A Novel Electrogenerated Chemiluminescence Reaction Scheme Using Core-Shell LuminoI-Based SiO2 Nanoparticles as a Regulator and Its Analytical Application

A novel core-shell luminol-based SiO2 nanoparticle While these nanoparticles were used as electrogenerated was synthesized by two step micro-emulsion method. chemiluminescence （ECL） reagent, the electrochemical （EC） reaction as well as the subsequent chemiluminescence （CL） reaction not only could be separated spatially, but also presented high efficiency for analytical purpose. In this case, the core-shell luminol-based SiO2 nanoparticles offered more potential to avoid the contradiction between the EC and the CL reaction conditions. A new ECL method based on the nanoparticle was developed, and isoniazid was selected as a model analyte to illustrate the characteristics of this new ECL method. Under the selected conditions, the proposed ECL response to isoniazid concentration was linear in the range of 1.0 ×10^-10 to 1.0 × 10^-6 g/mL with 2 × 10^-11g/mL detection limit.     

Comparative studies on electrogenerated chemiluminescence of luminol on gold nanoparticle modified electrodes

Comparative studies on the electrogenerated chemiluminescence (ECL) behavior of luminol on various electrodes modified with gold nanoparticles of different size were carried out in neutral solution by conventional cyclic voltammetry (CV). The results demonstrated that the gold nanoparticle modified electrodes could generate strong luminol ECL in neutral pH conditions. The catalytic performance of gold nanoparticle modified electrodes on luminol ECL depended not only on the gold nanoparticles but also on the substrate. Gold electrode and glassy carbon electrode were the most suitable substrates for the self-assembly of gold nanoparticles. Moreover, the gold nanoparticle modified gold and glassy carbon electrode had satisfying stability and reproducibility and did not need tedious pretreatment of electrode surface before each measurement. It was also found that luminol ECL behavior depended on the size of gold nanoparticles. The most intense ECL signals were obtained on a 16-nm-diameter gold nanoparticle modified electrode. The modified electrode prepared by the self-assembly method exhibited much better catalytic effect on luminol ECL than that prepared by the electrically deposited method. The ECL behavior of luminol on a gold nanoparticle self-assembled gold electrode was also investigated by other transient-state electrochemical techniques, such as chronoamperometry, differential pulse voltammetry, normal pulse voltammetry, and square wave voltammetry. The strongest ECL intensity was obtained under square wave voltammetric condition.     

Gold nanoparticles catalyzed chemiluminescence immunoassay for detection of herbicide 2,4-dichlorophenoxyacetic acid

We present a novel immunoassay format utilizing the catalytic properties of gold nanoparticles in the luminol-silver nitrate-gold nanoparticle based chemiluminescence (CL) system for the detection of widely used herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Highly sensitive anti-2,4-D antibody was produced and conjugated with gold nanoparticles of various sizes. In the present assay format, employing a competitive inhibition approach, a well-characterized hapten-protein conjugate (2,4-D-BSA) was used to coat the microtiter plates. The analyte (2,4-D) was pre-incubated with anti-2,4-D antibody labeled with gold nanoparticles and added to each well of the microtiter plate. The gold label triggered the reaction between luminol and silver nitrate generating a luminescence signal at 425 nm. Under the optimized conditions, the CL based immunoassay showed the detection limit of 2,4-D in standard water samples around 3 ng mL(-1). The CL based immunoassay format, based on gold nanoparticles as a catalyst, could be used as a fast screening methodology (<30 min) for pesticide detection.     

Silver and gold glyconanoparticles for colorimetric bioassays

The color changes associated with the aggregation of metal nanoparticles has led to the development of colorimetric-based assays for a variety of target species. We have examined both silver- and gold-based nanoparticles in order to establish whether either metal exhibits optimal characteristics for bioassay development. These silver and gold nanoparticles have been stabilized with a self-assembled monolayer of a mannose derivative (2-mercaptoethyl alpha-d-mannopyranoside) with the aim of inducing aggregation by exploiting the well-known interaction between mannose and the lectin Concanavalin A (Con A). Both metal glyconanoparticles were determined to be ca. 16 nm in diameter (using TEM measurements). Aggregation was observed on addition of Con A to both silver and gold nanoparticles resulting in a shift in the surface plasmon absorption band and a consequent color change of the solution, which was monitored using UV-visible spectrophotometry. Mannose-stabilized silver nanoparticles at a concentration of 3 nM provide an assay for Con A with the largest linear range (between 0.08 and 0.26 microM). Additionally, the kinetic rate of aggregation of the silver-nanoparticle-based bioassay was significantly greater than that of the gold-nanoparticle system. However, in terms of sensitivity, the mannose-stabilized gold-nanoparticle-based assay was optimum with a limit of detection of 0.04 microM Con A, as compared with a value of 0.1 microM obtained for the mannose-stabilized silver nanoparticles. Additionally, a lactose derivative (11-mercapto-3,6,9-trioxaundecyl beta-D-lactoside) was used to stabilize gold nanoparticles to induce aggregation upon addition of the galactose specific lectin Ricinus communis agglutinin (RCA(120)). To examine the specificity of the bioassay, lactose-stabilized gold nanoparticles were mixed with a solution of mannose-stabilized silver nanoparticles to give an aggregation assay capable of detecting two different lectins. When either Con A or RCA(120) was added to the mixed glyconanoparticles, selective recognition of the respective natural ligand was shown by aggregation of a single metal nanoparticle. Centrifugation and removal of the aggregated species enabled further bioassay measurements using the second glyconanoparticle system.     

