Single‐Atom Iron Boosts Electrochemiluminescence

The traditional luminol–H₂O₂ electrochemiluminescence (ECL) sensing platform suffers from self‐decomposition of H₂O₂ at room temperature, hampering its application for quantitative analysis. In this work, for the first time we employ iron single‐atom catalysts (Fe‐N‐C SACs) as an advanced co‐reactant accelerator to directly reduce the dissolved oxygen (O₂) to reactive oxygen species (ROS). Owing to the unique electronic structure and catalytic activity of Fe‐N‐C SACs, large amounts of ROS are efficiently produced, which then react with the luminol anion radical and significantly amplify the luminol ECL emission. Under the optimum conditions, a Fe‐N‐C SACs–luminol ECL sensor for antioxidant capacity measurement was developed with a good linear range from 0.8 μm to 1.0 mm of Trolox.     

Nickel Hydroxide Nanoparticles on Screen‐printed Electrodes as an Impedimetric Non‐enzymatic Glucose Sensor

In this study, the electrodeposition of nickel hydroxide nanoparticles onto a screen‐printed electrode (Ni(OH)₂/SPE) is described. Ni(OH)₂/SPE is proposed as an alternative non‐enzymatic glucose sensor based on Electrochemical Impedance Spectroscopy (EIS) measurements.The SPEs were modified by the cathodic electrodeposition of nickel, from a solution containing 0.010 M Ni(NO₃)₂ and 1 M NH₄Cl, at −1.3 V for 60 seconds. The SEM images show a uniform distribution of nickel spherical nanoparticles, with 60 nm average particle size. However, such morphology is not observed when the electrodeposition occurs in the absence of NH₄Cl. The electrochemical properties of the sensor were carefully evaluated by Cyclic Voltammetry. Ni(OH)₂/SPE shows a remarkable electrocatalytic behavior towards the oxidation of glucose in 0.1 M KOH. EIS measurements were carried out for Ni(OH)₂/SPE and a single‐frequency impedance method is proposed as transduction principle for glucose determination. The analysis of each parameter of complex impedance was performed. The best linear response was obtained for the module of impedance (|Z|) in the range of 0–2 mM of glucose at 0.1 Hz (R²=0.992) with a slope of 0.137 KΩ⁻¹⋅mM⁻¹ of glucose. Finally, Ni(OH)₂/SPE was utilized for quantification of glucose in blood samples.     

Electrochemiluminescence Sensor for Selective Preconcentration and Sensitive Detection of Napropamide Using Water‐Soluble Sulfonated Graphene

A novel electrochemiluminescence (ECL) sensor for napropamide determination was prepared using the water‐soluble sulfonated graphene (sulfonated‐G) as solid‐phase microextraction (SPME) material, based on selective preconcentration of target onto an electrode and followed by luminol ECL detection. The effects of pH, adsorption time, buffer solution and the luminescence agent on ECL intensity were optimized. Under the optimized conditions (pH 6; adsorption time 5 min; buffer solution pH 11.0 Na₂CO₃ aHCO₃; luminescence agent luminol; stirring speed 400 rpm), the lowest detection limits (1.0 µg L⁻¹) and good linear range (r²≥0.99) were obtained for the analyte, indicating the superior performance of Nafion/sulfonated‐G/GCE for detecting napropamide.     

The Hybrid of Gold Nanoparticles and 3D Flower‐like MnO2 Nanostructure with Enhanced Activity for Detection of Hydrogen Peroxide

