Electrogenerated chemiluminescence reaction of tris(2,2'-bipyridine)ruthenium(II) with 2,5-dimethylthiophene as co-reactant in aqueous solution

A novel effective co-reactant for electrogenerated chemiluminescence (ECL) of Ru(bpy)(3)(2+) has been found. Alpha-position-dialkylated thiophene derivatives such as 2,5-dimethylthiophene (DMT) could be used as a co-reactant for Ru(bpy)(3)(2+) ECL. The reaction mechanism of the Ru(bpy)(3)(2+)/DMT system was proposed on the basis of the identification of the reaction product, the relationship between the molecular structure and the chemiluminescent intensity, and the electrochemical study. The obtained reaction mechanism was similar to that of the Ru(bpy)(3)(2+)/aliphatic tertiary amine system. Based on these results, the preliminary studies of the Ru(bpy)(3)(2+) ECL detection system using DMT as a co-reactant were performed. Under the optimal ECL conditions, the plot of ECL intensity versus the concentration of Ru(bpy)(3)(2+) was linear over the concentration range 1.0x10(-8) to 1.5x10(-7) M (determination coefficient=0.9996).     

Electrochemiluminescence quenching as an indirect method for detection of dopamine and epinephrine with capillary electrophoresis

An electrochemiluminescence (ECL) inhibition method was developed as an indirect detection method for the determination of dopamine and epinephrine separated by capillary electrophoresis (CE). When the concentration of Ru(bpy)(3) (2+) was 50 muM diluted by 50 mM phosphate (pH 8.5) in the cell and 0.5 M tripropylamine (TPA) was added to the running buffer (10 mM phosphate, pH 9.0), an inhibition of ECL of the Ru(bpy)(3) (2+)/TPA system by the analytes was observed. Under the optimized conditions, the relative standard deviations of migration time and negative peak area were less than 1% and 3%, respectively, for 1 microM dopamine or 1 microM epinephrine (n = 10). Linear ranges of 0.1-10 microM for both analytes and the detection limits (signal-to-noise ratio S/N = 3) of 10 nM for dopamine and 30 nM for epinephrine were obtained.     

Using stannous ion as an excellent inorganic ECL coreactant for tris(2,2'-bipyridyl) ruthenium(II)

It was found that stannous chloride (SnCl(2)), as a popular inorganic reducing reagent, could obviously enhance the electrochemiluminescence (ECL) of tris(2,2'-bipyridyl) ruthenium(II) (Ru(bpy)(3)(2+)) in aqueous solution. Some factors affecting the ECL reactions between Ru(bpy)(3)(2+) and Sn(2+), including pH, concentrations of coreactant, and electrode materials, were investigated by comparison with a classic ECL coreactant tripropylamine (TPA). The Ru(bpy)(3)(2+)-Sn(2+) ECL coreactant system produces stronger and more stable ECL signals, can keep its excellent ECL activity over a wider pH range and has more choices in using electrode materials than the Ru(bpy)(3)(2+)-TPA ECL coreactant system. The ECL mechanism of the Ru(bpy)(3)(2+)-Sn(2+) coreactant system was also studied in detail.     

Electrochemical and electrogenerated chemiluminescence of clay nanoparticles/Ru(bpy)(3)(2+) multilayer films on ITO electrodes

The electrochemical and electrogenerated chemiluminescence of Ru(bpy)(3)(2+) immobilized in [clay/Ru(bpy)(3)(2+)](n) multilayer films by layer-by-layer assembly were investigated. The stable multilayer films of clay and Ru(bpy)(3)(2+) were assembled by alternate adsorption of negatively charged clay platelets and positively charged Ru(bpy)(3)(2+) from their aqueous dispersions. UV-vis spectroscopy, quartz crystal microbalance (QCM), cyclic voltammetry, and electrogenerated chemiluminescence (ECL) were used to monitor the immobilization of Ru(bpy)(3)(2+) and the regular growth of the [clay/Ru(bpy)(3)(2+)](n) multilayer films. The multilayer films modified electrode was used for the ECL detection of tripropylamine (TPA) and oxalate. The proposed novel immobilized method exhibited good stability, reproducibility and high sensitivity for the determination of TPA and oxalate, which mainly resulted from the contributing of clay nanoparticles with appreciable surface area, special structural features and unusual intercalation properties. Detection limits were 20 and 100 nM for TPA and oxalate, respectively and the linear concentration range extended from 60 nM to 0.66 mM for TPA.     

