Electrochemiluminescence Spectroscopy Research Articles

A dual mode immunosensing platform constructed on CdIn2S4 near-infrared electrochemiluminescence emitter and AuNPs@g-C3N4 for zearalenone sensing

In this study, a near-infrared (NIR) electrochemiluminescence (ECL) emitter CdIn2S4 was synthesized by a convenient hydrothermal strategy. The ECL properties of the obtained CdIn2S4 were examined in the presence of potassium persulfate coreactant at an excitation potential of − 1.25 V. The low trigger voltage of CdIn2S4 may be ascribed to its lower bandgap. This lower excitation potential could effectively reduce the side-effects induced by high voltages, while maintaining the biological activity of antibodides and antigens. The ECL features of CdIn2S4 were also investigated, demonstrating that CdIn2S4 exhibited excellent NIR characteristics, and surface state transitions led to the ECL emission. Importantly, CdIn2S4 was introduced into ECL and electrochemical impedance spectroscopy (EIS) to establish a dual-mode immunosensing interface. Meanwhile, AuNPs@g-C3N4 with excellent properties were used to promote electron transmission and increase the immobilization amount of zearalenone (ZEA) antibodies in the dual-mode sensing system. The developed immunosensing strategy displayed superior sensing performance in ZEA analysis. The detection limits of ZEA were 30 fg mL−1 (ECL model) and 10 fg mL−1 (EIS model), respectively. The desirable recovery results of ZEA in corn samples prove the application potential of the NIR emitter CdIn2S4 in developing a dual-mode immunosensing system for early real-time use.

Near-infrared electrochemiluminescence of defect-rich molybdenum disulfide quantum dots for sensitive bioanalysis

Developing high-efficiency near-infrared (NIR) electrochemiluminescence (ECL) active transition metal dichalcogenides quantum dots (TMDs QDs) for spectroscopic multiplex analysis and biological imaging poses a significant challenge in versatile bioanalysis. In this work, we report a facile one-step hydrothermal method for the synthesis of defect-rich molybdenum disulfide quantum dots (MoS2 QDs). Because of the defect effect on the nanocrystalline surface, the MoS2 QDs exhibit enhanced fluorescence (quantum yield is 7.7%) in comparison with those from top-down physical approaches. Moreover, the defect-rich MoS2 QDs exhibit remarkable ECL performance using K2S2O8 as a coreactant, with a maximum emission at ∼810 nm. The ECL mechanisms of potential-dependent emission from MoS2 QDs were elucidated based on electrochemistry, photoluminescence, and spooling ECL spectroscopy. Leveraging the good biocompatibility and defect-induced ECL enhancement of MoS2 QDs, a sandwich ECL immunosensor was developed for carcinoembryonic antigen (CEA) detection. Without any signal amplification techniques, the proposed biosensor demonstrated a detection limit of 0.005 ng/mL CEA with a linear range from 0.005 ng/mL to 400 ng/mL, and a good selectivity and potential for real human serum analysis. The defect engineering of MoS2 QDs in this study provides guidance for regulating their optical properties and exploring new bioanalysis applications.

Highly efficient electrochemiluminescence of nitrogen-doped carbon quantum dots

Nitrogen-doped carbon quantum dots (N-CQDs) are nanocomposites that can be synthesized by the hydrothermal method. In this work, N-CQDs with the size of 3.2 ± 1.7 nm was prepared from 1 g citric acid and 2 g urea precursor in 10 mL water. Electrochemiluminescence (ECL) of the prepared N-CQDs with K2S2O8 as a coreactant was found to reach a high ECL efficiency up to 109% relative to that of the Ru(bpy)32+/K2S2O8, coreactant system, revealing their great potential for electroanalysis. It is probably because that N elements were doped well in this N-CQDs and increased presence of surface states per mass of N-CQDs. From the spooling ECL spectroscopy, it can be found that the ECL spectra exhibited both a red shift compared with their photoluminescence (PL) spectrum and a wavelength shift during the potentiodynamic scan in the ECL evolution and devolution processes, due to various emissive excited states of N-CQDs leading to higher ECL efficiency. This work gives an insight into development of high ECL efficiency N-CQDs for bioanalytical and light emitting applications.