3D Flower‐like manganese dioxide (MnO₂) nanostructure with the ability of catalysis for hydrogen peroxide (H₂O₂) and super large area that can support gold nanoparticles (AuNPs) with enhanced activity of electron transfer have been developed. The nanostructure of hybrids was prepared by directly mixing citric‐capped AuNPs and 3‐aminopropyltriethoxysilane (3‐APTES)‐capped nano‐MnO₂ using an electrostatic adsorption strategy. The Au‐MnO₂ composite was extensively characterized by scanning electron microscope (SEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), the Brunauer‐Emmett‐Teller (BET) method and X‐ray photoemission spectroscopy (XPS). Electrochemical properties were evaluated through cyclic voltammetry (CV) and amperometric method. The prepared sensor showed excellent electrochemical properties towards H₂O₂ with a wide linear range from 2.5×10⁻³∼1.39 mM and 3.89∼13.89 mM. The detection limit is 0.34 μM (S/N=3) with the sensitivities of 169.43 μA mM⁻¹ cm⁻² and 55.72 μA mM⁻¹ cm⁻². The detection of real samples was also studied. The result exhibited that the prepared sensor can be used for H₂O₂ detection in real samples.     

Electrochemiluminescence Aptasensor for the MUC1 Protein Based on Multi‐functionalized Graphene Oxide Nanocomposite

The electrochemiluminescence (ECL) aptasensor was prepared for the detection of Mucin 1 based on its specific recognition by aptamer immobilized on multi‐functionalized graphene oxide nanocomposite, which was prepared with N‐(4‐aminobutyl)‐N‐ethylisoluminol (ABEI) and aptamer chemically bound to the surface of magnetic GO (nanoFe₃O₄@GO). ABEI and aptamer acted as the electrochemiluminophore and the capture device for Mucin 1 respectively. NanoFe₃O₄@GO brought multi‐functionalized graphene oxide nanocomposite attracted on the surface of magnetic glass carbon electrode through magnetism, enabled all the ABEI immobilized electrochemically active due to its good conductivity and thus then facilitated the sensitive detection of Mucin 1. In addition, the ECL aptasensor can be prepared through a one‐step process. Under optimal conditions, the ECL intensity of the aptasensor decreased proportionally to the logarithmic concentrations of Mucin 1 in the range of 0.005–1000 ng mL^?1. This aptasensor displays good specificity, stability, reproducibility and application. This method has a large potential because such a multi‐functionalized graphene oxide nanocomposite also may be applied to other ECL‐based aptasensors.     

A Novel Enzymatic Glucose Biosensor and Nonenzymatic Hydrogen Peroxide Sensor Based on (3‐Aminopropyl) Triethoxysilane Functionalized Reduced Graphene Oxide

In the present study, a novel enzymatic glucose biosensor using glucose oxidase (GOx) immobilized into (3‐aminopropyl) triethoxysilane (APTES) functionalized reduced graphene oxide (rGO‐APTES) and hydrogen peroxide sensor based on rGO‐APTES modified glassy carbon (GC) electrode were fabricated. Nafion (Nf) was used as a protective membrane. For the characterization of the composites, Fourier transform infrared spectroscopy (FTIR), X‐ray powder diffractometer (XRD), and transmission electron microscopy (TEM) were used. The electrochemical properties of the modified electrodes were investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The resulting Nf/rGO‐APTES/GOx/GC and Nf/rGO‐APTES/GC composites showed good electrocatalytical activity toward glucose and H₂O₂, respectively. The Nf/rGO‐APTES/GC electrode exhibited a linear range of H₂O₂ concentration from 0.05 to 15.25 mM with a detection limit (LOD) of 0.017 mM and sensitivity of 124.87 μA mM⁻¹ cm⁻². The Nf/rGO‐APTES/GOx/GC electrode showed a linear range of glucose from 0.02 to 4.340 mM with a LOD of 9 μM and sensitivity of 75.26 μA mM⁻¹ cm⁻². Also, the sensor and biosensor had notable selectivity, repeatability, reproducibility, and storage stability.     

