Bifunctional nanostructure of magnetic core luminescent shell and its application as solid-state electrochemiluminescence sensor material

Bifunctional nanoarchitecture has been developed by combining the magnetic iron oxide and the luminescent Ru(bpy)32+ encapsulated in silica. First, the iron oxide nanoparticles were synthesized and coated with silica, which was used to isolate the magnetic nanoparticles from the outer-shell encapsulated Ru(bpy)32+ to prevent luminescence quenching. Then onto this core an outer shell of silica containing encapsulated Ru(bpy)32+ was grown through the St?ber method. Highly luminescent Ru(bpy)32+ serves as a luminescent marker, while magnetic Fe3O4 nanoparticles allow external manipulation by a magnetic field. Since Ru(bpy)32+ is a typical electrochemiluminescence (ECL) reagent and it could still maintain such property when encapsulated in the bifunctional nanoparticle, we explored the feasibility of applying the as-prepared nanostructure to fabricating an ECL sensor; such method is simple and effective. We applied the prepared ECL sensor not only to the typical Ru(bpy)32+ co-reactant tripropylamine (TPA), but also to the practically important polyamines. Consequently, the ECL sensor shows a wide linear range, high sensitivity, and good stability.     

Confocal microscopy imaging of electrochemiluminescence at double band microelectrode assemblies: numerical solution of the inverse optical problem.

A realistic theoretical model describing the outcome of confocal microscopic imaging of electrochemiluminescence (ECL) light emission is derived for a two parallel band microelectrodes assembly operated under steady state. The model takes into account the experimental distortions ensuing from a) the specific finite shape of the sampling volume in confocal microscopy, b) the light arising directly from out-of-focus area but transmitted through the microscope diaphragm or c) transmitted after reflection from the polished platinum band electrodes. The model is based on a detailed optical, physico-mathematical and numerical analysis of the problem at hand, and on simulations of the concentration distribution of the species giving rise to the ECL generation. Its outcome allows the reconstruction of the real spatial distribution of ECL light emission based on the confocal microscopy measurements upon correcting for the effect of experimental distortions using numerical fitting procedure.     

Enhanced electrochemiluminescence of luminol-O2 system at gold–hydrophobic ionic liquid|water interface

A hydrophobic thiol-functionalized ionic liquid (IL) was synthesized and immobilized tightly on a gold electrode surface via Au–S bond to construct a stable Au–IL|water interface. At the Au–IL|water interface, the electrochemiluminescence (ECL) of luminol-O₂ system was investigated. The ECL intensity of luminol-O₂ system at the Au–IL|water interface was much larger and more stable than that at Au|water interface. The enhanced ECL mechanism at the Au–IL|water interface was studied and discussed in details.     

An Instrumental Analysis Laboratory Using Electrogenerated Chemiluminescence

An undergraduate instrumental analysis laboratory exercise is presented for the characterization of light emission generated using electrochemiluminescence (ECL). ECL involves the electrochemical generation of excited states and as such is a sensitive probe of electrochemical, electron-transfer and energy-transfer processes at electrified interfaces. An objective of this experiment is to have students develop an understanding of the mechanisms and factors affecting ECL. Also, this exercise gives students experience in coupling two powerful analytical techniques: electrochemistry and spectroscopy. With the recent development of ECL technology for use in clinical diagnostics applications, this exercise also facilitates discussions on the importance of basic research and the practical aspects of taking a technology from the bench top to commercial reality.     

Remote NADH imaging through an ordered array of electrochemiluminescent nanoapertures

In this report, we present an ordered array comprising thousands of nanoapertures for the electrochemiluminescent (ECL) detection of NADH. It was fabricated on the distal face of a coherent optical fiber bundle. Such a high-density array of nanoapertures combines optical, imaging and electrochemical properties. Indeed, each nanoaperture is surrounded by a gold nanoring, which acts as an electrode material. The behavior of the array was characterized by cyclic voltammetry and it shows excellent electrochemical performances. NADH is the analyte, which is measured in presence of Ru(bpy)3(2+). The ruthenium complex mediates the NADH oxidation and this coenzyme acts as a co-reactant in the ECL mechanism. ECL light is generated at the distal face of the array by each gold ring electrode. A fraction of this ECL light is collected by the corresponding nanoaperture, transmitted through the optical fiber bundle and finally imaged on the proximal face with a CCD camera. In this work, we show that NADH concentration is remotely detected by an oxidative-reductive ECL mechanism. We present also some preliminary results about the ECL process of NADH with Ru(bpy)3(2+). The ECL behavior of NADH on gold surface is reported. The influence of the applied potential on the collected light intensity was investigated. The variation of the ECL intensity measured through the nanoaperture array with NADH concentration is linear. Remote ECL detection of NADH is spatially resolved over a large area with a micrometer resolution through the array. Therefore, such array integrates several complementary functions: ECL light generation, collection, transmission and remote imaging in an array format.     

