Spontaneous formation and electrogenerated chemiluminescence of tris(bipyridine) Ru(II) derivative nanobelts

The single crystalline nanobelts were successfully fabricated with an ionic compound by a simple reprecipitation method. The compound used is the water-insoluble derivative of tris(bipyridine) Ru(II), [Ru(bpy)2(4,4'-(CH3(CH2)14COO)2-bpy)](ClO4)2. The prepared nanobelts show an enhanced fluorescence emission and relatively strong electrogenerated chemiluminescence (ECL), that have potential analytical applications. More interesting, ECL of a single nanobelt deposited on an ultramicroelectrode was observed. The observation of ECL in such nanostructures leads to the development of a new class of ECL systems that may prove useful for a variety of purposes.     

Solid-supported chemiluminescence and electrogenerated chemiluminescence based on a tris(2,2'-bipyridyl)ruthenium(II) derivative

We report a simple and efficient technique for the covalent immobilisation of a tris(2,2'-bipyridyl)ruthenium(II) derivative suitable for both chemiluminescence and electrochemiluminescence detection.     

Hot electron-induced electrogenerated chemiluminescence of 1-aminonaphthalene-4-sulphonate at oxide-covered aluminium electrodes in aqueous solution

Electrogenerated chemiluminescence of 1-aminonaphthalene-4-sulphonate (ANS) provides a sensitive means for the detection of the ANS in aqueous solution when oxide-covered aluminium electrodes are used as tunnel emission electrodes and cathodic pulse polarisation is used for the excitation of the luminophore. During the pulse polarisation of insulating oxide film-coated aluminium cathodes, hot electrons are tunnel emitted from the aluminium to the aqueous electrolyte solution by direct field-assisted tunnelling (in the case of oxide films of thickness 2-6 nm) or by Fowler-Nordheim (FN) tunnelling in the cases of thicker oxide films. As a result of direct tunnel emission of these energetic electrons, the generation of hydrated electrons (e_aq⁻) becomes possible. These electrochemically generated, extremely strong reductants (dry hot or hydrated electrons) make the efficient excitation of various types of luminophores at thin insulating film-covered electrodes possible and provide a means for sensitive immunoassays and DNA-probing assays when these luminophores are used as label molecules.     

Aryl-diamide bridged binuclear ruthenium (II) tris(bipyridine) complexes: Synthesis, photophysical, electrochemical and electrochemiluminescence properties

Several new symmetrical aromatic hydrocarbon bridged bipyridine ligands and their binuclear Ru (II) complexes have been designed, synthesized and characterized on the basis of ¹H NMR, MS and HRMS. Their absorption and emission properties, electrochemical behaviors and electrochemical luminescence were investigated. All ruthenium complexes show characteristic MLCT absorption and similar redox potential. Among the three complexes reported, 4c has the best electrochemical luminescence property.     

Construction and Characterization of Ru(II)Tris(bipyridine)‐Based Silica Thin Film Electrochemiluminescent Sensors

