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).     

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.     

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.     

Design of an electrochemiluminescence detection system through the regulation of charge density in a microchannel

Rare electrochemiluminescence (ECL) sensors have been developed based on the direct regulation of ionic current because it is difficult to establish a relationship between ionic current and ECL reporting. Ionic current can be adjusted by the effective radius and charge density of a functionalized microchannel and is frequently adopted to develop electrical sensors. Here, we show a novel ECL sensing platform that combines the microchannel-based electrical sensing technology with an ECL reporting system for the first time. The target regulated the effective radius and charge density of a microchannel which in turn adjusted the ionic transport in it and finally caused the change of ECL reporting of a tris(1,10-phenanthroline)ruthenium(ii)/tripropylamine system. The developed system has already been applied to detect aflatoxin B1 for demonstration. This configuration separated the target sensing and reporting reactions to achieve direct regulation of ECL reporting by ionic current and expanded the application of the ECL detection technology to microanalysis.

The microchannel-based target sensing and ECL reporting reactions were combined for the first time. This configuration separated the sensing and reporting reactions to achieve ionic current direct regulating ECL reporting.     

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.     

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.     

Highly stable ECL active films formed by the electrografting of a diazotized ruthenium complex generated in situ from the amine

The electrodeposition of the electrochemiluminescent (ECL) ruthenium complex, bis(2,2'-bipyridyl)(4'-(4-aminophenyl)-2,2'-bipyridyl)ruthenium(II), [Ru(bpy)(2)(apb)](2+), via the in situ formation of a diazonium species from aqueous media is reported. Surface characterization undertaken using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) determined that the layer is bound to the substrate via azo bonding. The layer displays good ECL activity and is stable over a long period of time. The excellent potential of this system for ECL sensing applications is demonstrated using the well-known ECL coreactant 2-(dibutylamino)ethanol (DBAE) as a model analyte, which can be detected to a level of 10 nM with a linear range between 10(-8) and 10(-4) M.     

Novel cathodic electrochemiluminescence of tris(bipyridine) ruthenium(II) on a gold electrode in acidic solution

The novel phenomenon of cathodic electrochemiluminescence on a gold electrode in tris(bipyridine) ruthenium(II) (Ru(bpy)(3)(2+)) solution is described for the first time. A cathodic electrochemiluminescence (ECL) was found to mainly occur at 0.4-0.8 V with continuous potential scanning from 0.2-1.4 V and the ECL peak was observed around 0.68 V, which was quite different from generally reported Ru(bpy)(3)(2+) ECL. Our group speculated that Ru(bpy)(3)(2+) possibly reacts with the gold electrode in the acidic phosphate buffer solution (PBS) to generate luminescence. The possible ECL mechanism was discussed according to the presented results. Moreover, it is revealed that the Au as co-reactant in the Ru-system contributed dominantly to the whole ECL. Therefore, the reaction between Ru(bpy)(3)(2+) and the newly formed Au implied that the inert metal Au could become a promising material for ECL investigations.     

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.     

Synthesis, structure, photophysical and electrochemiluminescence properties of Re(I) tricarbonyl complexes incorporating pyrazolyl-pyridyl-based ligands

Three rhenium carbonyl complexes 1-3 were synthesized by reaction of the appropriate bidentate pyrazolyl-pyridyl-based ligand L1, L2 (L1 = 2-[1-{4-(bromomethyl)benzyl}-1H-pyrazol-3-yl]pyridine; L2 = 1,4-bis(3-(2-pyridyl)pyrazol-1-ylmethyl)benzene) with [Re(CO)(5)Cl] in toluene. They were characterized by elemental analyses, ESI-MS, (1)H spectroscopy, and X-ray crystallography for 1 and 2. Compounds 1-3 exhibit bright yellow-green luminescence in the solid state and in solution at 298 K with the lifetimes in the microsecond range. It is noteworthy that the luminescent quantum efficiencies of compounds 1-3 are between 0.040 and 0.051, which are much higher than that of the [Re(bpy)(CO)(3)Cl] complex (= 0.019) (M. M. Richter et al., Anal. Chem., 1996, 68, 4370; J. Van Houten et al., J. Am. Chem. Soc., 1976, 98, 4853). Electrogenerated chemiluminescence (ECL) was observed in solutions of these complexes in the absence or presence of coreactant tri-n-propylamine (TPrA) or 2-(dibutylamino)ethanol (DBAE) by stepping the potential of a Pt disk working electrode. The ECL spectra are identical to the photoluminescence spectra, indicating that the chemical reactions following electrochemical oxidation or reduction form the same (3)MLCT excited states as that generated in the photoluminescence experiments. In most cases, the ECL quantum efficiencies of complexes 1-3 are comparable to that of the [Re(L)(CO)(3)Cl] (L = bpy or phen) system. Oxygen tends to substantially decrease ECL intensities of the three rhenium complexes-TPrA system, which could allow them to be used as oxygen sensors.     