Self-quenching in the electrochemiluminescence of tris(2,2'-bipyridyl) ruthenium(ii) using metabolites of catecholamines as co-reactants

Electrochemiluminescence (ECL) of Ru(bpy)(3)(2+) using metabolites of catecholamines: homovanillic acid (HVA) and vanillylmandelic acid (VMA) as co-reactants were investigated in aqueous solution for the first time. When HVA and VMA were co-existent in the buffer solution containing Ru(bpy)(3)(2+), ECL peaks were observed at a potential corresponding to the oxidation of Ru(bpy)(3)(2+), and the ECL intensity was increased noticeably when the concentrations of HVA and VMA were at lower levels. The linear calibration range was from 8.0 × 10(-5) to 1.0 × 10(-9) M for HVA and VMA. The detection limit (S/N = 3) of HVA and VMA was 4.0 × 10(-10) M. The formation of the excited state Ru(bpy)(3)(2+*) was confirmed to result from the reaction between Ru(bpy)(3)(3+) and the intermediates of HVA or VMA radicals. Moreover, it was found that the ECL intensity was quenched significantly when the concentrations of HVA and VMA were relatively higher. The mechanism of self-quenching processes involved in the Ru(bpy)(3)(2+)-HVA and -VMA ECL systems are proposed in this study.     

Microfluidic chip with electrochemiluminescence detection using 2-(2-aminoethyl)-1-methylpyrrolidine labeling

A tertiary amine derivative, 2-(2-aminoethyl)-1-methylpyrrolidine (AEMP) was successfully developed as electrochemiluminescence (ECL) probe within microfluidic chip using ECL detection in this paper. The system was characterized by the interaction between biotin and avidin. In principle, tertiary amine derivatives containing active group can be used as a potential alternative of traditional tris(2,2'-bipyridine)ruthenium(II) [Ru(bpy)3(2+)] label. Firstly, The ECL efficiency of AEMP was characterized via comparing with that of two coreactants enhancing Ru(bpy)3(2+) ECL, TPA and proline. At same condition, AEMP has a similar ECL efficiency to TPA, and much higher than proline. After AEMP reacted with NHS-LC-biotin (succinimidyl-6-(biotinamido) hexanoate), the products and their ECL were analyzed by directly injecting it in the microfluidic chip. A 4.5 cm microchannel was used to separate the mixture of AEMP and biotinylated AEMP. The present works indicated that AEMP has a good reactivity to the analytes containing carboxyl group with a similar ECL efficiency to TPA. Under optimal condition, the detection limits (based on 3 S/N) of AEMP was 2.7 microM. The system was also validated by the reaction between biotin and avidin. The calculated binding ratio between avidin and biotin based on the present method was 4.4.     

New capillary electrophoresis-electrochemiluminescence detection system equipped with an electrically heated Ru(bpy)3(2+)/multi-wall-carbon-nanotube paste electrode

A new capillary electrophoresis-electrochemiluminescence (ECL) detection system equipped with an electrically heated Ru(bpy)(3)(2+)/multi-wall-carbon-nanotube paste electrode (Ru(bpy)(3)(2+)/MWNTPE) was developed. Ru(bpy)(3)(2+) was immobilized in the electrode by directly mixing with the multi-wall-carbon-nanotube paste (MWNTP). This modified electrode could be electrically heated and temperature of the electrode (Te) could be accurately controlled. Tri-n-propylamine (TPrA) was used as coreactant to investigate CE-ECL signals under different conditions. Compared with the conventional electrode at room temperature, the heated electrode has been shown to provide some advantages, such as higher sensitivity, lower RSD, and decreasing width of the peak. Furthermore, wider range of capillary-to-electrode distance and larger-area electrode are a benefit to CE-ECL. In addition, this system has been applied to separation and detection of acephate and dimethoate. The results indicated that the present CE-ECL system coupled with heated modified-electrode could provide high sensitivity, wide linear range, satisfying linear relationship and excellent reproducibility.     