Ru(II) tris‐bipyridine based ECL sensors were produced by embedding the complex inside silica glass thin films deposited via a sol‐gel dipping procedure on K‐glass conducing substrates. Films were prepared starting from a pre‐hydrolyzed ethanolic solution of Si(OC₂H₅)₄ and Ru(bpy)₃Cl₂. Transparent, crack‐free and homogeneous reddish silica layers, having a thickness of 200±20 nm, were obtained. The films, either deposited at room temperature or thermally annealed at 100, 200 and 300 °C for 30 h, were structurally and chemically characterized. Ru(bpy)₃Cl₂ thermal stability was previously checked by thermogravimetric analysis (TGA). The films were investigated by X‐Ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and UV‐vis spectroscopy. XPS in‐depth profiles revealed a homogeneous distribution of the ruthenium complex inside the silica thin layers. SIMS data suggested that the embedded Ru(bpy)₃Cl₂ did not react with oxygen inside the oxygen‐rich silica matrix to give Ru‐O bonds. Electrochemical and ECL characterization of the thin film electrodes were made by means of cyclic voltammetry (CV) and controlled potential step experiments. The ECL sensor showed a diffusive redox behavior of the Ru(bpy)₃²⁺/Ru(bpy)₃³⁺ system. Light emission produced from the reaction between oxalic acid and the electrogenerated Ru(bpy)₃³⁺ was larger and stable when thermally treated electrodes were used after a suitable hydration period. The 300 °C treated sample was the best performing sensor both in terms of low complex leakage and sensitivity. Calibration plots relative to oxalic acid were obtained both in stationary and in flowing solutions in the concentration range 2×10^?6?3×10^?4 M. A linear behavior appeared in the former case, while in the latter a slight curvature was evident as a consequence of a finite diffusion time of the analyte inside the thin film. The signal repeatability, obtained by multiple 100 μL of 10^?5 M oxalic acid injections in flowing solutions, was better than 4%. The obtained detection limit (computed as three times the standard deviation of the base‐line noise) was 10^?6 M as oxalic acid.     

Electrogenerated chemiluminescence: an oxidative-reductive mechanism between quinolone antibiotics and tris(2,2'-bipyridyl)ruthenium(II)

The cyclic voltammetry and electrogenerated chemiluminescent (ECL) reactions of a series of quinolone and fluoroquinolone antibiotics were investigated in a flow injection analysis (FIA) system. 7-Piperazinyl fluoroquinolone antibiotics were found to participate as a coreactant in an oxidative-reductive ECL mechanism with tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) as the luminescent reagent. The reaction mechanism was investigated in order to understand and optimize the processes leading to light emission. The optimal conditions included a solution pH ∼7 at a flow rate of 3.0 mL min⁻¹ with no added organic modifier and application of 1.2 V vs. a Pt quasi-reference electrode (QRE). Fluoroquinolones containing a tertiary distal nitrogen on the piperazine ring, such as enrofloxacin and ofloxacin, reacted to produce more intense ECL than those with a secondary nitrogen, such as ciprofloxacin and norfloxacin. The method linear range, precision, detection limits, and sensitivity for the detection of enrofloxacin and ciprofloxacin were compared to that of tripropylamine. The method was applied to the determination of the ciprofloxacin content in a pharmaceutical preparation. The assay is discussed in terms of its analytical figures of merit, ease of use, speed, accuracy and application to pharmaceutical samples.     

Application of electrogenerated chemiluminescence of luminol to determination of traces of cobalt(II) in aqueous alkaline solution

A selective method for determination of traces of cobalt(II) in aqueous alkaline solution has been developed, based on the electrochemical generation of luminescence from luminol at a rotating ring—disc electrode. The detection limit is 10^-8 M, and the linear calibration range extends up to 3 × 10^-6 M; the r.s.d. for 2.0 × 10^-7 M cobalt is 6%. Of 21 metal ions, only chromium(III) and copper(II) interfere seriously; EDTA also interferes.     

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).     

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.     

Characterization of the low-oxidation-potential electrogenerated chemiluminescence of tris(2,2′-bipyridine)ruthenium(II) with tri-n-propylamine as coreactant

The electrogenerated chemiluminescence (ECL) of the Ru(bpy)₃²⁺ (bpy, 2,2′-bipyridine)/tri-n-propylamine (TPrA) system can be produced at an oxidation-potential well before the oxidation of Ru(bpy)₃²⁺. Here, we describe the unique features of the low-oxidation-potential (LOP) ECL. The LOP ECL exhibited strong dependence on solution pH with the maximum emission at pH  7.7. Compared with the conventional ECL, the LOP ECL was much more significantly diminished at high pH (>10), probably due to the short lifetime of TPrA cation radical which is a crucial intermediate for the LOP emission. It was also found that the preceding deprotonation step played an important role in TPrA oxidation at neutral pH and would remarkably influence the emission intensity. As excess intermediate radicals were produced upon rapid TPrA oxidation, only 5 mM TPrA was needed to achieve the maximum LOP ECL intensity in detecting trace Ru(bpy)₃²⁺ (<1 μM) and the LOP ECL response to Ru(bpy)₃²⁺ concentration was linear. Compared with the conventional Ru(bpy)₃²⁺/TPrA ECL, the LOP ECL technique not only produces higher emission intensity at lower oxidation-potential, but also significantly reduces the amount of the coreactant.     