A Highly Sensitive Electrochemiluminescence Choline Biosensor Based on Poly(aniline‐luminol‐hemin) Nanocomposites

Poly(aniline‐luminol‐hemin) nanocomposites are prepared on an electrode surface through electropolymerization, and a highly sensitive electrochemiluminescence (ECL) biosensor for choline is developed based on the poly(aniline‐luminol‐hemin) nanocomposites and an enzyme catalyzed reaction of choline oxidase (CHOD). The obtained nanocomposites are characterized by scanning electron microscopy (SEM), atomic absorption spectrometry (AAS) and ECL. The results indicate that hemin can be incorporated into the poly(aniline‐luminol) nanocomposites using the facile electropolymerization method, and the poly(aniline‐luminol‐hemin) nanocomposites are rod shaped porous nanostructure. Moreover, the poly(aniline‐luminol‐hemin) nanocomposites exhibit higher ECL intensity than poly(aniline‐luminol) nanocomposites in alkaline media due to the catalytic effect of hemin on the ECL of the polymerized luminol and the electron transfer ability of hemin in the nanocomposites. CHOD is immobilized on the surface of the poly(aniline‐luminol‐hemin) nanocomposites modified electrode with glutaraldehyde, and the ECL biosensor based on poly(aniline‐luminol‐hemin)/CHOD exhibits a wider linear range for the choline detection. The enhanced ECL signals are linear with the logarithm of concentration of choline over the range of 1.0×10^?11～1.0×10^?7 mol L^?1 with a low detection limit of 1.2×10^?12 mol L^?1. Moreover, the proposed biosensor is successfully applied to the detection of choline in milk.     

Direct Electrochemical Nano‐immunosensor for Microcystin‐LR in Seawater

Microcystins are potent hepatotoxins produced by cyanobacteria, which proliferate in wastewaters with high nutrient content. Due to their high toxicity and potential risk to human health, even at low concentrations, the development of a sensitive and rapid method for the monitoring of microcystin‐LR (MC‐LR) in water samples is of great importance. In this context, a new direct electrochemical nano‐immunosensor for MC‐LR detection using the liquid crystal (E)‐1‐decyl‐4‐[(4‐decyloxyphenyl)diazenyl]pyridinium bromide (Br‐Py) as a redox probe and gold nanoparticles stabilized in bovine serum albumin (AuNP‐BSA) is described herein. The microcystin‐LR antibody (anti‐MC‐LR) was covalently immobilized using N‐(3‐dimethylaminopropyl)‐N‐ethylcarbodiimide hydrochloride (EDC) and N‐hydroxysuccinimide (NHS) on an AuNP‐BSA/BrPy film. The proposed sensor response is based on the inhibition of the Br‐Py electrochemical signal after the specific interaction of MC‐LR with immobilized anti‐MC‐LR on the electrode surface. The electrochemical behavior of the immunosensor was studied by square‐wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). Under optimized conditions, using SWV and an incubation time of 15 min, the immunosensor exhibits a linear response to MC‐LR concentrations of 0.05 to 500.0 ng mL⁻¹ with a detection limit of 0.05 ng mL⁻¹. The anti‐MC‐LR/AuNP‐BSA/Br‐Py/GCE was successfully applied in the determination of MC‐LR in spiked seawater samples.     

Detection of DNA hybridization by ABEI electrochemiluminescence in DNA-chip compatible assembly

The electrochemiluminescence (ECL) of a luminol derivate (ABEI) generated both by a carbon electrode and a polypyrrole-coated carbon electrode was examined. It was found that the polypyrrole film (ppy) did not inhibit the ECL. After that, ABEI anchored on a single stranded DNA target (ODNt) has been used for the ECL detection of the hybridization between a complementary single stranded DNA probe (ODNp) covalently linked to a polypyrrole support and the ODNt. The ECL detection has been performed using a DNA sensor having a low surface concentration of ODNp probes, constituted of a polypyrrole copolymer electrosynthesized from a pyrrole-ODNp/pyrrole monomer ratio of 1/20,000.     

Novel Sn Doped Co3O4 Thin Film for Nonenzymatic Glucose Bio‐Sensor and Fuel Cell

A facile chemical solution deposition via two‐step spin coating technique was used to fabricate nano‐particulate novel Sn doped Co₃O₄ thin film for glucose sensor and fuel cell applications. Substitution of Sn into Co₃O₄ host lattice lead to a remarkable increase in the electrocatalytic activity of the Co₃O₄ electrode material. Film thickness played a significant role in enhancing the charge transferability of the electrode as was observed from electrochemical impedance spectroscopy (EIS). The best sensor exhibited two wide linear response ranges (2 μM up to ∼0.5 mM and 0.6 mM up to ∼5.5 mM respectively) with sensitivities of 921 and 265 μA cm⁻² mM⁻¹ respectively and low limit of detection of 100 nM (S/N=3). The sensor was very selective towards glucose in the presence of various interference and showed long term stability. Moreover, the developed thin film modified electrode could generate one electron current in nonenzymatic fuel cell setup at room temperature.     