Electrochemiluminescence of Ru(II) complexes immobilized on a magnetic microbead surface: distribution of magnetic microbeads on the electrode surface and effect of azide ion

The electrochemiluminescence (ECL) of magnetic microbeads modified with tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) was studied in the presence of tri-n-propylamine (TPA) to develop highly sensitive ECL detection system, where the employed microbead has a diameter of 4.5 microm. The ECL signal of the [Ru(bpy)3]2+ derivative-modified magnetic microbeads was found to be affected by the geometrical distribution of the magnetic microbeads on the electrode surface. The ECL peak intensity increased with increasing the number of the beads on the electrode surfaces up to 1.6 x 10(6) beads cm(-2), although above 1.6 x 10(6) beads cm(-2), it decreased. The ECL decrease arises from the physical prevention of the ECL from reaching the photomultiplier tube by the excessive beads. The observed peak ECL signal of the [Ru(bpy)3]2+ derivative-modified magnetic microbeads in the presence of NaN3, which serves as a preservative substance, mainly appeared at a potential of +0.90 V vs Ag/AgCl where [Ru(bpy)3]2+ is hardly oxidized, whereas the ECL signal in the absence of NaN3 appeared at a potential of +1.15 V. The presence of NaN3 on the electrode surface retards formation of an oxide layer on the electrode surfaces and promotes TPA oxidation. The ECL response at +0.90 V was mainly attributed to ECL reaction of excited-state [Ru(bpy)3]2+* formed by oxidation of [Ru(bpy)3]+ with TPA radical cation, where the [Ru(bpy)3]+ was generated by reduction of [Ru(bpy)3]2+ with TPA radical.     

Nanoscale-enhanced Ru(bpy)3(2+) electrochemiluminescence labels and related aptamer-based biosensing system

A unique multilabeling at a single-site protocol of the Ru(bpy)(3)(2+) electrochemiluminescence (ECL) system is proposed. Nanoparticles (NPs) were used as assembly substrates to enrich ECL co-reactants of Ru(bpy)(3)(2+) to construct nanoscale-enhanced ECL labels. Two different kinds of NP substrates [including semiconductor NPs (CdTe) and noble metal NPs (gold)] capped with 2-(dimethylamino)ethanethiol (DMAET) [a tertiary amine derivative which is believed to be one of the most efficient of co-reactants of the Ru(bpy)(3)(2+) system] were synthesized through a simple one-pot synthesis method in aqueous media. Although both CdTe and gold NPs realized the enrichment of ECL co-reactants, they presented entirely different ECL performances as nanoscale ECL co-reactants of Ru(bpy)(3)(2+). The different effects of these two NPs on the ECL of Ru(bpy)(3)(2+) were studied. DMAET-capped CdTe NPs showed enormous signal amplification of Ru(bpy)(3)(2+) ECL, whereas DMAET-capped gold NPs showed a slight quenching effect of the ECL signal. DMAET-capped CdTe NPs can be considered to be excellent nanoscale ECL labels of the Ru(bpy)(3)(2+) system, as even a NP solution sample of 10(-18) M was still detectable after an electrostatic self-assembly concentration process. DMAET-capped CdTe NPs were further applied in the construction of aptamer-based biosensing system for proteins and encouraging results were obtained.     

Solid-state electrochemiluminescence sensor based on the Nafion/poly(sodium 4-styrene sulfonate) composite film

An effective electrochemiluminescence (ECL) sensor based on Nafion/poly(sodium 4-styrene sulfonate) (PSS) composite film-modified ITO electrode was developed. The Nafion/PSS/Ru composite film was characterized by atomic force microscopy, UV-vis absorbance spectroscopy and electrochemical experiments. The Nafion/PSS composite film could effectively immobilize tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) via ion-exchange and electrostatic interaction. The ECL behavior of Ru(bpy)₃²⁺ immobilized in Nafion/PSS composite film was investigated using tripropylamine (TPA) as an analyte. The detection limit (S/N = 3) for TPA at the Nafion/PSS/Ru composite-modified electrode was estimated to be 3.0 nM, which is 3 orders of magnitude lower than that obtained at the Nafion/Ru modified electrode. The Nafion/PSS/Ru composite film-modified indium tin oxide (ITO) electrode also exhibited good ECL stability. In addition, this kind of immobilization approach was simple, effective, and timesaving.     

