Electrogenerated Chemiluminescence System Research Articles

Chemical Measurement and Analysis: from Phenomenon to Essence

Comprehensive SummaryThe review summaries our achievements in optical, electrochemical, as well as mass spectrometry analysis and imaging with high sensitivity, specificity, and spatiotemporal resolution. We promoted the plasmonic imaging system, and developed ultra‐sensitive plasmonic nanoprobes for the tracking of single molecules in single living cells, as well as plasmonic nanocatalysts for highly efficient energy conversion. In addition, we contributed a lot in electrogenerated chemiluminescence (ECL) analysis and imaging. Pioneering works including localized surface plasmon resonance (LSPR) enhanced ECL, ECL ratiometric detection, BPE based ECL system, multi‐color ECL sensing as well as super‐resolved ECL imaging have been initiated by our group. Furthermore, we also dedicated in nanopipette based electrochemical analysis in single living cells, as well as ESI‐MS analysis on short time scale. The research works of our group promoted the development of chemical measurement and analysis. What is the most favorite and original chemistry developed in your research group?LSPR enhanced ECL and Bipolar electrochemistry analysis, single particle based single cell analysis and super‐resolved imaging.What is the most important personality for scientific research?Strong curiosity, perseverance, strong hands‐on ability.How do you supervise your students?Encourage students to read more, think more, discuss more, and try more.How do you keep balance between research and family?Allocating time reasonably.Who influences you mostly in your life?My PhD director, Prof. Hong‐Yuan Chen.What are your hobbies?I used to like to play badminton, now I'm learning to play table tennis.

Electrogenerated Chemiluminescence Immunoassays on Nanoelectrode Ensembles Platform with Magnetic Microbeads for the Determination of Carbohydrate Antigen.

This work reports a gold nanoelectrode ensembles (Au-NEE) platform taken as a disposable electrogenerated chemiluminescence (ECL) platform with immunomagnetic microbeads for ECL immunoassays for the first time. The peak-shaped voltammograms were obtained at the Au-NEE, attributed to the total diffusional overlap. The ECL intensity at Au-NEE was 12.9 folds in the Ru(bpy)32+-tri-n-propylamine (TPA) ECL system and 19.6 folds in the luminol-H2O2 system, compared with that at the Au macroelectrode using the normalized active area of the electrodes, mainly attributed to the diffusion overlap of the Au-NEE and the edge effect of the individual gold nanodisks of the Au-NEE. The ECL immunoassay on the Au-NEE platform with magnetic microbeads for the determination of cancer biomarkers was developed. Carbohydrate antigen 19-9 (CA 19-9) was chosen as a model analyte while CA 19-9 antibody on the magnetic microbeads was taken as the capture probe, and ruthenium complex-labeled CA 19-9 antibody was used as the signal probe. A "sandwich" bioconjugates on the magnetic beads were transferred onto the ECL platform, and then the ECL measurements were performed in TPA solution. The developed method showed that the ECL peak intensity was directly in proportion to the concentration of CA 19-9 in the range from 0.5 to 20 U/mL with a limit of detection of 0.4 U/mL. This work demonstrates that the Au-NEE can be employed as a useful disposable ECL platform with the merits of cheapness, low nonspecific adsorption and practical application. The proposed approach will open a new avenue in the point-of-care test for the determination of protein biomarkers.