Enhanced electrochemiluminescence of luminol at the gold nanoparticle/carbon nanotube/electropolymerised molecular imprinting composite membrane interface for selective recognition of triazophos

This paper reports a surface molecular self-assembly strategy for imprinting triazophos in the electropolymerised poly(aminthiophenol) (PATP) membranes at the surface of gold nanoparticle (AuNP)/carbon nanotube (CNT) composites modified glassy (GC) electrode for electrochemiluminescent (ECL) detection of pesticide triazophos. The electrochemical and ECL behaviours of luminol at the imprinted PATP/AuNP/CNT/GC electrode were investigated before and after the rebinding of triazophos. It was also found that the ECL intensity was strikingly enhanced by the adsorbed triazophos molecules in the imprinted PATP/AuNP/CNT composite membranes, which was about 5.2-fold as compared with the blank ECL intensity. On this basis, the molecularly imprinted polymer (MIP)-ECL sensor is established for high sensitive and selective detection of triazophos residues in vegetable samples. The resulting MIP-ECL sensor shows wide linear ranges from 3.1 × 10^?8 to 3.1 × 10^?5 g L^?1 with lower detection limit of 3.1 × 10^?9 g L^?1 for triazophos. Moreover, the MIP-ECL sensor has the advantages of high sensitivity, speed, specificity, stability and can become a promising technique for organophosphate pesticide detection.     

Electrochemiluminescent detection of the hybridization of oligonucleotides using an electrode modified with nanocomposite of carbon nanotubes and gold nanoparticles

We report on an electrochemiluminescent (ECL) sensing technique for the detection of the hybridization between oligonucleotides. A glassy carbon electrode was first functionalized with a composite prepared from gold nanoparticles and carbon nanotubes, and a sensor was then constructed by immobilizing the probing oligonucleotide. The ECL of luminol acts as the sensing signal. It is quenched, to a different degree, by the hybridized double strands of the oligonucleotide depending on the match status. The slope of the ECL response as a function of the status of hybridization drops with increasingly matched hybridization. The response is attributed to the interaction between luminol and the strands of oligomers, and also related to the reduction of reactive oxygen species.

Electrochemiluminescence Characterization of Poly(luminol‐benzidine) Composite Films and Their Analytical Application

A composite film of poly(luminol‐benzidine) was prepared on the graphite electrode surface by electropolymerizing luminol and benzidine in acidic medium. It was found that the poly(luminol‐benzidine) composite film presented better electrochemiluminescence (ECL) analytical performances for H₂O₂ than that of the polyluminol film. Based on these findings, a more sensitive ECL sensor for H₂O₂ was developed. At the same time, our investigating results on this composite film revealed that, as a real ECL luminophor in this composite film, the polymeric 3‐aminophthalate presented higher fluorescence quantum yield than that in the pure polyluminol film, which suggested that the excellent ECL performances of the composite film may originate from the enhancement of the ECL luminophor quantum yield. Based on these results, a new method to improve the ECL analytical performances of the polymeric luminol was also proposed.     