Electrogenerated chemiluminescence 69: the tris(2,2'-bipyridine)ruthenium(II), (Ru(bpy)3(2+))/tri-n-propylamine (TPrA) system revisited-a new route involving TPrA*+ cation radicals

The reaction occurring on electrooxidation of Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) and tri-n-propylamine (TPrA) leads to the production of Ru(bpy)(3)(2+) and light emission. The accepted mechanism of this widely used reaction involves the reaction of Ru(bpy)(3)(3+) and a reduced species derived from the free radical of the TPrA. However, this mechanism does not account for many of the observed features of this reaction. A new route involving the intermediacy of TPrA cation radicals (TPrA(*+)) in the generation of Ru(bpy)(3)(2+) was established, based on results of scanning electrochemical microscopy (SECM)-electrogenerated chemiluminescence (ECL) experiments, as well as cyclic voltammetry simulations. A half-life of approximately 0.2 ms was estimated for TPrA(*+) in neutral aqueous solution. Direct evidence for TPrA(*+) in this medium was obtained via flow cell electron spin resonance (ESR) experiments at approximately 20 degrees C. The ESR spectra of the TPrA(*+) species consisted of a relatively intense and sharp septet with a splitting of approximately 20 G and a g value of 2.0038.     

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.     

Electrochemical determination of diphenols and their mixtures at the multiwall carbon nanotubes/poly (3-methylthiophene) modified glassy carbon electrode

This paper describes a sensitive electrogenerated chemiluminescence (ECL) method for cystine determination with improved analytical characteristics based on the combination of electrochemical parallel catalytic reaction and chemiluminescence (CL) signal sensing. Cystine can be electrochemically reduced and gives a parallel catalytic wave effect in the presence of potassium persulfate. The reaction circulated on the electrode and the amount of the reduced product of the potassium persulfate was accumulated at the electrode surface. Then the reduced product of potassium persulfate reacts with fluorescein to emit a sensitive CL signal. Investigation of the characteristics of the electrochemical and chemiluminescence reactions revealed that the speed of the electrochemical reaction was much faster than that of the subsequent CL reaction, which proved the possibility of the combination of electrochemical parallel catalytic reaction with CL signal sensing. The ECL intensity is linearly related to the cystine concentration in the range from 60 nM to 8.0 μM.     

Scanning electrochemical microscopy study of ion annihilation electrogenerated chemiluminescence of rubrene and [Ru(bpy)3]2+

Scanning electrochemical microscopy (SECM) was used for the study of electrogenerated chemiluminescence (ECL) in the radical annihilation mode. The concurrent steady-state generation of radical ions in the microgap formed between a SECM probe and a transparent microsubstrate provides a distance-dependent ECL signal that can provide information about the kinetics, stability, and mechanism of the light emission process. In the present study, the ECL emission from rubrene and [Ru(bpy)(3)](2+) was used to model the system by carrying out experiments with the SECM and light-detecting apparatus inside an inert atmosphere box. We studied the influence of the distance between the two electrodes, d, and the annihilation kinetics on the ECL light emission profiles under steady-state conditions, as well as the ECL profiles when carrying out cyclic voltammetry (CV) at a fixed d. Experimental results are compared to simulated results obtained through commercial finite element method software. The light produced by annihilation of the ions was a function of d; stronger light was observed at smaller d. The distance dependence of the ECL emission allows the construction of light approach curves in a similar fashion as with the tip currents in the feedback mode of SECM. These ECL approach curves provide an additional channel to describe the reaction kinetics that lead to ECL; good agreement was found between the ECL approach curve emission profile and the simulated results for a fast, diffusion-limited second-order annihilation process (k(ann) > 10(7) M(-1) s(-1)). In the CV mode at fixed distance, the ECL emission of rubrene showed two distinct signals at different potentials when fixing the substrate to generate the radical cation and scanning the tip to generate the radical anion. The first signal (pre-emission) corresponded to an emission well before reaching the generation of the radical anion and was more intense on Au than on Pt. The second ECL signal showed the expected steady-state behavior from the second-order annihilation reaction and agreed well with the simulation. A comparison of the emission obtained with rubrene and [Ru(bpy)(3)](2+) to test the direct formation of lower energy triplets directly at the electrode showed that triplets are not the cause of the pre-emission observed. Wavelength selection experiments for the rubrene system showed that the pre-emission ECL signal also appeared slightly red-shifted with respect to the main luminophore emission; a possible explanation for this phenomenon is inverse photoemission, where the injection of highly energetic holes by the oxidized species into the negatively biased tip electrode causes emission of states in the metal that appear at a different wavelength than the singlet emission from the ECL luminophore.     

