Electrochemiluminescence Peak Research Articles

Cathodic electrochemiluminescence of boron and nitrogen-codoped carbon dots for the detection of dissolved oxygen in seawater

Electrochemiluminescence (ECL) is widely used in various fields due to its high sensitivity and controllable characteristics. Carbon dots (CDs) have emerged as promising ECL emitters due to their simple synthesis, low toxicity, and excellent biocompatibility. However, the practical application of many CDs emitters is hindered by their limited luminous efficiency, often necessitating additional coreactants to enhance the ECL signal intensity. In this study, we synthesized boron and nitrogen-codoped carbon dots (BN-CDs) as ECL emitters, utilizing dissolved oxygen (DO) as the coreactant. The BN-CDs/DO system exhibited a strong cathodic ECL signal. We proposed a reaction mechanism for the BN-CDs/DO ECL system. Additionally, we developed an ECL sensor for DO detection based on this system, showing a linear correlation between ECL peak intensity and DO concentration from 0.5 to 19.8 mg/L, with a detection limit of 0.12 mg/L. It was proven reliable for DO analysis in seawater and freshwater environments. This study provides insights into the synthesis and utilization of BN-CDs, highlighting the potential of DO as an intrinsic coreactant in CDs ECL systems. Furthermore, it provides new perspectives on the detection of DO in seawater and the design of innovative DO sensors.

Sensitive detection of uric acid based on low-triggering-potential cathodic luminol electrochemiluminescence achieved by ReS2 nanosheets.

The majority of previously reported cathodic electrochemiluminescence (ECL) systems often required very negative potential to be carried out, which hasgreatly limited their applications in the sensing field. Screening high-performance cathodic ECL systems with low triggering potential is a promising way to broaden their applications. In this work, rhenium disulfide nanosheets (ReS2 NS) have been revealed as an efficient co-promoter to realize low-triggering-potential cathodic luminol ECL. One strong cathodic ECL signal appeared at a potential of -0.3V and one anodic ECL peak was obtained at -0.15V under the reverse potential scan, which were caused by electrogenerated reactive oxygen species (ROS) from hydrogen peroxide. The generation of strong luminol ECL at low potential was the result of the electrocatalytic effect of ReS2 NS on the reduction of H2O2. The scavenging effect of uric acid (UA) on the ROS could significantly inhibit the cathodic ECL. As a result, an ECL sensor was proposed, which showed outstanding performance for the detection of UA in the range of 10nM to 0.1mM with a low detection limit of 1.53nM. Moreover, the ECL sensor was successfully applied in the sensitive detection of UA in real samples. This work provides anew avenue to establish a low-potential cathodic ECL system, which will sufficiently expand the potential application of cathodic ECL in the sensing field.

Absolute quantum efficiencies for electrochemiluminescence and chemiluminescence of protoporphyrin IX dimethyl ester

Novel determination methods for absolute electrochemiluminescence (ECL) and chemiluminescence (CL) efficiencies of protoporphyrin IX dimethyl ester (Pro-IX) are reported here with values of 0.0018% and 0.0020%, respectively. The new strategies have significantly reduced the error caused by traditional ECL and CL efficiencies, which relies on the comparison to those of a “standard”. By applying spooling ECL and CL spectroscopies along with electrochemistry to Pro-IX, a great amount of valuable information was obtained regarding the molecular structure and its reaction mechanisms. Pro-IX was found to undergo two quasi-reversible reductions and three irreversible oxidation reactions at formal potentials of +0.92 V, +1.48 V, and +1.79 V, which determine stability of its radical anion and instability of its radical cation. Therefore, no appreciable ECL was generated in annihilation mechanism. The addition of coreactant tri-n-propylamine was discovered to enhance greatly ECL. Spooling ECL spectra were recorded, showing unambiguously the ECL evolution and devolution. The apparent unique ECL peak was curve-fitted to two ECL peaks at 634 nm ascribed to Q(0,0) band emission and 700 nm attributed to vibronic Q(0,1) band, which are consistent with the corresponding PL peaks. Pro-IX was found to give off a pinkish-red CL emission at a dominant peak wavelength of 700 nm and a shoulder at 634 nm in the presence of bis(2-carbopentyloxy-3,5,6-trichlorophenyl) oxalate (CPPO) and H2O2. It is plausible that these two were a result of the vibronic Q(0, 1) band and Q(0, 0) band, in correlation with those in ECL and PL spectra. It is anticipated that ECL and CL of Pro-IX and its analogue porphyrins might be important sensitizers in photodynamic diagnosis of live cells.

