Anodic Electrogenerated Chemiluminescence Research Articles

Electrogenerated chemiluminescence of luminol at a polyaniline/graphene modified electrode in neutral solution

Polyaniline (PANI) was in situ electrochemical polymerized on an electrochemical reduced graphene oxide (GO) modified glassy carbon electrode (GCE) to prepare PANI-graphene (GR) composite modified GCE (PANI-GR-GCE). The modified electrode was characterized by atomic force microscopy, IR and electrochemical techniques. The results showed that the multi-layer of PANI and graphene could be formed on a bare electrode. The electrochemical signal was improved greatly compared with the PANI or the GR modified electrodes, respectively. Electrogenerated chemiluminescence (ECL) of luminol was comparatively investigated at the PANI-GCE, the GR-GCE, and the PANI-GR-GCE in neutral phosphate buffer solution (PBS). The anodic luminol ECL was inhibited greatly and the cathodic luminol ECL was enhanced at the GR-GCE. Extremely weak luminol ECL peaks were obtained at the PANI-GCE except one strong ECL obtained at high potential range. The PANI-GR composite exhibited apparent electrocatalytical effect on luminol oxidation, and as a result, the intensity of anodic ECL located at 0.50V was enhanced two magnitudes compared with other two modified electrodes. Several impact factors, such as the supporting electrolytes, the pH, the potential scan rate, and the different atmosphere, were studied. The mechanism of luminol ECL was also proposed.

Enhanced Cathodic Electrogenerated Chemiluminescence of Luminol at a Graphene Modified Electrode in Neutral Solution

Graphene oxide (GO) and electrochemically reduced graphene (ERG) modified glassy carbon electrodes (GCE) were prepared and characterized by FT-IR, scanning electron microscopy (SEM), and electrochemical techniques, respectively. Electrogenerated chemiluminescence (ECL) of luminol was studied on the modified electrodes in neutral phosphate buffer solution (PBS). Either at the GO modified electrode or at the ERG modified electrode, the anodic ECL emission of luminol was inhibited greatly and only one cathodic ECL peak was obtained. The intensity of the cathodic ECL emission at the ERG modified electrode increased 123 times compared with that of the GO modified electrode or the bare electrode, which is due to the strong adsorption of dissolved oxygen by ERG film. Several impact factors of luminol ECL, such as the electrochemical reduction potential, the duration of the applied reduction potential, the pH values, the supporting electrolytes, and the potential scan rate were studied and the mechanism of the cathodic luminol ECL emission on the ERG modified electrode was proposed.

Ultrasensitive electrogenerated chemiluminescence biosensor for the determination of mercury ion incorporating G4 PAMAM dendrimer and Hg(II)-specific oligonucleotide

A novel electrogenerated chemiluminescence (ECL) biosensor for highly sensitive and selective detection of mercury ion was developed on the basis of mercury-specific oligonucleotide (MSO) served as a molecular recognition element and the ruthenium(II) complex (Ru1) as an ECL emitting species. The biosensor was fabricated on a glassy carbon electrode coated with a thin layer of single wall carbon nanotubes, where the ECL probe, NH 2-(CH 2) 6-oligo(ethylene oxide) 6-MSO ↔ Dend-Ru1, was covalently attached. The Dend-Ru1 pendant was prepared by covalent coupling Ru1 with the 4th generation polyamidoamine dendrimer (Dend), in which each dendrimer contained 35 Ru1 units so that a large amplification of ECL signal was obtained. Upon binding of Hg 2+ to thymine (T) bases of the MSO, the T–Hg–T structure was formed, and the MSO changed from its linear shape to a “hairpin” configuration. Consequently, the Dend-Ru1 approached the electrode surface resulting in the increase of anodic ECL signal in the presence of the ECL coreactant tri- n-propylamine. The reported biosensor showed a high reproducibility and possessed long-term storage stability (92.3% initial ECL recovery over 30 day's storage). An extremely low detection limit of 2.4 pM and a large dynamic range of 7.0 pM to 50 nM Hg 2+ were obtained. An apparent binding constant of 1.6 × 10 9 M −1 between Hg 2+ and the MSO was estimated using an ECL based extended Langmuir isotherm approach involving multilayer adsorption. Determination of Hg 2+ contents in real water samples was conducted and the data were consistent with the results from cold vapor atomic fluorescence spectroscopy.

Electrochemiluminescence of lucigenin/tributylamine system in ethanol solution

The electrogenerated chemiluminescence (ECL) behavior of lucigenin in the presence of tributylamine (TBA) or other amines in ethanol solution at a polycrystalline gold electrode was studied under conventional cyclic voltammetric conditions. An anodic ECL peak (ECL-1 at 0.91 V vs. SCE) with two shoulders (S 1 at 0.52 V and S 2 at 1.19 V) and their counter-peaks (ECL-2 at 0.66 V, S 3 at 0.33 V, and S 4 at 1.07 V) during reversal potential scan were found in the lucigenin/TBA system. The effects of various factors such as media, material of electrode, concentration of lucigenin and TBA, atmosphere, electrolytes, and potential scan rate on ECL peaks were examined. The emitter of all ECL peaks was identified as N-methylacridone (NMA) by analyzing the ECL spectra. The mechanism for these ECL peaks is proposed to be due to the reactions of lucigenin with the free radical reductant such as Bu 3N and Bu 2NH electrogenerated by TBA at different potentials.

