Electrochemiluminescence from tris(2,2′-bipyridyl)ruthenium(II)-graphene-Nafion modified electrode

An electrochemiluminescence (ECL) sensor based on Ru(bpy)₃²⁺-graphene-Nafion composite film was developed. The graphene sheet was produced by chemical conversion of graphite, and was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and Raman spectroscopy. The introduction of conductive graphene into Nafion not only greatly facilitates the electron transfer of Ru(bpy)₃²⁺, but also dramatically improves the long-term stability of the sensor by inhibiting the migration of Ru(bpy)₃²⁺ into the electrochemically inactive hydrophobic region of Nafion. The ECL sensor gives a good linear range over 1 × 10⁻⁷ to 1 × 10⁻⁴ M with a detection limit of 50 nM towards the determination of tripropylamine (TPA), comparable to that obtained by Nafion-CNT. The ECL sensor keeps over 80% and 85% activity towards 0.1 mM TPA after being stored in air and in 0.1 M pH 7.5 phosphate buffer solution (PBS) for a month, respectively. The long-term stability of the modified electrode is better than electrodes modified with Nafion, Nafion-silica, Nafion-titania, or sol-gel films containing Ru(bpy)₃²⁺. Furthermore, the ECL sensor was successfully applied to the selective and sensitive determination of oxalate in urine samples.     

3D nanostructured Ni(OH)2 microspheres as an efficient immobilization matrix of Ru(bpy)3 for high-performance electrochemiluminescence sensor

The electrochemistry and electrochemiluminescence (ECL) of novel three-dimensional nanostructured Ru(bpy)₃²⁺/Ni(OH)₂ microspheres were investigated for the first time. The negatively charged porous Ni(OH)₂ microspheres composed of Ni(OH)₂ nanowires were specifically designed to interact with Ru(bpy)₃²⁺. The large surface area and porous structure of Ni(OH)₂ microspheres enhance loading of Ru(bpy)₃²⁺ and mass transport of the model analyte, tripropylamine (TPA). Excellent ECL performance of the presented sensor was achieved including good stability and wide linear range from 7.7 × 10⁻¹⁰ to 3.8 × 10⁻³ M with the detection limit of 2.6 × 10⁻¹⁰ M to TPA.     

Tris(2,2′-bipyridyl)ruthenium(II) electrogenerated chemiluminescence sensor based on carbon nantube dispersed in sol-gel-derived titania-Nafion composite films

A highly sensitive and stable tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) electrogenerated chemiluminescence (ECL) sensor was developed based on carbon nanotube (CNT) dispersed in mesoporous composite films of sol-gel titania and perfluorosulfonated ionomer (Nafion). Single-wall (SWCNT) and multi-wall carbon nanotubes (MWCNT) can be easily dispersed in the titania-Nafion composite solution. The hydrophobic CNT in the titania-Nafion composite films coated on a glassy carbon electrode certainly increased the amount of Ru(bpy)₃²⁺ immobilized in the ECL sensor by adsorption of Ru(bpy)₃²⁺ onto CNT surface, the electrocatalytic activity towards the oxidation of hydrophobic analytes, and the electronic conductivity of the composite films. Therefore, the present ECL sensor based on the CNT-titania-Nafion showed improved ECL sensitivity for tripropylamine (TPA) compared to the ECL sensors based on both titania-Nafion composite films without CNT and pure Nafion films. The present Ru(bpy)₃²⁺ ECL sensor based on the MWCNT-titania--Nafion composite gave a linear response (R² = 0.999) for TPA concentration from 50 nM to 1.0 mM with a remarkable detection limit (S/N = 3) of 10 nM while the ECL sensors based on titania-Nafion composite without MWCNT, pure Nafion films, and MWCNT-Nafion composite gave a detection limit of 0.1 μM, 1 μM, and 50 nM, respectively. The present ECL sensor showed outstanding long-term stability (no signal loss for 4 months).     

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.     

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)₃²⁺ 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)₃²⁺ 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 × 10⁻⁶ M for alcohol (S/N = 3) with a linear range from 2.79 × 10⁻⁵ to 5.78 × 10⁻² M. With ECL detection, the biosensor exhibited wide linear range, high sensitivity and good stability.     

