Electrochemiluminescence Enhancement Research Articles

Tetraphenylethene‐Based Multicomponent Platinum (II) Metallacages with Tunable Luminescence and Aggregation‐Induced Electrochemiluminescence Properties

AbstractMetallacages (MCs) are one kind of functional 3D supramolecular complexes with controllable structures, their special cage structures lead to diverse photophysical properties, enabling their wide application in catalysis, bio‐imaging, and organic light‐emitting devices. Herein, a series of tetraphenylene (TPE)‐based MCs with tunable structures is reported via the coordination‐driven self‐assembly strategy. The resulting MCs demonstrate tunable fluorescence (FL) and electrochemiluminescence (ECL) due to their size‐dependent energy gaps. More importantly, their aggregation‐induced ECL (AIECL) property is observed, and the corresponding self‐catalytic ECL enhancement mechanism is proposed. In addition, a sensitive ECL sensor toward iodide ions (I−) is developed based on the competitive coordination of I− with the pyridine group of ligands. This study may promote the design of MCs materials and broaden their applications in the ECL study.

Titelbild: Lewis‐Pairing‐Induced Electrochemiluminescence Enhancement from Electron Donor‐Acceptor Diads Decorated with Tris(pentafluorophenyl)borane as an Electrochemical Protector (Angew. Chem. 21/2023)

Elaborate metal-free electrochemiluminescence (ECL) systems require highly robust organic emitters in the radical form. In their Research Article (e202301109), Keishiro Tahara, Masaaki Abe, and co-workers used a classical Lewis acid B(C6F5)3 as an electrochemical protector of donor–acceptor emitters, leading to the discovery of Lewis pairing-induced ECL enhancement. The Lewis acid also converted the molecular arrangements of the emitters, playing a unique role in crystalline film ECL.

Cover Picture: Lewis‐Pairing‐Induced Electrochemiluminescence Enhancement from Electron Donor‐Acceptor Diads Decorated with Tris(pentafluorophenyl)borane as an Electrochemical Protector (Angew. Chem. Int. Ed. 21/2023)

Elaborate metal-free electrochemiluminescence (ECL) systems require highly robust organic emitters in the radical form. In their Research Article (e202301109), Keishiro Tahara, Masaaki Abe, and co-workers used a classical Lewis acid B(C6F5)3 as an electrochemical protector of donor–acceptor emitters, leading to the discovery of Lewis pairing-induced ECL enhancement. The Lewis acid also converted the molecular arrangements of the emitters, playing a unique role in crystalline film ECL.

Aggregation-Induced Enhancement Electrochemiluminescence of Ag Nanoribbons as a Signal Probe for Ultrasensitive Detection of the Halogenase Gene Segment from Aspergillus Ochratoxin.

Here, an electrochemiluminescence (ECL) biosensor was developed based on aggregation-induced enhancement ECL of Ag nanoribbons (Ag NRs) as a signal probe and the mismatched bases-fueled DNA walker as the amplification strategy for ultrasensitive detection of the halogenase gene segment (target) from aspergillus ochratoxin to evaluate fungi capable of producing ochratoxin in dairy products. Compared with the existing agminated NCs, the Ag NRs displayed dramatically enhanced ECL emission due to effective electron transfer and less energy dissipation of excited-state Ag NRs based on the metallophilic interaction of Ag(I)-Ag(I). Impressively, the target was conversed mismatched bases-DNA walker to trigger a significant ECL response through toehold-mediated strand displacement amplification. Thus, the strategy realized trace analysis of the halogenase gene segment with a detection limit of 45 aM, which ushered a new detection method for toxin determination in the previous stage of toxin biosynthesis to protect people from toxic damage.

