Enhancement Of Electrogenerated Chemiluminescence Research Articles

Tuning Electrogenerated Chemiluminescence Intensity Enhancement Using Hexagonal Lattice Arrays of Gold Nanodisks.

Electrogenerated chemiluminescence (ECL) microscopy shows promise as a technique for mapping chemical reactions on single nanoparticles. The technique's spatial resolution is limited by the quantum yield of the emission and the diffusive nature of the ECL process. To improve signal intensity, ECL dyes have been coupled with plasmonic nanoparticles, which act as nanoantennas. Here, we characterize the optical properties of hexagonal arrays of gold nanodisks and how they impact the enhancement of ECL from the coreaction of tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate and tripropylamine. We find that varying the lattice spacing results in a 23-fold enhancement of ECL intensity because of increased dye-array near-field coupling as modeled using finite element method simulations.

Nanoelectrode-emitter spectral overlap amplifies surface enhanced electrogenerated chemiluminescence.

Electrogenerated chemiluminescence (ECL) is a promising technique for low concentration molecular detection. To improve the detection limit, plasmonic nanoparticles have been proposed as signal boosting antennas to amplify ECL. Previous ensemble studies have hinted that spectral overlap between the nanoparticle antenna and the ECL emitter may play a role in signal enhancement. Ensemble spectroscopy, however, cannot resolve heterogeneities arising from colloidal nanoparticle size and shape distributions, leading to an incomplete picture of the impact of spectral overlap. Here, we isolate the effect of nanoparticle-emitter spectral overlap for a model ECL system, coreaction of tris(2,2'-bipyridyl)dichlororuthenium(ii) hexahydrate and tripropylamine, at the single-particle level while minimizing other factors influencing ECL intensities. We found a 10-fold enhancement of ECL among 952 gold nanoparticles. This signal enhancement is attributed exclusively to spectral overlap between the nanoparticle and the emitter. Our study provides new mechanistic insight into plasmonic enhancement of ECL, creating opportunities for low concentration ECL sensing.

Effects of multi-walled carbon nanotubes on the electrogenerated chemiluminescence and fluorescence of CdTe quantum dots.

Effects of multi-walled carbon nanotubes (CNTs) that were immobilized on glassy carbon electrode (GCE) on the electrogenerated chemiluminescence (ECL) of CdTe quantum dots (QDs) using tri-n-propylamine (TPrA) and 2-(dibutylamino)ethanol (DBAE) as the anodic coreactant are reported. Depending on the solution concentration of coreactant and QDs, the surface-confined CNTs could either quench or enhance the ECL intensity. Lowering the solution concentration of QDs was found to be beneficial for enhancing ECL. A V-shaped profile of ECL intensity ratio (at CNTs over bare GCE) versus coreactant concentration suggested that either low or high concentrations of coreactant were needed for effective ECL generation. The ECL quenching by CNTs was believed to follow the typical dynamic quenching mechanism, which was confirmed by fluorescent data that provided a Stern-Volmer and an estimated quenching constant of 11.7g/L and 1.2 × 10(9)L/g•s, respectively, for the excited state CdTe* quenching by CNTs in solution. Furthermore, the ECL performance at CNTs was also affected by the type of the coreactant used, where up to 30 times enhancement in ECL was observed from the CdTe/DBAE system under the given experimental conditions. Graphical Abstract Illustration of anodic quantum dots ECL enhancement and quenching by multi-walled carbon nanotubes.

General Strategy for Enhancing Electrochemiluminescence of Semiconductor Nanocrystals by Hydrogen Peroxide and Potassium Persulfate as Dual Coreactants.