Electrochemiluminescence Imaging of Conducting Polymer Film Structures

Conducting polymers (CPs) is a class of attractive materials that, thanks to their unique properties, structures made on-demand and new composition mixtures, finds a wide variety of applications, ranging from material science to chemistry, from energy to environmental remediation and electroanalysis. Electrochemical synthesis of CPs is usually achieved by anodic oxidation, or electropolymerization, of suitable monomer species, which generally results in the formation of polymeric films deposited onto the surface of an electrode. Nevertheless, the use of this methodology makes rather difficult, or even impossible, to tune the morphology of the final CPs materials, limiting their applicability in material science. To overcome this limitation, electrosynthesis of CPs with different geometries such as brushes, films and fiber arrays has recently been achieved exploiting the unique wireless feature of bipolar electrochemistry1. In fact, this renewed technology enables electrochemical reactions at both extremities of a wireless electrode, or bipolar electrode (BPE), through the application of an external electric field generated in a low concentration of a supporting electrolyte.In this context, alternating current (AC)-bipolar electropolymerization of 3,4-ethylenedioxythiophene (EDOT) has recently been employed for the gradual in-plane growth of the corresponding poly(3,4-ethylenedioxythiophene) (PEDOT) films at the terminal of a gold BPE laid down on a glass surface2. This notable phenomenon could paved the way for the drawing of CPs on non-conductive substrates, opening up new perspectives for their potential application for circuit patterning in organic electronic devices. The possible mechanism of films formation seems to involve the generation of PEDOT fibers that propagate in an anisotropic morphology from the terminal of the BPE, in parallel to the external electric field under electrophoretic effect, resulting in colored film depositions visible at naked eye. However, very thin layers of PEDOT films underlying the main fibers are generally transparent, making their direct visualization rather difficult.In the present contribution, we propose the use of Electrogenerated Chemiluminescence (ECL) for the morphological imaging of PEDOT films synthetized by AC-bipolar electropolymerization. ECL is the emission of light at the electrode surface following an electrochemical stimulus and, nowadays, it is widely employed as an emerging microscopy technique3. The great success of ECL imaging technology is due to the electrochemical nature of light generation that allows very low background signal and the possibility to control the ECL emission both temporally and spatially by applying a suitable potential. Our approach employs the use of the well-known luminol/hydrogen peroxide ECL system for the visualization of PEDOT films grown on non-conductive substrates used as BPEs in bipolar systems. The different potential distribution on such PEDOT systems allows ECL emission only in confined areas of PEDOT films where the potential is sufficient to trigger the ECL reaction, allowing the visualization of different structural characteristics of the polymeric films (Figure 1). This technique would represent an innovative and promising tool to accurately control the morphology of the final polymer material, opening up new perspectives in the area of electrochemical synthesis of CPs. Figure 1: Schematic illustration of the bipolar setup used for ECL imaging of PEDOT films (a). Optical image of PEDOT film synthetized by AC-bipolar electropolymerization (b). Corresponding Luminol ECL images on PEDOT film working as BPE at 25 V (c) and 70 V (d).

Near-infrared electrogenerated chemiluminescence of Au22(glutathione)18 nanoclusters in aqueous solution and its analytical application

Gold nanoclusters (AuNCs) have attracted great attention in analytical sciences because they have unique optical and electrochemical properties with low biological toxicity. However, the analytical application of Au NCs-based electrogenerated chemiluminescence (ECL) still remains relatively unexplored largely due to their low ECL efficiency in aqueous solution. Moreover, the precise information of molecular formula of Au NCs have not been determined in large number of reports. In the present study, the ECL behavior of atomically precise Au22(SG)18 NCs, where SG is glutathione, were characterized in the aqueous solution. The oxidation of Au22(SG)18 NCs together with coreactant tripropylamine (TPA) at the working electrode potential of 1.25 V vs Ag/AgCl (3 M NaCl) has led to strong ECL emission at ~767 nm in the near-infrared region. The ECL intensity of the Au22(SG)18 NCs was about 14-fold higher than the ECL intensity obtained with the [email protected] NCs, which is most commonly used Au NCs in aqueous solution. The ECL intensity is strongly dependent upon the concentrations of Au22(SG)18 NCs and TPA. However, the ECL intensity of Au22(SG)18 NCs with TPA is diminished in the presence of phenolic compounds depending upon their concentrations. Using catechol as a model analyte, the present ECL system can detect it in the linear range from 1.0 × 10−7 to 1.0 × 10−4 M with a detection limit of 3.3 × 10−9 M (S/N = 3). The present study has demonstrated the potential application of the Au NCs-based ECL in real analytical problems.

