•A highly sensitive and stable amperometric biosensing interface for rapid detection of 1-pyrene butyric acid.•The alginate-polylysine microencapsulated hemoglobin and Au nanoparticles for construction of sensing interface.•Rapid electron transfer and high sensitivity with the quantification limit as low as 23.5 fM of 1-pyrene butyric acid.In the current work, a highly sensitive and stable amperometric biosensing interface for the rapid detection of 1-pyrene butyric acid (1-PBA) was constructed based on the functions of alginate-polylysine microencapsulated hemoglobin (AP@Hb) and Au nanoparticles (AuNPs). AP@Hb was simply prepared by a two-step template method. The morphology and size were characterized by scanning electron microscopy. AuNPs were employed to facilitate the electron transfer between the electrode and Hb. Through the electron tunneling effect of AuNPs and the catalysis of Hb, the resultant biosensor achieved rapid electron transfer and high sensitivity toward 1-PBA with a quantification limit as low as 23.5 fM. Thus, this biosensor is promising for the quantitative detection of 1-PBA in real samples and might provide assistance to public health agencies for the control and prevention of certain diseases caused by 1-PBA.

•A label free biosensor for I27L gene variant (diabetes) with electrochemiluminescence of luminol as output signal.•The Au nanoparticles (AuNPs) decorated ITO acted as the substrate.•The biosensor exhibited high sensitivity, stability, excellent reproducibility and selectivity toward mismatched DNA.The variation of I27L gene closely relates to increasing risk of type 2 diabetes, thus it is greatly significant to develop various methods for its identification or monitoring. We report here a novel label-free electrochemiluminescent (ECL) biosensor for simple and effective determination of I27L gene based on Au nanoparticles functionalized ITO electrode. The ECL technique is employed to monitor the hybridization of DNA strands by measuring the changes of its intensity. Here, the ECL signal was quenched by blocked access of probe (luminol anion) owing to the electrostatic repulsion of negatively charged sensor surface and the space resistance. The quantification of target strand can be directly realized by calibrating the quenched ECL signal toward its logarithm concentration in good linearity within the range from 1.0 × 10−11 to 1.0 × 10−7 M and a detection limit of 8.1 × 10−12 M. In addition, the biosensor exhibited good stability, excellent reproducibility and outstanding selectivity against one-base mismatched strand. What's more, the simple, low-cost, sensitive device could be easily miniaturized, makes it as an attractive candidate for integrating into portable platforms for point-of-care molecular diagnostics.Download high-res image (204KB)Download full-size image

In this work, a novel enzymatic electrochemiluminescent (ECL) biosensor based on the sensitization from Au/TiO2 nano-composite was prepared for noninvasive glucose detection. The Au/TiO2 nano-composite was deposited on the surface of indium tin oxide glass by Nafion, which significantly enhanced the ECL of luminol after calcination, and a sensitive response toward hydrogen peroxide was obtained. Glucose oxidase was cross-linked with bovine serum albumin by glutaraldehyde and immobilized on electrode surface. It worked as the sensing matrix and catalyzed the oxidation of glucose to produce H2O2, thus an enhanced ECL emission was resulted. Under the optimized conditions, this biosensor showed good stability, selectivity, sensitivity and simplicity. It has a wide linear range for the detection of glucose from 7.0 μM to 100 μM with a detection limit of 0.22 μM. The sensor has been successfully applied to detect glucose in diluted human serums and saliva samples. Therefore, this sensor could be regarded as a simple, practical and disposable device in a noninvasive manner of routine glucose monitoring for diabetics.

•The enhanced electrochemiluminescence of luminol by AuNPs/TiNTs.•An ECL biosensor for HbA1c assay with ultra-high sensitivity.•A promising disposable device for diabetic diagnosis and treatment even for POCT.•The excellent regression of detected results with gold-standard method.A glycated hemoglobin (HbA1c) biosensor with high performance has been constructed in this work. Here the fructosyl amino acid oxidase was immobilized onto a pre-functionalized indium tin oxide glass with titania nanotubes decorated with gold nanoparticles. The property of nanocomposite was characterized by transmission electromicroscopy, scanning electron microscopy, electrochemistry and spectroscopy. Under the optimum conditions, fructosyl valine was detected by this biosensor. It exhibited a linear detection range from 4.0 × 10−9 M to 7.2 × 10−7 M, and a limit of detection for 3.8 × 10−9 M at the signal-to-noise ratio of 3. Thus the HbA1c level in whole blood samples of healthy individuals or diabetic patients were evaluated with designed biosensor after pre-treatment of hydrolysis. The results of our detection were closely consistent with that of the standard method. At the same time, our biosensor has some advantages including high sensitivity, disposable usage and low cost, which implies its great promising application in point-of-care testing of HbA1c.