Simultaneous quantification of catecholamines in rat brain by high‐performance liquid chromatography with on‐line gold nanoparticle‐catalyzed luminol chemiluminescence detection

A new method based on high‐performance liquid chromatography (HPLC) coupled with on‐line gold nanoparticle‐catalyzed luminol chemiluminescence (CL) detection was developed for the simultaneous quantitation of catecholamines in rat brain. In the present CL system, gold nanoparticles were produced by the on‐line reaction of H₂O₂, NaHCO₃?Na₂CO₃ (buffer solution of luminol) and HAuCl_4. Norepinephrine (NE), epinephrine (EP) and dopamine (DA) could strongly enhance the CL signal of the on‐line gold nanoparticle‐catalyzed luminol system. The UV?visible absorption spectra and transmission electron microscopy studies were carried out, and the CL enhancement mechanism was proposed. Catecholamines promoted the on‐line formation of more gold nanoparticles, which better catalyzed the luminol–H₂O₂ CL reaction. The good separation of NE, EP and DA was achieved with isocratic elution using a mixture of methanol and 0.2% aqueous phosphoric acid (5:95, v/v) within 8.5 min. Under the optimized conditions, the detection limits, defined as a signal‐to‐noise ratio of 3, were in the range of 1.32–1.90 ng/mL, corresponding to 26.4?38.0 pg for 20 μL sample injection. The recoveries of catecholamines added to rat brain sample were >94.6%, with the precisions <5.5%. The validated HPLC?CL method was successfully applied to determine NE and DA in rat brain without prior sample purification. Copyright © 2014 John Wiley & Sons, Ltd.     

Gold Nanoparticles‐enhanced Chemiluminescence Determination of Fenfluramine

A simple and sensitive chemiluminescence method was developed for the determination of fenfluramine. The chemiluminescence signal arising from the reaction between alkaline luminol and N‐bromosuccinimide was found to be greatly enhanced by fenfluramine in the presence of gold nanoparticles. But fenfluramine alone slightly inhibited the CL signal of N‐bromosuccinimide‐luminol in the absence of gold nanoparticles. The experimental parameters that affected the chemiluminescence signal were thoroughly investigated. Under the optimum experimental conditions, the enhanced chemiluminescence intensity was proportional to the concentration of fenfluramine in the range of 0.005‐1.0 mg/L. The detection limit was 0.9 μg/L fenfluramine with a relative standard deviation of 2.5% for 0.1 mg/L fenfluramine solution (n = 11). The method was applied to the determination of fenfluramine in some weight‐reducing tonics and in spiked human urine. A possible CL reaction mechanism was proposed.     

Apparatus for mechanistic and analytical studies of the electrogenerated chemiluminescence of luminol

A new apparatus based on the rotating ring—disc electrode system is described. The symmetric double-step potential is connected to the ring electrode to oxidize luminol, while the disc electrode is maintained at a negative potential to reduce oxygen to hydrogen peroxide. Because of the electrode rotation, hydrogen peroxide is immediately transported to the ring electrode at which it reacts with luminol oxidation product to emit light. Preliminary electrogenerated chemiluminescence measurements indicate that the intensity of the chemiluminescence of luminol is highly dependent on the ring and disc electrode materials and that some metal ions have a catalytic or inhibitive effect on this luminescence reaction of luminol.     

