Enhanced Near-Infrared Electrochemiluminescence from Trinary Ag-In-S to Multinary Ag-Ga-In-S Nanocrystals via Doping-in-Growth and Its Immunosensing Applications

Structural Modification Strategies, Interfacial Charge-Carrier Dynamics, and Solar Energy Conversion Applications of Organic-Inorganic Halide Perovskite Photocatalysts

Over the past few decades, organic-inorganic halide perovskites (OIHPs) as novel photocatalyst materials have attracted intensive attention for an impressive variety of photocatalytic applications due to their excellent photophysical (chemical) properties. Regarding practical application and future commercialization, the air-water stability and photocatalytic performance of OIHPs need to be further improved. Accordingly, studying modification strategies and interfacial interaction mechanisms is crucial. In this review, the current progress in the development and photocatalytic fundamentals of OIHPs is summarized. Furthermore, the structural modification strategies of OIHPs, including dimensionality control, heterojunction design, encapsulation techniques, and so on for the enhancement of charge-carrier transfer and the enlargement of long-term stability, are elucidated. Subsequently, the interfacial mechanisms and charge-carrier dynamics of OIHPs during the photocatalytic process are systematically specified and classified via diverse photophysical and electrochemical characterization methods, such as time-resolved photoluminescence measurements, ultrafast transient absorption spectroscopy, electrochemical impedance spectroscopy measurements, transient photocurrent densities, and so forth. Eventually, various photocatalytic applications of OIHPs, including hydrogen evolution, CO2 reduction, pollutant degradation, and photocatalytic conversion of organic matter.

Development of a fluorometric and colorimetric dual-mode sensing platform for acid phosphatase assay based on Fe3+ functionalized CuInS2/ZnS quantum dots

BACKGROUND

The spectral dual-mode response towards analyte has been attracted much attention, benefiting from the higher detection accuracy of such strategy in comparison to single signal readout. However, the currently reported dual-mode sensors for acid phosphatase (ACP) activity are still limited, and most of them more or less exist some deficiencies, such as complicated construction procedure, high-cost, poor biocompatibility, aggregation-caused quenching and limited emission capacity.

RESULTS

Herein, we employed Fe3+ functionalized CuInS2/ZnS quantum dots (CIS/ZnS QDs) as nanosensor to develop a novel fluorometric and colorimetric dual-mode assay for ACP activity, combing with ACP-triggered hydrolysis of ascorbic acid 2-phosphate (AAP) into ascorbic acid (AA). The Fe3+ binding to CIS/ZnS QDs can be reduced into Fe2+ during the determination, resulting in the dramatically weakened photoinduced electron transfer (PET) effect and the disappearance of competition absorption. Thus, a highly sensitive ACP assay in the range of 0.22-12.5 U L-1 through fluorescence "turn-on" mode has been achieved with a detection of limit (LOD) of 0.064 U L-1. Meanwhile, the ACP activity can also be quantified by spectrophotometry based on the chromogenic reaction of the formed Fe2+ with 1,10-phenanthroline (Phen). Moreover, the designed nanosensor with good biocompatibility was successfully applied to image and monitor the ACP levels in living cells.

SIGNIFICANCE

We believe that the proposed method has remarkable advantages and potential application for ACP assay in terms of the high accuracy, simplicity, low cost, as well as its adequate sensitivity.

Newly Developed Electrochemiluminescence Based on Bipolar Electrochemistry for Multiplex Biosensing Applications: A Consolidated Review

Recently, there has been an upsurge in the extent to which electrochemiluminescence (ECL) working in synergy with bipolar electrochemistry (BPE) is being applied in simple biosensing devices, especially in a clinical setup. The key objective of this particular write-up is to present a consolidated review of ECL-BPE, providing a three-dimensional perspective incorporating its strengths, weaknesses, limitations, and potential applications as a biosensing technique. The review encapsulates critical insights into the latest and novel developments in the field of ECL-BPE, including innovative electrode designs and newly developed, novel luminophores and co-reactants employed in ECL-BPE systems, along with challenges, such as optimization of the interelectrode distance, electrode miniaturization and electrode surface modification for enhancing sensitivity and selectivity. Moreover, this consolidated review will provide an overview of the latest, novel applications and advances made in this field with a bias toward multiplex biosensing based on the past five years of research. The studies reviewed herein, indicate that the technology is rapidly advancing at an outstanding purse and has an immense potential to revolutionize the general field of biosensing. This perspective aims to stimulate innovative ideas and inspire researchers alike to incorporate some elements of ECL-BPE into their studies, thereby steering this field into previously unexplored domains that may lead to unexpected, interesting discoveries. For instance, the application of ECL-BPE in other challenging and complex sample matrices such as hair for bioanalytical purposes is currently an unexplored area. Of great significance, a substantial fraction of the content in this review article is based on content from research articles published between the years 2018 and 2023.