Diabetes mellitus is a worldwide proliferated noninfectious disease in these years. Although it is not dangerous for life, but the complications such as kidney disease, blindness, foot disease or nerve damage will result in severe degradation of the vital quality of the diabetics. So, the monitoring of those diabetes related indexes is very important for controlling and treatment of the disease. More accurate and convenient methods for their assay are in expect. The electrochemiluminescent (ECL) and chemiluminescent (CL) analysis have received high attention because of their excellent sensitivity, low back-ground signal and other advantages. Especially combined with some biological measures, they have shown excellent specificity, and flexibility for a wide range of analytes, leading to their usefulness in clinical tests including diabetes. This paper will review the progress of this luminescent assay for diabetes mellitus in present years.

This paper describes a novel approach to promote the analytical performance of electrochemiluminescent (ECL) biosensor of cholesterol by a nanocomposite (Au nanoparticles/ion liquid/hollowed TiO2 nano-shell) pre-functionalized indium tin oxide glass to load the cholesterol oxidase. Here the enzymatically produced hydrogen peroxide greatly intensified the ECL of luminol under the catalysis of the nanocomposite. The quantification of cholesterol was directly accomplished by calibrating the ECL sensing output. The formation and properties of the nanocomposite and the functionalized electrode have been confirmed by electrochemistry, spectroscopy and electron-microscopy. The prepared biosensor exhibits a linear regression ranged from 8.33 × 10−9 M to 4.17 × 10−7 M with an ultralow detection limit (LOD) of 6.30 × 10−9 M. It also possesses the excellent specificity for cholesterol from potential interferents, the favorable repeatability/stability for use or storage, the good reproducibility and adequate recovery for real sample test. In addition, for the detection of clinical serum sample, it is well consistent with the datum from medical cholesterol kit, indicating its reliability. It is in promising of the application for the cholesterol detection in those clinical specimens of teeny amount of sample and limited concentration.

A hemoglobin (Hb)-modified electrode based on chitosan/Fe3O4 nanocomposite coated glassy carbon has been constructed for trichloroacetic acid (TCA) detection. The structure of chitosan/Fe3O4 nanocomposite was investigated using energy-dispersive X-ray analysis (EDS) and X-ray diffraction (XRD) patterns. The electron transfer rate constant (ks) of Hb was estimated for as high as 3.12 s−1. The immobilized Hb exhibited excellent electro-catalytic activity toward the reduction of TCA. The response current regressed to the concentration of TCA within the range of 5.70 μM to 205 μM with a detection limit of 1.9 μM (S/N = 3).

•A new luminol-based ECL cell was designed by bi-potentiostatic excitation.•Four electrodes were artfully fixed in a home-made flow ECL cell.•Continuous and constant ECL signal could be obtained on this ECL cell.•The cell provides higher sensitivity than pulsed mode and successfully employed to determine the activity of antioxidants.A new designed luminol-based electrochemiluminescent (ECL) cell by bi-potentiostatic excitation was developed for the utilization as a coupled-detector of a flow injection analysis system (Bi-ECL–FIA). In this flow cell, four electrodes were fixed in, here a piece of indium tin oxide coated glass was applied as one of the working electrodes while another Pt net served as second one. Two electrolysis voltages from a dual-potentiostat powered two working electrodes. Thus, continuous and constant ECL signal could be obtained. After optimizing the experimental conditions, it was showed that the Bi-ECL–FIA system provided higher sensitivity than conventional pulsed mode. The response of hydrogen peroxide or resveratrol on this system was investigated, indicating a 7.4 × 10−11 mol/L of detection limit for H2O2 and 8.8 × 10−8 mol/L for resveratrol. The system was successfully employed to value the gross activity of antioxidants of peanut using resveratrol as the index. The results suggested a good recovery within the range from 88.8% to 109.1%.

