donor-acceptor pair. Fe–CN-3, a carbon nitride that combines the advantages of metal ion doping as well as morphology modulation, is used in ECL luminophores to provide more excellent ECL performance, which makes a significant contribution to the application and development of carbon nitride in the field of ECL biosensors. The regular shape, high specific surface area and excellent biocompatibility of the quencher Cu2O nanocubes facilitate the labeling of secondary antibodies and the construction of sensors. Meanwhile, as an energy acceptor, the UV absorption spectrum of Cu2O can overlap efficiently with the energy donor's ECL emission spectrum, making it prone to the occurrence of ECL-RET and thus obtaining an excellent quenching effect. These merits of the donor-acceptor pair enable the sensor to have a wide detection range of 0.00005–100 ng/mL and a low detection limit of 17.4 fg/mL (S/N = 3), which provides a new approach and theoretical basis for the clinical detection of lung cancer.

Critical Aspects and Challenges in the Design of Small Molecules for Electrochemiluminescence (ECL) Application.

Electrochemiluminescence (ECL) has gained renewed interest due to the strong parallel development of luminophores in the field of organic light emitting diodes (OLEDs) with which this technique shares several aspects. In this perspective review we discuss the most relevant advances of the past 15 years in the study of organic and organometallic compounds as ECL emitters, by dividing them in three different classes: i) fluorescent emitters, ii) phosphorescent emitters and iii) Thermally Activated Delayed Fluorescence (TADF) emitters; then, water-soluble organic luminophores will be also discussed. We focus on how their design, their photo- and electrochemical properties and, in particular, the nature of the emitter, affect their efficiency in ECL. Regardless of the type of luminophore or the photoluminescence quantum yield (PLQY), the literature converges on the fact that the most determining aspect is the stability of the oxidized/reduced form of the emitter. Even if phosphorescent emitters can show outstanding efficiency, this often requires the absence of oxygen. In the case of TADFs, there is also a strong dependence of photoluminescence both in terms of PLQY and emission energy on the polarity of the media, so compounds, that appear promising in organic solvents, may be very inefficient in aqueous media.

Highlighting the operating regimes of microchannel electrodes under laminar flow: Mapping of photoluminescence and electrochemiluminescence through semi-transparent electrodes

Semi-transparent platinum electrodes were designed and optimized to implement photoluminescence (PL) and electrochemiluminescence (ECL) in microchannels under flow conditions. The luminescence properties of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)32+) were used to map steady-state emitted light through semi-transparent microchannel electrodes. Several diffusive-convective regimes were thus imposed in order to experimentally highlight the operating conditions of the electrodes, in particular the active zones at their upstream edges contributing to the Faradaic current. PL and ECL profiles were established on the electrode surfaces as a function of flow rate. The PL profiles confirmed the control of the process by mass transport. The data were validated by numerical simulations within the limits of experimental accuracy. ECL emission in presence of the co-reactant tri-n-propylamine (TPA) was also limited by mass transport. However, in comparison the characteristics of the ECL profiles demonstrated the complexity of the underlying mechanism involving Ru(bpy)32+ regeneration and TPA consumption.

A novel electrochemiluminescence immunosensor: BiOBr/Bi2WO6 heterojunction for ultrasensitive detection of CA19-9

Bi2WO6, an environmentally friendly material with certain electrochemiluminescence (ECL) properties, has been used as a novel ECL luminescent material. In the present work, bismuth tungstate (Bi2WO6) was composited with bismuth bromide (BiOBr) to form a S-type heterojunction with a flower like morphology where the Bi2WO6 core was wrapped with BiOBr outer shell. The interface of the heterojunction is closely contacted, which can promote electron transfer, improve conduction and enhance ECL emission to a certain extent. The BiOBr/Bi2WO6 (BBW) heterojunction with K2S2O8 as a co-reactant demonstrates cathodic ECL emission at 550–800 nm in the potential range of −1.8–0 V. Cu2O@Ag with a special sea urchins morphology was introduced into the system to catalyze the reduction of S2O82− to generate more SO4•−, which further enhances the ECL emission. The ECL immunosensor constructed with the heterojunction for CA19–9 detection exhibits a robust linear relationship in the concentration range from 0.1 mU·mL−1 to 100 U·mL−1 and detection limit as low as 87.6 μU·mL−1. The immunosensor successfully detected CA19–9 in serum, showing great application potential in the clinical practice.

