Plasmon-Boosted Cu-Doped TiO2 Oxygen Vacancy-Rich Luminol Electrochemiluminescence for Highly Sensitive Detection of Alkaline Phosphatase

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.

Coreactant-free aggregation-induced electrochemiluminescence system based on the novel zinc-luminol metal-organic gel for ultrasensitive detection of PiRNA-823

Aggregation-induced electrochemiluminescence (AIECL) technology has aroused widespread interest due to the significant improve in ECL response by solving the problems of aggregation-caused quenching and poor water solubility of the luminophore. However, the existing AIECL emitters still suffer from low ECL efficiency, additional coreactants and complex synthesis steps, which greatly limit their applications. Herein, luminol, as a kind of AIE molecule, was assembled with Zn2+ nodes to obtain a novel microflower-like Zinc-luminol metal-organic gel (Zn-MOG) by one-step method. In the light of the strong affinity of N atoms in luminol ligand to Zn2+, Zn-MOG with vigorous viscosity and stability can be formed immediately after vortex oscillation, overcoming the main difficulties of the complicated synthesis steps and poor film-forming performance encountered in current AIECL materials. Impressively, an AIECL resonance energy transfer (RET) biosensor was constructed using Zn-MOG as a donor and Alexa Fluor 430 as an acceptor in combination with DNA-Fuel-driven target recycling amplification for the ultrasensitive detection of PiRNA-823. The fabricated biosensor exhibited a wide linear relationship in the range of 100 aM to 100 pM and a detection limit as low as 60.0 aM. This work is the first to realize the construction of ECL emitters using the AIE effect of luminol, which provides inspiration for the design of AIECL systems without adding coreactants.

Ultrastable Luminol-OH--(Ni-WOx-CNT) ECL System with High Strength and Its Applications in Sensing

In traditional luminol electrochemiluminescence (ECL) systems, hydrogen peroxide (H2O2) and dissolved oxygen (DO) are the commonly used coreactants to generate reactive oxygen species (ROS) for ECL emission. However, the self-decomposition of hydrogen peroxide and the limited solubility and content of oxygen in solution undoubtedly restrict the luminescence efficiency and stability of the luminol ECL system. Inspired by the ROS-mediated ECL mechanism, we pioneered hydroxide ion as an advanced luminol ECL coreactant using nickel-doped and carbon nanotube-modified tungsten oxide (Ni-WOx-CNT) as the coreactant accelerator. Owing to the excellent catalytic activity of Ni-WOx-CNT, amounts of ROS were generated from OH- at a low excitation voltage, which subsequently reacted with luminol anion radicals and triggered intense ECL signals. Experiments confirmed an impressive ECL behavior in terms of high luminescent intensity (85,563 a.u.) and super stability over 1300 consecutive tests; both are superior to those recently reported luminol-H2O2 and luminol-DO systems with smaller ECL intensities and consecutive tests less than 25 times. To validate the feasibility and versatility of the developed system in sensor, traditional three-electrodes system and closed bipolar electrodes system with various sensing strategies of direct oxidation, "gate-effect" of molecularly imprinted polymer, immune reaction, and enzyme-catalyzed reaction were proposed to monitor uric acid (UA), C-reactive protein (CRP), immunoglobulin G (IgG), and glucose (Glu). The superior sensing performances confirmed the great application potential of the developed ROS-mediated ECL system.

Boosting Electrochemiluminescence Performance of a Dual-Active Site Iron Single-Atom Catalyst-Based Luminol-Dissolved Oxygen System via Plasmon-Induced Hot Holes