Electrochemiluminescence of Tris(2,2′‐bipyridine)ruthenium with Various Co‐reactants under Ultrasound Irradiation

Electrochemiluminescence (ECL) of tris(2,2′‐bipyridine)ruthenium, Ru(bpy)₃²⁺ in the presence of various co‐reactants, such as tripropylamine (TPA), oxalate ion (C₂O₄^2?), ascorbic acid (H₂A) and dehydroascorbic acid (DHA), were investigated under ultrasound irradiation. In sono‐ECL experiments, an indium‐thin‐oxide (ITO) was used as working electrode, and a titanium tipped sonic horn probe (diameter 2 mm) which operated at a frequency of 20 kHz was set in the front of the ITO electrode. Under the ultrasound irradiation, ECL signals were found to be significantly enhanced when TPA and C₂O₄^2? were used as co‐reactants, only slightly enhanced in Ru(bpy)₃²⁺/DHA system, but total quenched in Ru(bpy)₃²⁺/H₂A system. The difference of Ru(bpy)₃²⁺ ECL behaviors for various co‐reactant could to be due to the different kinetics of catalytic reactions associated in ECL schemes. ECL quenching effect observed in Ru(bpy)₃²⁺/H₂A system was suggested to be due to electron transfer (ET) route between the excited state *Ru(bpy)₃²⁺ and ascorbate anion HA^? diffused from the bulk solution, where the diffusional HA^? species served as electron donor. The effect becomes more pronounced upon sonication because the effective collision frequency between *Ru(bpy)₃²⁺ and HA^? would be significantly increased by the enhanced mass transport effect of ultrasound.     

Electrochemical sensing in microfluidic systems using electrogenerated chemiluminescence as a photonic reporter of redox reactions

This paper describes a microfluidics-based sensing system that relies on electrochemical detection and electrogenerated chemiluminescent (ECL) reporting. The important result is that the ECL reporting reaction is chemically decoupled from the electrochemical sensing reaction. That is, the electrochemical sensing reaction does not participate directly in the ECL process, but because electrochemical cells require charge balance, the sensing and ECL reactions are electrically coupled. This provides a convenient and sensitive means for direct photonic readout of electrochemical reactions that do not directly participate in an ECL reaction and thus broadens the spectrum of redox compounds that can be detected by ECL. The approach can be implemented in either a two-electrode or bipolar (single-electrode) configuration. By manipulating the placement and dimensions of the conductors, the photonic response can be enhanced. The system is used to electrochemically detect benzyl viologen present in solution and report its presence via Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) luminescence.     

A ruthenium(II) complex based turn-on electrochemiluminescence probe for the detection of nitric oxide

Electrochemiluminescence (ECL) detection technique using bipyridine-ruthenium(II) complexes as probes is a highly sensitive and widely used method for the detection of various biological and bioactive molecules. In this work, the spectral, electrochemical and ECL properties of a chemically modified bipyridine-ruthenium(II) complex, [Ru(bpy)(2)(dabpy)](2+) (bpy: 2,2'-bipyridine; dabpy: 4-(3,4-diaminophenoxy)-2,2'-bipyridine), were investigated and compared with those of its nitric oxide (NO)-reaction derivative [Ru(bpy)(2)(T-bpy)](2+) (T-bpy: 4-triazolephenoxy-2,2'-bipyridine) and [Ru(bpy)(3)](2+). It was found that the ECL intensity of [Ru(bpy)(2)(dabpy)](2+) could be selectively and sensitively enhanced by NO due to the formation of [Ru(bpy)(2)(T-bpy)](2+) in the presence of tri-n-propylamine. By using [Ru(bpy)(2)(dabpy)](2+) as a probe, a sensitive and selective ECL method with a wide linear range (0.55 to 220.0 μM) and a low detection limit (0.28 μM) was established for the detection of NO in aqueous solutions and living cells. The results demonstrated the utility and advantages of the new ECL probe for the detection of NO in complicated biological samples.     

