Electrochemiluminescence resonance energy transfer immunoassay based on a porphyrin metal-organic framework and AuNPs/NSG for the sensitive detection of zearalenone

In this study, a novel electrochemiluminescence resonance energy transfer (ECL-RET) immunoassay was developed for the first time for the detection of zearalenone (ZEN). A porphyrin metal-organic framework (PCN-222), an emerging porphyrin-based ECL luminophore, was prepared by a simple hydrothermal method using tetrakis(4-carboxyphenyl) porphyrin, which has excellent ECL emission as well as good ECL efficiency. Because the ECL emission spectrum of PCN-222 is highly matched to the absorption spectrum of gold nanoparticle-modified graphene oxide (AuNPs/NSG) nanocomposites, they were used as donor-acceptor counterparts in this work for the ECL-RET strategy. Under optimal conditions, the ECL immunosensor showed a sensitive response to ZEN in a wide detection range, with a linearity of 0.0005-1000 ng mL-1 and a detection limit of 0.15 pg mL-1. In addition, the sensor showed good potential for application in the detection of wheat and corn samples, providing a new approach for the detection of mycotoxin-like contaminants such as ZEN in food grains.

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.

Bifunctional Au@Pt/Au nanoparticles as electrochemiluminescence signaling probes for SARS-CoV-2 detection

A novel immunosensor based on electrochemiluminescence resonance energy transfer (ECL-RET) for the sensitive determination of N protein of the SARS-CoV-2 coronavirus is described. For this purpose, bifunctional core@shell nanoparticles composed of a Pt-coated Au core and finally decorated with small Au inlays (Au@Pt/Au NPs) have been synthesized to act as ECL acceptor, using [Ru (bpy)₃]²⁺ as ECL donor. These nanoparticles are efficient signaling probes in the immunosensor developed. The proposed ECL-RET immunosensor has a wide linear response to the concentration of N protein of the SARS-CoV-2 coronavirus with a detection limit of 1.27 pg/mL. Moreover, it has a high stability and shows no response to other proteins related to different virus. The immunosensor has achieved the quantification of N protein of the SARS-CoV-2 coronavirus in saliva samples. Results are consistent with those provided by a commercial colorimetric ELISA kit. Therefore, the developed immunosensor provides a feasible and reliable tool for early and effective detection of the virus to protect the population.

Sandwich-Type Electrochemiluminescence Immunosensor Based on CDs@dSiO2 Nanoparticles as Nanoprobe and Co-Reactant

In general, co-reactants are essential in highly efficient electrochemiluminescence (ECL) systems. Traditional co-reactants are usually toxic, so it is necessary to develop new environmentally friendly co-reactants. In this work, carbon dots (CDs) were assembled with dendritic silica nanospheres (CDs@dSiO₂ NPs) to form a co-reactant of Ru(bpy)₃²⁺. Subsequently, a sandwich immunosensor for detecting human chorionic gonadotropin (HCG) was constructed based on CDs@dSiO₂ NPs as co-reactants, the nanoprobe loaded with the secondary antibody, and Ru(bpy)₃²⁺ as a luminophore. In addition, compared to directly as a signal probe, the luminophore Ru (bpy)₃²⁺ as a part of the electrolyte solution is simpler in this work. The immunosensor has an extremely low limit of detection of 0.00019 mIU/mL. This work describes the synthesis of low-toxic, efficient, and environmentally friendly CDs, which have become ideal co-reactants of Ru(bpy)₃²⁺, and proposes an ECL immunosensor with excellent stability and selectivity, which has great potential in clinical applications.

Gold nanoparticles-oxidized multi-walled carbon nanotubes as electrochemiluminescence immunosensors

Oxidized multi-walled carbon nanotube/nano-gold (AuNP-ox-MWCNT) composites with strong electrochemiluminescence (ECL) activity were applied to construct a new ECL immunosensor for the detection of carcinoembryonic antigen (CEA). The immunosensor showed a linear response range of 10-100 ng mL^-1 and detection limit of 0.76 ng mL^-1 (at a signal-to-noise ratio of 3). The as-developed immunosensor exhibited several advantages, including being simple to fabricate and being label free. The results indicated that ox-MWCNTs as a luminescent material have great application potential in analysis.