TiO2 nanoparticles modified graphitic carbon nitride with potential-resolved multicolor electrochemiluminescence and application for sensitive sensing of rutin.

Recently, nanocomposites with potential-resolved multicolor electrochemiluminescence (ECL) property have attracted new research interests. Herein, TiO2 nanoparticles modified graphitic carbon nitride (TiO2-NPs/g-C3N4) with inherent potential-resolved multicolor ECL emission was prepared via a simple synthesis method. The morphology and chemical composition of the synthesized TiO2-NPs/g-C3N4 were characterized. The obtained TiO2-NPs/g-C3N4 exhibited dual-peak multicolor ECL emission under cyclic voltammetry scanning by using K2S2O8 as co-reagent. The first ECL peak (ECL-1) is composed of turquoise blue ECL emission (471nm) located at -1.3V and olive green ECL emission (490nm) ranging from -1.4 to -2.0V. The second ECL peak (ECL-2) is composed of navy blue ECL emission (458nm) located at -3.0V. The ECL mechanism for the potential-resolved multicolor ECL emissionwas proposed. Furthermore, the first ECL imaging sensing method was fabricated for the sensitive quantitative detection of rutin based on the effective quenching effect of rutin on the ECL of TiO2-NPs/g-C3N4. The linear response range is 0.005-400µM with detection limit as low as 2nM. This work presents a simple way to prepare g-C3N4-based nanocomposites with potential-resolved multicolor ECL, which broadens the potential applications of g-C3N4-based nanocomposites for ECL imaging sensing and light-emitting devices.

A simple and sensitive approach to monitor the spectrum change during the electrochemiluminescence process and reveal the mutual promotion between g-C3N4 and co-reactant of S2O82-

Herein, we develop a high sensitive platform which is able to measure the electrochemiluminescence (ECL) spectrum of ultra-weak emitter (eg. S2O82-) and to monitor ECL spectrum change during ECL process. The rapid change in ECL intensity over detection time, which is the main obstacle in ECL spectrum measurement in wavelength scan model, is predicted by a cubic polynomial model based on the intensities in four adjacent indicator channels in a band-pass filter (BPF) turntable and normalized to stable ECL intensity in a measurement period. The potential dependent ECL spectrum of g-C3N4-S2O82- system reveals the mutual promotion in the ECL intensity between the emitter of g-C3N4 and co-reactant of S2O82-. At the g-C3N4 loading of 5.1 μg/cm2, a new ECL peak for S2O82- appeared at the potential of −1.084 V, with the ECL intensity of S2O82- enhanced 691 times and contributed 3.6% to the total ECL intensity of g-C3N4-S2O82- system at this potential. At the potential of −1.284 V, the proportion of the ECL intensity from S2O82- in total ECL intensity is reduced to 0.16%, because the weak-self ECL of g-C3N4 is enhanced 9280-folds with the help from S2O82- (100 mM) as the co-reactant.

Cover Feature: Efficient Near‐Infrared Electrochemiluminescence from Au18 Nanoclusters (Chem. Eur. J. 60/2021)

Near-infrared electrochemiluminescence (ECL) of Au18 nanoclusters revealed an extremely high quantum efficiency of 5.5 relative to that of Ru(bpy)32+, due to the exposed kernel facets, electrocatalytic loops and overlapped oxidation potentials of Au18 and tri-n-propylamine (TPrA) as co-reactant. ECL peak maxima at 832 and 850 nm were unambiguously identified as emissions from Au180*, Au181+* and Au182+* by means of spooling ECL and photoluminescence spectroscopy. More information can be found in the Communication by M. Hesari and Z. Ding (DOI: 10.1002/chem.202102926).

Wavelength-Dependent Surface Plasmon Coupling Electrochemiluminescence Biosensor Based on Sulfur-Doped Carbon Nitride Quantum Dots for K-RAS Gene Detection.

