Fundamentals and bioanalytical applications of functional quantum dots as electrogenerated emitters of chemiluminescence

Closed Bipolar Nanoelectrode Array for Ultra-Sensitive Detection of Alkaline Phosphatase and Two-Dimensional Imaging of Epidermal Growth Factor Receptors

The combination of closed bipolar electrodes (cBPE) with electrochemiluminescence (ECL) imaging has demonstrated remarkable capabilities in the field of bioanalysis. Here, we established a cBPE-ECL platform for ultrasensitive detection of alkaline phosphatase (ALP) and two-dimensional imaging of epidermal growth factor receptor (EGFR). This cBPE-ECL system consists of a high-density gold nanowire array in anodic aluminum oxide (AAO) membrane as the cBPE coupled with ECL of highly luminescent cadmium selenide quantum dots (CdSe QDs) luminophores to achieve cathodic electro-optical conversion. When an enzyme-catalyzed amplification effect of ALP with 4-aminophenyl phosphate monosodium salt hydrate (p-APP) as the substrate and 4-aminophenol (p-AP) as the electroactive probe is introduced, a significant improvement of sensing sensitivity with a detection limit as low as 0.5 fM for ALP on the cBPE-ECL platform can be obtained. In addition, the cBPE-ECL sensing system can also be used to detect cancer cells with an impressive detection limit of 50 cells/mL by labeling ALP onto the EGFR protein on A431 human epidermal cancer cell membranes. Thus, two-dimensional (2D) imaging of the EGFR proteins on the cell surface can be achieved, demonstrating that the established cBPE-ECL sensing system is of high resolution for spatiotemporal cell imaging.

Observation of anodic electrochemiluminescence from silicon quantum dots for the detection of hydrogen peroxide

Silicon quantum dots (QDs) with stable positively charged intermediates are prepared using chemical etching to generate strong anodic electrochemiluminescence (ECL) under a positive potential. Their surfaces could be passivated in the presence of strong oxidants, leading to enhanced ECL and offering the ability to carry out analysis for hydrogen peroxide.

Highly Active Coreactant-Capped and Water-Stable 3D@2D Core-Shell Perovskite Quantum Dots as a Novel and Strong Self-Enhanced Electrochemiluminescence Probe

Self-enhanced electrochemiluminescence (ECL) probes have attracted more and more attention in analytical chemistry for their significant simplification of the ECL sensing operation while improving the ECL sensing sensitivity. However, the development and applications of self-enhanced ECL probes are still in their infancy and mainly suffer from the requirement of a complicated synthesis strategy and relatively low self-enhanced ECL activity. In this work, we took advantage of the recently emerged perovskite quantum dots (PQDs) with high optical quantum yields and easy surface engineering to develop a new type of PQD-based self-enhanced ECL system. The long alkyl chain (C18) diethanolamine (i.e., N-octadecyldiethanolamine (ODA)) with high ECL coreactant activity was selected as a capping ligand to synthesize an ODA-capped PQD self-enhanced ECL probe. The preparation of the coreactant-capped PQDs is as simple as for the ordinary oleylamine (OAm)-capped PQDs, and the obtained ODA-capped PQDs exhibit very strong self-enhanced ECL activity, 82.5 times higher than that of traditional OAm-capped PQDs. Furthermore, the prepared ODA-PQDs have a unique nanostructure (ODA-CsPbBr3@CsPb2Br5), with the highly emissive 3D CsPbBr3 PQD as the core and the water-stable 2D CsPb2Br5 as the shell, which allows ODA-PQDs to be very stable in aqueous media. It is envisioned that the prepared ODA-3D@2D PQDs with the easy preparation method, strong self-enhanced ECL, and excellent water stability have promising applications in ECL sensing.