Ultrasensitive electrogenerated chemiluminescence detection of DNA hybridization using carbon-nanotubes loaded with tris(2,2′-bipyridyl) ruthenium derivative tags

An ultrasensitive electrogenerated chemiluminescence (ECL) detection method of DNA hybridization based on single-walled carbon-nanotubes (SWNT) carrying a large number of ruthenium complex tags was developed. The probe single strand DNA (ss-DNA) and ruthenium complex were loaded at SWNT, which was taken as an ECL probe. When the capture ss-DNA with a thiol group was self-assembled onto the surface of gold electrode, and then hybridized with target ss-DNA and further hybridized with the ECL probe to form DNA sandwich conjugate, a strong ECL response was electrochemically generated. The ECL intensity was linearly related to the concentration of perfect-matched target ss-DNA in the range from 2.4 × 10⁻¹⁴ to 1.7 × 10⁻¹² M with a detection limit of 9.0 × l0⁻¹⁵ M. The ECL signal difference permitted to discriminate the perfect-matched target ss-DNA and two-base-mismatched ss-DNA. This work demonstrates that SWNT can provide an amplification platform for carrying a large number of ECL probe and thus resulting in an ultrasensitive ECL detection of DNA hybridization.     

Modulated potential electrogenerated chemiluminescence of luminol and Ru(bpy) 3 2+

Chemiluminescence emission intensity is modulated by modulating the potential of a working electrode which is used to generate a key species in the electrogenerated Chemiluminescence (ECL) reaction. The emission is monitored synchronously using a lock-in amplifier. The reactions used in the characterization are luminol with hydrogen peroxide and tris(2,2-bipyridyl)ruthenium (II) (or Ru(bpy) ₃ ²⁺ ) with oxalate. Modulation widths of ± 50 mV yield maximum signals for luminol when centered at 0.45 V (vs Ag/AgCl) and for Ru(bpy) ₃ ²⁺ when centered at 1.05 V. The resulting signal decreases with increasing modulation frequency and shows that luminol/H₂O₂ is a faster ECL system than Ru(bpy) ₃ ²⁺ /oxalate. Working curves for luminol and for oxalate have essentially the same linear range and slope with the modulated potential approach as with a DC electrode potential. This approach provides capability for differentiating the analytical signal from constant background emission or stray light.     

Sensitive determination of metal ions by liquid chromatography with tris(2,2'-bipyridine) ruthenium (II) complex electrogenerated chemiluminescence detection.

Emetine dithiocarbamate metal complex, which is prepared from emetine, carbon disulfide, and metal (II), was found to indicate a large chemiluminescence intensity on the electrogenerated chemiluminescence of tris(2,2'-bipyridine)ruthenium(II). Liquid chromatography equipped with the chemiluminescence detection was developed for analyzing trace metal ions by use of the metal complex formation. The mixture of the Cu(II) and Co(II) complexes as a model sample was injected into the LC system. The two metal complexes and an excess emetine were successfully separated. The Cu(II) and Co(II) complexes were determined over the range 1-300 nM (the detection limit of 650 fg) and 30-5000 nM (the detection limit of 17 pg), respectively.     