Enhanced Sensitivity of the Tris(Bipyridine)Ruthenium(II) Chloride Electrogenerated Chemiluminescence Sensor with Porous Silica Nanoparticles

Mass transfer in electrogenerated chemiluminescence affects the sensitivity of sensors involving this technique. Herein, the characteristics of the porous Ru(bpy)₃²⁺/silica nanoparticles were investigated by transmission electron microscopy, fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, and electrogenerated chemiluminescence. The results showed that the pores inside the porous nanoparticles provided efficient mass transfer, resulting in significant enhancement of electrogenerated chemiluminescence. Consequently, a novel electrogenerated chemiluminescence sensor was developed and is reported herein. The sensitivity for tripropylamine was more than one order of magnitude higher compared to previously reported similar sensors, with a limit of detection of 3.3 × 10^?12 moles per liter.     

Potential - Resolved Electro Chemiluminescence of Luminol

Since the electrogenerated chemiluminescence (ECL) of luminol was first reported in 1929 by Harvey, a number of papers have been published for mechanistic and analytical studies of luminol ECL.     

A highly sensitive electrochemiluminescence immunosensor based on magnetic nanoparticles and its application in CA125 determination

A novel electrogenerated chemiluminescence (ECL) immunoassay based on enzyme amplification and magnetic nanoparticle enrichment was developed, and carbohydrate antigen 125 (CA125) was chosen as the analyte. Fe₃O₄ magnetic nanoparticles loaded with anti-CA125 were synthesized. The sandwich-type immunoassay was performed on the magnetic force-controlled carbon paste electrode via the immunoreactions among glucose oxidase-labeled anti-CA125, CA125, and anti-CA125 on the surface of magnetic nanoparticles. ECL was generated by the reaction between luminol and hydrogen peroxide. Hydrogen peroxide was produced during the enzymatic reaction with glucose and markedly increased in the presence of CA125 antigen. The CA125 concentrations were determined within the range of 0–10?mU?mL^?1, and the detection limit was 8.0 μU mL^?1. The CA125 immunosensor was more sensitive than those previously reported. The proposed ECL method also provided a simple selectivity immunoassay protocol, which was applied in the determination of CA125 in clinical serum samples.     

Label-Free Electrochemiluminescent Determination of DNA Using Luminol and Hemin Functionalized Nanoparticles

Luminol and hemin dual-functionalized silica nanoparticles were synthesized using a typical reverse water-in-oil microemulsion protocol. The obtained nanoparticles were further characterized by transmission electron microscopy, scanning electron microscopy, atomic absorption spectrometry, chemiluminescence, and electrochemiluminescence. The results indicated that the luminol and hemin dual-functionalized silica nanoparticles exhibited significantly higher chemiluminescence and electrochemiluminescence intensities than those of luminol functionalized silica nanoparticles due to the catalytic effect of hemin on the chemiluminescence and electrochemiluminescence of luminol. Furthermore, a simple and sensitive label-free electrochemiluminescence DNA biosensor was developed based on the chitosan modified luminol and hemin dual-functionalized silica nanoparticles and a single-stranded DNA probe. The chitosan modified luminol and hemin dual-functionalized silica nanoparticles were immobilized on the surface of an indium-doped tin oxide electrode and the single-stranded DNA probe was immobilized on the surface of the nanoparticles through electrostatic interactions between single-stranded DNA and chitosan, which allowed hybridization with the target DNA sequences. The hybridization events were evaluated by electrochemiluminescence, and only the complementary sequence formed double-stranded DNA with the DNA probe to give strong electrochemiluminescence signals. Finally, the electrochemiluminescence intensity was found to be linearly related to the concentration of the complementary sequence at concentrations from 1.0?×?10^?12 to 1.0?×?10^?6?mol·L^?1 with a detection limit of 5.0?×?10^?13?mol·L^?1.     

Homogenous electrogenerated chemiluminescence immunoassay for human immunoglobulin G using N-(aminobutyl)-N-ethylisoluminol as luminescence label at gold nanoparticles modified paraffin-impregnated graphite electrode

A homogeneous electrogenerated chemiluminescence (ECL) immunoassay for human immunoglobulin G (hIgG) has been developed using a N-(aminobutyl)-N-ethylisoluminol (ABEI) as luminescence label at gold nanoparticles modified paraffin-impregnated graphite electrode (PIGE). ECL emission was electrochemically generated from the ABEI-labeled anti-hIgG antibody and markedly increased in the presence of hIgG antigen due to forming a more rigid structure of the ABEI moiety. The concentration of hIgG antigen was determined by the increase of ECL intensity at a gold nanoparticles modified PIGE. It was found that the ECL intensity of ABEI in presence of hydrogen peroxide was dramatically enhanced at gold nanoparticles modified PIGE in neutral aqueous solution and the detection limit of ABEI was 2 x 10(-14)mol/L (S/N=3). The integral ECL intensity was linearly related to the concentration of hIgG antigen from 3.0 x 10(-11) to 1.0 x 10(-9)g/mL with a detection limit of 1 x 10(-11)g/mL (S/N=3). The relative standard deviation was 3.1% at 1.0 x 10(-10)g/mL (n=11). This work demonstrates that the enhancement of the sensitivity of ECL and ECL immunoassay at a nanoparticles modified electrode is a promising strategy.     