Although graphite phase carbon nitride quantum dots (GCN QDs) showed some advantages in the electrochemiluminescence (ECL) analytical research, the low ECL efficiency limited the potential sensing application. Herein, we synthesized sulfur-doped graphite phase carbon nitride quantum dots (S-GCN QDs) to fabricate a sandwich sensor based on amplified surface plasmon coupling ECL (SPC-ECL) mode. Sulfur doping can change the surface states of QDs effectively and produced new element vacancy. As a result, the ECL efficiency of S-GCN QDs was 2.5× over GCN QDs. Furthermore, compared with the big gap between the ECL peak of GCN QDs (620 nm) and the absorption peak of Au NPs, the doped sulfur elements in S-GCN QDs generated new ECL emission peaks at 555 nm, which was closed to the absorption peak of Au NPs at 530 nm. Due to the wavelength-dependent surface plasmon coupling effect, the ECL peak of S-GCN QDs at 555 nm had greater amplitude of enhancement in the sensing system. The proposed biosensor can quantify the K-RAS gene from 50 fM to 1 nM with a limit of detection (LOD) of 16 fM. We were the first to provide insight into the role of wavelength-dependent surface plasmon coupling in enhancing the sensitivity of ECL biosensor.

Perylene Diimide and Luminol as Potential-Resolved Electrochemiluminescence Nanoprobes for Dual Targets Immunoassay at Low Potential

In the field of clinical diagnosis, it is important to construct a potential-resolved multiplex electrochemiluminescence (ECL) biosensor for decreasing the false-positive rate and improving the diagnostic accuracy. However, the shortage of low-potential cathodic luminophores between -1 and 0 V (vs Ag/AgCl) severely limited the development of the biosensor. Herein, we synthesized a novel luminophore N,N-bis-(3-dimethyl aminopropyl)-3,4,9,10-perylene tetracarboxylic acid diimide (PDI), which gave dual emissions at -0.25/-0.26 V with K2S2O8 as a co-reactant in aqueous solution. The ECL was assigned to excited J-type PDI dimers. Then, PDI and luminol were used as luminophores to respectively combine with graphite oxide and gold nanoparticles and form potential-resolved ECL nanoprobes. Also, this potential-resolved ECL nanoprobes were respectively functionalized by secondary antibodies (Ab2) to construct a low-potential sandwiched ECL immunosensor for tumor markers carcinoembryonic antigen (CEA) and α-fetoprotein (AFP) simultaneous determination during linear scanning potential range from -0.6 to 0.6 V. The prepared multiplex immunosensor exhibited sensitive ECL response for CEA at -0.6 V due to PDI and that for AFP at 0.6 V due to luminol, and both linear semilogarithmical ranges were from 0.1 pg to 1 ng mL-1. In addition, PDI with dual ECL peaks showed enticing prospect of built-in self-calibration for a precise quantitative and bioimaging analysis.

An enzymatic calculation system based on electrochemiluminescence and fluorescence of luminol and cyclic voltammetry of ferrocene methanol

In this work, a biomolecular calculation system was developed based on electrochemiluminescence (ECL) and fluorescence emission (FL) of luminol and cyclic voltammetry (CV) of ferrocene methanol (FMA). When triethylamine (TEA) was added in luminol solution as a coreactant, a great ECL peak at 1.1 V was observed. While the further addition of enzymatic system, esterase/ethyl butyrate (EB), would significantly lower the ECL response. On the other hand, TEA could quench the FL signal of luminol at 430 nm, while the injection of esterase/EB in the luminol solution could enhance the FL signal. Furthermore, FMA exhibited a CV peak pair at 0.2 V and could decrease the ECL signal greatly in the luminol/TEA solution. Based on these interesting results, a 3-input and 5-output biomolecular logic gate was established with TEA, FMA and esterase/EB as inputs and the ECL, CV and FL signals as outputs. Moreover, some nonarithmetic logic devices, such as an encoder, a decoder, a 3-input keypad lock and two dual transfer gates were elaborately designed on the same platform. This work presented a new example of how the complexity of biocomputing system could be enhanced either by increasing the number of outputs of traditional logic gates or by fabricating some nonarithmetic logic devices based on the same simple electrochemical system.