An enhanced Nonenzymatic Electrochemical Glucose Sensor Based on Copper‐Palladium Nanoparticles Modified Glassy Carbon Electrodes

Novel copper‐palladium nanoparticles modified glassy carbon electrodes (Cu−Pd/GC) with enhanced nonenzymatic sensing for glucose were facilely prepared by one‐step electrodeposition. The structure and composition of the prepared nanoparticles were characterized by XRD, SEM, TEM and EDS, respectively. The electrode modified process was characterized by electrochemical impedance spectroscopy. Cyclic voltammetry and chronoamperometric experiments were used to evaluate the electrocatalytic activities of the electrodes toward glucose. The surface morphology and the electrocatalytic activities of Cu−Pd/GC was compared to Pd and Cu nanoparticles modified glassy carbon electrodes (Pd/GC and Cu/GC), respectively. Thanks to homogeneous distribution of Cu−Pd nanoparticles and the synergistic effect of Cu and Pd atoms, Cu−Pd/GC exhibited the highest sensitivity (298 μA mM⁻¹ cm⁻²) and the widest linear amperometric response (0.01 mM to 9.6 mM, R²=0.996) toward glucose compared to Pd/GC and Cu/GC. The detection limit of Cu−Pd/GC was 0.32 μM (S/N=3). In addition, the as‐prepared Cu−Pd/GC glucose sensor also exhibited exceptional capabilities of anti‐interference, reproducibility and long‐term stability. The as‐prepared sensor was also evaluated for determination of glucose concentration in human blood serum samples, which exhibited high reliability and accuracy, having great potential in clinical application.     

Electrochemiluminescence Bioassays with a Water‐Soluble Luminol Derivative Can Outperform Fluorescence Assays

The most efficient and commonly used electrochemiluminescence (ECL) emitters are luminol, [Ru(bpy)₃]²⁺, and derivatives thereof. Luminol stands out due to its low excitation potential, but applications are limited by its insolubility under physiological conditions. The water‐soluble m‐carboxy luminol was synthesized in 15 % yield and exhibited high solubility under physiological conditions and afforded a four‐fold ECL signal increase (vs. luminol). Entrapment in DNA‐tagged liposomes enabled a DNA assay with a detection limit of 3.2 pmol L^?1, which is 150 times lower than the corresponding fluorescence approach. This remarkable sensitivity gain and the low excitation potential establish m‐carboxy luminol as a superior ECL probe with direct relevance to chemiluminescence and enzymatic bioanalytical approaches.     

Binder Free Modification of Glassy Carbon Electrode by Employing Reduced Graphene Oxide/ZnO Composite for Voltammetric Determination of Certain Nitroaromatics

Reduced Graphene oxide/ZnO nanoflowers ( rGO/ZnO‐NFs ) composite has been synthesized in‐situ using asymmetric Zn complex ( 1 ) as a single‐source molecular precursor (SSMP) with GO at 150 °C. The rGO/ZnO‐NFs composite was characterized by PXRD, UV‐vis, SEM, EDX mapping, TEM and SAED pattern to confirm its purity and morphology. The rGO/ZnO‐NFs composite shows uniform distribution of nanoflowers on graphene sheets. The modified glassy carbon electrode ( GCE ) was fabricated by drop wise layering of the rGO/ZnO‐NFs composite at the surface of the GCE without using binder. The binder free modified electrode ( GCE‐rGO/ZnO ) was explored for detection of nitroaromatics such as p‐nitro‐phenol ( p ‐NP ), 2,4‐dinitrophenol ( 2,4‐DNP ), 2,4‐dinitrotoluene ( 2,4‐DNT ) and 2,4,6‐trinitrophenol ( 2,4,6‐TNP ). The fabricated sensor showed remarkable response for the both toxicants and explosives. The LOD, sensitivity and linear range for the studied toxicants and explosives were found to be in a good range: p ‐NP= 0.93 μM, 240 μA mM⁻¹ cm⁻² and 0.2–0.9 mM; 2,4‐DNP= 6.2 μM, 203 μA mM⁻¹ cm⁻² and 0.1–0.9 mM; 2,4‐DNT= 10 μM, 371 μA mM⁻¹ cm⁻² and 0.2–0.9 mM; 2,4,6‐TNP= 16 μM, 514 μA mM⁻¹ cm⁻² and 0.2–0.9 mM, respectively.     