Gold nanoparticle-based signal amplified electrochemiluminescence for biosensing applications

Since the content levels of biomarkers at the early stage of many diseases are generally lower than the detection threshold concentration, achieving ultrasensitive and accurate detection of these biomarkers is still one of the major goals in bio-analysis. To achieve ultrasensitive and reliable bioassay, it requires developing highly sensitive biosensors. Among all kinds of biosensors, electrogenerated chemiluminescence (ECL) based biosensors have attracted enormous attention due to their excellent properties. In order to improve the performance of ECL biosensors, gold nanoparticles (Au NPs) have been widely utilized as signal amplification tags. The introduction of Au NPs could dramatically enhance the performance of the constructed ECL biosensors via diverse ways such as electrode modification material, efficient energy acceptor in ECL resonant energy transfer (ECL-RET), reaction catalyst, surface plasmon resonance (SPR) enhancer, and as nanocarrier. Herein, we summarize recent developments and progress of ECL biosensors based on Au NPs signal amplification strategies. We will cover ECL applications of Au NPs as a signal amplification tag in the detection of proteins, metal ions, nucleic acids, small molecules, living cells, exosomes, and cell imaging. Finally, brief summary and future outlooks of this field will be presented.

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.

Sensitive electrochemiluminescence biosensing of polynucleotide kinase using the versatility of two-dimensional Ti3C2TX MXene nanomaterials

Electrochemiluminescence (ECL) is a powerful readout method for the development of (bio)sensors, whose performances depend on the electrode materials and the architecture of its surface. Herein, we demonstrate that the precise control of the sensing interface using the versatility of two-dimensional (2D) transition metal carbides (Ti₃C₂T_X MXene) leads to the enhancement of the ECL signal. This electrode material, which exhibits remarkable structural and electrochemical properties was decorated by the in situ formation of gold nanoparticles (AuNPs) owing to the Ti reducibility. Then, a large amount of the luminophore, Ru(bpy)₃²⁺, was immobilized on Ti₃C₂T_X MXene thanks to its unique negative charge and large specific surface area to obtain Ru-Ti₃C₂T_X-AuNPs. The presented approach exploits the high catalytic activity and excellent conductivity of this 2D nanomaterial as illustrated by the enhanced ECL emission performance of the Ru-Ti₃C₂T_X-AuNPs nanoprobes. Finally, DNA phosphorylated with polynucleotide kinase (PNK) was recognized efficiently by the chelation between Ti and phosphate group. A highly sensitive and selective ECL biosensor was developed for the detection of PNK and the screening of its inhibitors. A lower detection limit of 0.0002 U mL^-1 and wide linear relationship ranged from 0.002 to 10 U mL^-1 were obtained. Furthermore, the practicality of our method was tested in MCF-7 cell lysate, which opens enticing perspectives for future applications of Ti₃C₂T_X materials in the ECL bioanalysis field.

Electrochemiluminescence detection of oxygen vacancies in layered double hydroxides

A novel electrochemiluminescence (ECL) platform was established to screen oxygen vacancies in layered double hydroxides (LDHs) by fabricating graphitic carbon nitride/LDH nanocomposites. The oxygen vacancy concentrations determined by the developed ECL platform were in good agreement with those obtained by XPS.

Aggregation-Induced Emission in Electrochemiluminescence: Advances and Perspectives

The discovery of aggregation-induced electrochemiluminescence (AIECL) in 2017 opened new research paths in the quest for novel, more efficient emitters and platforms for biological and environmental sensing applications. The great abundance of fluorophores presenting aggregation-induced emission in aqueous media renders AIECL a potentially powerful tool for future diagnostics. In the short time following this discovery, many scientists have found the phenomenon interesting, with research findings contributing to advances in the comprehension of the processes involved and in attempts to design new sensing platforms. Herein, we explore these advances and reflect on the future directions to take for the development of sensing devices based on AIECL.