Microwave-assisted solution synthesis and photocatalytic activity of Ag nanoparticles supported on ZnO nanostructure flowers

Ag nanoparticles supported on the surface of three-dimensional (3D) flower-like ZnO nanostructure were synthesized by a microwave-assisted solution method. The obtained products were characterized by X-ray diffraction analysis, field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectrophotometry, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. The analytical results confirmed homogeneously distributed Ag nanoparticles supported on the surface of flower-like ZnO nanostructure. The photocatalytic effect of the heterostructure Ag/ZnO nanocomposites was investigated using photodegradation under ultraviolet (UV) light of methylene blue as model dye. The heterostructure Ag/ZnO nanocomposites exhibited much higher photocatalytic activity than pure ZnO flowers. The improved photocatalytic properties are attributed to formation of a Schottky barrier at the metal–semiconductor interface of the Ag/ZnO nanocomposites.     

Magnetic electrochemiluminescent Fe3O4/CdSe-CdS nanoparticle/polyelectrolyte nanocomposite for highly efficient immunosensing of a cancer biomarker

Magnetic electrochemiluminescent Fe₃O₄/CdSe–CdS nanoparticle/polyelectrolyte nanostructures have been synthesized and used to fabricate an electrochemiluminescence (ECL) immunosensor for the detection of carcinoembryonic antigen (CEA). CEA is a protein used as a biomarker for several cancers; particularly, to monitor response to treatment in colon and rectal cancer patients. The nanocomposites can be easily separated and firmly attached to an electrode owing to their excellent magnetic properties. This represents a promising advantage for bioassay applications. More importantly, the nanostructures exhibit intense and stable ECL emissions in neutral solution, which makes them ideal for ECL immunosensing. The 3‐aminopropyltriethoxysilane (APS) polyelectrolyte shell on the nanostructure surface not only enhances the intensity and stability of the ECL signal, but also acts as a crosslinker for immunosensor fabrication. A CEA antibody immobilized onto a nanocomposite/APS/electrode with gold nanoparticles comprises the ECL immunosensor. The principle of ECL detection for CEA is based on a change in steric hindrance after immunoreaction, which leads to a decrease in ECL intensity. A wide detection range (0.064 pg ml^?1–10 ng ml^?1) and low detection limit (0.032 pg ml^?1) are achieved. The immunosensor is highly sensitive and selective, and exhibits excellent stability and good reproducibility. It thus has great potential for clinical protein detection. In particular, this approach uses a novel class of bifunctional nanocomposites that display both intense ECL and excellent magnetism, which renders them suitable for a large range of bioassay applications.     

Facile synthesis of PbSe hollow nanostructure assemblies via a solid/liquid-phase chemical route and their electrogenerated chemiluminescence properties

Spherical PbSe hollow nanostructure assemblies (HNSAs) were synthesized by a simple one‐pot solid/liquid‐phase reaction in which solid KPbI₃ ? 2 H₂O and SeO₂ are heated in oleic acid/dodecylamine/1‐octadecene at 250 °C for 30 min. XRD analysis shows that the obtained product is cubic‐phase PbSe and well crystallized. FESEM and TEM images reveal that the obtained spherical PbSe assemblies are made up of small, irregular, and fused hollow nanostructure building blocks. On the basis of temperature‐ and time‐dependent investigations as well as control experiments, molten‐salt corrosion of solid PbSe nanocrystal aggregates formed in situ during the high‐temperature ripening stage is suggested to explain the formation of such novel assemblies. Moreover, when the reaction temperature is further increased to 280 or 320 °C with other conditions unchanged, cubic and orthorhombic mixed‐phase PbSe HNSAs is generated. The obtained PbSe HNSAs exhibit excellent electrogenerated chemiluminescence (ECL) performance. Two strong and stable emission peaks at about ?1.4 and +1.5 V (vs. Ag/AgCl) are observed. In particular, the ECL intensity is influenced by the crystal phase of PbSe.     