Dual-signals electrochemiluminescence ratiometry based the synergic effect between luminol and CdSe quantum dots for direct detection of hydrogen peroxide

In the present work, a dual signals electrochemiluminescence (ECL) ratiometric strategy was designed based on the synergic effect of the catalysis effect and ECL resonance energy transfer. It was found that CdSe quantum dots (CdSe QDs) can catalyze the oxidation of luminol to promote the signal intensity of luminol at 0.45 V. At the same time, a stronger cathodic ECL peak at −0.75 V from CdSe QDs was observed, which could be attributed to the resonance energy transfer between luminol as a donor and CdSe QDs as an acceptor. Moreover both signals from two different potentials increased with the increase hydrogen peroxide concentration. On the basis of the above results, an enzyme-free ECL sensor was fabricated by immobilization of coating CdSe QDs on Au-graphite oxide (GO-Au) composites modified glassy carbon electrode (GCE), and luminol solution as probe solution, which was used to detect rapidly and sensitively hydrogen peroxide in the range of 0.5–500 μM with a detection limit of 0.5 μM based on the ration of two signals. The sensor exhibited good reproducibility and sensitivity, suggesting that the simple method will be promising in the detection of active oxygen in environmental samples.

Dual-signal ratiometric electrochemiluminescence assay for detecting the activity of human methyltransferase.

In this paper, a dual-signal ratiometric electrochemiluminescence (ECL) assay was developed to detect human DNA (cytosine-5)-methyltransferase1 (DNMT1) activity. Mercaptopropionic acid (MPA)-modified Eu3+-doped CdS nanocrystals (MPA-CdS:Eu NCs) and luminol were used as two different ECL emitters, which showed ECL signals at different electrochemical potentials. The resultant ECL peaks exhibited opposite trends in the DNMT1 system. According to the ratio of the ECL responses of CdS to luminol, the DNMT1 activity was detected in the range of 1.0-30.0 U mL-1 in buffer solution. The limit of detection (LOD) was estimated to be 0.07 U mL-1 at a signal-to-noise ratio of 3. The assay was extended to detect the DNMT1 activity from crude lysates of cancer cells, along with the effect of DNMT1 inhibitors such as 5-aza and 5-aza-2'-dC.

Potential-Resolved Multicolor Electrochemiluminescence of N-(4-Aminobutyl)-N-ethylisoluminol/tetra(4-carboxyphenyl)porphyrin/TiO2 Nanoluminophores.

Most electrochemiluminescence (ECL) studies involve single luminophore with a unique emission process, which severely limits its applications. Recently, multicolor ECL has attracted considerable interests. Herein, we report a novel nanoluminophore prepared by coating 5,10,15,20-tetrakis(4-carboxyphenyl)-porphyrin (TCPP) and N-(4-aminobutyl)-N-ethylisoluminol (ABEI) on the surface of TiO2 nanoparticles (TiO2-TCPP-ABEI), which exhibited unique potential-resolved multicolor ECL emissions using H2O2 and K2S2O8 as coreactants in an aqueous solution. Three ECL peaks, ECL-1 at 458 nm, ECL-2 at 686 nm, and ECL-3 at 529 nm, were obtained with peak potentials of 1.05, -1.65, and -1.85 V, which were attributed to the ECL emission of ABEI, TCPP, and TiO2 moiety of the nanoluminophores, respectively. Potential-resolved multicolor ECL from a nanoluminophore was observed for the first time in an aqueous solution. It opens a new research area of multicolor ECL of nanoluminophores, which is of great importance in ECL field from fundamental studies to practical applications.

Electrochemiluminescence and voltammetry of tris(2,2′-bipyridine)ruthenium (II) with amphetamine-type stimulants as coreactants: an application to the discrimination of methamphetamine

We have tried to establish an electrochemical detection method for screening of the stimulants in the forensic samples using electrochemiluminescence (ECL) and voltammetric techniques. Amphetamine-type stimulants (ATSs), such as methamphetamine (MA), amphetamine (AM), dimethylamphetamine (DMA), and methoxyphenamine (MP) have been studied as coreactants in the [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) ECL system. There were two specific ECL peaks located at + 1.1 and + 1.4 V for MP, whereas there was only one ECL peak at + 1.1 V for MA and DMA, and no ECL response for AM. Different reaction mechanisms were proposed to understand the generation of ECL by the [Ru(bpy)3]2+/ATS system. Because the voltammetric responses of these ATSs at a glassy carbon electrode were also different, it was possible to detect MA without a separation process based on the characteristic ECL and cyclic voltammetric signals. By a combination of ECL and voltammetric measurements, a simple and rapid screening method for MA could be proposed, and was applied in the determination of MA in human urine samples with sufficient sensitivity. The present electrochemical approach seems to provide a new way for primary screening of MA in forensic application.