Electrochemiluminescence in Graphitic Carbon Nitride Decorated with Silver Nanoparticles for Dopamine Determination Using Machine Learning.

Electrochemiluminescence (ECL) luminophores with wavelength-tunable multicolor emissions are essential for multicolor ECL imaging detection and multiplexed analysis. In this work, silver nanoparticle (Ag NP)-decorated graphitic carbon nitride (g-CN@Ag) nanocomposites were synthesized. The morphology, chemical composition, structure, and ECL property of g-CN@Ag were investigated. The prepared g-CN, g-CN@Ag1, g-CN@Ag5, and g-CN@Ag10 can produce blue, blue-green, chartreuse, and yellow colored ECL emissions, respectively, by using K2S2O8 as the coreagent. The ECL emission wavelength of g-CN@Ag can be regulated from 460 to 565 nm by modulating the content of the immobilized Ag NPs. Then, a multicolor ECL detection array was fabricated by using g-CN, g-CN@Ag1, g-CN@Ag5, and g-CN@Ag10 as four ECL luminophores. Dopamine was detected based on its inhibition effect on the multicolor ECL emissions. The linear range is from 0.1 nM to 1 mM with the lowest detection limit of 44 pM. Then, machine learning-assisted multiparameter concentration prediction of dopamine was further carried out by combining the deep neural network (DNN) algorithm. This work provides a new avenue to regulate the ECL emission wavelength of g-CN by using the metal nanoparticle modification strategy and presents an effective machine learning-assisted multicolor ECL detection strategy for accurate multiparameter quantitative detection.

Single-Atom Iron Doped Carbon Dots with Highly Efficient Electrochemiluminescence for Ultrasensitive Detection of MicroRNAs.

Herein, single-atom iron doped carbon dots (SA Fe-CDs) were successfully prepared as novel electrochemiluminescence (ECL) emitters with high ECL efficiency, and a biosensor was constructed to ultrasensitively detect microRNA-222 (miRNA-222). Importantly, compared with the conventional without single-atom doped CDs with low ECL efficiency, SA Fe-CDs exhibited strong ECL efficiency, in which single-atom iron as an advanced coreactant accelerator could significantly enhance the generation of reactive oxygen species (ROS) from the coreactant S2O82- for improving the ECL efficiency. Moreover, a neoteric amplification strategy combining the improved strand displacement amplification with Nt.BbvCI enzyme-induced target amplification (ISDA-EITA) could produce 4 output DNAs in every cycle, which greatly improved the amplification efficiency. Thus, a useful ECL biosensor was built with a detection limit of 16.60 aM in the range of 100 aM to 1 nM for detecting traces of miRNA-222. In addition, miRNA-222 in cancer cell lysate (MHCC-97L) was successfully detected by using the ECL biosensor. Therefore, this strategy provides highly efficient single-atom doped ECL emitters for the construction of sensitive ECL biosensing platforms in the biological field and clinical diagnosis.

Local electrochemiluminescence imaging using scanning electrochemical cell microscopy

In this communication, local electrochemiluminescence (ECL) imaging is achieved using scanning electrochemical cell microscopy (SECCM) to create a localized region for the occurrence of ECL reaction. The system is demonstrated using a droplet at the micropipette that is contact with the prepared Ru-Silica@Au particles at indium tin oxide (ITO) slide. Tri-n-propylamine (TPrA) in the droplet reacts with ruthenium complex in a 10 μm-diameter-region to produce ECL emission, which is recorded by photo multiplier tube (PMT) underneath the ITO slide. By contacting each local region consecutively, the distribution of steady-state current and the related ECL emission at the ITO surface is imaged. The local ECL intensity show an approximately linear dependence with the current, but obvious deviation from the linear curve is observed at some regions. This result suggests that the ECL emission is not only determined by the transferred electron number in the electrochemical reaction, and also affected by local environments at ITO surface. As compared with the traditionally used ECL imaging in the bulk solution, this strategy avoids the cross-talking of ECL emission from nearby regions, and could offer a new way to unveil more molecular mechanism in the ECL reaction.