Functionalized Gold Nanoparticles – Octadecylamine Hybrid Langmuir‐Blodgett Film for Enzyme Sensor

Mediator free enzyme sensor has been fabricated by covalently immobilizing cholesterol oxidase (ChOx) onto 11‐mercaptoundecanoic acid functionalized gold nanoparticles (MUDA‐AuNPs) – octadecylamine (ODA) hybrid Langmuir–Blodgett film. The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) studies reveal that MUDA‐AuNP/ODA LB film has good affinity for ChOx and provides favorable microenvironment for direct electron transfer between enzyme and electrode. Interference free estimation of cholesterol has been realized at 0.3 V with linear range from 25 to 500 mg/dL, detection limit of 23.38 mg/dL, sensitivity of 1.085 μA mM^?1 and response time of 20 s at pH 7.0.     

Enzyme‐free Glucose Sensor Fabricated by Nanorods Decorated Nanopore Arrays on Biomedical Stainless Steel

A novel enzyme‐free glucose sensor was proposed by preparation of nanorods decorated nanopore arrays (NRs/NPAs) on 316L stainless steel simply by electrochemical treatments. The NRs/NPAs sensor displays two linear ranges towards glucose determination, one range from 1 μM to 1.2 mM with a sensitivity of 202.2 μA ? cm^?2 ? mM^?1, another range from 1.2 mM to 7.7 mM with a sensitivity of 59.18 μA?cm^?2 ? mM^?1. The detection limit is 0.5 μM. The NRs/NPAs electrode exhibits excellent stability, good selectivity and reproducibility, rendering it suitable for glucose monitoring.     

Cathodized Gold Nanoparticle‐Modified Graphite Pencil Electrode for Non‐Enzymatic Sensitive Voltammetric Detection of Glucose

A highly sensitive enzymeless electrochemical glucose sensor has been developed based on the simply prepared cathodized gold nanoparticle‐modified graphite pencil electrode (AuNP‐GPE). Cyclic voltammetry (CV) experiments show that AuNP‐GPE is able to oxidize glucose partially at low potential (around −0.27) whereas the bare GPE cannot oxidize glucose in the entire tested potential windows. Besides, fructose and sucrose cannot be oxidized at potential lower than +0.1 V at AuNP‐GPE. As a result, the glucose oxidation peak at around −0.27 V is suitable enough for selective detection of glucose in the presence of fructose and sucrose. Cathodization of AuNP‐GPE under optimum condition (‐1.0 V for 30 s) in the same glucose solution before voltammetric measurement enhanced glucose oxidation peak current around −0.27 V to achieve an efficient electrochemical sensor for glucose with a detection limit of 12 μM and dynamic range between 0.05 to 5.0 mM with a good linearity (R²= 0.999). Almost no interference effect was observed for sensing of glucose in the presence of ascorbic acid, alanine, phenylalanine, fructose, sucrose, and NaCl.     

Non‐enzymatic Fructose Sensor Based on Co3O4 Thin Film

In this study, we report on the selective of fructose on Co₃O₄ thin film electrode surface. A facile chemical solution deposition technique was used to fabricate Co₃O₄ thin film on fluorine doped tin oxide, FTO, glass. Electrode characterization was done using XRD, HRTEM, SEM, AFM, and EIS. The constructed sensor exhibited two distinctive linear ranges (0.021–1.74 mM; 1.74–∼15 mM) covering a wide linear range of up to ∼15 mM at an applied potential of +0.6 V vs Ag/AgCl in 0.1 M NaOH solution. The sensor demonstrated high, reproducible and repeatable (R.S.D of <5 %) sensitivity of 495 (lower concentration range) & 53 (higher concentration range) μA cm⁻² mM⁻¹. The sensor produced a low detection limit of ∼1.7 μM (S/N =3). The electrode was characterised by a fast response time of <6 s and long term stability. The repeatability and stability of the electrode resulted from the chemical stability of Co₃O₄ thin film. The sensor was highly selective towards fructose compared to the presence of other key interferences i. e. AA, AC, UA. The ease of the electrode fabrication coupled with good electrochemical activity makes Co₃O₄ thin film, a promising candidate for non‐enzymatic fructose detection.