Bipolar Aggregation-Induced Electrochemiluminescence of Thiophene-Fused Conjugated Microporous Polymers

Dual emitting aggregation-induced electrochemiluminescence from tetrastyrene derivative for chloramphenicol detection

Chloramphenicol (CAP) poses a threat to human health due to its toxicity and bioaccumulation, and it is very important to measure it accurately and sensitively. This work explored a host-guest recognition strategy to mediate dual aggregation-induced electrochemiluminescence (AIECL) of 1,1,2,2-tetrakis(4-(pyridin-4-yl) phenyl)-ethene (TPPE) for ratio detection of CAP, in which, cucurbit[8]uril (CB[8]) served as host to assemble guest TPPE. The resulting supramolecular complex CB[8]-TPPE exhibited excellent dual-AIECL-emission with signal strength approximately four times that of TPPE aggregates and black hole quencher-1 (BHQ1) could efficiently quench dual-AIECL signal. CB[8]-TPPE coupled dual-function quencher BHQ1 and high-efficiency DNA reactor to achieve ultra-sensitive detection of CAP, exhibiting a linearity range of 10 fmol·L-1-100 nmol·L-1 and limit of detection of 1.81 fmol·L-1. CB[8]-TPPE provides a novel way to improve the dual-emission of TPE derivatives and sets up a promising platform for CAP detection, demonstrating a good practical application potential.

Heterojunction of branched benzopyrazine-based polymers coating on graphene for electrochemical sensing of vanillin

Vanillin finds widespread applications in various industries, such as food, pharmaceuticals, and cosmetics. However, excessive intake of vanillin could pose risks to human health. This study detailed the successful creation of a heterojunction of branched benzopyrazine-based polymers coating on graphene (CMP-rGO) through the Sonogashira-Hagihara coupling reaction. Utilizing the CMP-rGO, a novel electrochemical sensor for vanillin detection was developed. Besides, the synthesized materials were validated using standard characterization techniques. Both cyclic voltammetry and differential pulse voltammetry techniques were employed to investigate vanillin's electrochemical characteristics on this sensor. The findings indicated a significant enhancement in vanillin's electrochemical signal responsiveness with the application of CMP-rGO. Under optimal conditions, the sensor demonstrated a linear response to vanillin concentrations ranging from 0.08 to 33 μM and achieved a detection limit as low as 0.014 μM. Also, the constructed electrochemical sensor exhibited excellent selectivity, stability, and reproducibility. It has been effectively employed to detect vanillin in real samples such as human serum, human urine, and vanillin tablets, with a recovery rate of 99.13-103.6 % and an RSD of 3.46-1.26 %. Overall, this innovative sensor offers a novel approach to the efficient and convenient detection of vanillin.

Electrochemiluminescence enhanced by molecular engineering linear π-conjugated polymer: An ingenious ECL emitter for the construction of exosome sensing platform

Linear π-conjugated polymers (LCPs) with π-electron conjugation system have many remarkable optical characteristics such as fluorescence and electrochemiluminescence (ECL). However, the extremely strong interchain interaction and π-π stacking limit the luminescence efficiency. In this work, 1H-1,2,4-triazole-3,5-diamine was chosen as the polymer monomer and reacted with terephthalaldehyde via simple Schiff base condensation to synthesize LCPs. Subsequently, molecular engineering strategy was adopted to construct zirconium-based LCPs (MLCPs), which not only prevented π-π stacking but also ensured that extended π-coupling was maintained in the LCPs, thus effectively promoting charge transport and achieving strong luminescence. Second, the coreactant polyethyleneimine (PEI) was assembled onto the MLCPs (MLCPs@PEI) to further promote the emission of ECL. To further explore the potential of the obtained MLCPs@PEI as emerging ECL emitter, colorectal cancer exosome was chosen as model biomarker, and an innovative ECL ratiometric system based on MLCPs@PEI and luminol was designed to improve the validity and accuracy of the sensors. This research provides a fresh nanoplatform for exosome detection and broadens the application of LCPs in ECL immunoassay.