One-step synthesis of triethanolamine-capped Pt nanoparticle for colorimetric and electrochemiluminescent immunoassay of SARS-CoV spike proteins

Platinum nanoparticles (PtNPs) have been attracted worldwide attention due to their versatile application potentials, especially in the catalyst and sensing fields. Herein, a facile synthetic method of triethanolamine (TEOA)-capped PtNPs (TEOA@PtNP) for electrochemiluminescent (ECL) and colorimetric immunoassay of SARS-CoV spike proteins (SARS-CoV S-protein, a target detection model) is developed. Monodisperse PtNPs with an average diameter of 2.2 nm are prepared by a one-step hydrothermal synthesis method using TEOA as a green reductant and stabilizer. TEOA@PtNPs can be used as a nanocarrier to combine with antigen by the high-affinity antibody, which leads to a remarkable inhibition of electron transfer efficiency and mass transfer processes. On the basis of its peroxidase-like activity and easy-biolabeling property, the TEOA@PtNP can be used to establish a colorimetric immunosensor of SARS-CoV S-protein thought catalyzing the reaction of H₂O₂ and 3,3',5,5'-tetramethylbenzidine (TMB). Especially, the Ru(bpy)₃ ²⁺ ECL reaction is well-achieved with the TEOA@PtNPs due to their great conductivity and loading abundant TEOA co-reactants, resulting in an enhancing ECL signal in immunoassay of SARS-CoV S-protein. As a consequence, two proposed methods could achieve sensitive detection of SARS-CoV S-protein in wide ranges, the colorimetric and ECL detection limits were as low as 8.9 fg /mL and 4.2 fg /mL (S/N = 3), respectively. We believe that the proposed colorimetric and ECL immunosesors with high sensitivity, good reproducibility, and good stability will be a promising candidate for a broad spectrum of applications.

Surface-Defect-Involved and Eye-Visible Electrochemiluminescence of Unary Copper Nanoclusters for Immunoassay

A single-stabilizer-capped strategy is proposed for achieving highly efficient and surface-defect-involved electrochemiluminescence (ECL) from unary copper nanoclusters (NCs) via employing l-cysteine (Cys) as a capping agent of luminophore. The Cys-capped CuNCs (Cys-CuNCs) can be electrochemically injected with valence band (VB) holes and exhibit eye-touchable ECL processes around +0.95 and +1.15 V upon employing TPrA as a coreactant. Both accumulated ECL spectra and spooling ECL spectra demonstrated that the two ECL processes are of the same single waveband and spectrally identical to each other with the same maximum emission wavelength of 640 nm. Promisingly, ECL of the Cys-CuNCs/TPrA system is obviously red-shifted for ∼150 nm to PL of Cys-CuNCs, indicating that the bandgap-engineered routes for ECLs of Cys-CuNCs are completely blocked. The oxidative-reduction ECL process of the Cys-CuNCs/TPrA system is a kind of highly efficient, eye-visible, and single-color emission in surface-defect-involved route. The capping agent of Cys can enable the CuNCs/TPrA system with a stronger ECL than other thiol capping agents, so that Cys-CuNCs are utilized as ECL tags for sensitive and selective immunoassays, which exhibit a wide linear response range from 0.05 pg/mL to 0.5 ng/mL and a limit of detection of 0.01 pg/mL (S/N = 3) with carcinoembryonic antigen as the analyte. Moreover, both the luminophore Cys-CuNCs and conjugates Ab₂-CuNCs can be safely stored in aqueous media without any protector, which is promising for the evolution and clinic application of metal NC ECL in the surface-defect-involved route.