A novel electrochemiluminescence aptasensor for sensitive detection of kanamycin based on the synergistic enhancement effects between black phosphorus quantum dots and silver-decorated high-luminescence polydopamine nanospheres

Black phosphorus quantum dots (BPQDs), as a new type of nanomaterial, have excellent electrical and optical properties. In this work, an efficient monitoring method for kanamycin (KAN) was developed based on a sensitive and selective electrochemiluminescence (ECL) aptasensor. The construction of the ECL illuminant was based on BPQDs loaded on silver-nanoparticle modified high-luminescence polydopamine nanospheres (HLPNs@Ag). HLPNs possessed a large specific surface area and strong adhesion, which could support a great deal of BPQDs. Meanwhile, Ag NPs could accelerate the electron-transfer (ET) rate of the sensor and amplify the ECL signal of the BPQDs. Based on the synergistic enhancement effects between the above materials, the as-fabricated nanocomposites exhibited superior ECL performance. With the assistance of a KAN aptamer, the sensor can detect KAN sensitively and selectively. Under optimal conditions, the aptasensor could detect KAN in a wide linear range from 1 × 10^-12 to 1.0 × 10^-7 M with a detection limit of 1.7 × 10^-13 M (S/N = 3). More importantly, this ultra-sensitive and rapid ECL aptasensor-based KAN detection system provided excellent applicability for the monitoring of environmental safety.

Enhanced electrochemiluminescence of CdS quantum dots capped with mercaptopropionic acid activated by EDC for Zika virus detection

Enhanced electrochemiluminescence (ECL) signals of CdS quantum dots capped with 3-mercaptopropionic acid (MPA@CdS QDs) have been observed after using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) to activate the carboxyl groups. The generated ECL signals are strong enough that their images can be captured using a Huawei mobile phone. A possible mechanism for the generation of enhanced ECL signals has been proposed. Then, a sandwich immunosensor platform for detecting Zika virus (ZIKV) was fabricated with silica microspheres as the carrier and MPA@CdS QDs as ECL signal labels. Due to the dual signal amplification of EDC activation and microsphere enrichment, good linearity from 1.0 fg mL-1 to 1.0 ng mL-1 was exhibited by the QD-based ECL immunosensor for ZIKV detection. The detection limit was 0.3 fg mL-1.

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.

High potential and robust ternary LaFeO3/CdS/carbon quantum dots nanocomposite for photocatalytic H2 evolution under sunlight illumination

Exploitation of the novel, robust, and advanced photocatalytic systems with high efficiency is the present demand for clean, green, and sustainable energy production. Carbon quantum dots (CQDs) have attracted tremendous interest in efficient H₂ evolution from photocatalysis due to its remarkable visible-light harvesting and electron transport properties. Here, for the first time, a smart ternary nanocomposite comprises encapsulated CQDs with LaFeO₃ spherical nanoparticles and CdS nanorods is synthesized by a simple hydrothermal procedure for the efficient photocatalytic H₂ evolution under sunlight illumination. PXRD, FT-IR, FE-SEM, TEM, and XPS studies are performed to ensure the successful fabrication of ternary LaFeO₃/CdS/CQD nanocomposite. The efficient H₂ evolution rate (HER) of 25,302 μmol h^-1 g_cat^-1 is achieved for LaFeO₃/CdS/CQD nanocomposite, which is 602.4, 2.6, 29.8, 2.0 and 1.1 times higher than that of pristine LaFeO₃, pristine CdS, and composites such as LaFeO₃/CdS, LaFeO₃/CQD, and CdS/CQD. Photocurrent and lifetime PL studies reveal, encapsulation of CQDs with the LaFeO₃/CdS heterojunction can facilitate easy and efficient separation of photo-generated excitons. Altogether the fabrication of CQDs provides an ideal avenue for the development of high potential advanced photocatalytic systems for sustainable H₂ production with remarkable efficiencies.