(Invited) Wireless Electrochemiluminescence Devices

Traditional electrochemical systems generally require the direct connection of working electrode with potentiostat. They often employ two electrodes (a working electrode and a counter electrode) or three electrodes (a working electrode, a counter electrode, and a reference electrode) for a single electrochemical experiment. Different from traditional electrochemical systems, wireless electrochemical systems do not require the direct connection of working electrode with potentiostat. Conventional ipolar electrochemical system is a well-known wireless electrochemical system. It exerts potential control over electrolyte solutions with driving electrodes and redox reactions occur at the two opposite poles of the bipolar electrode. This enables simultaneous control of many bipolar electrode arrays with only two driving electrodes for multiplex experiments.Electrochemiluminescence, also called electrogenerated chemiluminescence (ECL), is light-emitting phenomenon generated from electrochemical reaction. The combination of bipolar electrochemical systems with ECL enables facile multiplex analysis.We present here several new wireless ECL systems, including wireless electrochemiluminescence, single-electrode ECL system, and wireless single-electrode ECL system [1-5].AcknowledgmentWe are grateful for financial support from the National Key Research and Development Program of China (No. 2016YFA0201300), National Natural Science Foundation of China (Nos. 21804127,21874126,21675148), the Chinese Academy of Sciences (CAS)-the Academy of Sciences for the Developing World (TWAS), and President’s Fellowship Program, the CAS President's International Fellowship Initiative (PIFI) project. References Wenjing Qi, Jianping Lai, Wenyue Gao, Suping Li, Saima Hanif, Guobao Xu. Wireless Electrochemiluminescence with Disposable Minidevice. Chem., 2014, 86, 8927–8931. Liming Qi, Yong Xia, Wenjing Qi, Wenyue Gao, Fengxia Wu, Guobao Xu. Increasing Electrochemiluminescence Intensity of a Wireless Electrode Array Chip by Thousands of Times Using a Diode for Sensitive Visual Detection by a Digital Camera Chem., 2016, 88, 1123–1127.Fan Yuan, Liming Qi, Tadesse Haile Fereja, Dmytro V. Snizhko, Zhongyuan Liu, Wei Zhang, Guobao Xu. Regenerable bipolar electrochemiluminescence device using glassy carbon bipolar electrode, stainless steel driving electrode and cold patch. Electroc Acta, 2018, 262, 182-186.Xiangui Ma, Liming Qi, Wenyue Gao, Fan Yuan, Yong Xia, Baohua Lou, Guobao Xu. A portable wireless single-electrode system for electrochemiluminescent analysis. Electroc Acta, 2019, 308, 20-24.Wenyue Gao, Kateryna Muzyka, Xiangui Ma, Baohua Lou, Guobao Xu, A single-electrode electrochemical system for multiplex electrochemiluminescence analysis based on a resistance induced potential difference. Chem. Sci. 2018, 9, 3911-3916.

Nanoelectrode-emitter spectral overlap amplifies surface enhanced electrogenerated chemiluminescence.

Electrogenerated chemiluminescence (ECL) is a promising technique for low concentration molecular detection. To improve the detection limit, plasmonic nanoparticles have been proposed as signal boosting antennas to amplify ECL. Previous ensemble studies have hinted that spectral overlap between the nanoparticle antenna and the ECL emitter may play a role in signal enhancement. Ensemble spectroscopy, however, cannot resolve heterogeneities arising from colloidal nanoparticle size and shape distributions, leading to an incomplete picture of the impact of spectral overlap. Here, we isolate the effect of nanoparticle-emitter spectral overlap for a model ECL system, coreaction of tris(2,2'-bipyridyl)dichlororuthenium(ii) hexahydrate and tripropylamine, at the single-particle level while minimizing other factors influencing ECL intensities. We found a 10-fold enhancement of ECL among 952 gold nanoparticles. This signal enhancement is attributed exclusively to spectral overlap between the nanoparticle and the emitter. Our study provides new mechanistic insight into plasmonic enhancement of ECL, creating opportunities for low concentration ECL sensing.

Efficient Electrogenerated Chemiluminescence of Tris(2,2'-bipyridine)ruthenium(II) with N-Hydroxysulfosuccinimide as a Coreactant for Selective and Sensitive Detection of l-Proline and Mercury(II).

Developing rapid, specific, and low-cost electrogenerated chemiluminescence (ECL) systems remains a compelling goal for many applications including environmental analysis, clinical diagnostics, and food safety. In this study, N-hydroxysuccinimide (NHS) esters, especially N-hydroxysulfosuccinimide (NHSS), was exploited for the first time as an efficient coreactant for anodic Ru(bpy)32+ ECL in neutral medium. Among the three tested NHS esters (NHS, NHSS, NHPI), the NHSS exhibited much higher ECL intensity and stability than the sulfonate-free esters, suggesting the essential role of both the N-hydroxy (NOH) and sulfonate (SO3H) moieties in the developed Ru(bpy)32+ ECL system. The ECL generation process is rather straightforward, not requiring time-consuming fabrication/modification steps of electrodes. The anodic Ru(bpy)32+-NHSS system achieved ECL detections with high selectivity and sensitivity toward l-proline (LOD = 50 nM) and Hg2+ (LOD = 10 nM), with a linear range of 0.5-200 μM and 0.1-25 μM, respectively. The method showed good recoveries (95.2-104.8%) for l-proline and Hg2+ detection in real samples. This study is a successful step toward the development of new coreactants and may open new avenues for the applications of N-hydroxy compounds in ECL sensing.