In situ generated CdTe quantum dot-encapsulated hafnium polymer membrane to boost electrochemiluminescence analysis of tumor biomarkers.

Exploring the construction of an interface with bright emission, fabulous stability, and good function to develop high-performance electrochemiluminescence (ECL) biosensors for tumor biomarkers is in high demand but faces a huge challenge. Herein, we report an oriented attachment and in situ self-assembling strategy for one-step fabrication of CdTe QD-encapsulated Hf polymer membrane onto an ITO surface (Hf-CP/CdTe QDs/APS/ITO). Hf-CP/CdTe QDs/APS/ITO is fascinating with excellent stability, high ECL emission, and specific adsorption toward ssDNA against dsDNA and mononucleotides (mNs). These interesting properties make it an ideal interface to rationally develop an immobilization-free ECL biosensor for cancer antigen 125 (CA125), used as a proof-of-concept analyte, based on target-aptamer recognition-promoted exonuclease III (Exo III)-assisted digestion. The recognition of ON by CA125 leads to the formation of CA125@ON, which hybridizes with Fc-ssDNA to switch Exo III-assisted digestion, decreasing the amount of Fc groups anchored onto the electrode's surface and blocking electron transfer. As compared to the case where CA125 was absent, significant ECL emission recovery is determined and relies on CA125 concentration. Thus, highly sensitive analysis of CA125 against other biomarkers was achieved with a limit of detection down to 2.57pg/mL. We envision this work will provide a new path to develop ECL biosensors with excellent properties, which shows great potential for early and accurate diagnosis of cancer.

Bis-tridentate Iridium(III) Complex with the N-Heterocyclic Carbene Ligand as a Novel Efficient Electrochemiluminescence Emitter for the Sandwich Immunoassay of the HHV-6A Virus.

Human herpesvirus type 6A (HHV-6A) can cause a series of immune and neurological diseases, and the establishment of a sensitive biosensor for the rapid detection of HHV-6A is of great significance for public health and safety. Herein, a bis-tridentate iridium complex (BisLT-Ir-NHC) comprising the N-heterocyclic carbene (NHC) ligand as a novel kind of efficient ECL luminophore has been unprecedently reported. Based on its excellent ECL properties, a new sensitive ECL-based sandwich immunosensor to detect the HHV-6A virus was successfully constructed by encapsulating BisLT-Ir-NHC into silica nanoparticles and embellishing ECL sensing interface with MXene@Au-CS. Notably, the immunosensor illustrated in this work not only had a wide linear range of 102 to 107 cps/μL but also showed outstanding recoveries (98.33-105.11%) in real human serum with an RSD of 0.85-3.56%. Undoubtedly, these results demonstrated the significant potential of the bis-tridentate iridium(III) complex containing an NHC ligand in developing ECL-based sensitive analytical methods for virus detection and exploring novel kinds of efficient iridium-based ECL luminophores in the future.

N vacancy and self-enhancement induced high anodic electrochemiluminescence of 3D g-C3N4 for sensitive staphylococcus aureus analysis