Nanobiosensing Based on Electro-Optically Modulated Technology

At the nanoscale, metals exhibit special electrochemical and optical properties, which play an important role in nanobiosensing. In particular, surface plasmon resonance (SPR) based on precious metal nanoparticles, as a kind of tag-free biosensor technology, has brought high sensitivity, high reliability, and convenient operation to sensor detection. By applying an electrochemical excitation signal to the nanoplasma device, modulating its surface electron density, and realizing electrochemical coupling SPR, it can effectively complete the joint transmission of electrical and optical signals, increase the resonance shift of the spectrum, and further improve the sensitivity of the designed biosensor. In addition, smartphones are playing an increasingly important role in portable mobile sensor detection systems. These systems typically connect sensing devices to smartphones to perceive different types of information, from optical signals to electrochemical signals, providing ideas for the portability and low-cost design of these sensing systems. Among them, electrochemiluminescence (ECL), as a special electrochemically coupled optical technology, has good application prospects in mobile sensing detection due to its strong anti-interference ability, which is not affected by background light. In this review, the SPR is introduced using nanoparticles, and its response process is analyzed theoretically. Then, the mechanism and sensing application of electrochemistry coupled with SPR and ECL are emphatically introduced. Finally, it extends to the relevant research on electrochemically coupled optical sensing on mobile detection platforms.

Recent advances and challenges in developing electrochemiluminescence biosensors for health analysis

This Feature Article simply introduces principles and mechanisms of electrochemiluminescence (ECL) biosensors for the determination of biomarkers and highlights recent advances of ECL biosensors on key aspects including new ECL reagents and materials, new biological recognition elements, and emerging construction biointerfacial strategies with illustrative examples and a critical eye on pitfalls and discusses challenges and perspectives of ECL biosensors for health analysis.

Target-cycling synchronized rolling circle amplification strategy for biosensing Helicobacter pylori DNA

Helicobacter pylori is closely linked to many gastric diseases such as gastric ulcers and duodenal ulcers. Therefore, biosensing H. pylori has attracted wide attention from both scientists and clinicians. Here, we proposed an electrochemiluminescence (ECL)-based platform that could sensitively detect H. pylori DNA. In this platform, a novel target-cycling synchronized rolling circle amplification was used for signal amplification. Silver nanoclusters (Ag NCs) were synthesized on the circle DNA products, embedding them with the ability to catalyze the electrochemical reduction of K₂ S₂ O₈ , in turn resulting in rapid consumption of the ECL co-reactant near the working electrode, and leading to a decrease in the ECL emission intensity. In addition to its excellent stability and selectivity, the proposed strategy had a low detection limit of 10 pM, an indication that it can be beneficially applied to test biosamples. Furthermore, a biosensing chip was designed to improve the throughput and shed new light on large-scale clinical biosensing applications.

Low-Triggering-Potential Electrochemiluminescence from a Luminol Analogue Functionalized Semiconducting Polymer Dots for Imaging Detection of Blood Glucose

In recent years, semiconducting polymer dots (Pdots) as environmentally friendly and high-brightness electrochemiluminescence (ECL) nanoemitters have attracted intense attention in ECL biosensing and imaging. However, most of the available Pdots have a high ECL excitation potential in the aqueous phase (>1.0 V vs Ag/AgCl), which causes poor selectivity in actual sample detection. Therefore, it is particularly important to construct a simple and universal strategy to lower the trigger potential of Pdots. This work has realized the ECL emission of Pdots at low-trigger-potential based on the electrochemiluminescence resonance energy transfer (ERET) strategy. By covalently coupling the Pdots with a luminol analogue, N-(4-aminobutyl)-N-ethylisoluminol (ABEI), the ABEI-Pdots showed an anodic ECL emission with a low onset potential of +0.34 V and a peak potential at +0.45 V (vs Ag/AgCl), which was the lowest trigger potential reported so far. We further explored this low-triggering-potential ECL for imaging detection of glucose in buffer and serum. By imaging the ABEI-Pdots-modified screen-printed electrodes (SPCE) at +0.45 V for 16 s, the ECL imaging method could quantify the glucose concentration in buffer from 10 to 200 μM with detection limits of 3.3 μM, while exhibiting excellent selectivity. When applied to real serum, the results of our method were highly consistent with a commercial blood glucose meter, with the relative errors ranging from 3.2 to 13%. This work provided a universal strategy for constructing low potential Pdots and demonstrated its application potential in complex biological sample analysis.