Due to the commonly low content of biomarkers in diseases, increasing the sensitivity of electrochemiluminescence (ECL) systems is of great significance for in vitro ECL diagnosis and biodetection. Although dissolved O2 (DO) has recently been considered superior to H2O2 as a coreactant in the most widely used luminol ECL systems owing to its improved stability and less biotoxicity, it still has unsatisfactory ECL performance because of its ultralow reactivity. In this study, an effective plasmonic luminol-DO ECL system has been developed by complexing luminol-capped Ag nanoparticles (AgNPs) with plasma-treated Fe single-atom catalysts (Fe-SACs) embedded in graphitic carbon nitride (g-CN) (pFe-g-CN). Under optimal conditions, the performance of the resulting ECL system could be markedly increased up to 1300-fold compared to the traditional luminol-DO system. Further investigations revealed that duple binding sites of pFe-g-CN and plasmonically induced hot holes that disseminated from AgNPs to g-CN surfaces lead to facilitate significantly the luminous reaction process of the system. The proposed luminol-DO ECL system was further employed for the stable and ultrasensitive detection of prostate-specific antigen in a wide linear range of 1.0 fg/mL to 1 μg/mL, with a pretty low limit of detection of 0.183 fg/mL.

Co3O4/NiCo2O4 heterojunction as oxygen evolution reaction catalyst for efficient luminol anode electrochemiluminescence

Luminol has garnered significant attention from analysts as one of the most effective and commonly used electrochemiluminescence (ECL) reagents. However, the efficient luminescence of luminol anode is limited by the excitation of various reactive oxygen species (ROS). Typically, ROS are generated through co-reactive reagents and dissolved oxygen. Unfortunately, the former suffers from two drawbacks, namely biotoxicity and instability, while the latter cannot offer sufficient oxygen due to its limited solubility in aqueous solutions. Consequently, a low decomposition rate is usually obtained, leading to insufficient ROS. Therefore, there is an urgent need to develop efficient luminol anode systems. This study focuses on the use of zeolitic imidazolate framework-67 (ZIF-67) as a template, employing a controlled chemical etching method to create a ZIF-67/Ni-Co-layered double hydroxide (LDH). The intermediate composite is then annealed in air, resulting in the formation of a Co3O4/NiCo2O4 double-shelled nanobox (DSNB) heterostructure. Due to its structural advantages, the DSNB exhibits excellent electrocatalytic performance in the oxygen evolution reaction (OER). Furthermore, it was found that both the intermediates and products of OER can directly participate in the luminol chemiluminescence process, ultimately resulting in a 700-fold increase in the electrochemiluminescence (ECL) signal compared to an equal molar concentration of luminol solution. This work not only establishes the OER-mediated ECL system but also deepens the understanding of the relationship between ROS and luminol, providing a new pathway to study the luminol anodic ECL luminescence system.

Palladium nanospheres-embedded metal-organic frameworks to enhance the ECL efficiency of 2,6-dimethyl-8-(3-carboxyphenyl)4,4'-difluoroboradiazene in aqueous solution for ultrasensitive Cu2+ detection

Nowadays, organic emitters suffer from insufficient electrochemiluminescence (ECL) efficiency in aqueous solutions, and their practical applications are severely restricted in the bio-sensing field. In this work, palladium nanospheres-embedded metal-organic frameworks (Pd@MOFs) were exploited to enhance the ECL efficiency of 2,6-dimethyl-8-(3-carboxyphenyl)4,4'-difluoroboradiazene (BET) prepared by a one-pot method in aqueous environment. First, the Pd@MOFs were generated via in situ reduction of Pd nanospheres anchored onto the MOFs, and fabricated by orderly coordination of palladium chloride (PdCl2) with 1,2,4,5-benzenetetramine (BTA) tetrahydrochloride. Then, the influence of protons on the ECL response of BET was studied in detail to obtain stronger ECL emission using potassium persulfate (K2S2O8) as co-reactant in aqueous environment. As a result, a 1.47-fold ECL efficiency enlargement of BET/K2S2O8 was harvested at the Pd@MOFs/GCE, where Ru(bpy)32+ behaved as a standard. Based on the fact that the ECL signals of the BET-covered Pd@MOFs modified glassy carbon electrode (simplified as BET/Pd@MOFs/GCE) can be quenched by Cu2+, the as-built ECL sensor showed a wide linear range (1.0-100.0 pM) and a limit of detection (LOD) as low as 0.12 pM. Hence, such research offers huge potential to promote the development of organic emitters in ECL biosensors and environmental monitoring.