Here, 3D g-C3N4 with dense N vacancy in its 3D porous interconnected open-framework was synthesized, and the co-reactive 3-(dibutylamino)propylamine (DBAPA) was further covalently coupled onto the surface, resulting in a strong self-enhanced anodic electrochemiluminescence (ECL). Through introduction of high-density N vacancy, for the obtained 3D g–C3N4–NV, the band gap was broadened and the electrical conductivity was enhanced, realizing an obvious ECL improvement. Moreover, after the covalent binding of co-reactive DBAPA, the obtained 3D g–C3N4–NV-DBAPA exhibited a more intensive self-enhanced ECL signal due to the higher co-reaction efficiency originated from shorter electron transfer distance and lower energy loss. Based on the high initial signal of the proposed 3D g–C3N4–NV-DBAPA, a sensitive ECL biosensor with signal “on-off” was fabricated in assistance with multiple horizontal ordered hybridization chain reaction (HO-HCR). Through orderly fixing the reacted DNA chains on the Y-shape DNA structure on the electrode could effectively decrease diffusion process and improve the reaction efficiency of HCR process, resulting in the formation of numerous long horizontal double-strand DNA that could immobilize abundant ferrocene-doxorubicin (Fc-Dox) with ECL quenching effect. Meanwhile, compared to the traditional vertical HCR, the HO-HCR could make the quench reagent closer to the ECL emitter on the electrode surface and obtain a more effective quenching effect to enhance the sensing sensitivity. As a result, the proposed ECL biosensor archived the sensitive measurement of staphylococcus aureus with a detection limit of 10.3 aM.

Self-Assembly-Induced Enhancement of Cathodic Electrochemiluminescence of Copper Nanoclusters for a Split-Type Matrix Metalloproteinase 14 Sensing Platform.

The unique optoelectronic and tunable luminescent characteristics of copper nanoclusters (Cu NCs) make them extremely promising as luminophores. However, the limited luminescence intensity and stability of Cu NCs have restricted their application in the field of electrochemiluminescence (ECL). Herein, a self-assembly-induced enhancement strategy was successfully employed to enhance the cathodic ECL performance of flexible ligand-stabilized Cu NCs. Specifically, Cu NCs form ordered sheetlike structures through intermolecular force. The restriction of ligand torsion in this self-assembled structure leads to a significant improvement in the ECL properties of the Cu NCs. Experimental results demonstrate that the assembled nanoscale Cu NC sheets exhibit an approximately three-fold increase in cathodic ECL emission compared to the dispersed state of Cu NCs. Furthermore, assembled nanoscale Cu NCs sheets were utilized as signal probes in conjunction with a specific short peptide derived from the catalytic structural domain of matrix metalloproteinase 14 (MMP 14) as the identification probe, thereby establishing a split-type ECL sensing platform for the quantification of NMP 14. The investigation has revealed the exceptional performance of assembled nanoscale Cu NCs sheets in ECL analysis, thus positioning them as novel and promising signal probes with significant potential in the field of sensing.

Tuning electrochemical water activation over NiIr single-atom alloy aerogels for stable electrochemiluminescence

The anodic oxygen evolution reaction is a well-acknowledged side reaction in traditional aqueous electrochemiluminescence (ECL) systems due to the generation and surface aggregation of oxygen at the electrode, which detrimentally impacts the stability and efficiency of ECL emission. However, the effect of reactive oxygen species generated during water oxidation on ECL luminophores has been largely overlooked. Taking the typical luminol emitter as an example, herein, we employed NiIr single-atom alloy aerogels possessing efficient water oxidation activity as a prototype co-reaction accelerator to elucidate the relationship between ECL behavior and water oxidation reaction kinetics for the first time. By regulating the concentration of hydroxide ions in the electrolyte, the electrochemical oxidation processes of both luminol and water are finely tuned. When the concentration of hydroxide ions in electrolyte is low, the kinetics of water oxidation is attenuated, which limits the generation of oxygen, effectively mitigates the influence of oxygen accumulation on the ECL strength, and offers a novel perspective for harnessing side reactions in ECL systems. Finally, a sensitive and stable sensor for antioxidant detection was constructed and applied to the practical sample detection.

Regulating Reactive Oxygen Species over M-N-C Single-Atom Catalysts for Potential-Resolved Electrochemiluminescence.

