One-step synthesis of Ru(2,2 '-bipyridine)(3)Cl-2-immobilized silica nanoparticles for use in electrogenerated chemiluminescence detection

One-step synthesis of Ru (bpy)(3) Cl-2-immobilized (bpy = 2,2'-bipyridine) silica nanoparticles (Ru-silica nanoparticles) for use in electrogenerated-chemiluminescence (ECL) detection is reported. Ru-silica nanoparticles are prepared by using the Stober method. Compared with free Ru(bpy)(3)Cl-2, Ru-silica nanoparticles are seen to exhibit a red-shift of the UV-vis absorbance peak and a longer fluorescence lifetime, which are attributed to the electrostatic interaction of Ru(bpy)(3)(2+) and silica. Because silica nanoparticles are used as immobilization matrices, the surfaces of Ru-silica nanoparticles are easily modified or functionalized via the assembly of other nanoparticles, such as Au. For ECL detection, Au-colloid-modified Ru-silica nanoparticles are immobilized on a 3-mercaptopropyl-trimethoxysilane-modified indium tin oxide electrode surface by Au-S interaction; the surface concentration of electroactive Ru(bpy)(3)Cl-2 is obviously higher than that in silica films.

Application of Ru(bpy)(3)(2+) in control and formation of gold surface nanostructure through oxidation-reduction cycling

It was studied that the nanostructure formed on a gold surface via a simple oxidation-reduction cycles (ORC) in 0.1 M KCl containing Ru(bpy)(3)(2+) with different concentrations. Atomic force microscopy (AFM) and energy-dispersed spectroscopy (EDS) were used to characterize the nanostructure formed on the gold surface. Sweep-step voltammetry and corresponding electroluminescence (ECL) response, in situ electrochemical quartz crystal microbalance (EQCM) measurement were used to monitor the ORC. procedure. It was found that the surface structure became more uniform in the presence of Ru(bpy)(3)(2+), and the surface roughness was decreasing with the increasing of Ru(bpY)(3)(2+) concentration, suggesting a simple and effective method to control the formation of nanostructure on the gold surface.

Tris(2,2 '-bipyridyl) ruthenium(II) doped silica film modified indium tin oxide electrode and its electrochemiluminescent properties

An approach was reported to synthesize silica hybridized ruthenium bipyridyl complex through amidation reaction by covalent attachment of bis(bipyridyl)-4,4'-dicarboxy-2,2'-bipyridyl-ruthenium to (3-aminopropyl)-triethoxysilane. The hybrid complex then was gelatinized through acid catalytic hydrolysis method and a sol-gel modified indium, tin oxide electrode was prepared via spin coating technique. As prepared indium tin oxide electrode possesses good stability therein with excellent electrochemiluminescence behavior.

A novel alcohol dehydrogenase biosensor based on solid-state electrogenerated chemiluminescence by assembling dehydrogenase to Ru(bpy)(3)(2+)-Au nanoparticles aggregates

Based on electrogenerated chemiluminescence (ECL), a novel method for fabrication of alcohol dehydrogenase (ADH) biosensor by self-assembling ADH to Ru(bpy)(3)(2+) -AuNPs aggregates (Ru-AuNPs) on indium tin oxide (ITO) electrode surface has been developed. Positively charged Ru(bpy)(3)(2+) could be immobilized stably on the electrode surface with negatively charged AuNPs in the form of aggregate via electrostatic interaction. On the other hand, AuNPs are favourable candidates for the immobilization of enzymes because amine groups and cysteine residues in the enzymes are known to bind strongly with AuNPs. Moreover, AuNPs can act as tiny conduction centers to facilitate the transfer of electrons. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate, and it displayed wide linear range, high sensitivity and good stability.

Tris(2,2 '-bipyridyl)ruthenium(II) electrochemiluminescent detection of coreactants containing aromatic diol group by the interaction between diol and borate anion

Previous studies show that aromatic diols inhibited Ru(bpy)(3)(2+) electrochemiluminescence (ECL), and all reported Ru(bpy)(3)(2+) ECL methods for the determination of aromatic diols-containing coreactants are based on inhibition of Ru(bpy)(3)(2+)/tripropylamine ECL. In this study, the interaction between diol and borate anion was exploited for Ru(bpy)(3)(2+) ECL detection of coreactants containing aromatic diol group using epinephrine as a model analyte. The interaction prevented from the inhibition of Ru(bpy)(3)(2+) ECL by aromatic diol group of epinephrine. As a result, epinephrine was successfully detected in the absence of tripropylamine simply by using borate buffer solution as the supporting electrolyte. Under the optimum conditions, the log of the ECL intensity increases linearly with the log of epinephrine concentrations over the concentration range of 1.0x10(-9)-1.0x10(-4) M. The detection limit is 5.0x10(-10) M at a signal-to-noise ratio of three. The proposed method exhibit wider dynamic range and better detection limit than that by inhibited Ru(bpy)(3)(2+) ECL method. The relative standard deviation for 14 consecutive determinations of 5 mu M epinephrine was 3.5%. The strategy by interaction with borate anion or boronate derivatives is promising for the determination of coreactants containing aromatic diol group or aromatic hydroxyl acid group. Such interaction can also be used to avoid interference from aromatic diols or aromatic hydroxyl acids.