Dual-channel MIRECL portable devices with impedance effect coupled smartphone and machine learning system for tyramine identification and quantification

We designed a novel, portable, and visual dual-potential molecularly imprinted ratiometric electrochemiluminescence (MIRECL) sensor for tyramine (TYM) detection based on smartphone and deep learning-assisted optical devices. Molecularly imprinted polymer-Ce2Sn2O7 (MIP-Ce2Sn2O7) layers were fabricated by in-situ electropolymerization method as the capture and signal amplification probe. Oxygen vacancies in Ce2Sn2O7 not only enhance the electrochemical redox capability but also accelerate the energy transfer, thereby enhancing the luminescence of cathode ECL. Under optimal conditions, the ECL signals of MIP-Ce2Sn2O7 at the cathode and the anode response of Ru(bpy)32+ was reduced, thus a wide linear range from 0.01 μM to 1000 μM with the detection limit as low as 0.005 μM. Interestingly, combined with an artificial intelligence image recognition algorithm and the principle of optical signal reading by smartphone, the developed MIRECL sensor has been applied to the portable and visual determination of TYM in aquatic samples, and its practicability has been satisfactorily verified.

Nitrogen Defect-Rich Graphitic Carbon Nitride for Highly Sensitive Voltammetric Determination of Tryptophan

Here, a highly sensitive electrochemical sensor for detection of tryptophan (Trp) using a nitrogen defect graphitic carbon nitride-modified glassy carbon electrode (ND-CN/GCE) was introduced. ND-CN/GCE showed a higher oxidation current for Trp than the graphitic carbon nitride-modified glassy carbon electrode (g-CN/GCE) and bare glassy carbon electrode (BGCE). The synthesized nitrogen defect-rich graphitic carbon nitride (ND-CN) was characterized using X-ray photoelectron spectroscopy, X-ray diffraction spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Electrochemical impedance spectroscopy and cyclic voltammetry were used to further analyze the electrochemical properties of BGCE, g-CN/GCE, and ND-CN/GCE. The oxidation of Trp at ND-CN/GCE is a diffusion-controlled process at pH 3.0. It was calculated that the transfer coefficient, rate constant, and diffusion coefficient of Trp were 0.53, 2.24 × 103 M-1 s-1, and 8.3 × 10-3 cm2 s-1, respectively, at ND-CN/GCE. Trp was detected using square wave voltammetry, which had a linear range from 0.01 to 40 μM at pH 3.0 and a limit of detection of about 0.0034 μM (3σ/m). Analyzing the presence of Trp in a milk and multivitamin tablet sample with a percentage recovery in the range of 97.0-108% satisfactorily demonstrated the practical usability of the electrochemical sensor. The ND-CN/GCE additionally displays good repeatability and reproducibility and satisfactory selectivity.

Voltammetric determination of tryptophan at graphitic carbon nitride modified carbon paste electrode

Herein, we reported carbon paste electrode modified with graphitic carbon nitride (g-C3N4-CPE) to determine of tryptophan (Trp) using voltametric techniques. Various spectroscopic and electrochemical techniques were used to characterize the as-synthesized g-C3N4 and the assembled electrodes. The transfer coefficient, rate constant and the diffusion coefficient of Trp in this system were found to be 0.28, 1.9 × 104 M-1s-1 and 3.2 × 10-5 cm2s-1, respectively. The linear range was obtained for the detection of Trp using LSV is from 0.1 μM to 120 μM at pH 5. The limit of detection (LOD) (3σ/m) was 0.085 μM. The demonstrated modified CPE was also effectively used for the detection of Trp in milk with percentage recovery of 98 %-105.2 %. Furthermore, the modified CPE exhibited good repeatability, reproducibility and appropriate selectivity.