•A new strategy for label-free electrochemiluminescent immunosensor using luminol as probe.•The highly sensitive response toward methamphetamine to the level of 0.3 ng mL−1.•A nano-Au functionalized indium tin oxide glass acting as the substrate electrode.•The mass-transportation controlled mechanism about the sensing response.In this paper, a new strategy to prepare the label-free immunosensor signaling with the electrochemiluminescence (ECL) of luminol will be reported. The gold nano-particles (AuNPs) functionalized indium tin oxide coated glass is used as the substrate for antibody immobilization. These AuNPs also improve the ECL behavior of luminol. This strategy for immunosensor construction is simple, fast, cheap, and with no requirements of expensive apparatus. For validating the practicability of this new strategy, with methamphetamine (MA) as target model, an MA sensor was built by immobilizing the MA-antibody onto the surface of previously mentioned substrate. The ECL intensity on resultant sensor, after the direct immuno-interaction, decreased proportional to the concentration of MA in a wide linear range from 2 to 500 ng mL−1 with a detection limit of 0.3 ng mL−1. This proposed sensor is sensitive, specific, stable and reliable. It has been successfully applied to detect the MA in spiked human serums.

We report here the development of an immunosensor for morphine based on electrochemiluminescence using luminol as the probe. Gold nanoparticles were attached to the surface of indium–tin oxide coated glass via hydrolyzed 3-amino-propyltrimethoxysilane. This coating acted as a matrix to directly immobilize an antibody to morphine as the sensing host via adsorption. The electrochemiluminescence intensity of luminol on this sensor decreased with the concentration of morphine after immuno-incubation. There was a linear relationship with the logarithm of the morphine concentration in the range 2–200 ng mL−1 and a detection limit of 0.82 ng mL−1 (S/N = 3). The sensor was used to determine the concentration of morphine in spiked urine samples with a satisfactory recovery. This label-free sensor has the potential to be developed as a disposable, portable and mass-produced device as a result of its simplicity of preparation and utilization.

•A greatly enhanced electrochemiluminescence of luminol by titania nanotubes.•Functionalisation for indium tin oxide coated glass to act as the working electrode.•Very sensitive response toward oxidant or antioxidant.•Determination of gross antioxidant efficiency of blueberry and kiwi.The titania nanotubes (TiNTs) had been immobilised onto the indium tin oxide (ITO) coated glass to intensify the electrochemiluminescence (ECL) of luminol. The morphology, structure and properties such as specific surface area and transmittance of synthesised TiNTs were characterised. The results indicated that the TiNTs was several hundred nanometres in length with the diameter of 20 nm. In flow injection analysis (FIA) mode, the TiNTs dramatically enhanced the ECL emission of luminol for about 25 multiple, meanwhile decreased the requirement of buffer pH and exciting potential. The ECL emission of luminol on functionalised ITO electrode has sensitive response toward hydrogen peroxide, and extraordinarily responsive toward the antioxidant. Under the optimal conditions, the ECL emission exhibited a linear response within the concentration range from 0.1 mg L−1 to 30 mg L−1 and an absolute detection limit of 1.65×10−10 g of resveratrol. The gross antioxidant activity of blueberry and kiwi were determined with satisfactory recoveries.

•The bi-potentiostatic mode for electrochemiluminescence excitation•The resonance energy transfer between reactive oxygen species and luminol•The stronger and constant electrochemiluminescence of luminolA novel luminol-based bi-potentiostatic electrochemiluminescent (ECL) system has been established. Two potentials were exerted on two working electrodes respectively with a dual-potentiostat. More reactive oxygen species and the oxidative intermediate of luminol were generated in the vicinity of the working electrodes during the ECL process and then stronger and constant ECL emission can be obtained through energy transfer between those active species. After optimizing the experimental conditions, it was demonstrated that the developed ECL system provided great potency for quantified assay.

•Highly sensitive immunosensor for detection of morphine and methamphetamine.•Electrochemical impedance as readout signal.•Self-assembly modified Au electrode as substrate for antibody immobilization.In this paper, immunosensors based on a self-assembly modified (SAM) Au electrode for the specific detection of two illicit drugs, morphine (MO) and methamphetamine (MA), are reported. Using 3-mercaptopropionic acid SAM and activation by 1-ethyl-3-(3-dimethylaminoprophyl) carbodiimide (EDC)/n-hydroxysulfsuccinimide (NHS) with an adequate quantity of the antibody of MO or MA immobilized onto the surface to act as the sensing host, the sensors specifically respond to their respective target based on specific covalent bonding. Electrochemical impedance spectroscopy (EIS) is used as the read-out signal. The value of the electron transfer resistance (Ret) responded to the concentration of drug in spiked blood samples with an ultra-low detection limit and satisfactory recovery. In conclusion, the developed sensors are demonstrated to be more advantageous compared to those previously reported in terms of sensitivity.