Electrogenerated chemiluminescence on smartphone with graphene quantum dots nanocomposites for Escherichia Coli detection

Graphene quantum dots (GQDs) have recently exhibited great potential in electrogenerated chemiluminescence (ECL) due to their catalyst and amplification effect towards luminophores. Here, we prepared GQDs nanocomposites to amplify the ECL signals in tris(2,2′-bipyridyl)ruthenium(II)/tripropylamine (Ru(bpy)32+/TPA) assay. Universal serial bus interface on smartphone was used as the excitation source for ECL. The luminescence signals were then captured by the smartphone camera and processed by a smartphone-based image analysis application (APP). By immobilizing layer of sensitive Escherichia coli (E.coli) antibody on the electrode surface, our smartphone-based ECL system exhibited excellent linear response towards detection of E.coli in the concentration range of 10 cfu/mL to 107 cfu/mL. Due to the vast popularity and portability of smartphone, the scope of application in our system would be able to greatly satisfy the need for point-of-care testing. Thus, in this work, the quantum dots-amplified luminescence detection was integrated with portable analytical devices, offering low-cost and real-time electrochemical analysis.

Electrogenerated chemiluminescence of ZnO nanorods and its sensitive detection of cytochrome C

Various kinds of ZnO nanoparticles have been successfully used in gas sensing applications, however, these nanomaterials have been rarely investigated in electrogenerated chemiluminescence (ECL). In the present work, ZnO nanorods (ZnONRs) were synthesized by hydrothermal method, and characterized by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). ECL behaviors of ZnONRs were investigated in neutral aqueous condition in the presence of K2S2O8. Cyclic voltammetry (CV) results revealed that ZnONRs can react with K2S2O8 to generate strong light emission, revealing that K2S2O8 can act as coreactant of ZnONRs ECL. ZnONRs synthesized under different pH conditions exhibited different ECL intensities, and the most intense ECL signal was obtained at pH 7.0. Cytochrome C could compete with ZnONRs to react with K2S2O8, and exhibited apparent inhibiting effect on ZnONRs ECL, which can be sensitively detected in the range of 1.0 × 10–11–5.0 × 10−9molL−1, with a detection limit of 4.7 × 10−12molL−1 (3σ). The present ECL system exhibited high sensitivity and good stability, which is suitable for the fabrication of novel ECL sensors.

Electrochemiluminescence sensor based on methionine-modified gold nanoclusters for highly sensitive determination of dopamine released by cells

The electrogenerated chemiluminescence (ECL) of methionine stabilized gold nanoclusters (Met-AuNCs) is presented. The Met-AuNCs were used to modify a glassy carbon electrode (Met-AuNC/GCE) which is shown to exhibit a stable and strong cathodic ECL signal (at −1.86 V) when using potassium peroxodisulfate (K2S2O8) as the coreactant in aqueous solution of pH 7.4. Compared to a GCE modified with BSA-AuNCs, the ECL intensity of Met-AuNCs is 5-fold enhanced. The possible ECL reaction mechanism of the ECL system was studied, and a method for the determination of dopamine (DA) was worked out. The modified GCE has a linear response in the 0.1 to 4 μM DA concentration range, with a detection limit of 32 nM (at an S/N ratio of 3). The method was applied to the determination of DA released by PC12 cells. In our perception, the Met-AuNC/GCE provides a viable new tool in ECL based bioanalysis that also paves new routes to the design and application of new sensors.

A fluorine-doped tin oxide electrode modified with gold nanoparticles for electrochemiluminescent determination of hydrogen peroxide released by living cells

An electrogenerated chemiluminescence (ECL) based method is described for the determination of hydrogen peroxide (H2O2) released by living cells. It is making use of a fluorine-doped tin oxide (FTO) electrode that was modified with gold nanoparticles (AuNPs). The AuNP-FTO was fabricated by electrodeposition of AuNP on the surface of the FTO electrode and characterized by scanning electron microscopy and electrochemical techniques. The AuNP-FTO exhibits a significant electrocatalytic activity towards luminol-based ECL system compared to a bare FTO. The calibration plot covers the 10 nM to 1 μM H2O2 concentration range, with a 8 nM detection limit (at a signal-to-noise ratio of 3). The method enabled (a) the monitoring of drug-stimulated production of H2O2 released by living cells including RAW 264.7 macrophage cells and HeLa cells; and (b) the determination of inhibitors of H2O2 secretion. The method, due to strong signal amplification by AuNPs, provides a viable tool for determination of H2O2 in biological systems.