Tris(2,2'-bipyridine)ruthenium(II) electrogenerated chemiluminescence of alkaloid type drugs with solid phase extraction sample preparation

An electrogenerated chemiluminescence (ECL) method for the determination of pethidine, atropine, homatropine and cocaine is described. The optimum conditions were found to be similar for all of these compounds although the ECL emission intensity for cocaine was an order of magnitude lower than for pethidine due to their different chemical structures. Linear calibrations were obtained for all the compounds at pH 10 in borate buffer (0.05 mol l-1) at 1.3 V. Limits of detection of 6.8 x 10(-8), 2.2 x 10(-7), 3.2 x 10(-7) and 6.5 x 10(-7) mol l-1, respectively, were achieved for pethidine, atropine, homatropine and cocaine in standard solutions. Solid-phase extraction was used to separate the drugs from their matrix and the method was applied to the determination of spiked urine samples. The limits of quantitation for pethidine, atropine, homatropine and cocaine in urine were 1.0 x 10(-6), 2.0 x 10(-6), 2.0 x 10(-6) and 4.0 x 10(-6) mol l-1, respectively, with recoveries of between 90 and 110%.     

Electrochemistry and electrogenerated chemiluminescence of a spirobifluorene-based donor (triphenylamine)-acceptor (2,1,3-benzothiadiazole) molecule and its organic nanoparticles

A new D-A-π-A-D molecule (Spiro-BTA) containing two 2,1,3-benzothiadiazole (BTA) as the acceptor (A) and triphenylamine as the donor (D) bridged by a spirobifluorene moiety has been synthesized. The novel D-A molecule shows intense red emission (612 nm) with a high PL quantum yield (Φ(PL) = 0.51) in a solid film. A cyclic voltammogram of Spiro-BTA in 1:2 MeCN:benzene/0.1 M Bu(4)NPF(6) shows two reversible oxidation waves and one reversible reduction wave. The first oxidation wave and reduction wave were assigned as two successive electron transfer peaks separated by ～50 mV related to the oxidation of the two noninteracting donors and the reduction of the two noninteracting acceptors, respectively. Electrogenerated chemiluminescence (ECL) of Spiro-BTA upon cyclic oxidation and reduction in MeCN:benzene 1:2 shows a very bright and stable red emission that could be seen in a well-lit room. Using a reprecipitation method, well-dispersed organic nanoparticles (NPs) of the Spiro-BTA were prepared in aqueous solution. The nanoparticles were analyzed by dynamic light scattering (DLS) and scanning electron microscopy (SEM), yielding a NP size (without surfactant) of 130 ± 20 nm, while with surfactant, 100 ± 20 nm. Bathochromic shifts of absorption spectra (～16 ± 2 nm), as compared to that of the dissolved Spiro-BTA in THF, were observed for both NPs in water and as a thin film. While blue shifts (14 ± 2 nm) were observed for the photoluminescence (PL). The PL intensity of the Spiro-BTA nanoparticles was slightly enhanced (Φ(PL) of nanoparticles in water = 48%) over that of the dissolved Spiro-BTA in THF. The ECL of the organic Spiro-BTA nanoparticles in aqueous solution could be observed upon oxidation with tri-n-propylamine as a coreactant.     

Determination of diphenhydramine by capillary electrophoresis with tris(2,2'-bipyridyl)ruthenium(II) electrochemiluminescence detection

Tris(2,2′-bipyridyl)ruthenium(II) electrochemiluminescence detection in a capillary electrophoresis separation system was used for the determination of diphenhydramine. In this study, platinum disk electrode (300 μm in diameter) was used as a working electrode and the influence of applied potential and buffer conditions were investigated. Under optimal conditions: 1.2 V applied potential, pH 8.50, 15 kV separation voltage and 10 mmol l⁻¹ running buffer, the calibration curve of diphenhydramine was linear over the range of 4×10⁻⁸ to 1×10⁻⁵ mol l⁻¹. This technique gave satisfactory precision, and relative standard deviations of migration times and chemiluminescence peak intensities were less than 1 and 6%, respectively. The technique was applied to animal studies for determination of diphenhydramine extracted from rabbit plasma and urine samples, and the extraction efficiency were between 92 and 98.5%.     