Vesicles as a Multifunctional Microenvironment for Electrochemiluminescence Signal Amplification

Vesicles as a typical interface-rich microenvironment can promote the reaction rate and the intermediate stability, which are promising for introduction in electrochemiluminescence (ECL) signal amplification. In this work, a kind of multilamellar vesicle obtained from sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was used to modify the electrode surface. The AOT vesicle-modified microenvironment could significantly enhance the ECL performances for the luminol/O2 system in a neutral medium. The mechanism study demonstrated that the nanoscale multilamellar vesicles could maintain the vesicle structure on the electrode surface, which substantially improved the electron transfer and reaction rate, luminescence efficiency of the excited-state 3-aminophthalate anion, and stability of the superoxide anion radical. Alternatively, such a multifunctional microenvironment was also able to enhance the ECL signals from the tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+)/tripropylamine (TPrA) system. Moreover, another dodecyl dimethyl(3-sulfopropyl) ammonium hydroxide inner salt (DSB)-based vesicle was constructed to further verify the versatility of the vesicle-modified microenvironment for ECL signal amplification. Our work not only provides a versatile microenvironment for improving the efficiency of various ECL systems but also offers new insights for the microenvironment construction using the ordered assemblies in ECL fields.

Atomically Fe-anchored MOF-on-MOF nanozyme with differential signal amplification for ultrasensitive cathodic electrochemiluminescence immunoassay

The successful application of electrochemiluminescence (ECL) in immunoassays for clinical diagnosis requires stable electrodes and high-efficient ECL signal amplification strategies. Herein, the authors discovered a new class of atomically dispersed peroxidase-like nanozymes with multiple active sites (CoNi-MOF@PCN-224/Fe), which significantly improved the catalytic performance and uncovered the underlying mechanism. Experimental studies and theoretical calculation results revealed that the nanozyme introduced a Fenton-like reaction into the catalytic system and the crucial synergistic effects of definite active moieties endow CoNi-MOF@PCN-224/Fe strong electron-withdrawing effect and low thermodynamic activation energy toward H2O2. Benefiting from the high peroxidase-like activity of the hybrid system, the resultant ECL electrode exhibited superior catalytic activity in the luminol-H2O2 system and resulted in an ≈17-fold increase in the ECL intensity. In addition, plasmonic Ag/Au core-satellite nanocubes (Ag/AuNCs) were designed as high-efficient co-reactant quenchers to improve the performance of the ECL immunoassay. On the basis of the differential signal amplification strategy (DSAS) proposed, the immunoassay displayed superior detection ability, with a low limit of detection (LOD) of 0.13 pg mL-1 for prostate-specific antigen (PSA). The designed atomically anchored MOF-on-MOF nanozyme and DSAS strategy provides more possibilities for the ultrasensitive detection of disease markers in clinical diagnosis.

High-Intensity Focused Ultrasound Combined with Ti3C2-TiO2 to Enhance Electrochemiluminescence of Luminol for the Sensitive Detection of Polynucleotide Kinase

Luminol is a classic electrochemiluminescence (ECL) luminophore. The luminol-O₂ ECL system suffers from a problem, that is, the conversion rate of dissolved O₂ into reactive oxygen species (ROS) is low. In this work, we used high-intensity focused ultrasound (HIFU) pretreatment combined with Ti₃C₂-TiO₂ to construct a highly sensitive luminol-O₂ ECL system for the specific detection of polynucleotide kinase (PNK) first. On the one hand, HIFU generated ROS in situ as a coreactant via the cavitation effect to boost the luminol emission. On the other hand, Ti₃C₂-TiO₂ was prepared in situ via Ti₃C₂ as a reducing agent, and it can aggregate and catalyze ROS generated in situ by HIFU. Moreover, the Ti on the Ti₃C₂-TiO₂ surface could bind to phosphate groups through chelation, thereby realizing highly specific detection of PNK. The sensor has a linear relationship range of 1.0 × 10^-5 to 10.0 U mL^-1, and the limit of detection is 1.48 × 10^-7 U mL^-1, which is superior to most existing methods. The sensor performance in HeLa cell lysate was measured with a satisfactory result. The designed ECL biosensor has potential applications in biological analysis and clinical diagnosis.