Electrochemiluminescene Resonance Energy Transfer Between Traditional Luminescent Reagents and Nanomaterials and Their Biosensing Application

Luminescence resonance energy transfer (LRET) is a powerful technique for probing changes in the distance between energy donors and acceptors, which has often been used in bioassays.1 Electrochemiluminescence (ECL) technique has been widely used in sensing applications, however, it has been seldom reported in LRET due to the difficulty in finding suitable energy donor/acceptor pair. In order to expand its application, it is very important to establish more suitable ECL resonance energy transfer (ECL-RET) pairs. Recently, we found that some traditional ECL reagents, such as luminol, Ru(bpy)3 2+, and lucigenin, can transfer their ECL energy to nanomaterials including semiconductor quantum dots and graphene. The obtained ECL-RET signals are usually stronger than the original ECL signals, which makes the ECL-RET more suitable for biosensing application. Electrochemluminescence resonance energy transfer (ECL-RET) between luminol as a donor and CdSe@ZnS quantum dots (QDs) as an acceptor can be obtained in neutral condition. CdSe@ZnS quantum dots modified on a glassy carbon electrode can catalyze the luminol oxidation to promote the anodic luminol ECL without coreactant. The intensity of anodic luminol ECL (0.60 V) at the CdSe@ZnS/GCE was enhanced more than one magnitude compared with that at the bare GCE. Another strong anodic ECL peak observed at more positive potential (1.10 V) could be assigned to the ECL-RET between the excited state of luminol and the QDs. A label-free ECL aptasensor for the detection of thrombin was fabricated based on the synergic effect of the electrocatalysis and the ECL-RET. The approach showed high sensitivity, good selectivity, and wide linearity for the detection of thrombin in the range of 10 fM-100 pM with a detection limit of 1.4 fM (S/N=3). The energy transfer between lucigenin and CdSe QDs was investigated. Strong anodic ECL can be obtained in neutral lucigenin solution at a CdSe quantum dots modified glassy carbon electrode in the presence of bromide. Electrochemical results suggested that CdSe quantum dots can catalyze the oxidation of lucigenin and bromide, which can generate the anodic ECL. The fluorescence and the ECL spectra revealed that the ECL-RET can occur between lucigenin and CdSe quantum dots. The oxidation product of bromide can promote the ECL-RET and increase the anodic ECL signal significantly. Cytochrome c exhibited apparent inhibiting effect on the anodic ECL emission, based on which a sensitive ECL sensor for the detection of cytochrome c was established.3 The ECL-RET can also occur between Ru(bpy)3 2+ ECL and gold nanoparticles/graphene oxide nanocomposite. Strong anodic Ru(bpy)3 2+ ECL was observed at a graphene oxide modified glassy carbon electrode (GO/GCE) in the absence of coreactants. The catalytical effect of GO on the oxidation of Ru(bpy)3 2+ suggested that GO itself can act as the coreactant of Ru(bpy)3 2+ ECL. Thiol group terminated adenosine triphosphate (ATP) aptamer was immobilized on the GO film via DNA hybridization. When gold nanoparticles/graphene oxide (AuNPs/GO) nanocomposites were modified on the aptamer through S-Au bond to form sandwich-like structure, the ECL-RET could occur between Ru(bpy)3 2+and AuNPs/GO nanocomposites, resulting in apparent decrease of ECL signal. After the ECL sensor was incubated in ATP solution, the AuNPs/GO nanocomposites were released from the electrode due to the specific interaction between aptamer and ATP, leading to the increased ECL signal. Based on these results, an ECL aptasensor was fabricated and could be used in the sensitive and selective detection of ATP in the range of 0.02-200 pM with a detection limit of 6.7 fM (S/N=3). The above results suggested that the ECL-RET between the traditional luminescent reagents and nanomaterials can be used to fabricate different kinds of biosensors for the detection of protein and DNA, which will sufficiently expand the application of ECL technique in biosensing field.