The development of potential-resolved electrochemiluminescence (ECL) systems with dual emitting signals holds great promise for accurate and reliable determination in complex samples. However, the practical application of such systems is hindered by the inevitable mutual interaction and mismatch between different luminophores or coreactants. In this work, for the first time, by precisely tuning the oxygen reduction performance of M-N-C single-atom catalysts (SACs), we present a dual potential-resolved luminol ECL system employing endogenous dissolved O2 as a coreactant. Using advanced in situ monitoring and theoretical calculations, we elucidate the intricate mechanism involving the selective and efficient activation of dissolved O2 through central metal species modulation. This modulation leads to the controlled generation of hydroxyl radical (·OH) and superoxide radical (O2·-), which subsequently trigger cathodic and anodic luminol ECL emission, respectively. The well-designed Cu-N-C SACs, with their moderate oxophilicity, enable the simultaneous generation of ·OH and O2·-, thereby facilitating dual potential-resolved ECL. As a proof of concept, we employed the principal component analysis statistical method to differentiate antibiotics based on the output of the dual-potential ECL signals. This work establishes a new avenue for constructing a potential-resolved ECL platform based on a single luminophore and coreactant through precise regulation of active intermediates.

A dual-signal ECL-RET immunosensor based on VC-g-C3N4 and Ru-Zr-MOF for the detection of β2-MG

This work proposes a novel dual-signal electrochemiluminescence (ECL) immunosensor based on energy resonance transfer (RET) for the detection of β2-Microglobulin (β2-MG). Introducing carbon vacancy into g-C3N4 (VC-g-C3N4) can lead to the narrowing of the band gap and the reduction of LUMO, thereby significantly enhancing the ECL efficiency of the material. Meanwhile, Zr-MOF can effectively load Ru(bpy)32+ (Ru-Zr-MOF), enabling its stable existence on the electrode. The ECL emission spectrum of VC-g-C3N4 overlaps well with the fluorescence excitation spectrum of Ru-Zr-MOF, indicating an effective ECL-RET effect between them. As the concentration of β2-MG increases, the intensity of anodic ECL signal gradually increases, while the intensity of cathodic ECL signal gradually decreases. The difference between the cathodic and anodic ECL signals has a good linear relationship within the concentration range from 0.2 pg/mL to 200 ng/mL, with a detection limit of 27.73 fg/mL. The constructed immunosensor can be used for practical analysis in human serum. The proposed sensor has great potential in clinical detection of β2-MG, providing new insights for biomolecular detection and disease diagnosis.

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.

The carbon dots with near-infrared electrochemiluminescence emission and low excitation potential for ultrasensitive analysis of microRNA-222

In this work, nitrogen and sulfur codoped near-infrared emission carbon dots (N,S-NIR-CDs) were used as neoteric electrochemiluminescence (ECL) emitters with high efficiency to construct a biosensor for ultrasensitive analysis of microRNA-222 (miRNA-222), which has been regarded as prospective biomarkers for early cancer diagnosis. Impressively, compared to conventional CDs with short ECL wavelength and large excitation voltage, N,S-NIR-CDs possessed wide sp2 domains and narrow band gap, leading to the near-infrared ECL emission at 680 nm and low excitation potential from −1.0 to 0 V, which not only decreased the photochemical damage for biomolecules but also reduced the side reaction. Moreover, an improved T7 Exonuclease induced cascade amplification (EICA) strategy was designed to transform trace miRNA-222 into plentiful output DNA in dual-cycle for greatly improving the target conversion efficiency. Therefore, by combining the N,S-NIR-CDs as neoteric ECL emitters and EICA strategy as signal amplifier, the constructed ECL biosensor could realize the ultrasensitive analysis of miRNA-222 with a identification limit of 5.65 aM and successfully employed in miRNA-222 analysis from liver cancer cell (HCCLM3 and MHCC-97L) lysate. This strategy developed a kind of neoteric CDs with NIR ECL emission and low excitation potential to establish a highly efficient biosensor for biomarker analysis, which prepared a road for early diseases diagnosis and lied a foundation for biological ECL imaging.

Tripedal DNA Walker as a Signal Amplifier Combined with a Potential-Resolved Multicolor Electrochemiluminescence Strategy for Ultrasensitive Detection of Prostate Cancer Staging Indicators.