Generation of Oxygen Vacancies in Metal-Organic Framework-Derived One-Dimensional Ni0.4Fe2.6O4 Nanorice Heterojunctions for ppb-Level Diethylamine Gas Sensing

Metal-organic frameworks (MOFs) are ideal sensing materials due to their distinctive morphologies, high surface area, and simple calcination to remove sacrificial MOF scaffolds. Oxygen vacancies (O_vs) can be efficiently generated by the thermal annealing of metal oxides in an inert atmosphere. Herein, MIL-53-based Fe and Fe/Ni-MOFs nanorices (NRs) were first prepared by using a solvothermal method, and then one-dimensional (1D) Fe₂O₃ and Ni_0.4Fe_2.6O₄ NRs were derived from the MOFs after calcination at 350 °C in an air and argon (Ar) atmosphere, respectively. It was found that Ar-annealed Ni_0.4Fe_2.6O₄ NRs have higher O_vs concentrations (82.11%) and smaller NRs (24.3 nm) than air-annealed NRs (65.68% & 31.5 nm). Beneficially, among the synthesized NRs, the Ar-Ni_0.4Fe_2.6O₄ NRs show a higher sensitivity to diethylamine (DEA) (R_a/R_g = 23 @ 5 ppm, 175 °C), low detection limit (R_a/R_g = 1.2 @ 200 ppb), wide dynamic response (R_a/R_g = 93.5@ 30 ppm), high stability (30 days), and faster response/recovery time (4 s/38 s). Moreover, the 1D nanostructure containing heterostructures offers excellent sensing selectivity and a wide detection range from 200 ppb to 30 ppm in the presence of DEA. The outstanding gas sensing behavior can be attributable to synergistic impact, structural advantages, high concentration of O_vs, and the heterojunction interface, which can have profound effects on gas sensor performance. This study provides a unique technique for constructing high-performance gas sensors for ppb-level DEA detection and the formation of O_vs in metal oxides without the need for any additives.

Boosting the electrochemiluminescence of luminol by high-intensity focused ultrasound pretreatment combined with 1T/2H MoS2 catalysis to construct a sensitive sensing platform

In the luminol-O₂ ECL system, O₂ as an endogenous coreactant has the advantages of non-toxicity and stability. Improving the efficiency to generate radicals of O₂ is a challenge currently. In this work, a strategy combining physical method - ultrasound and nanomaterial with unique physicochemical properties was designed to enhance the ECL signal of luminol-O₂ system. Specifically, high-intensity focused ultrasound (HIFU) pretreatment as a non-invasive method could generate ROS (H₂O₂, O₂^•-, OH•, ¹O₂) in situ, triggering and boosting the ECL signal of luminol. In addition, 1T/2H MoS₂ with excellent catalytic activity could catalyze the H₂O₂ produced in situ, accelerate the oxidation of luminol and further enhance the ECL response. At the same time, combined with the catalytic hairpin assembly (CHA) reaction, the constructed ECL biosensing platform showed excellent performance for the detection of miRNA-155. The concentration range of 0.1 fM ∼ 1 nM with the detection limit as low as 0.057 fM were obtained. Furthermore, the ECL biosensor was also successfully applied to the determination of miRNA-155 in human serum samples. The established ECL sensing platform opens up a promising method for the detection of clinical biomarkers.

Supramolecular host-guest interaction-driven electrochemical recognition for pyrophosphate and alkaline phosphatase analysis

Herein, we report an electrochemical biosensor based on the supramolecular host-guest recognition between cucurbit[7]uril (CB[7]) and L -Phenylalanine-Cu(II) Complex for pyrophosphate (PPi) and alkaline phosphatase (ALP) analysis. First, L -Phe-Cu(II) Complex is simply synthesized by the complexation of Cu(II) (metal node) with L -Phe (bioorganic ligand), which can be immobilized onto CB[7] modified electrode via host-guest interaction of CB[7] and L -Phe. In this process, the signal of the Complex triggered electro-catalytic reduction of H 2 O 2 can be captured. Next, in the view of strong chelation between PPi and Cu(II), a biosensing system of the model "PPi and Cu(II) premixing, then adding L -Phe" is designed and the platform can be applied for PPi analysis well by hampering the formation of L -Phe-Cu(II) Complex. Along with ALP introduction, PPi can be hydrolyzed into orthophosphate (Pi), where abundant Cu(II) ions are released to form L -Phe-Cu(II) Complex, which gives rise to the catalytic reaction of Complex to H 2 O 2 reduction. The quantitative analysis of H 2 O 2 , PPi and ALP activity is achieved successfully and the detection of limits are 0.067 μM, 0.42 μM and 0.09 mU/mL ( S / N =3), respectively. With the merits of high sensitivity and selectivity, cost-effectiveness, and simplification, our developed analytical system has great potential to act on diagnosis and treatment of ALP-related diseases.