A sensitive solid-state electrochemiluminescence sensor for clenbuterol relying on a PtNPs/RuSiNPs/Nafion composite modified glassy carbon electrode

In this work, a highly sensitive electrochemiluminescence (ECL) sensor for the detection of clenbuterol (CBT) in pork is reported. The fabrication of the sensor was carried out by modification of a glassy carbon electrode (GCE) with platinum nanoparticles (PtNPs)/silica nanoparticles doped with [Ru(bpy)3]2+ (RuSiNPs)/Nafion composite. The morphology, composition and electrochemical behavior of the PtNPs/RuSiNPs were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and electrochemical impedance spectroscopy, respectively. It was found that all the PtNPs are formed on the surface of RuSiNPs and the electron transfer resistance was obviously reduced on the PtNPs/RuSiNPs GCE. Taking the advantage of the Si-O-Si grid of RuSiNPs, the [Ru(bpy)3]2+ luminophore leaching from the modified electrode could largely be prevented, benefiting the ECL signal stability. Moreover, due to the enhanced electron transfer rate and electrocatalytical property of the PtNPs, the sensitivity of the PtNPs/RuSiNPs-based sensor was greatly improved. Under optimized conditions, the ECL peak intensity was linear with the concentration of CBT in the range of 5–100ngmL−1, with a detection limit as low as 0.8ngmL−1. The recoveries of the CBT obtained from spiked pork samples at PtNPs/RuSiNPs/Nafion GCE were between 89.5% and 106.3% and the RSDs were lower than 6.21%. The proposed ECL sensor based on PtNPs/RuSiNPs composite presented good characteristics for CBT determination in terms of rapid, high sensitivity and good stability, promising the applicability of this sensor in real samples.

Intrinsic "Vacancy Point Defect" Induced Electrochemiluminescence from Coreless Supertetrahedral Chalcogenide Nanocluster.

A deep understanding of distinct functional differences of various defects in semiconductor materials is conducive to effectively control and rationally tune defect-induced functionalities. However, such research goals remain a substantial challenge due to great difficulties in identifying the defect types and distinguishing their own roles, especially when various defects coexist in bulk or nanoscale material. Hereby, we subtly selected a molecular-type semiconductor material as structural mode composed of supertetrahedral chalcogenide Cd-In-S nanoclusters (NCs) with intrinsic vacancy point defect at the core site and antisite point defects at the surface of supertetrahedron and successfully established the correlation of those point defects with their own electrochemiluminescence (ECL) behaviors. The multichannel ECL properties were recorded, and the corresponding reaction mechanisms were also proposed. The predominant radiation recombination path of ECL emission peak at 585 nm was significantly distinguished from asymmetrically broad PL emission with a peak at 490 nm. In addition, the ECL performance of the coreless supertetrahedral chalcogenide nanocluster can be modulated by atomically precise doping of monomanganese ion at the core vacant site. A relatively high ECL efficiency of 2.1% was also gained. Actually, this is the first investigation of ECL behavior of semiconductor materials based on supertetrahedral chalcogenide nanocluster in aqueous solution. Current research may open up a new avenue to probe the roles of various different defects with defined composition and position in the NC. The versatile and bright ECL properties of Cd-In-S NC combined with tunable ECL potential and ECL peak suggest that the new kind of NC-based ECL material may hold great promising for its potential applications in electrochemical analysis, sensing, and imaging.

Electrochemiluminescence of Luminol-Tripropylamine System

Hydrogen peroxide is a dominating coreactant of most luminol electrochemiluminescence (ECL) studies though it is unstable and sensitive to many metal ions. Tripropylamine is an eminent coreactant of tris(2,2'-bipyridine)ruthenium ECL. In comparison with H2O2, tripropylamine is much more stable. In this study, tripropylamine has been exploited as a new coreactant of luminol ECL for the first time. The emission spectrum reveals that the ECL peak was aroused by excited 3-aminophthalate. Under optimized conditions, a biphasic linear relationship is obtained between the ECL intensities and luminol concentrations in the presence of 10mM tripropylamine over the range of 1.0×10−11 −1.0×10−7M and 1.0×10−7 −1.0×10−4M with a detection limit of 6.9×10−12M. The detection of tripropylamine showed a linear relationship between ECL intensities and tripropylamine concentrations in the range of 1.0×10−6 to 1.0×10−2M with a detection limit of 7.7×10−7M. Compared to luminol-H2O2 ECL, luminol-tripropylamine ECL system displays not only high stability but also high sensitivity. Hence, it shows great potential in many fields including immunoassay or non-immunoassay diagnostic, clinical, pharmaceutical, environmental and food analysis in the future.