Semiconductor nanocrystals usually suffer from weak electrogenerated chemiluminescence (ECL) emissions compared with conventional organic emitters. In this work, we propose, for the first time, a very convenient but effective way to greatly enhance ECL emission of semiconductor TiO2 nanotubes (NTs) by H2O2 and K2S2O8 as dual coreactants, generating ECL emission ca. 6.3 and 107 times stronger than that of K2S2O8 or H2O2 as an individual coreactant, respectively. Scanning electron microscopy, X-ray diffraction, and electron paramagnetic resonance spectral studies were carried out to investigate the ECL enhancement mechanism. The ECL enhancement of TiO2 NTs by the K2S2O8-H2O2 system was supposed to originate from the coordination of H2O2 to the TiO2 surface and the synergy effect between H2O2 and K2S2O8 in the ECL process. The coordination of H2O2 to the surface of TiO2 could stabilize the electrogenerated coreactant-related radical OH(•) (hydroxyl radical), which could obviously promote the amount of sulfate radical anion (SO4(•-)) near the electrode surface by inducing decomposition of K2S2O8 into SO4(•-) or inhibiting the consumption of SO4(•-) by its reaction with H2O. The holes (h(+)) released from SO4(•-) were injected into the valence band of TiO2, resulting in more TiO2(+), which combined with the electrons coming from the conduction band with an enhanced light emission. Moreover, this enhancement effect was also applicable to ECL of a CdS nanocrystal film on a glass carbon electrode, with ca. 2.74- and 148.3-fold enhanced ECL intensity correspondingly, indicating wide applications in the development of semiconductor nanocrystal-based ECL biosensors.

A CdTe/CdS quantum dots amplified graphene quantum dots anodic electrochemiluminescence platform and the application for ascorbic acid detection in fruits

Herein, a CdTe/CdS QDs (with a CdTe core and a CdS shell) amplified electrogenerated chemiluminescence (ECL) of nitrogen functional graphene quantum dots (NGQDs) platform is reported. The utilization of CdTe/CdS QDs could facilitate the production of NGQDs radical, and then, a high yield of NGQDs* was formed due to the interaction of NGQDs radical with O2−, leading to an ∼21-fold ECL enhancement. This ECL enhancing system does not require the addition of coreactant and modification of electrode which is carried out in homogeneous solution. Benefiting from the remarkable ECL enhancement effect, a feasible and sensitive ECL sensor was constructed for ascorbic acid (AA) quantification. The proposed method features a detection limit of 70nM with a linear calibration range from 100nM to 100μM, and exhibits good stability, practicability, and acceptable fabrication reproducibility, showing promising application in real-sample.

An ultrasensitive biosensor for glucose based on solid-state electrochemiluminescence on GOx/CdS/GCE electrode

In this paper a GOx/CdS/GCE electrode modified with CdS nanorods was prepared using solvothermal route under simple conditions. The electrode shows unexpectedly electrogenerated chemiluminescence (ECL) behavior after immobilization of CdS nanorods on the electrode surface, whereas the CdS nanorod itself only gives weak ECL signal. The possible mechanism of the ECL enhancement on the modified electrode was investigated thoroughly. In addition, the strong ECL emission from the CdS-K2S2O8 electrode was exploited as a useful biosensor for glucose determination. The experimental results demonstrated that this ECL biosensor showed good stability and reproducibility. An excellent linear relationship of the ECL response to he concentration of glucose was obtained within the range of 4.0 × 10−13 mol L−1 to 4.0 × 10−10 mol L−1 with a detection limit of 2.0 × 10−13 mol L−1 (S/N = 3).

Efficient electrogenerated chemiluminescence from CdTe quantum dots with coreactants

While quantum dots (QDs) have attracted much interest in electrogenerated chemiluminescence (ECL) as a light emitter due to their high quantum yield and bandgap tunability, the fundamental ECL characteristics of QDs in various conditions still remain elusive. In this study, we investigate the ECL generation from CdTe QDs dispersed in organic solvents in the presence of a coreactant. ECL generation via the annihilation between the radical cation of CdTe QDs and their radical anion is not efficient because of the short-lived, unstable radical cation of CdTe QDs. The coreactant, tetra-n-butylammonium peroxydisulfate, can facilitate the ECL generation from CdTe QDs via more efficient generation of the radical cation formed by direct oxidation of the radical anion of CdTe QDs. A poor ECL emitter, Ir(III) complex ((pq)2Ir(dbm)), is examined as a novel coreactant for CdTe QDs, and it turns out that this new ECL system is a very efficient ECL generator. This great improvement is attributed to the collaborative enhancement of ECL from both CdTe and (pq)2Ir(dbm).