A Signal Amplification Strategy Using ATP as a Co‐Reaction Accelerator for the Electrochemiluminescence of Ru(bpy)32+/HEPES System and Detection of Iodide Anions**

AbstractAdenosine triphosphate is an important biological molecule that provides energy and substrate for various cellular biochemical processes,it's ubiquitous in our lives. In this work, a novel electrochemiluminescence (ECL) sensor composed of Ru(bpy)32+, 2‐[4‐(2‐hydroxyethyl)piperazin‐1‐yl] ethanesulfonic acid (HEPES) and adenosine 5’‐triphosphate disodium salt (ATP) was developed for the first time. In this ECL system, Ru(bpy)32+ was used as the luminophore, HEPES buffer was served as the co‐reactant, and ATP was added to the system to amplify the luminous signal to investigate the ECL behavior. Through fluorescence spectroscopy, ECL spectroscopy, and cyclic voltammetry (CV), it can be hypothesized that the possible ECL mechanism is that ATP acts as an advanced co‐reaction promoter to accelerate the oxidation of HEPES to HEPES+⋅, more HEPES⋅ can be generated, which then reacts with oxidized Ru(bpy)33+ to emit stronger ECL signals. Subsequently, the influence of the ATP concentrations and the CV scanning speed was investaged. Moreover, it was observed that I− could quench the ECL intensity, the linear relationship range of I− concentration is from 10−3 to 10−6 m, the limit of detection is 3.7×10−8 m (signal/noise=3), therefore, a new, highly sensitive, and selective ECL approach for I− detection was created.

Significantly enhanced electrochemiluminescence of nalidixic acid/S2O82− system by isonicotinic as Co-reaction accelerator for ultrasensitive detection of tetraethylenepentamine

• A novel ECL system consisting of nalidixic acid (NA) and K 2 S 2 O 8 was investigated. • 4-Pyridinecarbohydrazide as a co-reactant accelerator that significantly amplifies the ECL signal of the NA system. • A tetraethylenepentamine detection strategy based on ECL technology was developed. This work presents a method for the establishment of a highly sensitive and selective nalidixic acid and S 2 O 8 2- (NA/S 2 O 8 2- ) electrochemiluminescence (ECL) system using isonicotinic (INH) as a co-reaction accelerator. After optimizing the experimental conditions including scan rate, pH value of buffer solution, concentration, etc., the chemiluminescence mechanism of the system was studied in detail using fluorescence spectroscopy, ECL spectroscopy and cyclic voltammetry (CV). The results show that INH is an efficient co-reaction accelerator, which interacts with the co-reactant S 2 O 8 2- but not the luminophore NA to promote the production of more oxidant SO 4 ·– , which then further reacts with NA to generate excited state species NA * with strong ECL signal, indicating that co-reaction accelerators can provide a simple, efficient, and low-cost method for signal amplification. Based on the great ECL enhancement of INH for the NA/S 2 O 8 2- system, under the optimal experimental conditions, highly sensitive and selective electrochemiluminescence detection of tetraethylenepentamine (TEPA) was achieved.

Insights into enhanced electrochemiluminescence of a multiresonance thermally activated delayed fluorescence molecule

AbstractThe electrochemiluminescence (ECL) behavior of a multiresonance thermally activated delayed fluorescence molecule has been investigated for the first time by means of ECL‐voltage curves, newly designed ECL‐time observatory, and ECL spectroscopy. The compound, Mes3DiKTa, shows complex ECL behavior, including a delayed onset time of 5 ms for ECL generation in both the annihilation pathway and the coreactant route, which we attribute to organic long‐persistent ECL (OLECL). Triplet‐triplet annihilation, thermally activated delayed fluorescence and uncompensated solution resistance cannot be ruled out as contributing mechanisms to the ECL. A very long ECL emission decay was attributed to OLECL as well. The absolute ECL efficiencies of Mes3DiKTa were enhanced and reached 0.0013% in annihilation route and 1.1% for the coreactant system, which are superior to those of most other organic ECL materials. It is plausible that ECL materials with comparable behavior as Mes3DiKTa are desirable in applications such as ECL sensing, imaging, and light‐emitting devices.