Electrochemiluminescence with semiconductor (nano)materials

Electrochemiluminescence (ECL) is the light production triggered by reactions at the electrode surface. Its intrinsic features based on a dual electrochemical/photophysical nature have made it an attractive and powerful method across diverse fields in applied and fundamental research. Herein, we review the combination of ECL with semiconductor (SC) materials presenting various typical dimensions and structures, which has opened new uses of ECL and offered exciting opportunities for (bio)sensing and imaging. In particular, we highlight this particularly rich domain at the interface between photoelectrochemistry, SC material chemistry and analytical chemistry. After an introduction to the ECL and SC fundamentals, we gather the recent advances with representative examples of new strategies to generate ECL in original configurations. Indeed, bulk SC can be used as electrode materials with unusual ECL properties or light-addressable systems. At the nanoscale, the SC nanocrystals or quantum dots (QDs) constitute excellent bright ECL nano-emitters with tuneable emission wavelengths and remarkable stability. Finally, the challenges and future prospects are discussed for the design of new detection strategies in (bio)analytical chemistry, light-addressable systems, imaging or infrared devices.

Electrodeposition immobilized molybdenum disulfide quantum dots and their electrochemiluminescence application in the detection of melamine residues in milk powder

In this paper, one-step hydrothermal and electrodeposition methods were used to prepare a MoS2 quantum dot (QD) solid-phase electrochemiluminescent (ECL) electrode for the detection of melamine residues in milk powder. With the assistance of chitosan, MoS2 QDs fixed by the one-step electrodeposition method show better ECL performance than those by traditional deposition methods due to better dispersibility and stability. Based on the quenching of the MoS2 QDs ECL signal by melamine, quantitative detection of melamine in the sample was performed. The structure and morphology of a MoS2-CHIT/indium tin oxide (ITO) solid-phase ECL electrode were characterized by TEM and XPS, and melamine was detected by the ECL method using a three-electrode system. The proposed sensor exhibited good linearity in the range of 1.00 × 10-11 to 1.00 × 10-7 mol L-1 (ΔI = 12 100.62 + 1009.93 lg c (mol L-1), R2 = 0.997), and the method shows the advantages of simplicity and sensitivity compared to traditional detection methods. The interference of common ions in milk powder on the modified electrode was within 5%, and the recovery rate of real sample detection was within 97-98%. As a result, the proposed method is suitable for detecting melamine residues in milk powder.

Development of portable CdS QDs screen-printed carbon electrode platform for electrochemiluminescence measurements and bioanalytical applications

In this work, a portable and disposable screen-printed electrode-based platform for CdS QDs electrochemiluminescence (ECL) detection is presented. CdS QDs were synthesized in aqueous media and placed on top of carbon electrodes by drop casting. The CdS QDs spherical assemblies consisted of nanoparticles about 4 nm diameters and served as ECL sensitizers to enzymatic assays. The nanoparticles were characterized by optical techniques, TEM and XPS. Besides, the electrode modification process was optimized and further studied by SEM and confocal microscopy. The ECL emission from CdS QDs was triggered with H₂O₂ as cofactor and enzymatic assays were employed to modulate the CdS QDs ECL signal by blocking the surface or generating H₂O₂ in situ. Thiol-bearing compounds such as thiocholine generated through the hydrolysis of acetylthiocholine by acetylcholinesterase (AChE) interacted with the surface of CdS QDs thus blocking the ECL. The biosensor showed a linear range up to 5 mU mL^-1 and a detection limit of 0.73 mU mL^-1 for AChE. Moreover, the inhibition mechanism of the enzyme was studied by using 1,5-bis-(4-allyldimethylammonium-phenyl)pentan-3-one dibromide with a detection limit of 79.22 nM. Furthermore, the natural production of H₂O₂ from the oxidation of methanol by the action of alcohol oxidase was utilized to carry out the ECL process. This enzymatic assay presented a linear range up to 0.5 mg L^-1 and a detection limit of 61.46 μg L^-1 for methanol. The reported methodology shows potential applications for the development of sensitive and easy to hand biosensors and was applied to the determination of AChE and methanol in real samples.