微纳电化学传感界面的构建及其用于单细胞实时监测

细胞是生物体形态结构和生命活动的基本单位.常规检测群体细胞的方法往往会掩盖细胞间的个体差异,因此亟需发展高效的单细胞分析策略,深入研究细胞生命活动过程,揭示疾病发生发展机制,推动个体化诊疗.超微电化学传感器具有尺寸小、灵敏度高、时空分辨率高等特点,在单细胞实时动态监测方面发挥了非常重要的作用.目前,微纳电化学传感器在电极制备、高性能传感界面构建、理论分析等方面已取得重要进展,且在单细胞实时监测及相关细胞机制研究方面取得突破.然而,单细胞内环境复杂、活性分子浓度低且随时空高度动态变化,这对微纳电化学传感器的灵敏度和选择性等综合性能提出了更高要求.我们课题组长期从事基于微纳电化学传感的单细胞与亚细胞实时动态监测研究,本文主要介绍了我们近10年来在该领域的研究进展,并对未来的挑战与机遇进行了探讨.     

Highly efficient quenching of coreactant electrogenerated chemiluminescence by phenolic compounds

We describe the quenching effects of phenolic compounds on the electrogenerated chemiluminescence (ECL) of the Ru(bpy)3(2+) (bpy = 2,2'-bipyridine)/tri-n-propylamine (TPrA) system in aqueous solution. First, the emissions via different ECL routes were examined in the presence of 1,4-benzoquinone. It was found that the interception of the ECL intermediate radicals by the quencher molecules significantly influenced the light emission, especially when the direct coreactant oxidation played a predominant role in producing ECL. The most efficient quenching was observed for the low-oxidation-potential (LOP) ECL at a low concentration of TPrA (<5 mM). The Stern-Volmer constant (K(SV)) of the LOP ECL quenching could be as high as 1.3 x 10(6) M(-1), approximately 700 times larger than that of the photoluminescence quenching. Other phenolic compounds, such as phenol, hydroquinone, catechol, and dopamine, would be oxidized at the potential where the ECL was generated, and the benzoquinone-containing products exhibited ECL quenching effects similar to that of 1,4-benzoquinone. The highly efficient quenching of the LOP ECL by the phenolic compounds may provide a new approach for the determination of these pharmaceutically and environmentally important molecules.     

3D electrogenerated chemiluminescence: from surface-confined reactions to bulk emission

Among luminescence techniques, electrogenerated chemiluminescence (ECL) provides a unique level of manipulation of the luminescent process by controlling the electrochemical trigger. Despite its attractiveness, ECL is by essence a 2D process where light emission is strictly confined to the electrode surface. To overcome this intrinsic limitation, we added a new spatial dimension to the ECL process by generating 3D ECL at the level of millions of micro-emitters dispersed in solution. Each single object is addressed remotely by bipolar electrochemistry and they generate collectively the luminescence in the bulk. Therefore, the entire volume of the solution produces light. To illustrate the generality of this concept, we extended it to a suspension of multi-walled carbon nanotubes where each one acts as an individual ECL nano-emitter. This approach enables a change of paradigm by switching from a surface-limited process to 3D electrogenerated light emission.     

A Highly Sensitive Electrochemiluminescence Choline Biosensor Based on Poly(aniline‐luminol‐hemin) Nanocomposites