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.

Cu2O@PdAg-quenched CdS@CeO2 heterostructure electrochemiluminescence immunosensor for determination of prostate-specific antigen

Based on the resonance energy transfer between CdS@CeO₂ and Cu₂O@PdAg, a quenching immunosensor for sensitive detection of prostate specific antigen (PSA) was constructed. The CdS@CeO₂ heterostructure was obtained by in situ growth of CeO₂ particles on the surface of CdS nanorods, and stable cathodic ECL emission was achieved using K₂S₂O₈ as coreactant. Cu₂O@PdAg was composed of Cu₂O with tetradecahedral structure and bimetallic PdAg nanospheres and has a UV-V is absorption range between 600 and 800 nm. It overlaps with the ECL emission spectrum of CdS@CeO₂, realizing the effective quenching of the ECL signal, which provides feasibility for subsequent practical application. The immunosensor exhibited good linearity in the concentration range 10 fg·mL^-1 ~ 100 ng·mL^-1, with a detection limit of 5.6 fg·mL^-1. In sample analysis, the recoveries were 99.8-101%, and the relative standard deviation (RSD) was 0.85-1.6% showing great potential and development value for the sensitive detection of prostate cancer.

Fluorescence immunosensor based on functional nanomaterials and its application in tumor biomarker detection

An immunosensor is defined as an analytical device that detects the binding of an antigen to its specific antibody by coupling an immunochemical reaction to the surface of a device called a transducer. Fluorescence immunosensing is one of the most promising immunoassays at present, and has the advantages of simple operation, fast response and high stability. A traditional fluorescence immunosensor often uses an enzyme-labelled antibody as a recognition unit and an organic dye as a fluorescence probe, so it is easily affected by environmental factors with low sensitivity. Nanomaterials have unique photostability, catalytic properties and biocompatibility, which open up a new path for the construction of stable and sensitive fluorescence immunosensors. This paper briefly introduces different kinds of immunosensors and the role of nanomaterials in the construction of immunosensors. The significance of fluorescent immunosensors constructed from functional nanomaterials to detect tumor biomarkers was analyzed, and the strategies to further improve the performance of fluorescent immunosensors and their future development trend were summarized.

Electrochemiluminescence Systems for the Detection of Biomarkers: Strategical and Technological Advances

Electrochemiluminescence (ECL)-based sensing systems rely on light emissions from luminophores, which are generated by high-energy electron transfer reactions between electrogenerated species on an electrode. ECL systems have been widely used in the detection and monitoring of diverse, disease-related biomarkers due to their high selectivity and fast response times, as well as their spatial and temporal control of luminance, high controllability, and a wide detection range. This review focuses on the recent strategic and technological advances in ECL-based biomarker detection systems. We introduce several sensing systems for medical applications that are classified according to the reactions that drive ECL signal emissions. We also provide recent examples of sensing strategies and technologies based on factors that enhance sensitivity and multiplexing abilities as well as simplify sensing procedures. This review also discusses the potential strategies and technologies for the development of ECL systems with an enhanced detection ability.

Surface Defect-Involved and Single-Color Electrochemiluminescence of Gold Nanoclusters for Immunoassay

Single-color electrochemiluminescence (ECL) of nanoparticles is normally achieved in a bandgap engineered route via passivating the nanoparticle surface. Herein, when linear mercaptoalkanoic acids are employed as the thiol-capping agent of unary Au nanoclusters (NCs), a single-stabilizer-capped strategy is proposed to achieve surface defect-involved and single-color ECL from the AuNCs with hydrazine (N2H4) as the coreactant. The carbon skeleton of the linear mercaptoalkanoic acids exhibits important effects on the ECL of the AuNCs, and efficient oxidative-reductive ECL is achieved with 8-mercaptooctanoic acid (MOA), 11-mercaptoundecanoic acid (MUA), and 12-mercaptododecanoic acid (MDA) capped AuNCs, respectively. The ECL of these AuNCs not only exhibits similar ECL intensity-potential profiles with the same maximum emission potential of ∼1.20 V (vs Ag/AgCl), but also demonstrates almost identical spectral ECL profiles of the same maximum emission wavelength around 713 nm as well as the same fwhm of 64 nm. The ECL of AuNCs/N2H4 is obviously red-shifted to the photoluminescence of AuNCs, which not only provides unambiguous evidence that bandgap-engineered ECL of these AuNCs is quenched but also manifests that the capping agent of linear mercaptoalkanoic acid is promising for the achievement of surface defect-involved and single-color ECL from AuNCs. The MUA capped AuNCs can be utilized as an ECL tag for a sensitive and selective immunoassay, which exhibits a broad linear range from 0.5 mU/mL to 1 U/mL with a low limit of detection of 0.1 mU/mL (S/N = 3) with CA125 as the model analyte. This work provides a promising alternative to the traditional surface-passivating strategy for the achievement of single-color ECL from nanoparticle luminophores.