•The hollow titania nano-shell intensify the electrochemiluminescence of luminol for 150 times.•The highly sensitive response toward hydrogen peroxide to the level of 10−10 mol/L.•A nano-functionalized indium tin oxide glass for practicable electrochemiluminescent application.Hollow titania nanoshells (HTNSs), which were synthesized by a SiO2 sacrificial template method, were used to intensify the electrochemiluminescence (ECL) of luminol. The size, shell thickness and crystal phase, factors that are important in determining the efficiency, can be controlled by adjusting the template size, precursor concentration and calcination temperature, respectively. The structure of the HTNSs was characterized by transmission electron microscopy, scanning electron microscopy and X-ray diffraction spectroscopy. After structural optimization, the surface of indium tin oxide (ITO)-coated glass was modified with the HTNSs to act as a working electrode for a flow-injection analytical system. The heterostructure demonstrated an ECL emission intensity 150 times higher than that of the bare ITO. The research also revealed that the ECL of luminol on this modified electrode showed a very sensitive response to hydrogen peroxide with a detection limit of 4.6×10−10 M. In addition to discussing the intensifying mechanism of luminol ECL by HTNSs, we demonstrate that can be successfully applied to evaluate the gross antioxidant activity of garlic.Synthesized hollow titania nano-shell, after immobilized onto indium tin oxide glass to act as working electrode, intensify the electrochemiluminescence (ECL) of luminol. The ECL got a 150 times multiplication than on bare electrode. It is also closely related to the content of reactive oxygen species in solution, got a detection limit for H2O2 at the level of 10−10 mol/L.

This paper reports on the synthesis of AuAg and PtAg alloy nanoclusters (NCs) and their enhancement effect on the electrochemiluminescence (ECL) of luminol. The conditions of synthesis were optimized, and the structure and properties of the NCs were characterized by X-ray diffraction, transmission electron microscopy, electrochemistry, and optical spectroscopy. The NCs are found to intensify (by up to 20 times) the ECL of luminol in solution of pH 8.5. This finding can largely extend the useful pH range of the ECL of luminol. The enhanced ECL is strongly affected by oxygen and hydrogen peroxide, and the mechanism of enhancement is attributed to the accelerated production of reactive oxygen species. The enhanced ECL is also affected by phenolic artificial estrogens, and this was used for their determination with detection limits as low as 700 pg L−1 (with AuAg) and 1.6 ng L−1 (with PtAg). The method was applied to the determination of such estrogens in egg samples using diethylstilbestrol as a reference substance.

•An AuAg/TiO2 nano-hybrid was synthesized and modified onto ITO surface to act as an ECL electrode.•The ECL of luminol is greatly intensified on this electrode coupled with microemulsion matrix.•The synergic effect of nano-hybrid and microemulsion resulted in the recordable ECL at pH 6.0.•The ECL response for H2O2 gains a descended detection limit for two orders of magnitudes.A nano-hybrid of nano-titania supported AuAg alloy nanocluster was synthesized. It was then modified onto the surface of indium tin oxide (ITO) coated glass to act as a working electrode for exciting the electrochemiluminescence (ECL) of luminol. The properties of the nano-hybrid and the functionalized electrode were characterized by X-ray diffraction spectroscopy (XRD), electrochemistry, spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Coupled with microemulsion as a carrying matrix with the flow-injection analysis (FIA) mode, the ECL emission of luminol is greatly intensified on this functionalized electrode. Till to pH 6.0, needless any added co-reactant, the synergic sensitizing effect of nano-hybrid and microemulsion increased the ECL signal of luminol to a recordable level for the first time. The ECL response for H2O2 on this functionalized electrode gains a descended mass detection limit (LODM) for 1/230 than before. This research very significantly extended the area of ECL applications due to the extended practicable pH range which was suitable for environmental or biological targets etc. As an example, this intensified ECL was successfully applied to evaluate the gross antioxidant activity of some fruits with satisfactory results.Graphical abstractA nano-hybrid of nano-TiO2 supported AuAg alloy nanocluster was synthesized and modified onto the surface of indium tin oxide coated glass to act as a working electrode. It intensifies the electrochemiluminescence of luminol coupled with the use of microemulsion as carrier matrix in pH range of 6.0–8.0 without any added co-reactant.