Poly(aniline‐luminol‐hemin) nanocomposites are prepared on an electrode surface through electropolymerization, and a highly sensitive electrochemiluminescence (ECL) biosensor for choline is developed based on the poly(aniline‐luminol‐hemin) nanocomposites and an enzyme catalyzed reaction of choline oxidase (CHOD). The obtained nanocomposites are characterized by scanning electron microscopy (SEM), atomic absorption spectrometry (AAS) and ECL. The results indicate that hemin can be incorporated into the poly(aniline‐luminol) nanocomposites using the facile electropolymerization method, and the poly(aniline‐luminol‐hemin) nanocomposites are rod shaped porous nanostructure. Moreover, the poly(aniline‐luminol‐hemin) nanocomposites exhibit higher ECL intensity than poly(aniline‐luminol) nanocomposites in alkaline media due to the catalytic effect of hemin on the ECL of the polymerized luminol and the electron transfer ability of hemin in the nanocomposites. CHOD is immobilized on the surface of the poly(aniline‐luminol‐hemin) nanocomposites modified electrode with glutaraldehyde, and the ECL biosensor based on poly(aniline‐luminol‐hemin)/CHOD exhibits a wider linear range for the choline detection. The enhanced ECL signals are linear with the logarithm of concentration of choline over the range of 1.0×10^?11～1.0×10^?7 mol L^?1 with a low detection limit of 1.2×10^?12 mol L^?1. Moreover, the proposed biosensor is successfully applied to the detection of choline in milk.     

Electrogenerated chemiluminescence of conjugated polymer films from patterned electrodes

A new phenomenon is presented in which electrogenerated chemiluminescence (ECL) is generated and propagates laterally as self-reinforcing waves as a result of the oxidation of a poly(9,9-dioctylfluorene-co-benzothiadiazole) thin film. In an ordered array of Au electrode posts that act as effective ECL nucleation sites, soliton-like waves were observed to expand from each site and annihilate upon collision with each other. Simulations of the ECL response supported the experimental observations that the ECL waves propagate at a constant speed. A correlated diffusion mechanism involving the correlated motion of ions, injected holes, and solvent molecules is proposed to interpret the experimental data qualitatively. A rapid increase in the diffusion coefficient of these species in the polymer results in a sharp interface between non-oxidized and oxidized polymer phases wherein the electrochemical (EC) oxidation and mass transport of all pertinent species take place. EC oxidation of conjugated polymers of this type has important implications for the understanding of these materials and their modes of operation in EC conjugated polymer devices.     

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.     

Determination of ascorbic acid in individual rat hepatocyte cells based on capillary electrophoresis with electrochemiluminescence detection

A novel method to detect ascorbic acid (AA) in individual rat hepatocyte cells was developed by combining CE with electrochemiluminescence (ECL) based on tris(2,2'-bipyridine) ruthenium(II) (Ru(bpy)(3)2+). A single cell, followed by 0.1% SDS as cell lysis solution, was injected into the inlet of the separation capillary by electromigration. After optimizing the analytical conditions, the RSDs of migration time and peak height were 0.38% and 2.6% for 1.0x10(-5) M AA (n=10), respectively. The linear range of AA was from 1.0x10(-8) to 5.0x10(-5) M with a correlation coefficient of 0.9979 and the LOD (S/N=3) was estimated to be 1.0x10(-8) M. This method has been successfully applied to determine AA in single rat hepatocytes and the amount of AA in seven rat hepatocytes ranged from 16 to 62 fmol. The above results demonstrated that CE coupled with ECL is convenient, sensitive, and will become an attractive alternative method for single-cell analysis.     

Chemiluminescence of Electrochemically Oxidized 9‐(Phenylthiophosphoryloxymethylidene)‐10‐methylacridan Derivatives

The electrochemistry and electrochemiluminescence (ECL) properties of acridan phosphate ester are reported. Electrochemical oxidation of 9‐(phenylthiophosphoryloxymethylidene)‐10‐methylacridan disodium salt (Compound 1) yields the corresponding acridinium ester. The latter undergoes a fast reaction with hydrogen peroxide forming an intermediate, which produces electronically excited 9‐methyl acridone and emits blue light after relaxation to the ground state. The electrochemical oxidation of this compound appears to occur in two one‐electron steps and light emission is observed for both steps. The chemiluminescence reaction could also be triggered by electrochemical oxidation of Compound 1 in the absence of H₂O₂ when the solution was saturated with O₂. Mechanisms for these reactions based on ECL, voltammetry and in situ UV‐vis identification of the oxidation products are proposed. Due to the low electrode potential required to achieve ECL emission and the occurrence of light emission in the absence of hydrogen peroxide, this compound is proposed as a label for rapid and sensitive determination of biomolecules in automated analysis.     