Plasmon-Boosted Fe, Co Dual Single-Atom Catalysts for Ultrasensitive Luminol-Dissolved O2 Electrochemiluminescence Detection of Prostate-Specific Antigen

Improving the sensitivity of electrochemiluminescence (ECL) systems is highly desired for in vitro ECL diagnosis and bio-detections due to the often-low content of biomarkers in diseases. And dissolved O₂ (DO) as a co-reactant is considered superior to H₂O₂ in the most commonly used luminol ECL systems due to better stability and low biotoxicity, but it still suffers from low ECL performance due to the low reactivity of DO. In this study, an efficient luminol-DO ECL system was developed through the complexing of Fe, Co dual single-atom catalysts (D-SACs) supported by N-doped graphene with the luminol-capped Ag nanoparticles (AgNPs). Benefiting from the electronic interaction between Fe and Co metal sites in the relevant D-SACs and plasmon enhancement of AgNPs, the performance of the corresponding ECL system could be significantly boosted up to ≈677-fold under optimal testing conditions, comparable to the classic luminol-O₂ system. Furthermore, the developed luminol-DO ECL system was successfully applied for the stable ultrasensitive detection of prostate-specific antigen (PSA) in a wide linear range of 1 fg/mL to 1 μg/mL, with a low limit of detection (0.98 fg/mL).

G-quadruplex-selective iridium(III) complex as a novel electrochemiluminescence probe for switch-on assay of double-stranded DNA

In this work, we synthesized an iridium(III) complex and studied its selective ability to interact with a specific G-quadruplex DNA sequence (GTGGGTAGGGCGGGTTGG). Results showed that the iridium(III) complex exhibits high selectivity for the G-quadruplex DNA and could be used as an efficient electrochemiluminescence (ECL) probe in a switch-on assay format for the detection of double-stranded DNA (dsDNA). To construct the assay, a hairpin-structured capture probe (CP) which was modified by thiol at its 3' end and contained the G-quadruplex sequence at its 5' end was firstly immobilized on a gold electrode. Upon the specific recognition of the dsDNA sequence with the corresponding CP, the hairpin structure of the CP was opened to free G-quadruplex sequence, forming the G-quadruplex structure with the assistance of K⁺. Then, the iridium(III) complex was able to specifically interact with the G-quadruplex to produce an obvious ECL signal that was proportional to the dsDNA concentration. Notably, this iridium(III) complex/G-quadruplex-based strategy was universal and was not limited to the analysis of DNA using specific sequences, thus opening a new avenue for the application of the G-quadruplex-selective iridium(III) complex in the field of ECL.

High-Entropy Oxide for Highly Efficient Luminol-Dissolved Oxygen Electrochemiluminescence and Biosensing Applications

The luminol-dissolved O₂ (DO) electrochemiluminescence (ECL) sensing system has recently gained growing interest; however, the drawback of the ultra-low ECL signal response greatly hinders its potential quantitative applications. In this work, for the first time, we explored the use of high entropy oxide (HEO) comprising five metal ingredients (Ni, Co, Cr, Cu, and Fe), to accelerate the reduction reaction of DO into reactive oxygen species (ROS) for boosting the ECL performance of the luminol-DO system. Benefiting from the existing abundant oxygen vacancies induced by the unique crystal structure of the HEO, DO could be efficiently converted into ROS, thus significantly boosting the performance of the corresponding ECL sensor (with an ∼240-fold signal enhancement in this study). As a proof of concept, under optimal conditions, the developed HEO-involved luminol-DO ECL sensing system was successfully applied for efficient biosensing of dopamine and alkaline phosphatase with a fine linear range from 1 pM to 10 nM and from 0.01 to 100 U/L as well as a low limit of detection of 5.2 pM and 0.008 U/L, respectively.