Preparation of novel polypyridyl ruthenium complex polymers with high sensitivity for electrogenerated chemiluminescence via copolymerization

We report two novel monomers, Ru1mono with one vinyl group, 4-[(4-vinylbenzylformamidyl)-4'-carboxylacid-2,2'-bipyridyl]-bis[2,2'-bipyridyl] ruthenium(II) perchlorate and Ru2mono with two vinyl groups, 4,4'-bis[(4-vinylbenzylformamidyl)-2,2'-bipyridyl]-bis[2,2'-bipyridyl] ruthenium(II) perchlorate. The molecular structures were demonstrated by NMR, mass spectrometry and elemental analysis. Polymers Ru1MVP and Ru2MVP were then co-polymerized under free radical polymerization from Ru1mono or Ru2mono and 4-vinylpyridine with the molar ratio of 9:1, respectively. Electrogenerated chemiluminescence (ECL) of Ru1MVP in a thin film on an electrode has been tested. It increased 17 times relative to cis-[Ru(bpy)(2)PVP(10)](ClO(4))(2) (RuPVP) reported in the presence of co-reactant tri-n-propylamine (TPA) at the oxidative peak around 1.16 V with scan rate of 100 mV s(-1). Relative to RuPVP ECL of Ru2MVP was 110 times greater with TPA, and 40 times greater with another co-reactant, sodium oxalate. The significant enhancement of ECL and improvement in making a stable film could be expected to lead to an applicable immobilized immunoassay technology via ECL.

Sensitive Determination of Hexamethylene Triperoxide Diamine Explosives, Using Electrogenerated Chemiluminescence Enhanced by Silver Nitrate

Sensitive detection and quantification of hexamethylene triperoxide diamine (HMTD), which is one of commonly used explosives by terrorists, was presented on the basis of electrogenerated chemiluminescence (ECL) technology coupled with silver nitrate (AgNO3) enhancement in acetonitrile at a platinum electrode. Upon anodic potential scanning, HMTD irreversibly oxidized at approximately 1.70 V vs Ag/Ag+ (10 mM) at a scan rate of 50 mV/s, and the ECL profile was coincident with the oxidation potential of HMTD in the presence of ruthenium(II) tris(bipyridine) (Ru(bpy)3(2+)) luminophore species, which showed a half-wave potential of 0.96 V vs Ag/Ag+. The addition of small amounts of AgNO3 (0.50-7.0 mM) into the HMTD/Ru(bpy)3(2+) system resulted in significant enhancement in HMTD ECL production (up to 27 times). This enhancement was determined to be largely associated with NO3(-) and was linearly proportional to the concentrations of NO3(-) and Ag+ in solution. Homogeneous chemical oxidations of HMTD by electrogenerated NO3* and Ag(II) species proximity to the electrode were proposed to be responsible for the ECL enhancement. On the basis of cyclic voltammetry (CV) and CV digital simulations, standard potential values of 1.79 V vs Ag/Ag+ (or 1.98 V vs NHE) and 1.82 V vs Ag/Ag+ (or 2.01 V vs NHE) were estimated for Ag(II)/Ag(I) and NO3*/NO3(-) couples, respectively. A detection limit of 50 microM of HMTD was achieved with the current technique, which was 10 times more sensitive than that reported previously, which was based on a high-performance liquid chromatography/Fourier transform infrared (HPLC/FT-IR) detection method.

Enhanced anodic Ru(bpy) 32+ electrogenerated chemiluminescence by polyphenols

Anodic Ru(bpy) 3 2+ electrogenerated chemiluminescence (ECL) can be enhanced by polyphenols in alkaline solution. Spin trapping-electron spin resonance (ESR) experiments verified that reactive oxygen species (ROS) were generated during the electrolysis of Ru(bpy) 3 2+ in alkaline solution, and oxidation of quercetin enhanced Ru(bpy) 3 2+ ECL at anodic potential by producing additional ROS. This ECL enhancement can be used to analyze real sample and evaluate antioxidant activity of polyphenols.