Electrogenerated chemi luminescence from Ru(BPY)(3)(2+) ion-exchanged in carbon nanotube/perfluorosulfonated ionomer composite films

The electrochemistry and electrogenerated chemiluminescence (ECL) of ruthenium(II) tris(bipyridine) (Ru(bpy)(3)(2+)) ion-exchanged in carbon nanotube (CNT)/Nafion composite films were investigated with tripropylamine (TPA) as a coreactant at a glassy carbon (GC) electrode. The major goal of this work was to investigate and develop new materials and immobilization approaches for the fabrication of ECL-based sensors with improved sensitivity, reactivity, and long-term stability. Ru(bpy)(3)(2+) could be strongly incorporated into Nafion film, but the rate of charge transfer was relative slow and its stability was also problematic. The interfusion of CNT in Nafion resulted in a high peak current of Ru(bpy)(3)(2+) and high ECL intensity. The results indicated that the composite film had more open structures and a larger surface area allowing faster diffusion of Ru(bpy)(3)(2+) and that the CNT could adsorb Ru(bpy)(3)(2+) and also acted as conducting pathways to connect Ru(bpy)(3)(2+) sites to the electrode. In the present work, the sensitivity of the ECL system at the CNT/Nafion film-modified electrodes was more than 2 orders of magnitude higher than that observed at a silica/Nafion composite film-modified electrode and 3 orders of magnitude higher than that at pure Nafion films.

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.

Electrogenerated chemiluminescence sensors using Ru(bpy)(3)(2+) doped in silica nanoparticles

A novel electrogenerated chemiluminescence (ECL) sensor based on Ru(bpy)(3)(2+)-doped silica (RuDS) nanoparticles conjugated with a biopolymer chitosan membrane was developed. These uniform RuDS nanoparticles ( similar to 40 nm) were prepared by a water-in-oil microemulsion method and were characterized by electrochemical and transmission electron microscopy technology. The Ru( bpy)(3)(2+)-doped interior maintained its high ECL efficiency, while the exterior nanosilica prevented the luminophor from leaching out into the aqueous solution due to the electrostatic interaction. This is the first attempt to branch out the application of RuDS nanoparticles into the field of ECL, and since a large amout of Ru(bpy)(3)(2+) was immobilized three-dimensionally on the electrode, the Ru( bpy)(3)(2+) ECL signal could be enhanced greatly, which finally resulted in the increased sensitivity. This sensor shows a detection limit of 2.8 nM for tripropylamine, which is 3 orders of magnitude lower than that observed at a Nafion-based ECL sensor. Furthermore, the present ECL sensor displays outstanding long-term stability.

Electrogenerated chemiluminescence sensing platform using Ru(bpy)(3)(2+) doped silica nanoparticles and carbon nanotubes

An effective electrogenerated chemiluminescence (ECL) sensor was developed by coimmobilization of the Ru(bpy)(2)(3+)-doped silica (RuDS) nanoparticles and carbon nanotubes (CNTs) on glassy carbon electrode through hydrophobic interaction. The uniform RuDS nanoparticles were prepared by a water-in-oil (W/O) microemulsion method and Ru(bpy)(3)(2+) doped inside could still maintain its high ECL efficiency. With such unique immobilization method, a great deal of Ru(bpy)(3)(2+) was immobilized three-dimensionally on the electrode , which could greatly enhance the ECL response and result in the increased sensitivity. On the other hand, CNTs played dual roles as matrix to immobilize RuDS nanoparticles and promoter to accelerate the electron transfer between Ru(bpy)(3)(2+) and the electrode. The as-prepared ECL sensor displayed good sensitivity and stability.

Electrogenerated chemiluminescence biosensor based on Ru(bpy)(3)(2+) and dehydrogenase immobilized in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) composite material

A new electrogenerated chemiluminescence biosensor was fabricated by immobilizing ECL reagent Ru(bPY)(3)(2+) and alcohol dehydrogenase in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) (PSS) organically modified composite material. The component PSS was used to immobilize ECL reagent Ru(bpy)(3)(2+) by ion-exchange, while the addition of chitosan was to prevent the cracking of conventional sol-gel-derived glasses and provide biocompatible microenvironment for alcohol dehydrogenase. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate and it was much simpler than previous double-layer design. The detection limit was 9.3 x 10(-6) M for alcohol (S/N = 3) with a linear range from 2.79 x 10(-5) to 5.78 x 10(-2) M. With ECL detection, the biosensor exhibited wide linear range, high sensitivity and good stability.