A bare fused silica capillary lacks enough efficiency for electrophoretic separation under some circumstances as a complex mixture of analogous compounds or stroma matrix. To improve the separation, a strategy of functionalization for the inner surface with nano-silica and polyelectrolytes is proposed in this paper. The results have demonstrated that the hybrid coating film of poly(diallyldimethylammonium chloride) (PDDA)–nano-SiO2–poly(styrenesulfonate) (PSS) on a silica capillary greatly promoted the separation efficiency. As a model, four analytes (naringenin, rutin, quercetin and ascorbic acid) are well separated with 24 mmol L−1 borate buffer solution (pH 8.3) as the carrier. The proposed approach was successfully applied for rapid determination of these analytes in artificial urine with satisfactory results.

In this paper, an immunosensor for ultrasensitive and specific detection of ketamine is reported with electrochemical impedance as read-out signal. It is constructed based on the self-assembly modification (SAM) of 3-mercaptopropionic acid on Au electrode, the activation strategy by 1-ethyl-3-(3-dimethylaminoprophyl) carbodiimide (EDC)/n-hydroxysulfsuccinimide (NHS) and the immobilization of ketamine antibody to form the sensing surface. The antibody acts as the sensing host due to its specific covalent bonding with ketamine. The technique of electrochemical impedance spectroscopy (EIS) is employed to read-out the sensing signal. The value of electron transfer resistance (Ret) responds to the concentration of ketamine with a detection limit of 0.41 pmol/L. The immunosensor can be regenerated for more than 5 times resorted to elution by NaOH–H3PO4 (pH 12.0). When it was applied to detect the ketamine in spiked serum samples after 2000-folds dilution, there were satisfactory recoveries from 89.0% to 136.4% and tolerable interference from blood components. The so-prepared sensor is proven as a dominant element than those once reported ones in terms of the sensitivity and simplicity.

► A reagentless electrochemiluminescent electrode for flow injection analysis.► Electrochemically deposited luminol/aniline nano-copolymer for immobilising luminal.► A nano-TiO2 functionalized indium tin oxide glass to act as an electrode matrix.► Greatly promoted enhancing response for reactive oxygen species.► Efficient approach for evaluating gross antioxidants by sensitive quenching effect.In this study, a nano-structured copolymer of luminol/aniline (PLA) was deposited onto nano-TiO2-functionalised indium tin oxide (ITO)-coated glass by electrochemical polymerisation using cyclic voltammetry (CV). The resulting reagentless electrochemiluminescent (ECL) electrode (ECLode) can be used for flow injection analysis (FIA). The properties of the ECLode were characterised by CV, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The ECLode has high background ECL emission as well as excellent stability and reproducibility, and yielding sensitive response towards target analytes. The ECL emissions of the ECLode were 50 times higher than PLA/ITO, and 500 times higher than polyluminol (PL)/ITO. The ECLode showed sensitive responses to reactive oxygen species (ROSs), permitting its application for determination of antioxidants by quenching. Under optimised conditions, an absolute detection limit of 69.9 pg was obtained for resveratrol, comparable to the highest levels of sensitivity achieved by other methods. Thus, the gross antioxidant content of red wine was determined, with satisfactory recoveries between 87.6% and 108.3%. These results suggest a bright future for the use of the ECLode for single-channel FIA due to its high sensitivity, accuracy and reproducibility.Graphical abstractA nano-structured luminol/aniline copolymer electrochemically deposited on nano-TiO2-functionalised indium tin oxide glass as reagentless electrochemiluminescent electrode for flow injection analytic use.

We hereby report the electrochemiluminescent resonance energy transfer (ECRET) between luminol, CdTe quantum dots (QDs) and oxygen. The process take placed between luminol and CdTe QDs could be further enhanced by oxygen. The mechanism and the rule of oxygen have been discussed. It could be attributed to the adsorption and catalysis of QDs for luminol and the formation of singlet oxygen. Thus, it provided an excellent basis for selective and sensitive detection methodology for trace oxygen with a detection limit of 5 μg/L, as well as for the formation of singlet oxygen. Furthermore, the research extended the practicability of luminol ECL in lower pH range to 8.0.Highlights► Electrochemiluminescent resonance energy transfer. ► Enhanced by singlet oxygen. ► Catalyzed redox by CdTe quantum dots; Sensitivity and selectivity for singlet oxygen.