A novel solid-state electrochemiluminescence detector for capillary electrophoresis based on tris(2,2'-bipyridyl)ruthenium(II) immobilized in Nafion/PTC-NH2 composite film

A new electrochemiluminescence (ECL) detector for capillary electrophoresis (CE) based on tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) immobilized in Nafion/PTC-NH₂ (an ammonolysis product of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA)) composite film was presented for the first time. The Nafion/PTC-NH₂ composite film could effectively immobilize tris(2,2′-bipyridyl)ruthenium(II) via ion-exchange and electrostatic interaction. Cyclic voltammetric and ECL behavior of Nafion/PTC-NH₂/Ru composite film was investigated compared to Nafion/Ru composite. The Nafion/PTC-NH₂/Ru composite film exhibited good ECL stability and simple operability. Then the CE with solid-state ECL detector system was successfully used to detect sophora - a quinolizidine type - alkaloids as sophoridine (SR) and matrine (MT). The CE-ECL parameters that affected separation and detection were optimized. Under the optimized conditions, the linear range was from 2.5 × 10⁻⁸ to 2 × 10⁻⁶ mol/L for SR, 1.0 × 10⁻⁸ to 1.0 × 10⁻⁶ mol/L for MT. The detection limit (S/N = 3) was estimated to be 5 × 10⁻⁹ and 10⁻⁹ mol/L for SR and MT, respectively. It was shown that the CE coupling with solid-state ECL detector system exhibited satisfying sensitivity of analysis.     

Mechanism study on inorganic oxidants induced inhibition of Ru(bpy)₃²+ electrochemiluminescence and its application for sensitive determination of some inorganic oxidants

Inhibited Ru(bpy)₃²⁺ electrochemiluminescence by inorganic oxidants is investigated. Results showed that a number of inorganic oxidants can quench the ECL of Ru(bpy)₃²⁺/tri-n-propylamine (TPrA) system, and the logarithm of the decrease in ECL intensity (ΔI) was proportional to the logarithm of analyte concentrations. Based on which, a sensitive approach for detection of these inorganic oxidants was established, e.g. the log-log plots of ΔI versus the concentration of MnO₄⁻, Cr₂O₇²⁻ and Fe(CN)₆³⁻ are linear in the range of 1 × 10⁻⁷ to 3 × 10⁻⁴ M for MnO₄⁻ and Cr₂O₇²⁻, and 1 × 10⁻⁷ to 1 × 10⁻⁴ M for Fe(CN)₆³⁻, with the limit of detection (LOD) of 8.0 × 10⁻⁸ M, 2 × 10⁻⁸ M, and 1 × 10⁻⁸ M, respectively. A series of experiments such as a comparison of the inhibitory effect of different compounds on Ru(bpy)₃²⁺/TPrA ECL, ECL emission spectra, UV-Vis absorption spectra etc. were investigated in order to discover how these inorganic analytes quench the ECL of Ru(bpy)₃²⁺/TPrA system. A mechanism based on consumption of TPrA intermediate (TPrA^·) by inorganic oxidants was proposed.     

Immobilization of tris(1,10-phenanthroline)ruthenium with graphene oxide for electrochemiluminescent analysis

Electrochemiluminescence (ECL) of ruthenium complexes has broad applications and the immobilization of Ru(bpy)₃²⁺ has received extensive attention. In comparison with Ru(bpy)₃²⁺, Ru(phen)₃²⁺ can be immobilized more easily because of its better adsorbability. In this study, immobilization of Ru(phen)₃²⁺ for ECL analysis has been demonstrated for the first time by using graphene oxide (GO) as an immobilization matrix. The immobilization of Ru(phen)₃²⁺ is achieved easily by mixing Ru(phen)₃²⁺ with GO without using any ion exchange polymer or covalent method. The strong binding of Ru(phen)₃²⁺ with GO is attributed to both the π–π stacking interaction and the electrostatic interaction. The Ru(phen)₃²⁺/GO modified electrode was characterized by using tripropylamine (TPA) as the coreactant. The linear range of TPA is from 3 × 10⁻⁷ to 3 × 10⁻² mol L⁻¹ with the detection limit of 3 × 10⁻⁷ mol L⁻¹. The ECL sensor demonstrates outstanding long-term stability. After the storage in the ambient environment for 90 days, the ECL response remains comparable with its original signal.     