Determination of silver ions based on the electrogenerated chemiluminescence of silver ions/peroxydisulfate.

In this work, a simple, sensitive, and selective method for the determination of silver ions (Ag(+)) was proposed on the basis of the enhancement of Ag(+) on the electrogenerated chemiluminescence (ECL) of peroxydisulfate (S2O8 (2-)), which can be attributed to the obvious electrocatalytic reduction of S2O8 (2-) by Ag(+), giving rise to more abundant sulfate radical anion (SO4 (•-)). Under optimal conditions, a linear range from 4 to 500nM (R = 0.997) with a detection limit of 2.5nM (S/N = 3) was achieved for the detection of Ag(+). The Ag(+)/S2O8 (2-) ECL system could not only provide an assay protocol forthe determination of Ag(+) but also offer an effective way to enhance the ECL of S2O8 (2-), which may act as a promising platform forthe detection of other species such as 4-chlorophenol. Graphical abstract ECL-potential curves of 0.1 M PBS (pH 8.5) containing (a) 500 nM AgNO3, (b) 50 mM K2S2O8,

Dual-peak electrogenerated chemiluminescence of carbon dots for iron ions detection.

Carbon dots (CDs) have rigorously been investigated on their unique fluorescent properties but rarely their electrogenerated chemiluminescence (ECL) behavior. We are here to report a dual-peak ECL system of CDs, one at -2.84 V (ECL-1) and the other at -1.71 V (ECL-2) during the cyclic sweep between -3.0 and 3.0 V at scan rate of 0.2 V s(-1) in 0.1 M tetrabutyl ammonium bromide (TBAB) ethanol solution, which is more efficiency to distinguish metallic ions than single-peak ECL. The electron transfer reaction between individual electrochemically reduced nanocrystal species and coreactants led to ECL-1, in which the electron injected to the conduction band of CDs in the cathodic process. Ion annihilation reactions induced direct formation of exciplexes that produced another ECL signal, ECL-2. ECL-1 showed higher sensitivity to the surrounding environment than ECL-2 and thus was used for ECL detection of metallic ions. Herein, we can serve as an internal standard method to detect iron ions. A linear relationship of the intensity ratio R of ECL-1 and ECL-2 to iron ions was observed in the concentration extending from 5 × 10(-6) to 8 × 10(-5) M with a detection limit of 7 × 10(-7) M.