With TiO2 nanoparticles as carrier, a supported nano-material of Au atomic cluster/TiO2 nano-hybrid was synthesized. It was then modified onto the surface of indium tin oxide (ITO) by Nafion to act as a working electrode for exciting the electrochemiluminescence (ECL) of luminol. The properties of the nano-hybrid and the modified electrode were characterized by XRD, XPS, electronic microscopy, electrochemistry and spectroscopy. The experimental results demonstrated that the modification of this nano-hybrid onto the ITO electrode efficiently intensified the ECL of luminol. It was also revealed that the ECL intensity of luminol on this modified electrode showed very sensitive responses to oxygen and hydrogen peroxide. The detection limits for dissolved oxygen and hydrogen peroxide were 2 μg L−1 and 5.5 × 10−12 M, respectively. Besides the discussion of the intensifying mechanism of this nano-hybrid for ECL of luminol, the developed method was also applied for monitoring dissolved oxygen and evaluating the scavenging efficiency of reactive oxygen species of the Ganoderma lucidum spore.

A rutin-modified glassy carbon electrode (R/GCE), which showed electro-catalytic capability for the oxidation of sertraline, was prepared by electrochemically bonding. The modification mechanism and electrochemical behavior of the R/GCE were systematically investigated. It was found that the hydroxyl groups on GCE which bonded with rutin acted as a Michael receptor by a nucleophilic reaction. The immobilized rutin molecules undertook a reversible 2e/2H+ redox, which contributed to a catalytic oxidation of sertraline. The oxidation mechanism of sertraline on R/GCE was investigated by infrared spectrum (IR) and electrochemical techniques. It was found that the catalytic oxidation of sertraline on R/GCE was an irreversible 2e/2H+ redox. Sertraline was detected using a differential pulse voltammetry method. The oxidation current of sertraline linearly related to its concentration in the range of 3.0–90.0 μM with a detection limit of 1.0 μM (S/N = 3). The content of sertraline in Zoloft tablets was also detected to validate the applicability of proposed modified electrode.Highlights► A rutin-modified glassy carbon electrode. ► Electrocatalytic oxidation for sertraline. ► The modification mechanism and electrochemical behavior. ► Determination of sertraline by the differential pulse voltammetry. ► The content of sertraline in Zoloft tablets.

An in-situ, facile and rapid method is developed to prepare a nano-functionalized gold electrode. After electrolysis at constant potential of +2 V in PBS (pH 7.0) for 10 min, a rough, nano-porous film formed on the surface of a polished gold plate electrode. This new nano-functionalized gold electrode could be applied for the rapid quantification of bacteria in milk. The detection was based on the catalysis of lipid peroxidation on cell membrane of bacteria by nano-porous Au film. The response of the current in chronoamperometry linearly responded to the bacterial content in milk, which was calibrated by the national standard method (Standard plate count method). Therefore the accurate quantity of bacteria was obtained from the current response on prepared electrode. The results showed that the bacteria could be detected in the range of 1.1 × 103−2.5 × 107 cfu mL−1 within 1 h.

An electrochemiluminescent (ECL) biosensor based on immobilized uricase has been developed for uric acid detection with luminol as signaler. The uricase has been embedded in polypyrrole (PPy) matrix on platinum electrode during the electropolymerization of pyrrole monomer at potential of 0.80 V versus Ag/AgCl. This ECL-based biosensor responds to uric acid due to yielded hydrogen peroxide during its catalytic oxidization by uricase with potassium ferricyanide acted as an electron receptor to promote the enzymatic reaction. The so-generated hydrogen peroxide enhanced the ECL intensity of luminol. The kinetic parameters of enzymatic reaction as maximum reaction rates (Vmax) and Michaelis–Menten constants (Km) are also evaluated for 1.42 × 10−3 A s−1 and 3.4 × 10−7 M in the presence of potassium ferricyanide, which were all greatly improved. The resulting biosensor showed excellent analytical performance for determination of uric acid as more than 50 times sensitivity than a bare electrode. It gives a 75 pM of detection limit and a relative standard deviation of 4.4% for 6.25 × 10−9 M uric acid (n = 6). This ECL-based biosensor has been successfully applied for determination of uric acid in porphyra and kelp samples.