Nanomaterial-enhanced chemiluminescence reactions and their applications

Chemiluminescence (CL) analysis is a trace analytical method that possesses advantages including high sensitivity, wide linear range, easy operation, and simple instruments. With the development of nanotechnology, many nanomaterial (NM)-enhanced CL systems have been established in recent years and applied for the CL detection of metal ions, anions, small molecules, tumor markers, sequence-specific DNA, and RNA. This review summarizes the research progress of the nanomaterial-enhanced CL systems the past five years. These CL reactions include luminol, peroxyoxalate, lucigenin, ultraweak CL reactions, and so on. The CL mechanisms of the nanomaterial-enhanced CL systems are discussed in the first section. Nanomaterials take part in the CL reactions as the catalyst, CL emitter, energy acceptor, and reductant. Their applications are summarized in the second section. Finally, the challenges and opportunities are discussed.

Graphene quantum dot electrochemiluminescence increase by bio-generated H2O2 and its application in direct biosensing

In this study, a novel signal-increase electrochemiluminescence (ECL) biosensor has been developed for the detection of glucose based on graphene quantum dot/glucose oxidase (GQD/GOx) on Ti foil. The proposed GQD with excellent ECL ability is synthesized through a green one-step strategy by the electrochemical reduction of graphene oxide quantum dot. Upon the addition of glucose, GOx can catalytically oxidize glucose and the direct electron transfer between the redox centre of GOx and the modified electrode also has been realized, which results in the bio-generated H₂O₂ for ECL signal increase in GQD and realizes the direct ECL detection of glucose. The signal-increase ECL biosensor enables glucose detection with high sensitivity reaching 5 × 10^-6 mol l^-1 in a wide linear range from 5 × 10^-6 to 1.5 × 10^-3 mol l^-1. Additionally, the fabrication process of such GQD-based ECL biosensor is also suitable to other biologically produced H₂O₂ system, suggesting the possible applications in the sensitive detection of other biologically important targets (e.g. small molecules, protein, DNA and so on).

Electrogenerated Chemiluminescence Biosensing

This Feature simply introduces the history and mechanism of classical electrogenerated chemiluminescence (ECL) systems for the detection of biomolecules, highlights new advances and emerging fields of the ECL biosensing with recent illustrative examples, and presents the challenges and perspectives of ECL biosensing.

High Sensitivity Detection of Copper Ions in Oysters Based on the Fluorescence Property of Cadmium Selenide Quantum Dots

Cadmium selenide (CdSe) quantum dots (QDs) were synthesized by water phase synthesis method using 3-mercaptopropionic acid (3-MPA) as a stabilizer, and they were applied to the detection of copper ions (Cu2+). The results showed that CdSe QDs have excellent selectivity and sensitivity toward Cu2+. The fluorescence intensity of CdSe QDs decreased with the increase of Cu2+ concentration. The linear range was from 30 nM to 3 μM, and the detection limit was 30 nM. Furthermore, CdSe QDs were used for detecting the concentration of Cu2+ in oysters. The content of Cu2+ was 40.91 mg/kg, which was close to the one measured via flame atomic absorption spectrometry (FAAS), and the relative error was 1.81%. Therefore, CdSe QDs have a wide application prospect in the rapid detection of copper ions in food.