Lighting Up Redox Propulsion with Luminol Electrogenerated Chemiluminescence

The development of systems at different scales that are remotely controlled or actuated in a wireless fashion is becoming a fast-developing area at the interface between chemistry and physics. In that framework, self-propelled macro-, microand nano-objects that are able to move in liquids when submitted to external physical fields or chemical fuels have recently been designed. In the latter case, the motion is induced by the conversion of locally available chemicals into mechanical energy via the production of gas bubbles. The mainstream strategy involves a metallic moiety which is able to catalyze the decomposition of hydrogen peroxide, resulting in the interfacial generation of oxygen bubbles. In contrast to this chemically-induced locomotion, physical methods involving electric fields have also been demonstrated. Bipolar electrochemistry (BPE) has recently encountered an important renewal thanks to the development of new applications in the fields of analytical chemistry and chemical sensing, surface science and generation of chemical gradients, catalysis and materials synthesis. The behaviour of a bipolar electrode (BE) is atypical with respect to conventional electrochemistry because it acts as an anode and a cathode at the same time. This asymmetric redox reactivity can also be advantageously used to set in motion conductive particles. The very first example of translational motion was proposed on the basis of an electrochemical self-regeneration with a zinc dendrite. Alternatively, water splitting at both reactive extremities of a BE is responsible for a spatially separated bubble production. This overall reaction generates twice more hydrogen bubbles at the cathodic pole when compared to oxygen at the anodic end. Here, the intrinsic stoichiometry controls the directionality of the resulting motion from the feeder anode to the feeder cathode. Enhancing the speed of motion can be achieved by introducing additive sacrificial redox compounds such as quinone or hydroquinone. In the latter case, the anodic counter reaction is not useful and simply allows to produce bubbles at only one pole of the BE. Interestingly, this recent approach allows as well the addition of new functionalities to dynamic systems like for example the emission of electrogenerated chemiluminescence (ECL). ECL is the light emission resulting from an initial electrochemical reaction. A model ECL system is based on the oxidation of luminol (5-Amino-2,3-dihydro-1,4-phthalazine-dione) in alkaline solution in the presence of hydrogen peroxide in order to promote blue light emission. Luminol and its derivatives are widely used in biochemical and clinical analysis such as enzymatic assays and immunoassays. For example, luminol ECL coupled to oxidasecatalysed reactions generating hydrogen peroxide constitutes a sensitive and versatile analytical strategy. ECL has not only been exploited in combination with BPE for analytical purposes, but also to design the first light emitting electrochemical swimmer involving [Ru(bpy)3] 2+ and tripropylamine (TPrA). The present contribution will show that this methodology can be generalized with another ECL system based on luminol, allowing to tune the wavelength of light emission. Moreover, all previously described BPE-driven motions were reported in neutral or acidic aqueous solutions with cathodic bubbles generation. In contrast, this first example in an alkaline solution proceeds through an alternative mechanism based on H2O2 oxidation and allowing the light emission at the same pole (anode) than the bubble production (Scheme 1). Simultaneous generation of gas bubbles and of ECL could be theoretically achieved when the interfacial difference of potential alongside a BE becomes sufficiently high. Preliminary

Study on the Influence of Carbon Quantum Dots on Electrogenerated Chemiluminescence Energy Transfer Sensing System of DNA

The effect of carbon quantum dots on the electrogenerated chemiluminescence (ECL) energy transfer sensing system for the determination of DNA was investigated. The results showed that the sig- nal-to-noise ratio of luminol-crystal violet ECL system was increased and its reproducibility was improved by the addition of carbon quantum dots. The conditions of the detection of DNA were optimized. Under op- timal conditions, the linear range for the determination of target DNA was 1.0×10 -11 ~1.0×10 -7 mol/L,

Carbon Optically Transparent Electrodes for Electrogenerated Chemiluminescence

This study investigates pyrolyzed photoresist film (PPF)-based carbon optically transparent electrodes (C-OTEs) for use in electrogenerated chemiluminescence (ECL) studies. Oxidative-reductive ECL is obtained with a well-characterized ECL system, C8S3 J-aggregates with 2-(dibutylamino)ethanol (DBAE) as coreactant. Simultaneous cyclic voltammograms (CVs) and ECL transients are obtained for three thicknesses of PPFs and compared to nontransparent glassy carbon (GC) and the conventional transparent electrode indium tin oxide (ITO) in both front face and transmission electrode cell geometries. Despite positive potential shifts in oxidation and ECL peaks, attributed to the internal resistance of the PPFs that result from their nanoscale thickness, the PPFs display similar ECL activity to GC, including the low oxidation potential (LOP) observed for amine coreactants on hydrophobic electrodes. Reductive-oxidative ECL was obtained using the well-studied ECL luminophore Ru(bpy)(3)(2+), where the C-OTEs outperformed ITO because of electrochemical instability of ITO at very negative potentials. The C-OTEs are promising electrodes for ECL applications because they yield higher ECL than ITO in both oxidative-reductive and reductive-oxidative ECL modes, are more stable in alkaline solutions, display a wide potential window of stability, and have tunable transparency for more efficient detection of ECL.

Efficient electrogenerated chemiluminescence from CdTe quantum dots with coreactants

While quantum dots (QDs) have attracted much interest in electrogenerated chemiluminescence (ECL) as a light emitter due to their high quantum yield and bandgap tunability, the fundamental ECL characteristics of QDs in various conditions still remain elusive. In this study, we investigate the ECL generation from CdTe QDs dispersed in organic solvents in the presence of a coreactant. ECL generation via the annihilation between the radical cation of CdTe QDs and their radical anion is not efficient because of the short-lived, unstable radical cation of CdTe QDs. The coreactant, tetra-n-butylammonium peroxydisulfate, can facilitate the ECL generation from CdTe QDs via more efficient generation of the radical cation formed by direct oxidation of the radical anion of CdTe QDs. A poor ECL emitter, Ir(III) complex ((pq)2Ir(dbm)), is examined as a novel coreactant for CdTe QDs, and it turns out that this new ECL system is a very efficient ECL generator. This great improvement is attributed to the collaborative enhancement of ECL from both CdTe and (pq)2Ir(dbm).