鲁米诺电致化学发光机理的研究

电致化学发光（简称电致发光）是某些化学物质电解过程伴随光产生的现象·鲁米诺（Lummol，3一氨基苯一甲酸讲）在碱性水溶液是一种典型的电致发光材料·Havey，Kuwana和H。即把k。等人［’－‘］分别在二十、六十和／＼十年代对其发光进行过研究．他们都采用共存于一室的电极体系同时实现阳、阴极电解得到电致发光．HaaPakka等采用旋转环盘电极研究其发光机理．他们在盘电极上维持一定的负电位，在环电极上施加对称双阶跃电位．因此，他们认为发光过程是盘电极首先将分子氧还原成过氧化氢，通过电极的旋转，盘上产物被输送到环电极附近…     

电压调制型高灵敏电化学发光分析

报道了一种电压调制型电化学发光分析技术, 通过在施加恒定电压的基础上叠加一个小脉冲电压, 可将鲁米诺-过氧化氢体系的电化学发光强度提升近2倍. 电化学发光强度与过氧化氢浓度在1.0 nmol/L~200 μmol/L范围内呈现良好的线性关系, 检出限低至0.24 nmol/L(S/N=3). 研究结果表明, 通过电压调制模式可有效提高电化学发光强度, 为深入理解电极界面电化学过程提供了新技术和数据.     

Electrochemiluminescence Waveguide in Single Crystalline Molecular Wires

Here we report the first observation of active waveguide of electrochemiluminescence (ECL) in single crystalline molecular wires self‐assembled from cyclometalated iridium(III) complexes, namely tris(1‐phenylisoquinoline‐C², N) (Ir(piq)₃). Under dark conditions, the molecular wires deposited on the electrode surface can act as both ECL emitters and active waveguides. As revealed by ECL microscopy, they exhibit the typical characteristics of optical waveguides, transmitting ECL and generating much brighter ECL emission at their terminals. Moreover, self‐generated ECL can be confined inside the molecular wire and propagates along the longitudinal direction as far as ≈100 μm to the terminal out of touch with the electrode. Therefore, this one‐dimensional crystalline molecular wire‐based waveguide offers the opportunity to switch the electrochemically generated ECL to remote light emission in non‐conductive regions and is promising for contactless electrochemical analysis and study of (bio)chemical systems.     

Highly sensitive electrogenerated chemiluminescence biosensor in profiling protein kinase activity and inhibition using a multifunctional nanoprobe

We presented a novel electrogenerated chemiluminescence (ECL) biosensor for monitoring the activity and inhibition of protein kinases based on signal amplification using enzyme-functionalized Au NPs nanoprobe. In this design, the biotin-DNA labeled glucose oxidase/Au NPs (GOx/Au NPs/DNA-biotin) nanoprobes, prepared by conjugating Au NPs with biotin-DNA and GOx, were bound to the biotinylated anti-phosphoserine labeled phosphorylated peptide modified electrode surface through a biotin−avidin interaction. The GOx assembled on the nanoprobe can catalyze glucose to generate H₂O₂ in the presence of O₂ while the ECL reaction occurred in the luminol ECL biosensor. At a higher concentration of kinase, there are more nanoprobes on the electrode, which gives a higher amount of GOx at the electrode interface and thus higher electrocatalytic efficiency to the luminol ECL reaction. Therefore, the activity of protein kinases can be monitored by ECL with high sensitivity. Protein kinase A (PKA), an important enzyme in regulation of glycogen, sugar, and lipid metabolism in the human body, was used as a model to confirm the present proof-of-concept strategy. The as-proposed biosensor presents high sensitivity, low detection limit of 0.013 U mL⁻¹, wide linear range (from 0.02 to 40 U mL⁻¹), and excellent stability. Moreover, this biosensor can also be used for quantitative analysis of kinase inhibition. On the basis of the inhibitor concentration dependent ECL signal, the half-maximal inhibition value IC₅₀ of ellagic acid, a typical PKA inhibitor, was estimated, which is in agreement with those obtained using the conventional kinase assay. The simple and sensitive biosensor is promising in developing a high-through assay of in vitro kinase activity and inhibitor screening for clinic diagnostic and drug development.