Coreactant-free and Near-Infrared Electrochemiluminescence Immunoassay with n-Type Au Nanocrystals as Luminophores

The electrochemiluminescence (ECL) bioassay is prominently carried out with the involvement of the coreactant. To remove the detrimental effects of the coreactant on the ECL of luminophores, herein, a promising ECL immunoassay strategy with biocompatible nanoparticles as the luminophore is proposed, which involves directly and electrochemically oxidizing the luminophore methionine-capped Au (Met@Au) nanocrystals (NCs) without the participation of any coreactant. Met@Au NCs are a kind of n-type nanoparticles, and they can be electrochemically injected with valence band (VB) holes around +0.80 and +1.10 V (vs Ag/AgCl). The electrochemically injected exogenous VB hole can recombine with the endogenous conduction band electron of Met@Au NCs and eventually bring out two coreactant-free and near-infrared ECL processes around 0.80 V (ECL-1) and 1.10 V (ECL-2). The intensity of coreactant-free ECL is primarily determined by the electrochemical oxidation-induced hole-injection process. ECL-2 is considerably stronger than ECL-1 and can be exploited for determining the carcinoembryonic antigen (CEA) in a sandwich immunoassay procedure with a linear range from 0.1 to 50 pg/mL as well as a limit of detection of 0.03 pg/mL (S/N = 3).

A General Route for Chemiluminescence of n-Type Au Nanocrystals

The photoluminescence, electroluminescence, and electrochemiluminescence from nanocrystals (NCs) have been extensively exploited for both fundamental and applied investigation over two decades, while the understanding of chemiluminescence (CL) from NCs is still far from clear by now. Herein, a general route for triggering CL from NC luminophore is proposed by extensively exploiting the charge transfer between n-type NCs and oxidants. Oxidants, such as K₂S₂O₈, H₂O₂, KMnO₄, and NaClO, can chemically inject the hole onto the valence band (VB) of methionine-capped n-type AuNCs (Met@AuNCs) and enable the occurrence of efficient radiative-charge-recombination between the chemically injected exogenous VB hole and the pre-existed endogenous conduction band (CB) electron, which eventually results in single-color and defect-involved CL with the maximum emission wavelength around 824 nm. The CL of Met@AuNCs/oxidant is qualified for ultrasensitive CL immunoassay in a similar procedure to the biotin-avidin and magnetic separation involved commercial CL immunoassay and exhibits acceptable performance for linearly determining carcinoembryonic antigen from 50 pg/mL to 100 ng/mL with a limit of detection of 10 pg/mL (S/N = 3). This strategy provides a general route to develop nanoparticulate CL luminophores and might eventually enable CL multiplexing assay via extensively exploiting the CL of different wavebands.

Electrochemiluminescent sensor based on an aggregation-induced emission probe for bioanalytical detection

In recent years, with the rapid development of electrochemiluminescence (ECL) sensors, more luminophores have been designed to achieve high-throughput and reliable analysis. Impressively, after the proposed fantastic concept of "aggregation-induced electrochemiluminescence (AIECL)" by Cola, the application of AIECL emitters provides more abundant choices for the further improvement of ECL sensors. In this review, we briefly report the phenomenon, principle and representative applications of aggregation-induced emission (AIE) and AIECL emitters. Moreover, it is noteworthy that the cases of AIECL sensors for bioanalytical detection are summarized in detail, from 2017 to now. Finally, inspired by the applications of AIECL emitters, relevant prospects and challenges for AIECL sensors are proposed, which is of great significance for exploring more advanced bioanalytical detection technology.