Carbon optically transparent electrodes for electrogenerated chemiluminescence

This study investigates pyrolyzed photoresist film (PPF)-based carbon optically transparent electrodes (C-OTEs) for use in electrogenerated chemiluminescence (ECL) studies. Oxidative-reductive ECL is obtained with a well-characterized ECL system, C8S3 J-aggregates with 2-(dibutylamino)ethanol (DBAE) as coreactant. Simultaneous cyclic voltammograms (CVs) and ECL transients are obtained for three thicknesses of PPFs and compared to nontransparent glassy carbon (GC) and the conventional transparent electrode indium tin oxide (ITO) in both front face and transmission electrode cell geometries. Despite positive potential shifts in oxidation and ECL peaks, attributed to the internal resistance of the PPFs that result from their nanoscale thickness, the PPFs display similar ECL activity to GC, including the low oxidation potential (LOP) observed for amine coreactants on hydrophobic electrodes. Reductive-oxidative ECL was obtained using the well-studied ECL luminophore Ru(bpy)(3)(2+), where the C-OTEs outperformed ITO because of electrochemical instability of ITO at very negative potentials. The C-OTEs are promising electrodes for ECL applications because they yield higher ECL than ITO in both oxidative-reductive and reductive-oxidative ECL modes, are more stable in alkaline solutions, display a wide potential window of stability, and have tunable transparency for more efficient detection of ECL.     

Emission of tris(2,2'-bipyridine)ruthenium(II) by coreactant electrogenerated chemiluminescence: from O2-insensitive to highly O2-sensitive

We describe the influence of dissolved oxygen on the emission of Ru(bpy)3(2+) (bpy = 2,2'-bipyridine) by electrogenerated chemiluminescence (ECL) with tertiary amine as coreactant in aqueous solutions. The significance of the reactions between molecular oxygen and the ECL intermediate reducing radicals has been demonstrated for the first time. By varying the experimental conditions, the oxygen effect on different ECL routes of the Ru(bpy)3(2+)/tri-n-propylamine (TPrA) system was examined. When coreactant direct oxidation played a predominant role in producing ECL, the maximum emission intensity, especially that of the low-oxidation-potential (LOP) ECL, could change from O2-insensitive to highly O2-sensitive with decreasing TPrA concentration. This behavior can be interpreted as follows: A large excess of intermediate reducing radicals was produced at high [TPrA], and the dissolved oxygen within the ECL reaction layer was completely reduced by these radicals and exerted no quenching effect on the emission. At low [TPrA], however, coreactant oxidation generated a relatively small amount of reducing intermediates, and molecular oxygen acted as an interceptor, destroying the intermediates before they participated in the ECL pathways, which led to the obvious reduction of the emission intensity. In the latter case, the less efficient LOP ECL route was more remarkably affected. When ECL was generated primarily via the catalytic route at high [Ru(bpy)3(2+)], the reactions consuming the intermediate radicals by O2 became insignificant, and he drop of emission intensity in the presence of oxygen could mainly be ascribed to the excited-state quenching. A similar oxygen effect was also observed for the Ru(bpy)3(2+)/triethylamine (TEA) system.     

分子印迹固相萃取-电化学发光检测牛奶中氯霉素

基于氯霉素(CAP)能强烈抑制Ru(bpy)32+/TPA体系的电化学发光(ECL)信号,结合分子印迹固相萃取(MISPE)样品前处理技术,建立了一种高灵敏度检测牛奶中CAP残留量的方法。在最优实验条件下,体系的ECL猝灭值ΔI与CAP浓度呈良好线性关系,线性范围为1.0×10-13～1.0×10-11g/mL,检测限为3×10-12g/mL,精密度和准确度好,可用于牛奶中CAP残留量的测定。     

Electrochemiluminescence from tris(2,2′-bipyridyl) ruthenium (Ⅱ) in the presence of aminocarboxylic acid co-reactants

Due to the highly sensitive electrochemiluminescence (ECL), tris(2,2′-bipyridyl) ruthenium(II) (Ru(bpy)32+) is often used in the field of bioarrays with the help of co-reactants. However, the generally used co-reactant, tripropylamine (TPA), is toxic, corrosive and volatile. Therefore, the search for safe, sensitive and economical co-reactants is critical. Herein, three aminocarboxylic acids, ethylenediamine-tetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and 2-hydroxyethylethylene diaminetriacetic ac...     