An off-on electrochemiluminescence detection for microRNAs based on TiO2 nanotubes sensitized with gold nanoparticles as enhanced emitters

A sensitive electrochemiluminescence (ECL) assay for microRNAs (miRNAs) based on a semiconductor nanomaterial sensitized with noble-metal Au nanoparticles (NPs) is successfully developed. TiO₂ nanotubes (NTs) were equipped with Au NPs to obtain an enhanced ECL emitter. Then, an ECL assay for miRNA-21 was fabricated, which was based on the use of probe 2 DNA-functionalized Pt/PAMAM nanocomposites (NCs) assembled on the surface of Au/TiO₂ NT conjugate via DNA hybridization between probe 1 DNA and capture DNA. The Pt/PAMAM NCs act as an ECL quencher of Au/TiO₂ NTs via resonance energy transfer. After the binding of target miRNA-21 and the capture DNA, the Pt/PAMAM NCs were released and the ECL signal was recovered. An "off-on" ECL assay was achieved with a linear response from 0.01 to 10,000 pM. Finally, this method has been validated to be sensitive and specific for miRNAs in human serum samples. The ECL enhancement strategy opens a new way for fabricating various sensitive biosensors. Graphical abstract A sensitive "off-on" electrochemiluminescence analysis method was developed, which combined Au NP-enhanced ECL emission of TiO₂ nanotubes and an efficient energy-transfer system between Au/TiO₂ nanotubes and Pt/PAMAM nanocomposites.

Highly Efficient Aggregation-Induced Electrochemiluminescence of Polyfluorene Derivative Nanoparticles Containing Tetraphenylethylene

The aggregation-induced electrochemiluminescence (AIECL) of polyfluorene derivative nanoparticles containing tetraphenylethylene (TPE) in aqueous media is reported in this work. The TPE unit limits the intramolecular free rotation of phenyl rings, as well as the π-π stacking interactions of molecules, which significantly enhances ECL signal of the polyfluorene nanoparticles. With co-reactants of tri-n-propylamine (TPrA) and S2O82-, the copolymer nanoparticles show visualized ECL emissions at both positive and negative potentials. The ECL efficiency of copolymer nanoparticles in solid state is 163% compared with that of standard ECL species, Ru(bpy)32+. And at negative potential, the ECL intensity of copolymer nanoparticles is even stronger with 6.5 times compared with that at positive potential. The ECL generation mechanisms are analyzed detailed by annihilation and co-reactant route transient ECL test (millisecond scale). This work provides a reference for the organic structure design for AIECL and shows promising potential in luminescent device and biological applications.

Recent Advances in Aggregation-Induced Electrochemiluminescence

The emergence of the rising alliance between aggregation-induced emission (AIE) and electrochemiluminescence (ECL) is defined as aggregation-induced electrochemiluminescence (AIECL). The booming science of AIE has proved to be not only distinguished in luminescent materials but could also inject new possibility into ECL analysis. Especially in the aqueous phase and solid state for hydrophobic materials, AIE helps ECL circumvent the dilemma between substantial emission intensity and biocompatible media. The wide range of analytes makes ECL an overwhelmingly interesting analytical technique. Therefore, AIECL has gained potential in clinical diagnostics, environmental assays, and biomarker detections. This review will focus on introduction of the novel concept of AIECL, current applied luminophores, and related applications developed in recent years.