Determination of ranitidine in urine by capillary electrophoresis-electrochemiluminescent detection

The fast analysis of ranitidine is of clinical importance in understanding its efficiency and a patient's treatment history. In this paper, a novel determination method for ranitidine based on capillary electrophoresis-electrochemiluminescence detection is described. The conditions affecting separation and detection were investigated in detail. End-column detection of ranitidine in 5 mM Ru(bpy)(3)(2+) solution at applied voltage of 1.20 V was performed. Favorable ECL intensity with higher column efficiency was achieved by electrokinetic injection for 10 s at 10 kV. The R.S.D. values of ECL intensity and migration time were 6.38 and 1.84% for 10(-4) M and 6.01 and 0.60% for 10(-5) M, respectively. A detection limit of 7 x 10(-8) M (S/N = 3) was achieved. The proposed method was applied satisfactorily to the determination of ranitidine in urine in 6 min.

Highly sensitive electrogenerated chemiluminescence produced at Ru(bpy)(3)(2+) in Eastman-AQ55D-carbon nanotube composite film electrode

The electrochemistry and electrogenerated chemilurninescence (ECL) of tris(2,2-bipyridyl)ruthenium(II) ion-exchanged in Eastman-AQ-carbon nanotube (CNT) composite films were investigated at a glassy carbon (GC) electrode. Eastman-AQ55D is a poly (ester sulfonic acid) cation exchanger available in a commercial dissolved form. It is much more hydrophilic than Nafion due to its unique structure, so Ru(bpy)(3)(2+) does not diffuse into the hydrophobic region where it may lose its electroactivity as that in Nafion. The interfused CNT could act as electronic wires that connect the electrode with Ru(bpy)(3)(2+), which made the composite film much more electronically which finally led to the increasing of Ru(bpy)(3)(2+) conductive. Besides, the negatively charged CNT could also absorb some Ru(bpy)(3)(2+). Moreover, the strong electrostatic interaction between AQ and Ru(bpy)(3)(2+) made the composite films much more stable. The combination of AQ and CNT brings excellent sensitivity with the detection limit as low as 3 x 10(-11) M for TPA.

Multifunctional organic-inorganic multilayer films of tris(2,2 '-bipyridine)ruthenium and decatungstate

A new multifunctional multilayer films consisting of tris(2,2'-bipyridyl)ruthenium(II) (Rubpy) and sodium decatungstate (W-10) have been prepared by the layer-by-layer (LbL) self-assembly method on ITO substrate. X-ray photoelectron spectra (XPS) confirmed the existence of W10 and Rubpy. Cyclic voltammetry (CV) and UV-Vis spectroscopy demonstrated the uniform assembly of (W-10/Rubpy) multilayer films. The multilayer films possess electrocatalytic activities on the reduction of iodate and oxidation of oxalate. Moreover, the films exhibited electrochemiluminescence (ECL) with tripropylamine (abbreviated as TPA) as the coreactant and the ECL response was proportional to the number of (W-10/Rubpy) layers. These characteristics of the multilayer films might find potential applications in the field of sensors and materials fields.

Flow injection analysis of histidine with enhanced electrogenerated chemiluminescence of luminol

A simple and sensitive flow injection method is presented for the determination of histidine based on its enhancement of electrogenerated chemiluminescence (ECL) of luminol. After optimization of the experimental parameters, the working range for histidine was in 1.0 x 10(-6) to 1.0 x 10(-3) mol/L with a detection limit (S/N = 3) of 0.56 mumol/L. The relative standard deviation was 1.6% for 11 measurements of 5 x 10(-5) mol/L histidine solution. The proposed method has been successfully applied to the determination of histidine in real pharmaceutical preparation.

Electrochemiluminescent microoptoprobe with mini-grid working electrode and self-contained sample container

A new electrochemiluminescence (ECL) microoptoprobe with simple structure. small sampling volume and high efficiency was developed. It was constructed by fixing the transparent gold mini-grid on the end surface of the optical fiber, and by surrounding the fiber with the counter- and reference electrodes to form a self-contained three-electrode system. The use of mini-grid electrode increased the surface area and collection efficiency. which resulted in higher ECL signal and better sensitivity. The counter electrode together with one end of the fiber formed a mini-vessel, which eliminated the need of additional container and allowed to perform ECL detection in a very small volume (about 10 mul). The microoptoprobe obtained was characterized with the Ru(bpy)(3)(2-)-tripropylamine system and was applied for the determination of oxalate and chlorpromazine (CPZ). Detection limits (S/N = 3) were 5 x 10(-7) and 1 x 10(-6) mol l(-1) for oxalate and CPZ. respectively. The linear range for oxalate and CPZ extended from 1 x 10(-6) to 1 x 10(-3) mol l(-1), and from 5 x 10(-6) to 5 x 10(-4) mol l(-1). respectively.