One-Dimensional Covalent Organic Framework with Improved Charge Transfer for Enhanced Electrochemiluminescence

We present a dimensional regulating charge transfer strategy to achieve an enhanced electrochemiluminescence (ECL) by constructing a one-dimensional pyrene-based covalent organic framework (1D-COF). The dual-chain-like edge architecture in 1D-COF facilitates the stabilization of aromatic backbones, the enhancement of electronic conjugations, and the decrease of energy loss. The 1D-COF generates enhanced anodic (92.5-fold) and cathodic (3.2-fold) signals with tripropylamine (TPrA) and K2S2O8 as the anodic and cathodic coreactants, respectively, compared with 2D-COF. The anodic and cathodic ECL efficiencies of 1D-COF are 2.08- and 3.08-fold higher than those of 2D-COF, respectively. According to density functional theory (DFT), the rotational barrier energy (ΔE) of 1D-COF enhances sharply with the increase of dihedral angle, suggesting that the architecture in 1D-COF restrains the intramolecular spin of aromatic chains, which facilitates the decrease of nonradiative transitions and the enhancement of ECL. Furthermore, 1D-COF can be used to construct an ECL biosensor for sensitive detection of dopamine.

Synthesis of silica-encapsulated tetraphenylethylene with aggregation-induced electrochemiluminescence resonance energy transfer for sensitively sensing microcystin-LR

The reported organic electrochemiluminescence (ECL) luminophors for the detection of various markers often suffer from intermolecular π-π stacking-induced luminophore quenching. Herein, we demonstrate one-pot synthesis of a new aggregation-induced electrochemiluminescence (AIECL) emitter (i.e., TPE@SiO2/rGO composite) for sensitive measurement of microcystin-leucine arginine (MC-LR). The TPE@SiO2/rGO composite is constructed by embedding the silica-encapsuled 1,1,2,2-tetra(4-carboxylphenyl)ethylene (TPE) in the reduced graphene oxide. In comparison with the monomer TPE, this composite exhibit high luminescence efficiency and strong ECL emission, because the AIECL phenomenon triggered by the spatial confinement effect in the SiO2 cage induces the restriction of the internal motion and vibration of molecules. Notably, this composite has distinct advantages of easy preparation, simple functionalization, and stable luminescence. Especially, the TPE@SiO2/rGO-based ECL-RET system exhibits a high quenching efficiency (ΦET) of 69.7%. When target MC-LR is present, it triggers DNA strand displacement reaction (SDR), inducing the quenching of the ECL signal of TPE@SiO2/rGO composite due to ECL resonance energy transfer between TPE@SiO2/rGO composite and methylene blue (MB). The proposed biosensor enables highly sensitive, low-cost, and robust measurement of MC-LR with a large dynamic range of 7 orders of magnitude and a detection limit of 3.78 fg/mL, and it displays excellent detection performance in complex biological matrices, holding potential applications in food safety and water monitoring.

Self-Assembled Tetraphenylethene-Based Nanoaggregates with Tunable Electrochemiluminescence for the Ultrasensitive Detection of E. coli

As an effective ECL emitter, tetraphenylethene (TPE)-based molecules have recently been reported with aggregation-induced electrochemiluminescence (AIECL) property, while it is still a big challenge to control its aggregation states and obtain uniform aggregates with intense ECL emission. In this study, we develop three TPE derivatives carrying a pyridinium group, an alkyl chain, and a quaternary ammonium group via the Menschutkin reaction. The resulting molecules exhibit significantly red-shifted FL and enhanced ECL emissions due to the tunable reduction of the energy gap between the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs). More importantly, the amphiphilicity of the as-developed molecules enables their spontaneous self-assembly into well-controlled spherical nanoaggregates, and the ECL intensity of nanoaggregates with 3 -CH2- (named as C3) is 17.0-fold higher compared to that of the original 4-(4-(1,2,2-triphenylvinyl)phenyl)pyridine (TPP) molecule. These cationic nanoaggregates demonstrate a high affinity toward bacteria, and an ECL sensor for the profiling of Escherichia coli (E. coli) was developed with a broad linear range and good selectivity in the presence of an E. coli-specific aptamer. This study provides an effective way to enhance the ECL emission of TPE molecules through their derivatization and a simple way to prepare well-controlled AIECL nanoaggregates for ECL application.

Near-infrared II aggregation-induced electrochemiluminescence of organic dots

For the first time, we report novel aggregation-induced electrochemiluminescence (AIECL) of organic dots in aqueous media, with near-infrared II (NIR-II) luminescence peaked at 906 nm. Furthermore, a hybrid mechanism of ECL generation is revealed by various experiments in conjunction with theoretical calculations. This work opens a window for exploring efficient organic dye-based NIR-II AIECL emitters.