Paper-based solid-state electrochemiluminescence sensor using poly(sodium 4-styrenesulfonate) functionalized graphene/nafion composite film

Herein, highly efficient solid-state ECL sensor was introduced for the first time onto the screen printed electrodes of the paper-based chips (PCs) based on the composite film of poly(sodium 4-styrenesulfonate) functionalized graphene (PSSG) and Nafion. Attributed to the cooperative characteristics of both PSS and graphene, PSSG ensured both effective Ru(bpy)₃²⁺ immobilization and fast electron transfer of Ru(bpy)₃²⁺ in the composite film. The ECL behaviors at the developed sensor were investigated using tripropylamine as a representative analyte and low detection limit (S N⁻¹ = 3) of 5.0 nM was obtained. It also exhibited more excellent reproducibility (relative standard deviations of 0.63% for continuous 45 cycles) and long-term stability (∼80% of its initial ECL intensity could be retained over 3 months). More importantly, assisted by the developed ECL sensor, discrimination of 1.0 nM single-nucleotide mismatch in human urine matrix could be realized on the PCs for the first attempt. Thus, the developed sensor was confirmed with the advantages of highly sensitivity, long-term stability, simplicity, low cost, disposability, high efficiency and potential applicability.     

Determination of itopride hydrochloride by high-performance liquid chromatography with Ru(bpy)3 electrogenerated chemiluminescence detection

In this work, a stable electrogenerated chemiluminescence (ECL) detector was developed. The detector was prepared by packing cation-exchanged resin particles in a glass tube, followed by inserting Pt wires (working electrode) in this tube and sealing. The leakage of Ru(bpy)₃²⁺ can be compensated by adding a small amount of Ru(bpy)₃²⁺ into solution phase. Coupled with high-performance liquid chromatography separation, the detector has been used for determination of itopride hydrochloride in human serum. Under the optimal conditions, the ECL intensity has a linear relationship with the concentration of itopride hydrochloride in the range of 1.0 × 10⁻⁸ g mL⁻¹ to 1.0 × 10⁻⁶ g mL⁻¹ and the detection limit was 3 × 10⁻⁹ g mL⁻¹ (S/N = 3). The as-prepared ECL detector displayed good sensitivity and stability.     

Disposable biosensor based on cathodic electrochemiluminescence of tris(2,2-bipyridine)ruthenium(II) for uric acid determination

A new method for uric acid (UA) determination based on the quenching of the cathodic ECL of the tris(2,2-bipyridine)ruthenium(II)–uricase system is described. The biosensor is based on a double-layer design containing first tris(2,2-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺) electrochemically immobilized on graphite screen-printed cells and uricase in chitosan as a second layer. The uric acid biosensing is based on the ECL quenching produced by uric acid over the cathodic ECL caused by immobilized Ru(bpy)₃²⁺ in the presence of uricase. The use of a −1.1 V pulse for 1 s with a dwelling time of 10 s makes it possible to estimate the initial enzymatic rate, which is used as the analytical signal. The Stern–Volmer type calibration function shows a dynamic range from 1.0 × 10⁻⁵ to 1.0 × 10⁻³ M with a limit of detection of 3.1 × 10⁻⁶ M and an accuracy of 13.6% (1.0 × 10⁻⁴ M, n = 5) as relative standard deviation. Satisfactory results were obtained for urine samples, creating an affordable alternative for uric acid determination.     

Solid-state electrochemiluminescence sensor through the electrodeposition of Ru(bpy)3/AuNPs/chitosan composite film onto electrode

Tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) has been successfully immobilized onto electrode through the electrodeposition of Ru(bpy)₃²⁺/AuNPs/chitosan composite film. In the experiments, chitosan solution was first mixed with Au nanoparticles (AuNPs) and Ru(bpy)₃²⁺. Then, during chronopotentiometry experiments in this mixed solution, a porous 3D network structured film containing Ru(bpy)₃²⁺, AuNPs and chitosan has been electrodeposited onto cathode due to the deposition of chitosan when pH value is over its pK_a (6.3). The applied current density is crucial to the film thickness and the amount of the entrapped Ru(bpy)₃²⁺. Additionally, these doping Ru(bpy)₃²⁺ in the composite film maintained their intrinsic electrochemical and electrochemiluminescence activities. Consequently, this Ru(bpy)₃²⁺/AuNPs/chitosan modified electrode has been used in ECL to detect tripropylamine, and the detection limit was 5 × 10⁻¹⁰ M.     

Electrochemiluminescence from Ru(bpy)3 immobilized in poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)-poly(vinyl alcohol) composite films

Electrochemical behavior and electrogenerated chemiluminescence (ECL) of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) immobilized in poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)-poly(vinyl alcohol) (PEDOT/PSS-PVA) composite films via ion-exchange have been investigated with tripropylamine (TPA) as the co-reactant at a glassy carbon electrode. The immobilized Ru(bpy)₃²⁺ performed a surface-controlled electrode reaction. The Ru(bpy)₃²⁺ modified electrode showed a fast ECL response to TPA, and was used for the ECL detection of TPA with high sensitivity. The ECL intensity was linearly related to concentrations of TPA over the range from 0.50 μmol L⁻¹ to 0.80 mmol L⁻¹, and the detection limit was 0.10 μmol L⁻¹ (S/N = 3). The as-prepared electrode exhibited good precision and long-term stability for TPA determination.     