Recent advances in electrogenerated chemiluminescence biosensing methods for pharmaceuticals

Electrogenerated chemiluminescence (electrochemiluminescence, ECL) generates species at electrode surfaces, which undergoes electron-transfer reactions and forms excited states to emit light. It has become a very powerful analytical technique and has been widely used in such as clinical testing, biowarfare agent detection, and pharmaceutical analysis. This review focuses on the current trends of molecular recognition-based biosensing methods for pharmaceutical analysis since 2010. It introduces a background of ECL and presents the recent ECL developments in ECL immunoassay (ECLIA), immunosensors, enzyme-based biosensors, aptamer-based biosensors, and molecularly imprinted polymers (MIP)-based sensors. At last, the future perspective for these analytical methods is briefly discussed.

Strong Electrochemiluminescence from MOF Accelerator Enriched Quantum Dots for Enhanced Sensing of Trace cTnI

The development of a sensitive and practical electrochemiluminescence (ECL) bioassay relies on the use of ECL signal tags whose signal intensity is high and stable. In this work, strong ECL emission was achieved from metal organic framework (MOF) accelerator enriched quantum dots (CdTe), which were applied as an efficient ECL signal tag for trace biomarker detection. It is particularly noteworthy that a novel mechanism to drastically enhance the ECL intensity of CdTe is established because isoreticular metal organic framework-3 (IRMOF-3) with 2-amino terephthalic acid (2-NH₂-BDC) as the organic ligand not only allows for loading a large amount of CdTe via the encapsulating effect and internal/external decoration but also functions as a novel coreactant accelerator for promoting the conversion of coreactant S₂O₈^2- into the sulfate radical anion (SO₄^•-), further boosting the ECL emission of CdTe. On the basis of the simple sandwich immunoreaction approach, cardiac troponin-I antigen (cTnI), a kind of biomarker related with myocardial infarction, was chosen as a detection model using an IRMOF-3-enriched CdTe labeled antibody as the signal probe. This immunosensor demonstrated desirable assay performance for cTnI with a wide response range from 1.1 fg mL^-1 to 11 ng mL^-1 and a very low detection limit (0.46 fg mL^-1). This suggested that the IRMOF-3-enriched CdTe nanocomposite strategy can integrate the coreactant accelerator and luminophore to significantly enhance the ECL intensity and stability, providing a direction for promising ECL tag preparation with broad applications.

Recent advances and developments on integrating nanotechnology with chemiluminescence assays

Chemiluminescence (CL) techniques are extensively utilized for detection of analytes due to their high sensitivity, rapidity and selectivity. With the advent of nanotechnology and incorporation of the nanoparticles in the CL system has revolutionized the assays due to their unique optical and mechanical properties. Several CL-based reactions have been developed where these nanoparticle based CL sensors have evolved as excellent prospects for sensing in various analytical applications. This review article addresses the nanoparticles based CL detection system that are recently developed, the mechanisms has been summarized and the role of luminophors have been discussed. This article critically analyzes the optimal conditions for the CL detection along with quantitative assessment of the analytes. We have included the use of semiconductor nanoparticles, metal nanoparticles, graphene based nanostructures, mesoporous nanospheres, layered double hydroxides, clays for CL detection. The scope and application of these nanoscale material based CL system in various branches of science and technology including chemistry, biomedical applications, pharmaceutics, food, environmental and toxicological applications has been critically summarized.

Efficient double-quenching of electrochemiluminescence from CdS:Eu QDs by hemin-graphene-Au nanorods ternary composite for ultrasensitive immunoassay

A novel ternary composite of hemin-graphene-Au nanorods (H-RGO-Au NRs) with high electrocatalytic activity was synthesized by a simple method. And this ternary composite was firstly used in construction of electrochemiluminescence (ECL) immunosensor due to its double-quenching effect of quantum dots (QDs). Based on the high electrocatalytic activity of ternary complexes for the reduction of H₂O₂ which acted as the coreactant of QDs-based ECL, as a result, the ECL intensity of QDs decreased. Besides, due to the ECL resonance energy transfer (ECL-RET) strategy between the large amount of Au nanorods (Au NRs) on the ternary composite surface and the CdS:Eu QDs, the ECL intensity of QDs was further quenched. Based on the double-quenching effect, a novel ultrasensitive ECL immunoassay method for detection of carcinoembryonic antigen (CEA) which is used as a model biomarker analyte was proposed. The designed immunoassay method showed a linear range from 0.01 pg mL⁻¹ to 1.0 ng mL⁻¹ with a detection limit of 0.01 pg mL⁻¹. The method showing low detection limit, good stability and acceptable fabrication reproducibility, provided a new approach for ECL immunoassay sensing and significant prospect for practical application.