Electrochemiluminescence enhanced by isolating ACQphores in imine-linked covalent organic framework for organophosphorus pesticide assay

Most of covalent organic frameworks (COFs) are non or weakly emissive due to either the molecular thermal motion-mediated energy dissipation or the aggregation-caused quenching (ACQ) effect. Herein, we synthesize an imine-linked COF (TFPPy-TPh-COF) with high electrochemiluminescence (ECL) emission and the capability of eliminating the ACQ effect and further construct an ECL sensor for malathion detection. The imine-linked COF is obtained by the condensation reaction of (1,1':3',1″-terphenyl)-4,4″-diamine (TPh) and 1,3,6,8-tetrakis(p-formylphenyl)pyrene (TFPPy), and it has higher ECL efficiency than TFPPy aggregates due to the separation of ACQ luminophores (i.e., TFPPy) from each other by TPh and the restriction of intramolecular motions of TFPPy and TPh to reduce the nonradiative decay. The efficient quenching of ECL is achieved by electrochemiluminescence resonance energy transfer (ERET) from the excited state of the TFPPy-TPh-COF to zeolite imidazolate framework-8 (ZIF-8) and the steric hindrance of ZIF-8. Acetylcholinesterase (AChE) can enzymatically hydrolyze acetylcholine (ACh) to generate acetic acid. The resultant acetic acid can trigger the dissolution of ZIF-8 to produce an enhanced ECL signal. Malathion as an organophosphorus pesticide serves as an AChE inhibitor to prevent the production of acetic acid, inducing the decrease of ECL signal. This sensor displays a limit of detection (LOD) of 2.44 pg/mL and a wide dynamic detection range of 0.01-1000 ng/mL. Furthermore, it can be used to detect other organophosphates pesticides (e.g., methidathion, chlorpyrifos, and paraoxon) and measure malathion in real samples (i.e., pakchoi, lettuce, and apples).

Electrochemiluminescence Systems for the Detection of Biomarkers: Strategical and Technological Advances

Electrochemiluminescence (ECL)-based sensing systems rely on light emissions from luminophores, which are generated by high-energy electron transfer reactions between electrogenerated species on an electrode. ECL systems have been widely used in the detection and monitoring of diverse, disease-related biomarkers due to their high selectivity and fast response times, as well as their spatial and temporal control of luminance, high controllability, and a wide detection range. This review focuses on the recent strategic and technological advances in ECL-based biomarker detection systems. We introduce several sensing systems for medical applications that are classified according to the reactions that drive ECL signal emissions. We also provide recent examples of sensing strategies and technologies based on factors that enhance sensitivity and multiplexing abilities as well as simplify sensing procedures. This review also discusses the potential strategies and technologies for the development of ECL systems with an enhanced detection ability.

Construction of Ultrastable Conjugated Microporous Polymers Containing Thiophene and Fluorene for Metal Ion Sensing and Energy Storage

In this study, we have used the one-pot polycondensation method to prepare novel 2D conjugated microporous polymers (Th-F-CMP) containing thiophene (Th) and fluorene (Fl) moieties through the Suzuki cross-coupling reaction. The thermogravimetric analysis (TGA) data revealed that Th-F-CMP (T_d10 = 418 °C, char yield: 53 wt%). Based on BET analyses, the Th-F-CMP sample displayed a BET specific surface area of 30 m² g^-1, and the pore size was 2.61 nm. Next, to show the effectiveness of our study, we utilized Th-F-CMP as a fluorescence probe for the selective detection of Fe³⁺ ions at neutral pH with a linear range from 2.0 to 25.0 nM (R² = 0.9349). Furthermore, the electrochemical experimental studies showed that the Th-F-CMP framework had a superior specific capacity of 84.7 F g^-1 at a current density of 0.5 A g^-1 and outstanding capacitance retention (88%) over 2000 cycles.

Construction of an aggregation-induced electrochemiluminescent sensor based on an aminal-linked covalent organic framework for sensitive detection of glutathione in human serum

We demonstrate the construction of an aggregation-induced electrochemiluminescent (AIECL) sensor for glutathione (GSH) assay by integrating an aminal-linked covalent organic framework (A-COF) with manganese dioxide (MnO₂) nanosheets. The AIECL of the A-COF is quenched by the MnO₂ nanosheets via electrochemiluminescent resonance energy transfer (ERET) from the excited A-COF to MnO₂. The presence of GSH can reduce the MnO₂ nanosheets into Mn²⁺, restoring the AIECL emission of the A-COF. This AIECL sensor has the characteristics of fast response, high sensitivity, and good selectivity toward GSH, and it can accurately measure GSH in human serum.