Electrogenerated Chemiluminescence in Polyelectrolyte Multilayers: Efficiency and Mechanism

The presence of an ultrathin film of polyelectrolyte complex, formed by the multilayering method, on an electrode was shown to enhance the intensity of electrogenerated chemiluminescence (ECL) from the tris(2,2')bipyridylruthenium(II)/tripropylamine system. Platinum electrodes coated with up to 17 layers of poly(diallyldimethylammonium chloride) or poly(vinylmethylpyridine), alternately layered with poly(styrenesulfonate), revealed significant differences in enhancement of ECL, depending on the identity of the multilayer. ECL following deposition of each layer showed an oscillating intensity of light emission, which alludes to the importance of surface and bulk charge. This effect, along with others, such as increased output with increasing tripropylamine concentration, was used to suggest a mechanism for enhanced ECL intensity at multilayer-coated electrodes.

Electrogenerated chemiluminescence of lucigenin enhanced by the modifications of electrodes with self-assembled monolayers and of solutions with surfactants

Electrogenerated chemiluminescence (ECL) of lucigenin (Luc 2+·2NO − 3, N, N′-dimethyl-9,9′-biacridinium dinitrate) in dioxygen-saturated alkaline aqueous solutions of pH 10 has been examined utilizing modifications of electrodes (i.e. self-assembled monolayer (SAM)-modified gold electrodes) and of solutions (i.e. micellar solutions containing a nonionic surfactant, Triton X-100) for the first time. In both cases of the modifications, enhanced ECL was observed, and the ECL was considered to be derived from the decomposition of a dioxetane-type intermediate formed by the radical–radical coupling reaction between an electrogenerated superoxide ion (O 2 − ) and a one-electron reduced form of Luc 2+ (i.e. a radical cation, Luc + ). The surface modification of gold electrodes was achieved with dimercaptosuccinic acid (DMSA) and dl-thioctic acid ( dl-TA) having carboxyl end groups. The amount of ECL at dl-TA-SAM-modified electrodes was about five times as great as that at the bare electrode. The enhancement of ECL at the SAM-modified electrodes would be due to the concentration effect of positively charged Luc 2+ ions, the prevention of adsorption of the electrogenerated chemiluminescent product (i.e. N-methylacridone (NMA)) and the two-electron reduced form of Luc 2+ (Luc 0) on the electrode surfaces, and the effective generation of O 2 − . On the other hand, the amount of ECL in the micellar solution increased by about six times in comparison with that in the solution containing no surfactant. The enhanced ECL in micellar solutions would result mainly from the inhibition of adsorption of NMA and Luc 0 insoluble in water on electrode surfaces.

Electrogenerated Chemiluminescence. 66. The Role of Direct Coreactant Oxidation in the Ruthenium Tris(2,2‘)bipyridyl/Tripropylamine System and the Effect of Halide Ions on the Emission Intensity

We describe the electrogenerated chemiluminescence (ECL) processes of the Ru(bpy)3(2+) (bpy = 2,2'-bipyridyl)/ tripropylamine (TPrA) system at glassy carbon, platinum, and gold electrodes. The electrochemical behavior of TPrA on different electrode materials and its influence on the ECL process are demonstrated. At glassy carbon electrodes, the direct oxidation of TPrA began at approximately 0.6 V vs SCE and exhibited a broad irreversible anodic peak. Two ECL waves were observed, one in the potential region more negative than 1.0 V vs SCE and one at more positive potentials. The first ECL process apparently occurs without the electrogeneration of Ru(bpy)3(3+), in contrast to that of the second ECL wave. At Pt and Au electrodes, however, the formation of surface oxides significantly blocked the direct oxidation of TPrA. An ECL wave below 1.0 V did not appear at Pt and was very weak at gold. The ECL peaks at potentials of 1.1-1.2 V were also much weaker than those observed at the glassy carbon electrode. These results showed that the direct oxidation of TPrA played an important role in the ECL processes. Therefore, the enhancement of the TPrA oxidation current might lead to an increase in the ECL intensity. Small amounts of halide species were found to inhibit the growth of surface oxides on Pt and gold electrodes and led to an obvious increase of TPrA oxidation current. The anodic dissolution of gold in halide-containing solution was also important in activating the gold electrode surface. The electrochemical catalytic effect of bromide further promoted the oxidation of TPrA. A halide effect on ECL at Pt and Au electrodes was also evident. The most effective enhancement of ECL was observed at Au electrode in a bromide-containing solution. This effect was also found in an commercial flow-through instrument (IGEN) and provided a simple way to improve the detection sensitivity at low concentrations of Ru(bpy)3(2+).