Polymer Carbon Nanodots: A Novel Electrochemiluminophore for Dual Mode Detection of Ferric Ions.

The development of simple and effective dual-mode analytical methods plays crucial regulatory roles in the discrimination of relevant target species, because of their built-in cross reference correction and high accuracy. In this work, a novel polymer carbon nanodots (PCNDs) prepared from a facile one-pot hydrothermal procedure using readily available l-tryptophan and l-phenylalanine as precursors, showed excellent aqueous solubility and blue fluorescence property with a high quantum yield of 29%. Moreover, the PCNDs was demonstrated to be a robust luminophore with electrochemiluminescence (ECL) efficiency of 43% was achieved by using K2S2O8 as a coreactant. The spooling ECL spectroscopy was employed to take insight into excited states responsible for the potential-dependent ECL emissions. Most importantly, when introduced into construction of the fluorescence and ECL dual mode sensing platform, for the first time, the PCNDs displayed prominent performance for the detection of ferric ions (Fe3+). The ferric ions could be quantified ranging from micromolar to millimolar with a detection limit of 0.22 and 5.3 μM, respectively. Such a dual-functional sensing platform also exhibits excellent selectivity, reproducibility and stability. Results from this work indicate that PCNDs showing great promise as a bright luminophore for the fabrication of low-cost, high-performance dual-signal readout platforms for ferric ions determination.

Determining absolute electrochemiluminescence efficiencies of two iridium complexes

• Two iridium complexes exhibit efficient ECL comparable to [Ru(bpy) 3 ] 2+ . • Radical stability and reactivity are the key factors affecting ECL. • Absolute ECL efficiencies are more applicable than the ones relative to [Ru(bpy) 3 ] 2+ , especially in case of co-reactant systems. • The methodology to determine absolute ECL efficiencies is an essential tool for ECL investigation. This work reports absolute electrochemiluminescence (ECL) quantum efficiencies (QEs) of two iridium(III) complexes, fac- Ir(ppy) 3 ( Ir-1 ) and [Ir(ppy) 2 (dtbubpy)] + ( [Ir-2] + ) in annihilation and coreactant pathways. With potentiodynamic scans and potential pulsing, ECL mechanisms were investigated by means of ECL-voltage curves, ECL-time curves and ECL spectroscopy. It was demonstrated that the radical stability and reactivity are the two main factors affecting ECL efficiencies in various processes, while intermediate charges have little effect. Considering the difference of such radical behaviors between [Ru(bpy) 3 ] 2+ and other luminophores, absolute ECL QEs are more applicable compared with the ones relative to [Ru(bpy) 3 ] 2+ as a standard.

Identifying Highly Photoelectrochemical Active Sites of Two Au21 Nanocluster Isomers toward Bright Near-Infrared Electrochemiluminescence.

Thus far, no correlation between nanocluster structures and their electrochemiluminescence (ECL) has been identified. Herein, we report how face-centered-cubic and hexagonal close-packed structures of two Au21(SR)15 nanocluster isomers determine their chemical reactivity. The relationships were explored by means of ECL and photoluminescence spectroscopy. Both isomers reveal unprecedented ECL efficiencies in the near-infrared region, which are >10- and 270-fold higher than that of standard Ru(bpy)32+, respectively. Photoelectrochemical reactivity as well as ECL mechanisms were elucidated based on electrochemistry, spooling photoluminescence, and ECL spectroscopy, unfolding the three emission enhancement origins: (i) effectively exposed reactive facets available to undergo electron transfer reactions; (ii) individual excited-state regeneration loops; (iii) cascade generations of various exited states. Indeed, these discoveries will have immediate impacts on various applications including but not limited to single molecular detection as well as photochemistry and electrocatalysis toward clean photon-electron conversion processes such as light-harvesting and light-emitting technologies.