A sensitive electrochemiluminescent aptasensor based on perylene derivatives as a novel co-reaction accelerator for signal amplification

Herein, a novel signal amplification strategy was designed using the perylene derivative as the co-reaction accelerator toward graphene-CdTe quantum dots (G-CdTe)/S2O8(2-) system to construct a highly sensitive electrochemiluminescent (ECL) aptasensor for thrombin (TB) detection. Firstly, the G-CdTe nanocomposites were prepared by one-step method of in situ generating CdTe quantum dots onto the surface of the graphene oxide by using 3-mercaptopropionic acid as the CdTe QDs stabilizer. Then, a kind of perylene derivative (PTC-Lys), was synthesized by covalently binding L-lysine to 3,4,9,10-perylenetetracarboxylic acid, which was further immobilized onto the G-CdTe by the π-π* stacking and cross-linked the detection thrombin aptamer (TBA II) to obtain the TBA II/PTC-Lys/G-CdTe signal probes. It is worth pointing out that PTC-Lys acting as an efficient co-reaction accelerator interacted with the co-reactant of S2O8(2-) rather than G-CdTe to promote the more oxidant mediators of SO4(•-), which could further react with G-CdTe to produce excited state species G-CdTe* for emitting light. Compared with the G-CdTe/S2O8(2-) ECL system, our proposed strategy with the introduction of co-reaction accelerator of PTC-Lys exhibited ultra-high sensitivity to quantify the concentration of TB from 1.0×10(-7)nM to 10nM with a detection limit of 34aM.

Investigation of perfluorooctanoic acid induced DNA damage using electrogenerated chemiluminescence associated with charge transfer in DNA

An electrogenerated chemiluminescence (ECL)-DNA sensor was designed and fabricated for the investigation of DNA damage by a potential environmental pollutant, perfluorooctanoic acid (PFOA). The ECL-DNA sensor consisted of a Au electrode that had a self-assembled monolayer of 15 base-pair double-stranded (ds) DNA oligonucleotides with covalently attached semiconductor CdSe quantum dots (QDs) at the distal end of the DNA. Characterization of the ECL-DNA sensor was conducted with X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), ECL, and cyclic voltammetry before and after the exposure of the sensor to PFOA. Consistent data revealed that the dsDNA on Au was severely damaged upon the incubation of the electrode in PFOA, causing significant increase in charge (or electron) transfer (CT) resistance within DNA strands. Consequently, the cathodic coreactant ECL responses of the Au/dsDNA-QDs electrode in the presence of K2S2O8 were markedly decreased. The strong interaction between DNA and PFOA via the hydrophobic interaction, especially the formation of F···H hydrogen bonds by insertion of the difluoro-methylene group of PFOA into the DNA base pairs, was believed to be responsible for the dissociation or loosening of dsDNA structure, which inhibited the CT through DNA. A linear relationship between the ECL signal of the sensor and the logarithmical concentration of PFOA displayed a dynamic range of 1.00 × 10(-14)-1.00 × 10(-4) M, with a limit of detection of 1.00 × 10(-15) M at a signal-to-noise ratio of 3. Graphical Abstract Illustration of ECL detection of PFOA on a Au/dsDNA-QDs ECL-DNA sensor.