Highly sensitive bioaffinity electrochemiluminescence sensors: Recent advances and future directions

Electrogenerated chemiluminescence (also called electrochemiluminescence and abbreviated ECL) has attracted much attention in various fields of analysis due to the potential remarkably high sensitivity, extremely wide dynamic range and excellent controllability. Electrochemiluminescence biosensor, by taking the advantage of the selectivity of the biological recognition elements and the high sensitivity of ECL technique was applied as a powerful analytical device for ultrasensitive detection of biomolecule. In this review, we summarize the latest sensing applications of ECL bioanalysis in the field of bio affinity ECL sensors including aptasensors, immunoassays and DNA analysis, cytosensor, molecularly imprinted sensors, ECL resonance energy transfer and ratiometric biosensors and give future perspectives for new developments in ECL analytical technology. Furthermore, the results herein discussed would demonstrate that the use of nanomaterials with unique chemical and physical properties in the ECL biosensing systems is one of the most interesting research lines for the development of ultrasensitive electrochemiluminescence biosensors. In addition, ECL based sensing assays for clinical samples analysis and medical diagnostics and developing of immunosensors, aptasensors and cytosensor for this purpose is also highlighted.

Nitrogen-doped graphene quantum dots coated with gold nanoparticles for electrochemiluminescent glucose detection using enzymatically generated hydrogen peroxide as a quencher

Nitrogen-doped graphene quantum dots (N-GQDs) were prepared from dicyandiamide and then used as both an electrochemiluminescence (ECL) emitter and a reductant to produce gold nanoparticles (Au-N-GQDs) on their surface without using any reagent. In order to avoid resonance energy transfer, the Au-N-GQDs were stabilized with chitosan. Transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), UV-vis spectroscopy (UV-vis) and ECL methods were used to characterize the nanocomposite. The materials was placed on a glassy carbon electrode (GCE), and the ECL signals are found to be strongly quenched by hydrogen peroxide that is enzymatically produced by oxidation of glucose. With the applied typical potential of -1.7 V, the ECL of the Au-N-GQDs modified GCE decreases linearly in the 10 nM to 5.0 μM glucose concentration range, and the lower detection limit is 3.3 nM. The influence of H₂O₂ to the signal has been discussed and a possible mechanism has been presented. Graphical abstract Schematic presentation of the reduction of gold nanoparticles with nitrogen-droped graphene quantum dots (N-GQDs) to form Au-N-GQDs. They were used to detect glucose by electrochemiluminescence through a signal off strategy.

Multiple Emitting Amphiphilic Conjugated Polythiophenes-Coated CdTe QDs for Picogram Detection of Trinitrophenol Explosive and Application Using Chitosan Film and Paper-Based Sensor Coupled with Smartphone

Novel multiple emitting amphiphilic conjugated polythiophene-coated CdTe quantum dots for picogram level determination of the 2,4,6-trinitrophenol (TNP) explosive are developed. Four biocompatible sensors, cationic polythiophene nanohybrids (CPTQDs), nonionic polythiophene nanohybrids (NPTQDs), anionic polythiophene nanohybrids (APTQDs), and thiophene copolymer nanohybrids (TCPQDs), are designed using an in situ polymerization method, which shows highly enhanced fluorescence intensity and quantum yield (up to 78%). All sensors are investigated for nitroexplosive detection to provide a remarkable fluorescence quenching for TNP and the quenching efficiency reached 96% in the case of TCPQDs. The fluorescence of the sensors are quenched by TNP through inner filter effect, electrostatic, π-π, and hydrogen bonding interactions. Under optimal conditions, the detection limits of CPTQDs, NPTQDs, APTQDs, and TCPQDs are 2.56, 7.23, 4.12, and 0.56 × 10-9 m, respectively, within 60 s. More importantly, portable, cost effective, and simple to use paper strips and chitosan film are successfully applied to visually detect as little as 2.29 pg of TNP. The possibility of utilizing a smartphone with a color-scanning APP in the determination of TNP is also established. Moreover, the practical application of the developed sensors for TNP detection in tap and river water samples is described with satisfactory recoveries of 98.02-107.50%.