Enhanced electrochemiluminescence immunoassay: 2. Enabling signal detection at an early stage of incubation for rapid point-of-care testing

Signal detection in a label-based immunoassay is performed normally when the antigen/antibody binding reaction reaches the equilibrium state during the incubation period of an assay process. Shortening the incubation period in an assay helps reduce the turnaround time and is particularly valuable for point-of-care testing, but the cost is the reduction of signal level and, possibly, measurement precision as well. This work demonstrates that the signal loss could be offset by the stronger emission of an electronically neutral ruthenium(II) complex label, Ru(2, 2′-bipyridine) (bathophenanthroline disulfonate)[4-(2, 2′-bipyridin-4-yl)butanoic acid], used in the electrochemiluminescence (ECL) immunoassay. Combined with the uniquely well-established flow-through washing process in the automated ECL analyzers and the precise control over liquid handling, the assays performed with a 5-minute incubation period showed the same signal level and measurement precision as those of conventional ECL assays. Additionally, the absence of biotin and streptavidin components in the reagent formulation avoids the biotin-streptavidin interaction during assay incubation and fundamentally eliminates the interference of biotin, especially when used in some high-dose therapies. The results obtained from the procalcitonin prototype kit and the supporting evidence from other preliminary reagents (for SARS-CoV-2 N protein and troponin T) are general. The nonequilibrium detection, along with the downsized instrument design, makes the enhanced ECL (EECL) technology a fast high-performance POCT platform that provides the same high-quality data as those generated from the widely deployed [Ru(bpy)3]2+based laboratorial ECL systems.The anticipated regulatory approval and follow-up clinical implementation will beasignificant stride in the decade-long pursuit of novel ECL labels.

Lewis-Pairing-Induced Electrochemiluminescence Enhancement from Electron Donor-Acceptor Diads Decorated with Tris(pentafluorophenyl)borane as an Electrochemical Protector.

This study reports an effective peripheral decoration of organic donor-acceptor diads with B(C6 F5 )3 for stabilizing electrogenerated radical ions. By employing a common p-type organic semiconductor benzothienobenzothiophene (BTBT) as the donor, tetracoordinate boron complexes showed improved solution electrochemiluminescence (ECL) intensity, reaching a 156-fold increase compared to that of the parent diad. The unprecedented Lewis-pairing-induced ECL enhancement is attributed to the multiple roles of B(C6 F5 )3 : 1) redistributing frontier orbitals, 2) facilitating electrochemical excitation, and 3) restricting molecular motions. Furthermore, B(C6 F5 )3 converted the molecular arrangement of BTBT from conventional 2D herringbones into 1D π-stacks. This robust, highly ordered columnar nanostructure allowed red-shifting of the crystalline film ECL with electrochemical doping through the electronic coupling pathways of BTBT. Our approach will facilitate the development of elaborate metal-free ECL systems.

Lewis‐Pairing‐Induced Electrochemiluminescence Enhancement from Electron Donor‐Acceptor Diads Decorated with Tris(pentafluorophenyl)borane as an Electrochemical Protector

AbstractThis study reports an effective peripheral decoration of organic donor‐acceptor diads with B(C6F5)3 for stabilizing electrogenerated radical ions. By employing a common p‐type organic semiconductor benzothienobenzothiophene (BTBT) as the donor, tetracoordinate boron complexes showed improved solution electrochemiluminescence (ECL) intensity, reaching a 156‐fold increase compared to that of the parent diad. The unprecedented Lewis‐pairing‐induced ECL enhancement is attributed to the multiple roles of B(C6F5)3: 1) redistributing frontier orbitals, 2) facilitating electrochemical excitation, and 3) restricting molecular motions. Furthermore, B(C6F5)3 converted the molecular arrangement of BTBT from conventional 2D herringbones into 1D π‐stacks. This robust, highly ordered columnar nanostructure allowed red‐shifting of the crystalline film ECL with electrochemical doping through the electronic coupling pathways of BTBT. Our approach will facilitate the development of elaborate metal‐free ECL systems.