Enhancing Built-in Electric Field via Molecular Dipole Control in Conjugated Microporous Polymers for Boosting Charge Separation

The built-in electric field (BEF) has been considered as the key kinetic factor for facilitating efficient photoinduced carrier separation and migration of polymeric photocatalysts. Enhancing the BEF of the polymers could enable a directional migration of the photogenerated carriers to accelerate photogenerated charge separation and thus boost photocatalytic performances. However, achieving this approach remains a formidable challenge, which has never been realized in conjugated microporous polymers (CMPs). Herein, we developed a molecular dipole control strategy to modulate the BEF in CMPs by varying the nature of the core. As a result, a series of CMPs with a tunable BEF were designed and prepared via FeCl₃-mediated coupling of bicarbazole with different acceptor cores. The optimized CbzCMP-9 featured the strongest BEF induced by its high molecular dipole, which grants it with a powerful driving force to accelerate exciton dissociation into electron-hole pairs and facilitates charge transfer along the backbone of CMPs to the surface, resulting in a remarkable photocatalytic performance toward thiocyano chromones and C-3 thiocyanation of indoles (up to 95 and 98% yields, respectively) and prominently surpassing many other reported photocatalysts. In brief, the proposed strategy highlights that enhancing the BEF by modulating molecular dipole can lead to a dramatic improvement in photocatalytic performance, which is expected to be employed for constructing other photocatalytic systems with high performance.

Electrochemiluminescent sensor based on an aggregation-induced emission probe for bioanalytical detection

In recent years, with the rapid development of electrochemiluminescence (ECL) sensors, more luminophores have been designed to achieve high-throughput and reliable analysis. Impressively, after the proposed fantastic concept of "aggregation-induced electrochemiluminescence (AIECL)" by Cola, the application of AIECL emitters provides more abundant choices for the further improvement of ECL sensors. In this review, we briefly report the phenomenon, principle and representative applications of aggregation-induced emission (AIE) and AIECL emitters. Moreover, it is noteworthy that the cases of AIECL sensors for bioanalytical detection are summarized in detail, from 2017 to now. Finally, inspired by the applications of AIECL emitters, relevant prospects and challenges for AIECL sensors are proposed, which is of great significance for exploring more advanced bioanalytical detection technology.

Hydrophobic Localized Enrichment of Co-reactants to Enhance Electrochemiluminescence of Conjugated Polymers for Detecting SARS-CoV-2 Nucleocapsid Proteins

The enrichment of co-reactants is one of the keys to improving the sensitivity of electrochemiluminescence (ECL) detection. This work developed a novel hydrophobic localized enrichment strategy of co-reactants utilizing the inner hydrophobic cavity of β-cyclodextrin (β-CD). Pt nanoparticles (Pt NPs) were grown in situ on the coordination sites for metal ions of β-CD to prepare the β-CD-Pt nanocomposite, which could not only enrich co-reactant 3-(dibutylamino) propylamine (TDBA) highly efficiently through its hydrophobic cavity but also immobilize TDBA via the Pt-N bond. Meanwhile, the carboxyl-functionalized poly[2,5-dioctyl-1,4-phenylene] (PDP) polymer nanoparticles (PNPs) were developed as excellent ECL luminophores. With SARS-CoV-2 nucleocapsid protein (ncovNP) as a model protein, the TDBA-β-CD-Pt nanocomposite combined PDP PNPs to construct a biosensor for ncovNP determination. The PDP PNPs were modified onto the surface of a glassy carbon electrode (GCE) to capture the first antibody (Ab1) and further capture antigen and secondary antibody complexes (TDBA-β-CD-Pt@Ab2). The resultant biosensor with a sandwich structure achieved a highly sensitive detection of ncovNP with a detection limit of 22 fg/mL. TDBA-β-CD-Pt shared with an inspiration in hydrophobic localized enrichment of co-reactants for improving the sensitivity of ECL detection. The luminophore PDP PNPs integrated TDBA-β-CD-Pt to provide a promising and sensitive ECL platform, offering a new method for ncovNP detection.

Covalent Organic Frameworks as Advanced Uranyl Electrochemiluminescence Monitoring Platforms

Electrochemiluminescence (ECL), as an advanced sensing process, can selectively control the generation of excited states by changing the potential. However, most of the existing ECL systems rely on poisonous coreactants to provide radicals for luminescence; although the ECL efficiency was improved, the athematic coreactants will cause unpredictable interference to the accurate analysis of trace targets. Herein, we realized the ECL of nonemitting molecules by performing intramolecular electron transfer in the olefin-linked covalent organic frameworks (COFs), with a high efficiency of 63.7%. Employing internal dissolved oxygen as the coreactant, it is well suitable for the analysis of various complex samples in the environment. Taking nuclear contamination analysis as the goal orientation, we further illustrated a design of a "turn-on" uranyl ion monitoring system integrating fast response, low detection limit, and high selectivity, showing that new ECL-COFs are promising to facilitate environment-related sensing analysis and structure-feature correlation mechanism exploration.