Sensitive electrochemiluminescence detection of cancer cells based on a CdSe/ZnS quantum dot nanocluster by multibranched hybridization chain reaction on gold nanoparticles

We prepared a novel amplified electrochemiluminescence signal probe based on CdSe/ZnS quantum dots by multibranched DNA hybridization chain reaction on gold nanoparticles, and developed a sensitive ECL biosensor for detection of cancer cells.

CdS-modified porous foam nickel for label-free highly efficient detection of cancer cells

CdS-modified foam nickel (FN) was successfully constructed for the effective detection of cancer cells based on an electrochemiluminescence (ECL) technique and provides a new platform for the realization of an ECL sensor for cancer cells.

New Signal Amplification Strategy Using Semicarbazide as Co-reaction Accelerator for Highly Sensitive Electrochemiluminescent Aptasensor Construction

A highly sensitive electrochemiluminescent (ECL) aptasensor was constructed using semicarbazide (Sem) as co-reaction accelerator to promote the ECL reaction rate of CdTe quantum dots (CdTe QDs) and the co-reactant of peroxydisulfate (S2O8(2-)) for boosting signal amplification. The co-reaction accelerator is a species that when it is introduced into the ECL system containing luminophore and co-reactant, it can interact with co-reactant rather than luminophore to promote the ECL reaction rate of luminophore and co-reactant; thus the ECL signal is significantly amplified in comparison with that in which only luminophore and co-reactant are present. In this work, the ECL signal probes were first fabricated by alternately assembling the Sem and Au nanoparticles (AuNPs) onto the surfaces of hollow Au nanocages (AuNCs) via Au-N bond to obtain the multilayered nanomaterials of (AuNPs-Sem)n-AuNCs for immobilizing amino-terminated detection aptamer of thrombin (TBA2). Notably, the Sem with two -NH2 terminal groups could not only serve as cross-linking reagent to assemble AuNPs and AuNCs but also act as co-reaction accelerator to enhance the ECL reaction rate of CdTe QDs and S2O8(2-) for signal amplification. With the sandwich-type format, TBA2 signal probes could be trapped on the CdTe QD-based sensing interface in the presence of thrombin (TB) to achieve a considerably enhanced ECL signal in S2O8(2-) solution. As a result, the Sem in the TBA2 signal probes could accelerate the reduction of S2O8(2-) to produce the more oxidant mediators of SO4(•-), which further boosted the production of excited states of CdTe QDs to emit light. With the employment of the novel co-reaction accelerator Sem, the proposed ECL biosensor exhibited ultrahigh sensitivity to quantify the concentration of TB from 1 × 10(-7) to 1 nM with a detection limit of 0.03 fM, which demonstrated that the co-reaction accelerator could provide a simple, efficient, and low-cost approach for signal amplification and hold great potential for other ECL biosensors construction.

Fabrication of graphene oxide decorated with nitrogen-doped graphene quantum dots and its enhanced electrochemiluminescence for ultrasensitive detection of pentachlorophenol

Nitrogen-doped graphene quantum dots (NGQDs), as a new class of quantum dots, have potential applications in fuel cells and optoelectronics fields due to their electrocatalytic activity, tunable luminescence and biocompatibility. Herein, a facile hydrothermal approach for cutting nitrogen-doped graphene into NGQDs has been proposed for the first time. The resulting NGQDs were homogeneously modified onto the surface of graphene oxide (GO) to form NGQDs-GO nanocomposites. Compared with NGQDs, the as-prepared NGQDs-GO nanocomposites exhibited excellent electrochemiluminescence (ECL) performances including 3.8-fold enhancement of ECL intensity and a decrease by 200 mV of the ECL onset potential, which are ascribed to the introduction of GO. Based on the selective inhibitory effect of pentachlorophenol (PCP) on the ECL intensity of the NGQDs-GO system, a novel ECL sensor for PCP concentration determination was constructed, with a wide linear response ranging from 0.1 to 10 pg mL(-1) and a detection limit of 0.03 pg mL(-1). The practicability of the sensing platform in real water samples showed satisfactory results, which could open the possibility of using NGQDs-based nanocomposites in the electroanalytical field.