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).

Discovering the Link between Electrochemiluminescence and Energy Transfer Pathways for Mn-Doped CsPbCl3 Quantum Dot Films

Electrochemiluminescence (ECL) of Mn-doped CsPbCl3 perovskite quantum dot (MPQ) films was investigated for the first time. The electrochemical properties of the perovskite quantum dots are probed by cyclic voltammetry and spooling ECL spectroscopy. It has been discovered that the ECL of the MPQ/benzoyl peroxide coreactant system proceeds through two channels: an energy transfer process from the band-edge exciton to Mn2+, producing emission centered at 595 nm from Mn2+ d–d transition, and a second emission peak centered at 660 nm, which is of a surface-state origin. This observation is drastically different from the frequently reported photoluminescence (PL) of MPQ, which contains dual emission from the host and the dopant, respectively. ECL of the undoped CsPbCl3 (UPQ) was also investigated, and the presence of the 660 nm peak further supports our proposed surface-state emission scheme.

Optimizing the Electrochemiluminescence of Readily Accessible Pyrido[1,2‐α]pyrimidines through “Green” Substituent Regulation

AbstractBright and low‐cost emitting organic molecules are very desirable for electrochemiluminescence (ECL). Here, we report a facile one‐step, three‐component reaction of readily available precursors to synthesize pyrido[1,2‐α]pyrimidine derivatives (1–4), all which give off green photoluminescence (PL). In contrast, the electrochemistry and ECL properties of these luminophores are affected by the extent of the conjugation and the nature of the peripheral substituents. Density functional theory (DFT) calculations identified the aromatic chain substitution could extend the conjugation of pyrido[1,2‐α]pyrimidine core and stabilize the electrogenerated radicals required for generation of an excited state, affording pyrido[1,2‐α]pyrimidine 3 the highest ECL activity among the studied samples. ECL in annihilation route confirmed weak emission, but great improvement was made using oxidizing co‐reactant species (benzoate radical from benzoyl peroxide, BPO) with an efficiency of 43 % relative to that of Ru(bpy)3(PF6)2. The pyrido[1,2‐α]pyrimidine 3/BPO system is more robust than those of reducing co‐reactant species [tri‐n‐propylamine radical or 2‐(dibutylamino) ethanol radical] and is one of the highest among the reported organic electrochemiluminophores. ECL spectroscopy revealed that the monomeric excited states were the main species to emit light. Their straightforward, one‐step, green synthesis, and their structure tunability represent significant advantages in the development of readily accessible dyes for PL and especially ECL applications.

Efficient White Electrochemiluminescent Emission From Carbon Quantum Dot Films.

Carbon quantum dots (CQDs) were manufactured from citric acid and urea in a gram-scale synthesis with a controlled size range between 1. 5 and 23.8 nm. The size control was realized by varying volume of the precursor solution in a hydrothermal synthesis method. The prepared CQDs were investigated using electrochemiluminescence (ECL) spectroscopy at interfaces of their electrode films and electrolyte solution containing coreactants rather than conventional optoelectronic tests, providing an in-depth analysis of light-emission mechanisms of the so-called half-cells. ECL from the CQD films with TPrA and K2S2O8 as coreactants provided information on the stability of the CQD radicals in the films. It was discovered that CQD•− has a powerful electron donating nature to sulfate radical to generate ECL at a relative efficiency of 96% to the Ru(bpy)3Cl2/K2S2O8 coreactant system, indicating a strong performance in light emitting applications. The smaller the CQD particle sizes, the higher the ECL efficiency of the film interface, most likely due to the increased presence of surface states per mass of CQDs. Spooling ECL spectroscopy of the system revealed a potential-dependent light emission starting from a deep red color to blue-shifted intensity maximum, cool bright white emission with a correlated color temperature of 3,200 K. This color temperature is appropriate for most indoor lighting applications. The above ECL results provide information on the performance of CQD light emitters in films, permitting preliminary screening for light emitting candidates in optoelectronic applications. This screening has revealed CQD films as a powerful and cost-effective light emitting layer toward lighting devices for indoor applications.