A multicolor electrochemiluminescence (ECL) biosensor based on a closed bipolar electrode (BPE) array was proposed for the rapid and intuitive analysis of three prostate cancer staging indicators. First, [Irpic-OMe], [Ir(ppy)2(acac)], and [Ru(bpy)3]2+ were applied as blue, green, and red ECL emitters, respectively, whose mixed ECL emission colors covered the whole visible region by varying the applied voltages. Afterward, we designed a simple Mg2+-dependent DNAzyme (MNAzyme)-driven tripedal DNA walker (TD walker) to release three output DNAs. Immediately after, three output DNAs were added to the cathodic reservoirs of the BPE for incubation. After that, we found that the emission colors from the anode of the BPE changed as a driving voltage of 8.0 V was applied, mainly due to changes in the interfacial potential and faradaic currents at the two poles of the BPE. Via optimization of the experimental parameters, cutoff values of such three indicators at different clinical stages could be identified instantly with the naked eye, and standard precision swatches with multiple indicators could be prepared. Finally, in order to precisely determine the prostate cancer stage, the multicolor ECL device was used for clinical analysis, and the resulting images were then compared with standard swatches, laying the way for accurate prostate cancer therapy.

L-Cysteine-Tuned the Hierarchical Structure Based on Benzimidazole: Synthesis, Characterization, and Application in Ratiometric Electrochemiluminescence Immunoassay.

Efficient and robust electrochemiluminescence (ECL) emitters are crucial for enhancing the ECL immunosensor sensitivity. This study introduces a novel ECL emitter, CoBIM/Cys, featuring a hierarchical core-shell structure. The core of the structure is created through the swift coordination between the sulfhydryl and carboxyl groups of l-cysteine (l-Cys) and cobalt ions (Co2+), while the shell is constructed by sequentially coordinating benzimidazole (BIM) with Co2+. This design yields a greater specific surface area and a more intricate porous structure compared to CoBIM, markedly enhancing mass transfer and luminophore accessibility. Moreover, the l-Cys and Co2+ core introduces Co-S and Co-O catalytic sites, which improve the catalytic decomposition of H2O2, leading to an increased production of hydroperoxyl radicals (OOH•). This mechanism substantially amplifies the ECL performance. Leveraging the competitive interaction between isoluminol and BIM for OOH• during ECL emission, we developed a ratiometric immunosensor for cardiac troponin I (cTnI) detection. This immunosensor demonstrates a remarkably broad detection range (1 pg mL-1 to 10 ng mL-1), a low detection limit (0.4 pg mL-1), and exceptional reproducibility and specificity.

Ultrastable Anion Radicals in Ligand-Dimerized Frameworks for Self-Accumulated Electrochemiluminescence.

Electrochemiluminescence (ECL) is a light-emitting process that occurs via an annihilation reaction among energetic radical intermediates, whose stabilities determine the ECL efficiency. In this study, a ligand-dimerized metal-organic framework (MOF) with ultrastable anion radical is designed as an efficient nanoemitter for self-accumulated ECL. Due to the nonplanar structure of perylene diimide (PDI) derivate, two PDI ligands in the framework form a J-dimer unit with a vertical distance of ∼5.74 Å. In cathodic scanning, the ligand-dimerized MOF demonstrates three-step ECL emissions with a gradual increase in ECL intensity. Unlike the decrease in the PDI ligand, the self-accumulated ECL of the MOF was observed with 16.8-fold enhancement due to the excellent stability of radical intermediates in frameworks. Electron paramagnetic resonance demonstrated the ultrastability of free radicals in the designed frameworks, with 82.2% remaining even after one month of storage. Density functional theory calculations supported that PDI dimerization was energetically favorable upon successive electron injection. Moreover, the ECL wavelength is 610 nm, corresponding to the emission of excited dimers. The radical-stabilized reticular nanoemitters open up a new platform for decoding the fundamentals of self-accumulated ECL systems.