DNA biosensor based on the electrochemiluminescence of Ru(bpy)3(2+) with DNA-binding intercalators

This paper reports a novel detection method for DNA hybridization based on the electrochemiluminescence (ECL) of Ru(bpy)(3)(2+) with a DNA-binding intercalator as a reductant of Ru(bpy)(3)(3+). Some ECL-inducible intercalators have been screened in this study using electrochemical methods combined with a chemiluminescent technique. The double-stranded DNA intercalated by doxorubicin, daunorubicin, or 4',6-diamidino-2-phenylindole (DAPI) shows a good ECL with Ru(bpy)(3)(2+) at +1.19 V (versus Ag/AgCl), while the non-intercalated single-stranded DNA does not. In order to stabilize the self-assembled DNA molecules during ECL reaction, we constructed the ECL DNA biosensor separating the ECL working electrode with an immobilized DNA probe. A gold electrode array on a plastic plate was assembled with a thru-hole array where oligonucleotide probes were immobilized in the side wall of thru-hole array. The fabricated ECL DNA biosensor was used to detect several pathogens using ECL technique. A good specificity of single point mutations for hepatitis disease was obtained by using the DAPI-intercalated Ru(bpy)(3)(2+) ECL.     

Capillary electrophoresis with gold nanoparticles enhanced electrochemiluminescence for the detection of roxithromycin

Tris(2,2'-bipyridyl) ruthenium(II) (Ru(bpy)(3)(2+))-roxithromycin based electrochemiluminescence (ECL) was enhanced greatly by gold nanoparticles 10 nm in diameter. Capillary electrophoresis (CE) was coupled with the resultant ECL system as a detector for roxithromycin. This ECL emission is explained by the coreactant mechanism where roxithromycin behaves as a coreactant to generate strong reducing species and gold nanoparticles act as "floating nanoelectrodes". The reaction of Ru(bpy)(3)(3+) with the generated strong reducing species on the Pt working electrode as well as on "floating nanoelectrodes" releases Ru(bpy)(3)(2+*), resulting in enhancement of ECL emission. The selectivity of this detection system towards roxithromycin was examined by CE. Under the optimized conditions, the intensity of ECL emission varies linearly with the concentration of roxithromycin from 24 nM to 0.24 mM. The detection limit is 8.4 nM, while without adding gold nanoparticles it is only 84 nM. The detection of roxithromycin in pharmaceutical and urine samples was also performed by the proposed CE-ECL method.     

Nitrate enhanced electrochemiluminescence determination of tris(2,3-dibromopropyl) isocyanurate with a gold nanoparticles-modified gold electrode

Tris(2,3-dibromopropyl) isocyanurate (TBC) is a heterocyclic hexabrominated flame retardant, which cannot be degraded even over a long time and may be a potential environmental pollutant. In this paper, TBC is for the first time as far as we know determined by silver nitrate-enhanced electrochemiluminescence (ECL) using a gold nanoparticles (AuNPs)-modified gold electrode. In our experiments, TBC was found to have the characteristics of increasing the ECL intensity of Ru(bpy)(3)(2+), and the ECL signal was proportional to the concentration of TBC. Based on this, we have successfully developed a novel, fast and sensitive method for the analysis of TBC. The main influencing factors including the volume ratio of acetonitrile and water, and the concentration of Ru(bpy)(3)(2+) were investigated in detail. Compared with using a bare gold electrode in MeCN without AgNO(3), the limit of detection is remarkably lowered by 20 times and the linear range is expanded by 5 times by using the AuNPs-modified gold electrode and AgNO(3). Under the optimal conditions, a limit of detection of 5.0 × 10(-8) M (S/N = 3) is achieved with a linear range of 1.0 × 10(-7) to 5.0 × 10(-5) M. The mechanism of the ECL enhancement of the system is also investigated.