Electrogenerated chemiluminescence from the monomer of a tetradentate chelate Pt(II) compound

Pt (II) compounds have drawn great attention due to their excellent phosphorescence properties. Interestingly, Pt (II) complexes with planar core structures have a great tendency to generate stacked dimers, leading to excimer emission in electrogenerated chemiluminescence or electrochemiluminescence (ECL) processes. It was found through this work that the excimer ECL could be adjusted to monomer excited one by introducing bulky substituents to the ligands. Here, the electrochemical and ECL properties of a tetradentate chelate Pt (II) complex (Ptm) containing an NˆC-chelate phenyl-1,2,3-triazolyl (ptrz) ligand and an NˆC-chelate pyridyl-1,2,4-triazolyl (pytrz) ligand in the central core, along with a diphenyl amino substituent in the phenyl of ptrz ligand, was investigated. Ptm showed weak ECL efficiency in the annihilation path and persulfate turned out to be a very good co-reactant to enhance dramatically the ECL intensity. Light emission mechanisms were probed by means of the spooling ECL spectroscopy. It was found that only monomer excited states were generated in the ECL process attributing to the large steric hindrance by bulky diphenyl amino substituent in the ptrz ligand. This is in contrast to ECL of some Pt complex where diphenyl amino substituent was replaced by two small size fluorine atoms leading to dominant excimer ECL emission. Those results well indicate that the ECL of Pt (II) complexes with planar core structures can be adjusted by simply increasing the steric hindrance.

Electrochemiluminescence of nitrogen- and sulfur-doped graphene quantum dots

Nitrogen- and sulfur-doped graphene quantum dots (NS-GQDs) have been synthesized via one-pot pyrolysis approach using citric acid and l-Cysteine as precursors. The obtained NS-GQDs have a size around 2.8 ± 1.0 nm. The fluorescence quantum yield of NS-GQDs was calculated to be 84 times that of Ru(bpy)3Cl2, which is 9.3-fold higher than that of undoped GQDs. Electrochemiluminescence (ECL) of NS-GQDs was found to be robust with K2S2O8 as a coreactant and an ECL efficiency of 32% relative to the Ru(bpy)3Cl2/K2S2O8 was reached, which is also 5.8-fold enhanced when compared with the same system of undoped GQDs. By means of spooling ECL spectroscopy, a potential-dependent ECL emission was discovered in the ECL processes of both NS-GQDs and GQDs. Scanning the applied potential to different values changed actually the driving force, and thus various emissive excited states were produced, leading to variable emission wavelengths. Importantly, because much more surface capturing centers of excitons for NS-GQDs than GQDs created by nitrogen and sulfur doping effect, the NS-GQDs can capture more holes from SO4− and thereby give higher ECL efficiency. The ECL and electron transfer mechanisms proposed here provide insight into development of new GQD for light emitting devices and bioanalytical applications.

Progress in electrochemistry and electrochemiluminescence of metal clusters

Summary Ultrasmall metal clusters with unique sizes of a few nanometers possess distinct optical, electronic, and magnetic properties different from their nanoparticle counterparts. Over 100 metal clusters with atomically precise designed structures have been reported. In this mini-review, research in the fields of electrochemistry, and electrochemiluminescence (ECL) of metal clusters, has been summarized. Quantized double layer charging voltammetry, or molecule-like voltammetry, could be observed for metal clusters with specific core sizes. These metal clusters always demonstrate rich valence states and can be designed as either electron donors or acceptors; hence, metal clusters are versatile luminophores for ECL. In most cases, the ECL of metal clusters through annihilation routes is very weak, so coreactants are required to enhance the ECL intensity. The mechanisms of these ECL processes can be identified through spooling ECL spectroscopy. This powerful technique yields time-evolved ECL peaks at their corresponding wavelength. The ECL signal could be quenched or amplified by specific biospecies, providing the foundation for ECL applications in biosensors. The thriving development of electrochemistry and ECL of metal clusters provides numerous possibilities for fundamental research and applications.