A new electrochemiluminescent detection system equipped with an electrically controlled heating cylindrical microelectrode

A new electrochemiluminescent (ECL) detection system equipped with an electrically controlled heating cylindrical microelectrode (HME) was developed in this paper. The cylindrical microelectrode made of platinum wire (25 μm in diameter, 6 mm in long) was used as the working electrode of the ECL detection system, the temperature of the electrode could be controlled electrically. The Ru(bpy)₃²⁺-ECL and Ru(bpy)₃²⁺-C₂O₄²⁻-ECL systems were used to evaluate this ECL detection system. The detection limit for oxalate was found to be 3.0 × 10⁻⁴ mol/L when T_e (temperature of the HME) was 22 °C, and found to be 3.0 × 10⁻⁶ mol/L at 80 °C, which indicates that the detection limit can be improved greatly at higher T_e, based on which, it is possible to establish a more sensitive method for measurement of ECL by using a heated microelectrode.     

Determination of Reduced Nicotinamide Adenine Dinucleotide Based on Immobilization of Tris(2,2′‐bipyridyl) Ruthenium(II) in Multiwall Carbon Nanotubes/Nafion Composite Membrane

Abstract

An electrochemiluminescence (ECL) method for reduced nicotinamide adenine dinucleotide (NADH) was proposed by immobilizing tris(2,2′‐bipyridyl) ruthenium(II) (Ru(bpy)₃ ²⁺) in multiwall carbon nanotubes (MWCNTs)/Nafion composite membrane that was formed on glassy carbon electrode surface. The electrochemical and ECL behaviors of the immobilized Ru(bpy)₃ ²⁺ were investigated. The cyclic votammogram of the modified electrode in pH 7.0 phosphate buffer solution showed a couple of redox peaks at +1190 and +1060 mV at 100 mV/s. The composite film had a more open structure and a large surface area allowing faster diffusion of Ru(bpy)₃ ²⁺. The presence of MWCNTs resulted in the improved ECL sensitivity and longer‐term stability of the modified electrode. The modified electrode showed a linear response to NADH in the concentration range of 1.0×10^?6 to 1.6×10^?5 M with a detection limit of 8.2×10^?7 M.     

Fabrication of a new electrochemiluminescent sensor for fentanyl citrate based on glassy carbon microspheres and ionic liquid composite paste electrode

Due to the high performance of glassy carbon in the aspects of mechanical strength, electrical conductivity and high corrosion resistance, etc., glassy carbon has been widely used in the electrochemistry. A new form of glassy carbon, glassy carbon microsphere, was utilized to couple with ionic liquid in preparing a new electrochemiluminescent platform for Ru(bpy)₃Cl₂. Room temperature ionic liquid has been proposed to be very interesting and efficient pasting binder to replace the non conductive organic binders for the fabrication of composite paste electrode. Attributed to the special characteristics of glassy carbon microspheres and room temperature ionic liquid [N-octylpyridium tetrafluoroborate (OPFP)], this new electrochemiluminescent sensor exhibited excellent electrochemiluminescent performance in Ru(bpy)₃²⁺ solution. We first found that fentanyl citrate could increase the ECL of Ru(bpy)₃²⁺, hence an ECL approach was developed for the determination of fentanyl citrate based on this glassy carbon microspheres based electrochemiluminescent platform with high sensitivity. Under the optimized conditions, the enhanced electrochemiluminescent intensity versus fentanyl citrate concentration was linear in the range of 1.0 × 10⁻⁸ to 1.0 × 10⁻⁴ mol L⁻¹ with a detection limit of 8.5 × 10⁻⁹ mol L⁻¹, and the relative standard deviation for 1.0 × 10⁻⁶ mol L⁻¹ fentanyl citrate was 1.90% (n = 10). This protocol has extended the application scopes of glassy carbon material and promoted the application of glassy carbon microspheres in electroanalysis.     