Potential controlling highly-efficient catalysis of wheat-like silver particles for electrochemiluminescence immunosensor labeled by nano-Pt@Ru and multi-sites biotin/streptavidin affinity

The potential controlling silver catalysis for Ru(bpy)(3)(2+) electrochemiluminescence (ECL) signal at a special potential -0.4～1.25 V was newly developed as the new ECL signal amplification strategy for ultrasensitive protein detection. Firstly, the wheat-like deposited silver (DpAg) particles were modified on the bare glass carbon electrode (GCE) surface by cyclic voltammetry deposition to capture the primary antibodies and then bind the antigen analytes. Secondly, as a sandwich immunoreaction format, the secondary antibodies conjugated with the Ru(bpy)(3)(2+)-doped Pt (Pt@Ru) nanoparticles by the multi-sites biotin/streptavidin (SA) affinity can be captured onto the electrode surface to generate ECL signal. In the proposed Ru(bpy)(3)(2+) ECL system without any co-reactant, the detected ECL signal was amplified due to following multiple amplification strategies: (1) the ECL catalysis for Ru(bpy)(3)(2+) was performed by electro-inducing the DpAg particles to generate Ag(+) ion and controlled by the special potential. The catalyzer Ag(+) was produced near the electrode surface and reproduced by cyclic potential scan, which improved the catalytic efficiency. (2) The amount of the ECL signal probes linked to secondary antibodies were amplified by the adsorption of Pt nanoparticles and the multiple sites bridge linkage of biotin/SA. These new multiple signal amplification strategies made the proposed ECL immunosensor achieve ultrasensitive detection for model protein human IgG with a detection limit down to 3 pg mL(-1), which can be further extended to the detection of disease biomarkers.     

Ultrasensitive gaseous NH3 sensor based on ionic liquid-mediated signal-on electrochemiluminescence

This work reports that ammonia (NH(3)) can be used as an efficient co-reactant for tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL) in ionic liquids (ILs), on the basis of which a signal-on ECL sensor for directly detecting gaseous NH(3) has been developed. The NH(3) ECL sensor has a very high sensitivity, with a detection limit of 10 ppt NH(3) (at signal-to-noise ratio of 3) without any preconcentration. The high sensitivity is mainly due to the zero ECL background of Ru(bpy)(3)(2+) in the ILs, strong co-reactant ECL activity of NH(3), and high solubility of NH(3) in imidazolium-based ILs. Additionally, the ECL sensor shows an excellent selectivity against common interfering gases and a wide linear response range from 10 ppt to 10 ppm.     

Quenching of the electrochemiluminescence of tris(2,2'-bipyridine)ruthenium(II) by ferrocene and its potential application to quantitative DNA detection

Efficient and stable quenching of electrochemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium(II) by oxidizing ferrocene methanol (FcMeOH) at the electrode is reported. Bimolecular energy or electron transfer between Ru(bpy)(3)(2+*) and ferrocenium (Fc(+)), the oxidized species of Fc, along with suppression of radical reactions is suggested as the mechanism for quenching ECL. Fc shows more efficient quenching of ECL compared with the known quenchers phenol and 1,1-dimethyl-4,4'-bipyridine dication (MV(2+)). The ECL quenching rate constant was 5.6 x 10(10) M(-)(1) s(-)(1). Using Fc as a quencher label on a complementary DNA sequence, an intramolecular ECL quenching in hybridized oligonucleotide strands has been realized. With essentially complete quenching efficiency, this system has the potential for application to sequence-specific DNA detection.     

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.     

Electrochemiluminescence analysis of folate receptors on cell membrane with on-chip bipolar electrode

In this paper we report a transparent bipolar electrode based microfluidic chip-electrochemiluminescence (ECL) system for sensitive detection of folate receptors (FR) on cell membranes. This integrated system consists of a poly(dimethylsiloxane) (PDMS) layer containing a microchannel and a glass bottom sheet with indium tin oxide (ITO) strips as bipolar detectors. The ITO strips are fabricated using a PDMS micromold with carbon ink as a protective layer in place of traditional photoresist. The configuration of the bipolar electrode has great influence on the ECL intensity of Ru(bpy)(3)(2+)/tripropylamine(TPA) system. Further studies show that folic acid (FA) can strongly inhibit the ECL of the Ru(bpy)(3)(2+)/TPA system. Based on specific recognition between FA and FR on cell membrane, this microfluidic chip-ECL system is successfully applied for detecting the level of FR on human cervical tumor (HL-60) cells and MEF cells. It is found that the ECL intensity increases with the number of HL-60 cells in the range of 21 to 3.28 × 10(4) cells/mL. The average level of FR on HL-60 cells is calculated to be 8.05 ± 0.75 × 10(-18) mol/cell. While for MEF cells, it shows a much slower ECL increment than HL-60 cells due to the much lower FR level on MEF cells (5.30 ± 0.61 × 10(-19) mol/cell). Moreover, exocytosis of FA after FR mediated endocytosis was observed according to the change of the ECL signal with the incubation time of HL-60 cells in the FA- Ru(bpy)(3)(2+)/TPA system.     

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.