Cathodic electrochemiluminescence of meso-tetra(4-carboxyphenyl) porphyrin/potassium peroxydisulfate system in aqueous media

A two-step cathodic electrochemiluminescence (ECL) of meso-tetra(4-carboxyphenyl) porphyrin (TCPP) in aqueous solution has been reported for the first time. ECL generates upon sweeping from -0.2V to -1.5V using potassium peroxydisulfate (K2S2O8) as a reductive–oxidative coreactant. Two cathodic ECL peaks are found simultaneously. One appears at -0.8V which is corresponding to the reduction of TCPP, another is at -1.1V that is attributed to the reduction of K2S2O8. ECL efficiency (φecl) is 0.22 for TCPP using Ru(bpy)32+/S2O82− as the standard (φecl=1). Under the optimum conditions, ECL intensity has a linear relationship with the concentration of TCPP in the range of 2.0×10−7 to 1.0×10−5molL−1 with the detection limit of 1.7×10−8molL−1. The practical application to determination pheophorbide which is obtained from fresh spinach leaves has been accomplished. The results demonstrate the facility and effectivity of our method for quantitative analysis of porphyrin. At the same time of building this method, the possible ECL mechanism is discussed in detail.

Synthesis, photophysical properties and electrochemiluminescence performances of a series of cationic iridium(III) complexes

A series cationic cyclometalated iridium(III) complexes, ([Ir(pq)2(bpy)][PF6] (1), [Ir(dpq)2(bpy)[PF6] (2), [Ir(pqcm)2(bpy)][PF6] (3), [Ir(pqca)2(bpy)][PF6] (4), pqH=2-phenyl-quinoline, dpqH=2,4-diphenyl-quinoline, pqcmH=2-phenyl-quinoline-4-carboxylic acid methyl ester, pqcaH=2-phenyl-quinoline-4-carboxylic acid adamantanemethyl ester, bpy=2,2′-bipyridine), have been synthesized. New iridium(III) complexes had been characterized by the NMR and mass spectroscopies, and the single crystal structure of complex 4 had been measured. In CH3CN solution, the iridium(III) complexes 1 and 2 showed yellow emission at 560nm, while the iridium(III) complexes 3 and 4 displayed pure red emission at 620nm. The iridium(III) complexes had quantum efficiencies between 1.1% and 8.5%. The electrochemiluminescence (ECL) of cationic cyclometalated iridium complexes was investigated in CH3CN/H2O (40:60 (v/v)) with Au electrode as working electrode. The ECL peaks were obtained when tri-n-propylamine was used as co-reactant and positive initial potential scan direction was adopted. The ECL intensity of iridium(III) complex 1 is 3.8 times of Ru(bpy)32+. The phosphorescence quantum efficiencies of complex 1 and Ru(bpy)32+ are close, so the better ECL performance suggests that iridium complexes have great application potential in ECL detection. The ECL intensities of iridium(III) complexes had almost the same sequence with the quantum efficiencies of iridium(III) complexes.

Gold Nanoparticle-Graphite-Like C3N4Nanosheet Nanohybrids Used for Electrochemiluminescent Immunosensor

Two-dimensional graphite-like carbon nitride nanosheets (g-C3N4 NSs) were hybridized with gold nanoparticles (Au NPs) to construct an electrochemiluminescence (ECL) immunosensor. The prepared Au NP-functionalized g-C3N4 NS nanohybrids (Au-g-C3N4 NHs) exhibit strong and stable cathodic ECL activity compared to g-C3N4 NSs due to the important roles of Au NPs in trapping and storing the electrons from the conduction band of g-C3N4 NSs, as well as preventing high energy electron-induced passivation of g-C3N4 NSs. On the basis of the improved ECL stability and ECL peak intensity of the Au-g-C3N4 NHs, a novel ECL immunosensor was developed to detect carcinoembryonic antigen (CEA) as a model target analyte. The ECL immunosensor has a sensitive response to CEA in a linear range of 0.02-80 ng mL(-1) with a detection limit of 6.8 pg mL(-1). Additionally, the proposed immunosensor shows high specificity, good reproducibility, and long-term stability.