Electrochemiluminescence immunosensor for ultrasensitive detection of biomarker using Ru(bpy)3-encapsulated silica nanosphere labels

Here, we describe a new approach for electrochemiluminescence (ECL) assay with Ru(bpy)₃²⁺-encapsulated silica nanoparticle (SiO₂@Ru) as labels. A water-in-oil (W/O) microemulsion method was employed for one-pot synthesis of SiO₂@Ru nanoparticles. The as-synthesized SiO₂@Ru nanoparticles have a narrow size distribution, which allows reproducible loading of Ru(bpy)₃²⁺ inside the silica shell and of α-fetoprotein antibody (anti-AFP), a model antibody, on the silica surface with glutaraldehyde as linkage. The silica shell effectively prevents leakage of Ru(bpy)₃²⁺ into the aqueous solution due to strong electrostatic interaction between the positively charged Ru(bpy)₃²⁺ and the negatively charged surface of silica. The porous structure of silica shell allowed the ion to move easily through the pore to exchange energy/electrons with the entrapped Ru(bpy)₃²⁺. The as-synthesized SiO₂@Ru can be used as a label for ultrasensitive detection of biomarkers through a sandwiched immunoassay process. The calibration range of AFP concentration was 0.05-30 ng mL⁻¹ with linear relation from 0.05 to 20 ng mL⁻¹ and a detection limit of 0.035 ng mL⁻¹ at 3σ. The resulting immunosensors possess high sensitivity and good analytical performance.     

Polyelectrolyte-based electrochemiluminescence enhancement for Ru(bpy)3 loaded by SiO2 nanoparticle carrier and its high sensitive immunoassay

In this paper the strong electrochemiluminescence (ECL) nanoparticles have been prepared based on the anionic polyelectrolyte sodium polyacrylate (PAA)-ECL enhancement for Ru(bpy)₃²⁺, which were loaded by the carrier of SiO₂ nanoparticle. There were two kinds of Ru(bpy)₃²⁺ for the as-prepared nanoparticles, the doped one and the exchanged one. The former was loaded inside the ECL nanoparticles by doping, in a form of ion-pair macromolecules PAA–Ru(bpy)₃²⁺. The corresponding ECL was enhanced about 2 times owing to the doping increase of Ru(bpy)₃²⁺. The latter was loaded on the PAA-doped Nafion membrane by ion exchange. The corresponding ECL was enhanced about 3 times owing to the ion-exchanging increase of Ru(bpy)₃²⁺. At the same time, ECL intensity of the doped-inside Ru(bpy)₃²⁺ was further enhanced 13 times because polyelectrolyte PAA in the doped membrane could obviously enhance electron transfer between the doped Ru(bpy)₃²⁺ and the working electrode. Furthermore, based on hydrophobic regions of the doped membrane antibody labeling could be easily realized by the as-prepared nanoparticles and then a high sensitive ECL immunoassay for HBsAg was developed. The linear range was between 1.0 and 100 pg mL⁻¹ (R² = 0.9912). The detection limit could be as low as 0.11 pg mL⁻¹ (signal-to-noise ratio = 3).     

十二烷基磺酸钠-盐酸维拉帕米-联吡啶钌体系电化学发光及其应用

在十二烷基磺酸钠(SDS)中,考察了盐酸维拉帕米-Ru(bpy)3(2+)体系在金电极上的电化学及其发光行为.结果表明:SDS对体系的电化学反应和电化学发光强度具有显著的增敏作用.据此,建立了一种高效、简便的测定盐酸维拉帕米的电化学发光新方法.在最佳实验条件下,盐酸维拉帕米浓度在1.0×10(-4)～1.0×10(-2...     

Determination of adrenaline by using inhibited Ru(bpy)3 electrochemiluminescence

Adrenaline was found to inhibit strongly the electrochemiluminescence (ECL) from the Ru(bpy)₃²⁺/tripropylamine system when a working Pt electrode was maintained at 1.05 V (versus Ag/AgCl) in pH 8.0 phosphate buffer. On this basis, a flow injection (FI) procedure with inhibited electrochemiluminescence detection has been developed for determination of adrenaline. The method exhibited a good reproducibility, sensitivity, and stability with a detection limit (signal-to-noise ratio = 3) of 7.0×10⁻⁹ mol l⁻¹ and dynamic concentration range of 2×10⁻⁸ to 1×10⁻⁴ mol l⁻¹. The relative standard deviation was 2.2% for 1.0×10⁻⁶ mol l⁻¹ adrenaline (n=11). The method was successfully applied to the determination of adrenaline in pharmaceutical samples. Moreover, ECL emission spectra, UV-Vis absorption spectra and cyclic voltammograms of Ru(bpy)₃²⁺/tripropylamine/adrenaline were studied. The inhibition mechanism has been proposed as the interaction of electrogenerated Ru(bpy)₃^2+* and the o-benzoquinone derivatives, adrenochrome and adrenalinequinone, at the electrode surface.