Ultrasensitive near-infrared aptasensor for enrofloxacin detection based on wavelength tunable AgBr nanocrystals electrochemiluminescence emission triggered by O-terminated Ti3C2 MXene

Toxic-free and easily accessible electrochemiluminescence (ECL) emitter/luminophore with near-infrared (NIR) emission is highly anticipated for ECL biosensor evolution. In this study, well-dispersed AgBr nanocrystals (NCs) decorated Ti₃C₂ MXene nanocomposites (Ti₃C₂-AgBrNCs) were prepared using a simple wet chemical technique and demonstrated highly efficient NIR ECL emission. For the first time, Ti₃C₂-AgBrNCs displayed wavelength-tunable ECL emission with varied Ti₃C₂ contents. Interestingly, further experimental data revealed that the ECL emission wavelength of Ti₃C₂-AgBrNCs red-shifted from 550 to 665 nm as Ti₃C₂ content increased, which can be attributed to the surface-defect effect generated by the oxygen-containing functional groups in Ti₃C₂ MXene. In particular, the ECL emission at 665 nm of Ti₃C₂-AgBrNCs nanocomposites not only revealed a 3.5 times increased ECL intensity but also a more stable ECL signal compared to pure AgBr NCs. As a proof of concept, a direct-type NIR ECL aptasensor with signal-on strategy was constructed with the Ti₃C₂-AgBrNCs nanocomposites as an ECL platform and enrofloxacin (ENR) as a model analyte. The NIR ECL aptasensor exhibited high sensitivity, a wide linear range from 1.0 × 10^-12 mol/L to 1.0 × 10^-6 mol/L and a low detection limit (5.97 × 10^-13 mol/L). This research offered a viable alternative way for producing toxic-free and efficient near-infrared ECL luminophores in bioanalysis and wavelength-tuning light-emitting devices.

Sensitive and selective "signal-off" electrochemiluminescence sensing of prostate-specific antigen based on an aptamer and molecularly imprinted polymer

Specific and sensitive determination of prostate-specific antigen (PSA) in complex real samples holds significant importance as it is an effective molecular biomarker for the clinical diagnosis of prostate cancer. Herein, we constructed a dual-recognition electrochemiluminescence (ECL) sensor based on both the recognition elements of an aptamer and molecularly imprinted polymers (MIP) for the selective and ultrasensitive determination of PSA. The aptamer was self-assembled on gold nanoparticle (AuNP) modified electrodes through Au-S bonds. Subsequently, a layer of MIP membrane was synthesized by electropolymerization of dopamine (DA) to fabricate an aptamer-MIP sensor. After the rebinding of PSA onto imprinted cavities, the ECL response of luminol in the solution decreased. This "signal-off" strategy was employed for PSA detection with a wide linear range and a low limit of detection of 5 pg mL^-1-50 ng mL^-1 and 3.0 pg mL^-1, respectively. Compared with individual aptamer sensors, the dual-recognition sensor showed higher specific recognition ability for the determination of PSA. Meanwhile, the good stability, reproducibility, and regenerability endowed the dual recognition sensor with favorable application value in early clinical diagnosis.

Analyzing Near-Infrared Electrochemiluminescence of Graphene Quantum Dots in Aqueous Media

Mechanisms of emissions, especially electrochemiluminescence (ECL), for graphene quantum dots (GQDs) are poorly understood, which makes near-infrared (NIR)-emitting GQDs difficult to create. To explore this poorly understood NIR ECL, two GQDs, nitrogen-doped GQDs (GQD-1) and nitrogen- and sulfur-doped ones (GQD-2), were prepared by a simple one-step solvothermal reaction with similar core structures but different surface states. The GQDs were analyzed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Photoluminescence results, with a comparable quantum efficiency of 13% to strong luminophores in aqueous media, suggested a mechanism that the emission mainly depends on the core structure while slightly adjusted by the heteroatom doping. ECL of GQD-2 dispersed in aqueous media with K₂S₂O₈ as the coreactant was measured by means of ECL-voltage curves and ECL spectroscopy, demonstrating strong NIR emissions between 680 and 870 nm, with a high ECL efficiency of 13% relative to that of the Ru(bpy)₃²⁺/K₂S₂O₈ system. Interestingly, ECL is generated by surface excited states emitting light at a much longer wavelength in the NIR region. The easily prepared GQD-2 has several advantages such as low cost and quite strong NIR-ECL in aqueous media, with which wide applications in biodetection are anticipated.