A microemulsion enhanced electrochemiluminescence (ECL) of luminol-H2O2 was studied with the flow-injection (FI) technique. The results revealed that the microemulsion composed with cetyltrimethylammonium bromide (CTAB), n-butanol, n-heptane and water greatly enhanced the ECL especially in acidic medium. The ECL emission increased for 20 to 2 times in this microemulsion medium over the pH range of 5.0–8.0 compared to that in aqueous solution. The mechanism of enhancement of surfactant and microemulsion for luminol-H2O2 ECL was discussed. It is mainly based on the electrostatic interaction between luminol anion and the head group of surfactant, which causes the adsorption and promotes the dissociation of luminol on the surfaces of the microemulsion droplets, favors the oxidation of luminol by the yielded reactive oxygen species (ROSs) during electrolysis. This research is very significant for ECL applications because of the extended practicable pH range which was suitable for environmental and biological systems. As an example, this FI-ECL technique can be applied for determination of oligo proanthocyanidin (OPC) because of its antioxidant property and to evaluate the total antioxidant activity of the grape skin using OPC as an index.Highlights► Microemulsion enhanced electrochemiluminescence of luminol-H2O2. ► Extend the practicability of electrochemiluminescence into acidic solution. ► Determination of antioxidant and to evaluate the scavenging efficiency of grape skin for reactive oxygen species.

A nano-liter sized flow-cell is developed for constructing a flow injection analysis (FIA) system with electrochemiluminescent (ECL) detection. A sensitive ECL electrode is applied as the working electrode in this flow-cell. It is obtained by immobilizing the composite of CdTe quantum dots (QDs), carbon nanotubes (CNTs) and chitosan (Chit) on indium tin oxide (ITO) glass. The CdTe QDs were synthesized in our lab and possessed a high quantum yield. It has been demonstrated as an efficient anodic ECL material with the triethylamine (TEA) as the co-reactant. The flow-cell gives the stable ECL background under optimized conditions for parameters such as electrolytic pulse, concentration of TEA and flow rate, etc. The sensitive ECL quenching response of dopamine (DA) is realized on this FIA system within the linear range from 10 pM to 4 nM and a detection limit as low as 3.6 pM. It is practically used to determine the neurotransmitters in cerebro-spinal fluid (CSF) with DA as the index and with an average recovery of 94%.

We have synthesized water-dispersible CdTe quantum dots (QDs) capped with thioglycolic acid. Their quantum yield is higher than 54%. A sensitive electrochemiluminescence (ECL) method was established based on the modification of the composite of the QDs, carbon nanotubes and chitosan on indium tin oxide glass. The sensor displays efficient and stable anodic ECL which is quenched by dopamine. A respective sensor was designed that responds to dopamine linearly in the range of 50 pM to 10 nM, and the detection limit is 24 pM. Dopamine was determined with this sensor in spiked cerebro-spinal fluid with average recoveries of 95.7%.

A flow injection analysis (FIA) system with electrochemiluminescent (ECL) detection has been established. Based on a specially designed flow-through ECL cell with a very simple structure, the system possesses rapid response and high sensitivity. With luminol as the ECL reagent, the response of hydrogen peroxide (H2O2) was investigated on the developed FIA-ECL system. After optimizing the experimental conditions, such as the electric parameters, the buffer condition and the flow rate, it was demonstrated that the developed FIA-ECL system works well for quantified assays. Compared with reported works, the present results indicate that the developed FIA-ECL system has the lowest limit of detection (S/N = 3) of 3.0 × 10−9 mol/L for H2O2, which is equal to the level of chemiluminescence (CL). The developed system was successfully used to monitor the yield of reactive oxygen species (ROSs) in water vapour during the work of an ultrasonic humidifier with H2O2 as index. And the amount of ROSs in some other real samples, including tap water, drinking water and river water was detected with recoveries from 92.0% to 106%.

In this work, the intensification of luminol electrochemiluminescence (ECL) by metallic oxide nanoparticles (MONPs), as ZnO, MnO2, In2O3 and TiO2, under alkaline condition is reported and the related mechanism is studied. It is found that all four types of those MONPs exhibit the effect toward the ECL intensification of luminol. Furthermore, the silica sol-gel film is taken to immobilize the MONPs onto the platinum electrodes. The so-obtained modified electrodes also show the enhanced ECL and better signal/noise ratio, as well improved signal stability. Finally, the ECL reagent, luminol, is immobilized together with the MONPs onto the electrode surface to perform as the ECL sensor. On resulting sensors, good linear responses are obtained toward hydrogen peroxide. The mechanism of intensification of luminol ECL by MONPs is discussed in this paper. It is proposed that the ECL intensification can be attributed to the production of reactive oxygen species, as well as the adsorption of luminol on surface of MONPs.