Electrogenerated Chemiluminescence of the Tris(2,2′-bipyridine)ruthenium(II)/Tri-n-propylamine (TPrA) System: Crucial Role of the Long Lifetime of TPrA•+ Cation Radicals Suggested by Electrode Surface Effects

We describe the effects of electrochemical pretreatment of glassy carbon electrodes (GCEs) on the electrogenerated chemiluminescence (ECL) of the Ru(bpy)32+ (bpy = 2,2′-bipyridine)/tri-n-propylamine (TPrA) system. It has been found that the oxidation of TPrA at the anodically pretreated GCEs became more facile, while the intensity of ECL could be greatly suppressed. The contravention between the electrochemical reaction kinetics and the light emission intensity of the coreactant ECL system was reported for the first time and has been attributed to the rapid deprotonation of TPrA•+ cation radicals by the aid of oxygen-containing surface species formed on the GCE during the pretreatment. Because the lifetime of TPrA•+ was reduced, the products of the deprotonation reaction, TPrA• free radicals, would be more subject to oxidative consumption on the electrode subsequently, leading to weaker ECL signals. When the ECL was produced mainly following a catalytic route, however, the electrode surface effect was much less significant. This study suggests that the long lifetime of TPrA•+ cation radicals may be crucial for the intense light emission, which allows a sufficient amount of highly reducing intermediate radicals, TPrA•, to participate in the ECL process within a relatively thick reaction layer before being destroyed by the electrode.

Multichannel electrogenerated chemiluminescence of lucigenin in neutral and alkaline aqueous solutions on a gold nanoparticle self-assembled gold electrode

The electrogenerated chemiluminescence (ECL) of lucigenin on a gold nanoparticle self-assembled gold electrode in neutral and alkaline solutions was studied under conventional cyclic voltammetry (CV) conditions. The gold nanoparticle self-assembled gold electrode exhibited excellent ECL property for the lucigenin ECL system. In alkaline solution, one sharp peak and a shoulder peak were observed at −0.24 and −0.36 V, respectively, on the curve of ECL intensity versus potential and the intensities of these peaks were enhanced by 2–3 orders of magnitude compared with those on a bare gold electrode. In neutral solution, two strong ECL peaks (ECL signal/noise = 100–1000) were also observed on a gold nanoparticle self-assembled gold electrode, whereas the two ECL peaks were undetectable on a bare gold electrode. These peaks were found to depend on gold nanoparticles on the surface of the electrode, potential scan direction and scan rate, the presence of O2 or N2, the pH, the concentration of lucigenin and electrolyte, and surfactant. The emitter of all ECL peaks was identified as N-methylacridone (NMA). The mechanism for the formation of these ECL peaks has been proposed. The results indicate that strong ECL signals of lucigenin system could be obtained on a gold nanoparticle self-assembled gold electrode both in alkaline and neutral solutions, which is even stronger than that of luminol system on a gold nanoparticle self-assembled gold electrode under the optimization conditions. Moreover, the gold nanoparticle self-assembled gold electrode also exhibits good stability for the lucigenin ECL system, overcoming the problem of electrode fouling on a traditional electrode.

Electrogenerated chemiluminescent behavior of MCLA at an indium-tin-oxide electrode

In this paper, the electrogenerated chemiluminescence (ECL) behavior of 6-(4-methoxyphenyl)-2-methylimidazo[1,2-a]pyrazin-3(7H)-one (MCLA) at an indium-tin-oxide (ITO) electrode in phosphate buffer solution has been investigated when linear sweep voltammetry was applied. The optimum chemical conditions and electrochemical parameters for this ECL system have been investigated in detail. Under the optimum conditions, it was found that the ECL intensity was linear with the concentration of MCLA in the range of 6.0 × 10 −7 to 1.0 × 10 −5 mol/L, and its detection limit for MCLA was 2.0 × 10 −7 mol/L. The possible mechanism for ECL of MCLA at the ITO electrode was also discussion. Furthermore, it was found that some sophora flavescens, such as matrine and oxymatrine, might enhance the ECL intensity of MCLA. Therefore, it is possible to develop a new ECL method for determination of matrine and oxymatrine.