A Facile Latex Agglutination Lectin Assay (LALA) for Weakly Binding Ligands

To apply the latex agglutination lectin assay (LALA) to carbohydrate ligands, monosaccharide derivatives were incorporated onto latex beads by various methods, and the usefulness of the resulting beads was evaluated. The best outcome, which resulted in aggregation with lectin concentrations of 1 to 4 μg/mL, was obtained when latex beads coated with bovine serum albumin were treated with divinylsulfone, a linker agent, and then with 2-aminoethyl glycosides. Monosaccharides with an amino or anomeric hydroxyl group other than N-acetylglucosamine were applicable in this direct LALA. For example, mannose- and 5-thiomannose-coupled latex beads showed aggregation with minimum concanavalin (ConA) concentrations of 4 and 32 μg/mL, respectively. An inhibition assay was more versatile than the direct LALA, and the standardized inhibition activity (EC⁰ ₅₀) was determined for several compounds. Representative EC⁰ ₅₀ data for mannose, methyl mannoside, and p-nitrophenyl mannoside (1, 0.12, and 0.06 mM, respectively) are consistent with those reported with other methods. We obtained EC⁰ ₅₀ values for some synthetic compounds with slightly different binding abilities to ConA, demonstrating a semiquantitative character of this method. The inhibition LALA can be performed without instrumentation or tedious derivatization and is thus suitable for the rapid evaluation of monovalent ligands prior to assemblage into multivalent ligands.     

Continuous Flow Determination of Carbon Dioxide in Water by Membrane Separation-Chemiluminescent Detection

Abstract

Carbon dioxide has been found to enhance the chemiluminescence of a luminol system. A determination method for carbon dioxide in water was developed by applying this reaction to a continuous flow membrane-separation system. Concentrations of carbon dioxide as low as 0.04 μ g C /mL were determined. Membrane-separation effectively eliminates interferences from Co(II), Cr(III), Fe(III), and other ions which also enhance chemiluminescence. The relative standard deviation for this method was 2.8% (n=5) for 4.0 μ g C /mL and the time required for the analysis of one sample was 3.0 min.     

Chemiluminescence reactions of luminol system catalyzed by nanoparticles of a gold/silver alloy

The chemiluminescence (CL) of luminol–H₂O₂ system is strongly enhanced on addition of nanoparticles composed of a gold/silver alloy (ratio 5:4). The effect is attributed to a catalytically enhanced decomposition of H₂O₂ to produce reactive oxygen species. A reaction mechanism is proposed. Organic compounds containing hydroxy, amino, or thiol groups (such as amino acids, dopamine, pyrocatechol) can inhibit the CL signal of the system. It is concluded that the system has a large potential in terms of the determination of such compounds.     

Electrogeneration of ferrate (VI) in low concentration NaOH solution for flow injection–chemiluminescence detection

The possibility of direct analytical applications of ferrate(VI) solution, which was freshly electrogenerated in low-concentration NaOH electrolyte, was studied by a flow-injection chemiluminescence (FI–CL) system. It was found that some inorganic ions, organic molecule and biomolecule could enhance the chemiluminescence emission caused by ferrate(VI)–luminol reaction. V(V), Ca(II), Mg(II), phloroglucinol, and bovine hemoglobin (Hb) chosen as samples were successfully detected by this developed method. The analytical characteristics of the system for the analytes determination including linear ranges, correlation coefficients, limits of detection combined with FI analysis were studied.     