Electrogenerated Chemiluminescence of Lucigenin in Ethanol Solution at a Polycrystalline Gold Electrode

AbstractThe electrogenerated chemiluminescence (ECL) behavior of lucigenin in ethanol solution at a polycrystalline gold electrode was studied under conventional cyclic voltammetric conditions. Compared with the ECL of lucigenin in aqueous solution, one cathodic ECL peak (ECL‐1 at −0.98 V versus SCE) with a shoulder (S1 at −0.42 V) and three new anodic ECL peaks (ECL‐2 at −0.53 V, ECL‐3 at 0.20 V, and ECL‐4 at 0.51 V) were observed, respectively, on the curve of ECL intensity versus potential. The effects of initial potential scan direction, the presence of O2 or N2, potential scan ranges, supporting electrolyte and the concentration of lucigenin on these ECL peaks were examined. The electrochemistry of lucigenin in ethanol solution was also studied. The emitter of all ECL peaks was identified as N‐methylacridone (NMA) by analyzing the ECL spectra. The mechanism for these ECL peaks is proposed to be due to the reactions of lucigenin and its redox products such as Luc and DBA with dissolved oxygen or O2 electrogenerated by the dissolved oxygen at different potentials. The formation of new anodic ECL peaks in ethanol solution is due to longer lifetime of superoxide ions and easier electro‐oxidation of DBA in nonaqueous solution, revealing that the solvent plays an important role in the lucigenin ECL reactions.

Electrogenerated chemiluminescence of CdSe hollow spherical assemblies in aqueous system by immobilization in carbon paste

Electrogenerated chemiluminescence (ECL) of CdSe hollow spherical assemblies (HSAs) was studied in aqueous system by entrapping them in carbon paste. In air-saturated strong alkaline solution three ECL processes were obtained at −1.2, +1.34 and +1.75 V versus Ag/AgCl without adding any special coreactants. The different ECL processes resulted from the electron transfer reactions between positively or negatively charged CdSe HSAs and some electrogenerated species. Selective quench of the anodic and cathodic ECL processes were achieved by controlling the solution pH value or the concentration of dissolved oxygen. Comparing the ECL processes of the entrapped CdSe nanocrystals with the entrapped HSAs, the architecture of the HSAs showed important effects on their ECL behaviors. The ECL features of HSAs entrapped in carbon paste depended on the applied potentials. CdSe HSAs could be developed as a new ECL system in aqueous system with some super points.

Electrogenerated chemiluminescence. 72. Determination of immobilized DNA and C-reactive protein on Au(111) electrodes using tris(2,2'-bipyridyl)ruthenium(II) labels.

Anodic electrogenerated chemiluminescence (ECL) with tri-n-propylamine (TPrA) as a coreactant was used to determine DNA and C-reactive protein (CRP) by immobilizations on Au(111) electrodes using tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) labels. A 23-mer synthetic single-stranded (ss) DNA derived from the Bacillus anthracis with an amino-modified group at the 5' end position was covalently attached to the Au(111) substrate precoated with a self-assembled thiol monolayer of 3-mercaptopropanoic acid (3-MPA) in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC) and then hybridized with a target ssDNA tagged with Ru(bpy)(3)(2+) ECL labels. Similarly, biotinylated anti-CRP species were immobilized effectively onto the Au(111) substrate precovered with a layer of avidin linked covalently via the reaction between avidin and a mixed thiol monolayer of 3-MPA and 16-mercaptohexadecanoic acid on Au(111) in the presence of EDAC and N-hydroxysuccinimide. CRP and anti-CRP tagged with Ru(bpy)(3)(2+) labels were then conjugated to the surface layer. ECL responses were generated from the modified electrodes described above by immersing them in a TPrA-containing electrolyte solution. A series of electrode treatments, including blocking free -COOH groups with ethanol amine, pinhole blocking with bovine serum albumin, washing with EDTA/NaCl/Tris buffer, and spraying with inert gases, were used to reduce the nonspecific adsorption of the labeled species. The ECL peak intensity was linearly proportional to the analyte CRP concentration over the range 1-24 microg/mL. CRP concentrations of two unknown human plasma/serum specimens were measured by the standard addition method based on this technique.

Clay‐Enhanced Electrochemiluminescence and Its Application in the Detection of Glucose

Clay‐modified electrodes were prepared with montmorillonite K10 and characterized in their ability to enhance the electrogenerated chemiluminescence (ECL) in a solution containing luminol and hydrogen peroxide. Montmorillonite K10 proved to be an effective catalyst for such a purpose, according to the anodic current and ECL intensity measured with the electrodes with and without clay particles. Under optimum conditions (pH 10 and 0.8 V vs. SCE), the ECL was enhanced by a factor of 10. Control experiments showed the enhanced ECL is likely due to a facilitation in the oxidation of luminol and by the iron species contained in the clay. Double‐step potential techniques suggested that superoxide is very likely to be the key reactive oxygen species involved in the clay‐enhanced ECL reaction. In addition, clay/luminol/ GOx electrodes were constructed by using aminopropyltrimethoxysilane as an immobilizing agent for the detection of glucose. Although the electrode sensitivity decreased by ca. 15% after 10 days, a linear calibration curve was attained, covering the concentrations of glucose from 10 μM to 0.5 mM with a detection limit at ca. 10 μM at pH 10.