An electrochemiluminescent (ECL) biosensor was constructed for selective assay of alanine aminotransferase (ALT) based on the enzymatically catalyzed oxidation of pyruvate by pyruvate oxidase (PYOD). The composite of potassium ferricyanide and carbon nanotube was adopted to pre-functionalize the basal platinum electrode while the potassium ferricyanide acted as the activator of PYOD. The ALT catalyzed the reaction of L-alanine and α-ketoglutarate to produce pyruvate which could be further enzymatically oxidized by PYOD to yield H2O2 to intensify the ECL of luminol. The biosensor showed rapid response for real-time measurement of ALT in the linear concentration range from 0.00475 to 350 U/L (r = 0.993) with a relatively standard deviation of 2.5% (CALT = 47.5 U/L, n = 6). The biosensor was applied to assay the ALT in rat serum with average recovery of 90.5%.

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.

The electrochemiluminescence (ECL) of luminol on indium tin oxide (ITO) glass was high even under a low potential around 0.4–0.5 V, which was quite different from other electrodes such as platinum. ITO nanoparticles were synthesized and used in the research on ITO glass in the ECL process. A static interaction between ITO and luminol is confirmed from UV–vis and fluorescence spectra. Then the ECL enhancement can be supposed to originate from the adsorption of luminol on ITO, which facilitated luminol’s oxidization to the excited state, giving out ECL. On the other hand, ITO can catalyze the generation of reactive oxygen species (ROSs), similar to some other nanomaterials, which also favored the ECL enhancement of luminol.

An electrochemiluminescent (ECL)-based lactate (LA) biosensor is developed with luminol as signaling species. LA was oxidized under the catalysis of immobilized lactic dehydrogenase (LDH) and pyruvate oxidase (PYOD) with nicotinamide adenine dinucleotide (NAD) as coenzyme. As a result, the reaction yielded the hydrogen peroxide, which enhanced the electrochemiluminescence of luminol, which was acceptable for sensing the LA concentration. The resulting biosensor showed excellent response for lactate. A detection limit of 8.9 × 10−12 mol/L was obtained with the relative standard deviation (RSD) of 4.13% (CLA 1.34 × 10−10 mol/L, n = 6) and an average recovery of 101.3% for real sweat sample. The research suggests that the ECL-based biosensor was practicable for detecting the LA in sweat samples of athletes during the exercitation for evaluation of exercise degree.

Based on electrodeposition of Prussian blue (PB) and chitosan (CS) directly on gold electrode, a hybrid film of PB/CS has been prepared. PB in this film shows a good stability compared with pure PB film when it worked in neutral and weak alkalescent solution and can act as redox mediator. It provides the potential application of such film in biosensor fabrication. A glucose biosensor was fabricated by electrodepositing glucose oxidase (GOD)/CS film on this PB/CS modified electrode. The optimum experimental conditions of biosensor for the detection of glucose have been studied in detail. Under the optimal conditions, a linear dependence of the catalytic current upon glucose concentration was obtained in the range of 2 × 10−6 to 4 × 10−4 M with a detection limit of 3.97 × 10−7 M. The resulting biosensor could be applied to detect the blood sugar in real samples without any pretreatment.

A bare fused silica capillary lacks enough efficiency for electrophoretic separation under some circumstances as a complex mixture of analogous compounds or stroma matrix. To improve the separation, a strategy of functionalization for the inner surface with nano-silica and polyelectrolytes is proposed in this paper. The results have demonstrated that the hybrid coating film of poly(diallyldimethylammonium chloride) (PDDA)–nano-SiO2–poly(styrenesulfonate) (PSS) on a silica capillary greatly promoted the separation efficiency. As a model, four analytes (naringenin, rutin, quercetin and ascorbic acid) are well separated with 24 mmol L−1 borate buffer solution (pH 8.3) as the carrier. The proposed approach was successfully applied for rapid determination of these analytes in artificial urine with satisfactory results.