Electrogenerated chemiluminescence using solution phase and immobilized tris(4,7-diphenyl-1,10-phenanthrolinedisulfonic acid)ruthenium(II)

Electrogenerated chemiluminescence (ECL) with tris(4,7-diphenyl-1,10-phenanthrolinedisulfonic acid)rathenium(II) (RuBPS) in solution and immobilized on an electrode surface is investigated. Flow injection analysis with a thin layer electrochemical cell modified for ECL detection is used to determine the analytical utility of solution phase RuBPS and RuBPS immobilized in a cationic polypyrrole derivative. The solution phase reaction of RuBPS with oxalate is investigated with regard to the dependence of ECL emission on RuBPS concentration, carrier stream flow rate, and pH. In the parameter range studied, ECL intensity is not linear with the concentration of RuBPS in the sample. A maximum ECL intensity is observed with a RuBPS concentration of approximately 250 M. Slower linear velocities give greater ECL intensities which is the opposite of what is observed for Ru(bpy) ₃ ³⁺ and oxalate. Greater ECL intensity is observed at lower pHs for oxalate and at higher pHs for proline. RuBPS ECL with oxalate yields a working curve with a linear range from 0.1–100 M oxalate. Solution phase ECL is observed for RuBPS and other amines such as NADH, proline, tripropylamine, and antibiotics including streptomycin and gentamicin. RuBPS is also immobilized by electrochemical polymerization of 1-methyl-3-(pyrrol-1-ylmethyl)pyridinium chloride (MPP) in the presence of RuBPS. This polymer-modified electrode yields ECL for oxalate and for amines.Deceased     

Simultaneous determination of pethidine and methadone by capillary electrophoresis with electrochemiluminescence detection of tris(2,2′-bipyridyl)ruthenium(II)

In this paper, we described a simple and rapid method, capillary electrophoresis with electrochemiluminescence (CE–ECL) detection using tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺), to simultaneously detect pethidine and methadone. Analytes were injected to separation capillary of 67.5 cm length (25 μm i.d., 360 μm o.d.) by electrokinetic injection for 10 s at 10 kV. Under the optimized conditions: ECL detection at 1.20 V, 30 mM sodium phosphate (pH 6.0) as running buffer, separation voltage at 14.0 kV, 5 mM Ru(bpy)₃²⁺ with 50 mM sodium phosphate (pH 6.5) in the detection cell, the linear range from 2.0 × 10^− 6 to 2.0 × 10^− 5 M for pethidine and 5.0 × 10^− 6 to 2.0 × 10^− 4 M for methadone and detection limits of 0.5 μM for both of them were achieved (S/N = 3). Relative standard derivations of the ECL intensity were 2.09% and 6.59% for pethidine and methadone, respectively.     

Study on Electrochemiluminesce of Ru(bpy3)2+ Immobilized in a Titania Sol‐Gel Membrane

The immobilization of tris(2,2′‐bipyridyl)ruthenium(II), Ru(bpy)₃²⁺, at a glassy carbon electrode was achieved by entrapping the Ru(bpy)₃²⁺ in a vapor deposited titania sol‐gel membrane. The electrogenerated chemiluminescence (ECL) of the immobilized Ru(bpy)₃²⁺ was studied. The Ru(bpy)₃²⁺ modified electrode showed a fast ECL response to both oxalate and proline. The ECL intensity was linearly related to concentrations of oxalate and proline over the ranges from 20 to 700 μmol L^?1 and 20 to 600 μmol L^?1, respectively. The detection limits for oxalate and proline at 3σ were 5.0 μmol L^?1 and 4.0 μmol L^?1, respectively. This electrode possessed good precision and stability for oxalate and proline determinations. The electrogenerated chemiluminescence mechanism of proline system was discussed. This work provided a new way for the immobilization of Ru(bpy)₃²⁺ and the application of titania sol‐gel membrane in electrogenerated chemiluminescence.     

Novel tris(2,2'-bipyridine)ruthenium(II) cathodic electrochemiluminescence in aqueous solution at a glassy carbon electrode

A novel approach of generating cathodic electrochemiluminescence of Ru(bpy)3(2+) at -0.4 V triggered by reactive oxygen species is reported for detecting alkylamines and some organic acids.