Analyzing Electrochemiluminescence Mechanisms of Thiophene–Triazole–Thiophene Luminophores with In Situ Spectroscopy

AbstractHerein, we report the electrochemical and electrochemiluminescence (ECL) study of thiophene luminophores, 1‐[2,2′]bithiophenyl‐4‐yl‐4‐thiophen‐2‐yl‐1H‐[1,2,3]triazole (TTT) and 4‐thiophen‐2‐yl‐1‐thiophen‐3‐yl‐1H‐[1,2,3]triazole (TT), in N,N‐dimethylformamide (DMF). Differential pulse voltammetry was used to determine the oxidation and reduction potentials of the two compounds. TTT and TT in DMF exhibited relatively weak ECL efficiencies following the annihilation mechanism. However, ECL was enhanced with co‐reactants, persulfate, benzoyl peroxide, and tri‐n‐propylamine. In these experiments, TTT displayed stronger ECL activity than TT, due to the quasireversible nature of the reduction reactions. Spooling ECL spectroscopy was utilized to gain analytical insight into light‐emission mechanisms. It was shown that whereas these two thiophene compounds could form photoinduced excited monomers, excimers were generated mainly in their co‐reactant ECL paths.

Comparison study of electrochemiluminescence of boron-dipyrromethene (BODIPY) dyes in aprotic and aqueous solutions

Boron-dipyrromethene (BODIPY) dye molecules are well known for their excellent absorption and emission optical properties. Here, we report the results of an electrochemical and electrochemiluminescence (ECL) study of an organic-soluble and a water-soluble BODIPY dye to explore their effectiveness as ECL luminophores. A combination of UV–visible, fluorescence, and spooling ECL spectroscopy was used to study the mechanisms of ECL light emission. It was discovered that excimers, the excited states of analyte dimers, contributed significantly to the production of ECL. These BODIPY molecules exhibited relatively weak ECL efficiencies following the annihilation mechanism. However, ECL was enhanced with co-reactants such as persulfate, and tri-n-propylamine. Spooling ECL spectroscopy was utilized to gain analytical insight into light emission mechanisms. It is shown that while these two BODIPY compounds can form photoinduced excited monomers, excimers were generated mainly in their co-reactant ECL pathways.

Highly Efficient Dual-Color Electrochemiluminescence from BODIPY-Capped PbS Nanocrystals.

Electrochemiluminescence (ECL) of a hybrid system consisting of PbS nanocrystals (NCs) and a BODIPY dye (BDY) capping ligand was discovered to produce highly efficient dual emissions with tri-n-propylamine as a coreactant. By means of spooling ECL spectroscopy, the strong dual ECL emission peaks of 984 and 680 nm were attributed to the PbS and BDY moieties, respectively, and found to be simultaneous during the light evolution and devolution. The ECL of the PbS was enhanced via NC collisions with the electrode and reached an efficiency of 96% relative to that of Ru(bpy)3(2+), which is the highest among the semiconductor NCs.

Enhanced Electrochemiluminescence of Luminol on Indium Tin Oxide Modified with Dendrimer‐Encapsulated Au Nanoparticles

AbstractEnhanced electrochemiluminescence (ECL) of luminol was reported with the use of dendrimer‐encapsulated Au nanoparticle (Au DEN)‐modified ITOs in the presence of hydrogen peroxide, which was applied for sensitive ECL‐based electroanalysis of hydrogen peroxide. The enhanced ECL of luminol in the presence of hydrogen peroxide was attributed to facile electrochemical oxidation of luminol/hydrogen peroxide on the Au DEN‐modified ITOs at potentials as low as ∼0.4 V (vs. Ag/AgCl). Spooling ECL spectroscopy measurements indicated that the enhanced ECL emission of luminol/hydrogen peroxide system on the Au DEN‐modified ITOs originated from excited 3‐aminophthalate as same as that obtained on bare ITOs. Stability of Au DENs on ITO surfaces was also addressed and found to be closely related with the presence of chloride ions in electrolyte solutions.