Electrochemical-Signal-Amplification Strategy for an Electrochemiluminescence Immunoassay with g-C3N4 as Tags

Signal amplification for electrochemiluminescence (ECL) has conventionally been achieved by employing effective matrixes that can accelerate the electrochemical redox processes or carry more electrochemiluminophores. Herein, a convenient signal-amplification strategy was proposed for an ECL immunoassay with carboxylated g-C₃N₄ nanosheets (NSs) as tags and carcinoembryonic antigen (CEA) as the model target via electrochemically pretreating the substrate: a glassy-carbon electrode (GCE) modified with a polymerized 2-aminoterephthalic acid (ATA) film (GCE/ATA). Bioconjugates of g-C₃N₄ NSs and the signal CEA antibody (Ab₂) (i.e., g-C₃N₄ NS-Ab₂) were immobilized on GCE/ATA via a sandwich immunoreaction to form GCE/ATA-Ab₁-Ag-Ab₂-NSs. Electrochemical-impedance spectroscopy and potential-resolved ECL characterization proved that GCE/ATA plays an important role in the electron-transfer resistance ( R_et) of the GCE/ATA-Ab₁-Ag-Ab₂-NSs for ECL and that successively scanning GCE/ATA-Ab₁-Ag-Ab₂-NSs from 0 to -1.6 V in K₂S₂O₈- and H₂O₂-containing medium could reduce the R_et and bring out 3.3-times-enhanced ECL at the 10th scan cycle compared with that of the 1st scan cycle, which was about 10.2 times the ECL of the GCE/ATA-Ab₁-Ag-Ab₂-NSs in medium containing merely K₂S₂O₈. Inspired by this, direct and successive scanning of GCE/ATA in K₂S₂O₈- and H₂O₂-containing medium was employed during fabrication, which dramatically reduced the R_et of GCE/ATA-Ab₁-Ag-Ab₂-NSs and brought out obviously enhanced ECL responses for selectively determining CEA from 0.1 pg/mL to 1 ng/mL, with a detection limit of 3 fg/mL.

Electrochemiluminescence detection of reduced and oxidized glutathione ratio by quantum dot-layered double hydroxide film

The ratio of reduced and oxidized glutathione (GSH/GSSG ratio) is a greater first indication of disease risk than the total concentration of GSH. However, the interferences from thiolated biomolecules, especially cysteine (Cys), make the accurate detection of GSH/GSSG ratio a technical problem. In this work, we successfully used a mixture of quantum dots (QDs) and ZnAl-LDH nanosheets to fabricate a high electrochemiluminescence resonance energy transfer (ERET) efficiency sensor for GSH from the disturbances of amino acids, especially Cys and GSSG. The mechanisms of high ERET efficiency and selectivity were well investigated with spectroscopy analysis and theoretical calculation. The results showed that the interaction force between ZnAl-LDH nanosheets and molecules proved a long-range-ordered space and selective transmission for molecules. On the basis of these interesting phenomena, we successfully measured the GSH/GSSG ratio in whole blood and serum samples.

Near-infrared electrochemiluminescence from orange fluorescent Au nanoclusters in water

We report the unusual generation of near-IR electrochemiluminescence from orange fluorescent Au nanoclusters soluble in water.

Electrochemiluminescent resonance energy transfer of polymer dots for aptasensing

This work designed a three-component polymer for the preparation of polymer dots (Pdots). The polymer contained 9-(diphenylmethylene)-9H-fluorene (DPF), 9,9-dioctyl-9H-fluorene (DOF) and 1,1'-binaphthyl moieties, and was synthesized via Pd-catalyzed Suzuki reaction. It exhibited obvious yellow-colored aggregation-induced emission (AIE) for fluorescence enhancement at 543nm via an intramolecular fluorescence resonance energy transfer from DOF moiety to DPF moiety. The Pdots prepared by nanoprecipitation could be conveniently cast on electrode surface and showed a stable anodic electrochemiluminescence (ECL) emission in the presence of triethylamine as a co-reactant. The ECL emission could be effectively quenched by rhodamine B via resonance energy transfer, which led to an "off-on" switch for the design of ECL sensing methodology. Using Pb²⁺ as a target model, an ECL aptasensor for the detection of trace Pb²⁺ was proposed, which showed a linear range of 100pM to 1.0μM with a detection limit down to 38.0pM This work demonstrated the first Pdots prepared with AIE-active polymer for highly efficient ECL sensing.