Absolute Electrochemiluminescence Efficiency Quantification Strategy Exemplified with Ru(bpy)32+ in the Annihilation Pathway

This work presents a thorough guide to procedures for absolute electrochemiluminescence (ECL) quantum efficiency (Φ_ECL) measurements, which if employed effectively should raise the research impact of ECL studies for any luminophore. Absolute measurements are not currently employed in ECL research. Instead, ECL efficiencies have been determined relative to Ru(bpy)₃²⁺ under similar conditions, regardless of whether the conditions are favorable for Ru(bpy)₃²⁺ emissions or not. In fact, the most cited Ru(bpy)₃²⁺ Φ_ECL is from the pioneering work by the Bard research group in 1973 by means of a rotating ring-disk electrode revolving at 52 rotations per second measured with a silicon photodiode. Our presented technique uses a common disk electrode, spectrometer, and photomultiplier tube to measure the Φ_ECL. The more common light detection hardware and electrodes combined with an in-depth calculation walkthrough will provide ECL researchers the necessary tools to implement Φ_ECL measurement procedures in their own laboratories. Following a facile instrument setup and calculation, a systematic study of Ru(bpy)₃²⁺ Φ_ECL finds comparable results to those performed by Bard and co-workers.

Electrochemiluminescence of water-dispersed nitrogen and sulfur doped carbon dots synthesized from amino acids

A facile one-pot hydrothermal approach for synthesizing water-dispersed nitrogen and sulfur doped carbon dots (NS-CDs) with high luminescence quantum yield was explored, using cysteine and tryptophan as precursors. The NS-CDs were characterized by means of FT-IR spectroscopy, XRD, TEM, etc. It was found that the absolute photoluminescence quantum yield (QY) of the NS-CDs determined with an integrating sphere can reach up to 73%, with an average decay time of 17.06 ns. Electrochemiluminescence (ECL) behaviors and mechanisms of the NS-CDs/K₂S₂O₈ coreactant system were investigated. When the working electrode was modified with the prepared NS-CDs, the ECL efficiency of the NS-CDs with K₂S₂O₈ was 24%, relative to Ru(bpy)₃Cl₂/K₂S₂O₈. This work shows great potential for the NS-CDs to be used in bioanalytical applications.

Rare Self-Luminous Mixed-Valence Eu-MOF with a Self-Enhanced Characteristic as a Near-Infrared Fluorescent ECL Probe for Nondestructive Immunodetection

Steady and efficient sensitized emission of Eu²⁺ to Eu³⁺ can be achieved through a rare mixed-valence Eu-MOF (L₄Eu^III₂Eu^II). Compared with the sensitization of other substances, the similar ion radius and configuration of the extranuclear electron between Eu²⁺ and Eu³⁺ make sensitization easier and more efficient. The sensitization of Eu²⁺ to Eu³⁺ is of great assistance for the self-enhanced luminescence of L₄Eu^III₂Eu^II, the longer luminous time, and the more stable electrochemiluminescence (ECL) signal. Simultaneously, L₄Eu^III₂Eu^II possesses near-infrared (NIR) fluorescence of around 900 nm and a mighty self-luminous characteristic, which render it useful as a NIR fluorescent probe and as a luminophore to establish a NIR ECL biosensor. This NIR biosensor can greatly reduce the damage to the detected samples and even achieve a nondestructive test and improve the detection sensitivity by virtue of strong susceptibility and environmental suitability of NIR. In addition, the CeO₂@Co₃O₄ triple-shelled microspheres further enhanced the ECL intensity due to two redox pairs of Ce³⁺/Ce⁴⁺ and Co²⁺/Co³⁺. The NIR ECL biosensor based on these strategies owns an ultrasensitive detection ability of CYFRA 21-1 with a low limit of detection of 1.70 fg/mL and also provides a novel idea for the construction of a highly effective nondestructive immunodetection biosensor.