Microsensor Chip Integrated with Gold Nanoparticles‐Modified Ultramicroelectrode Array for Improved Electroanalytical Measurement of Copper Ions

This paper presents a microsensor chip integrated with a gold nanoparticles‐modified ultramicroelectrode array (UMEA) as the working electrode for the detection of copper ions in water. The microsensor chip was fabricated with Micro‐Electromechanical System technique. Gold nanoparticles were electrodeposited onto the surface of UMEA at a constant potential of ?0.3 V. The ratio d/R_b of interelectrode spacing (d) over the individual electrode’s radius (R_b) was investigated to improve the electrochemical performance. The UMEA with a d/R_b of 20 showed the best hemispherical diffusion mode, resulted in fast response time and high current response. The gold nanoparticles increased the active surface area of UMEA by not changing the geometries of UMEA, and the current response was increased further. Incorporating the optimized characteristic of UMEA and gold nanoparticles, the microsensor showed a good linear range from 0.5 to 200 µg L^?1 of copper ions in the acetate buffer solutions with the method of square wave stripping voltammetry. Compared with the gold nanoparticles‐modified disk electrode, the gold nanoparticles‐modified UMEA showed higher sensitivity (0.024 µA mm^?2 µg^?1 L) and lower limit of detection (0.2 µg L^?1). Water samples from river water and tap water were analyzed by the microsensor chip with recovery ranging from 100.7 % to 107.8 %.     

Sensitive determination of Fenamiphos in water samples by flow injection photoinduced chemiluminescence

In this work, a sensitive flow injection chemiluminescence (FI-CL) method for the determination of nematicide Fenamiphos in a rapid and simple way is proposed. Fenamiphos is first photodegraded in basic medium. These photofragments react with Ce(IV) providing the chemiluminescence signal. To the authors’ knowledge, no chemiluminescence method has been described in the literature for the determination of the nematicide Fenamiphos. All physical and chemical parameters in the flow injection chemiluminescence system were optimized in order to obtain the best sensitivity, selectivity and sample throughput. Before the injection of the sample in the FI-CL system, a preconcentration step with solid phase extraction C18 cartridges was performed. By applying solid phase extraction (SPE) to 250?mL of standard (final volume 10?mL), the linear dynamic range was between 3.4 and 60?µg?L^?1, and the detection limit was 1?µg?L^?1. When SPE was applied to 500?mL of standard (final volume 10?mL), the detection limit was 0.5?µg?L^?1. These detection limits are below the emission limit value established by the Spanish Regulations of the Hydraulic Public Domain for pesticides (50?µg?L^?1) and of the same order as the limit established for total pesticides (0.5?µg?L^?1) at European Directive on the quality of water for human consumption. The sample throughput was 126 hour^?1. Intraday and interday coefficients of variation were below 10% in all cases. No interference was registered in presence of usual concentrations of anions, cations and other organophosphorus pesticides. The method was successfully applied to the analysis of environmental water samples, obtaining recoveries between 96 and 107.5%.     

Effect of gold nanoparticle as a novel nanocatalyst on luminol-hydrazine chemiluminescence system and its analytical application

In this work the catalytic role of unsupported gold nanoparticles on the luminol–hydrazine reaction is investigated. Gold nanoparticles catalyze the reaction of hydrazine and dissolved oxygen to generate hydrogen peroxide and also catalyze the oxidation of luminol by the produced hydrogen peroxide. The result is an intense chemiluminescence (CL) due to the excited 3-aminophthalate anion. In the absence of gold nanoparticles no detectable CL was observed by the reaction of luminol and hydrazine unless an external oxidant is present in the system. The size effect of gold nanoparticles on the CL intensity was investigated. The most intensive CL signals were obtained with 15-nm gold nanoparticles. UV–vis spectra and transmission electron microscopy studies were used to investigate the CL mechanism. The luminol and hydroxide ion concentration, gold nanoparticles size and flow rate were optimized. The proposed method was successfully applied to the determination of hydrazine in boiler feed water samples. Between 0.1 and 30 μM of hydrazine could be determined with a detection limit of 30 nM.     

A Green Approach for Synthesis of Gold and Silver Nanoparticles by Leishmania sp.

The application of microorganisms for the synthesis of metal nanoparticles as an eco-friendly and promising approach is ongoing. In this paper, an attempt has been made to investigate the capability of Leishmania sp. for synthesis of metal nanoparticles from aqueous silver and gold ions. The samples were analyzed by a UV?CVis spectroscopy and the results showed the absorbance peak values at 420 and 540?nm, respectively, for the surface plasmon resonance of silver and gold nanoparticles. The surface morphology of the nanoparticles in solution was visualized by atomic force microscope and scanning electron microscope images, which showed the production of metallic nanoparticles by this protozoan. Fourier transform infrared spectroscopy analyses confirmed the presence of different bands of protein as capping and stabilizing agent on the nanoparticles surfaces. The synthesized silver and gold nanoparticles were with dimensions ranging between 10 and 100?nm for silver and 50?C100?nm for gold. These results of the present study have demonstrated the efficiency of this protozoan for synthesis of nanoparticles, by offering the merits of environmentally friendly, amenability, and time saving for large-scale production.