Zn2+-Modified Nonmetal Porphyrin-Based Metal–Organic Frameworks with Improved Electrochemiluminescence for Nanoscale Exosome Detection

Exploring effective and robust strategies for enhancing electrochemiluminescence (ECL) emissions of porphyrin-based metal–organic frameworks (MOFs) is of great importance for expanding their applications in bioassays. Herein, a simple, convenient, and effective endogenous strategy of post-synthesis-modified Zn2+ was proposed to enhance ECL of nonmetal porphyrin-based MOFs. The ECL emissions of porphyrin-cobuilt UiO-66-NH2 (TCPP/UiO-66-NH2), PCN-224, PCN-222, and Ce–TCPP–LMOF could be enhanced 31.9, 47.1, 49.9, and 19.2 times, respectively. By studying TCPP/UiO-66-NH2 nanoluminophores as a model, Zn2+ was incorporated into TCPP/UiO-66-NH2 through the coordination of Zn and pyrrolic N of TCPP. The ECL enhancement was attributed to the conversion of TCPP to ZnTCPP with high emission efficiency and MOFs could enrich co-reactants, shorten the ion/electron-transfer distance, and render electrochemical activation of porphyrin luminophores. On this basis, a simple ECL biosensor for detecting nanoscale exosomes was developed based on the boosted ECL signal of Zn–TCPP/UiO-66-NH2 nanoluminophores without additional recognition and amplification elements. The ECL biosensor exhibited good sensitivity with a detection range from 1.00 × 104 to 3.16 × 106 particles/μL and a detection limit of 9.08 × 103 particles/μL (S/N = 3). The linear range and detection limit of the proposed label-free ECL biosensor are better than most of the existing label-free methods for detecting exosomes, indicating its good performance as a powerful tool for accurate and sensitive detection of HepG2-derived exosomes. As a result, this work provides inspiration for exploring strategies to enhance ECL efficiencies of porphyrin-based MOFs, which has important application prospects in sensitive bioassays.

Enhancing electrochemiluminescence by assembling ACQ ligands into Hf-based metal-organic framework nanosheet: A novel ECL emitter for fabricating ultrasensitive biosensor

Polycyclic aromatic hydrocarbons (PAHs) are classic electrochemiluminescence (ECL) materials. However, the ECL performance of PAHs aggregates in water phase is limited owing to the aggregation-induced quenching (ACQ) effect of PAHs. To surmount this shortcoming, we proposed an innovative strategy for enhancing the ECL performance by assembling PAH derivative ligands into metal-organic framework nanosheets (MONs), which can separate ACQphores to eliminate the ACQ effect. Gratifyingly, the ECL intensity of Hf-DEADB MON (DEADB = 4,4′-(diethylanthracene-9,10-diyl)dibenzoate) prepared according to the strategy was 5.71-fold higher than that of H2DEADB aggregates. This improvement occurred not only because the distance between the ACQphores in the Hf-DEADB MON was enlarged to surmount the ACQ effect but also because the ultrathin porous Hf-DEADB MON could shorten the diffusion pathways of ion/electron and co-reactant, which boosted electrochemical activation of DEADB luminophores. Given the prominent ECL performance of Hf-DEADB MON, it was used to fabricate a hypersensitive biosensor for detecting microRNA-21, displaying a broad response range (100 aM–10 nM) with an ultralow detection limit (24 aM). Overall, our work developed a promising strategy to eradicate the ACQ effect of PAHs for ECL enhancement, thus pointing out a new direction to design high-efficient ECL materials for constructing ultrasensitive ECL sensors.

Ruthenium(II) complex-grafted conductive metal-organic frameworks with conductivity- and confinement-enhanced electrochemiluminescence for ultrasensitive biosensing application

Improving the electrochemiluminescence (ECL) performance of luminophores is an ongoing research hotspot in the ECL realm. Herein, a high-performance metal-organic framework (MOF)-based ECL material (Ru@Ni3(HITP)2, HITP = 2,3,6,7,10,11-hexaiminotriphenylene) with conductivity- and confinement-enhanced ECL was successfully constructed by using conductive MOF Ni3(HITP)2 as the carrier to graft Ru(bpydc)34- (H2bpydc = 2,2′-bipyridine-4,4′-dicarboxylic acid) into the channels of Ni3(HITP)2. Compared to Ru@Cu3(HITP)2 and Ru@Co3(HITP)2 with relatively low conductivity, the ECL intensity of Ru@Ni3(HITP)2 was prominently increased about 6.76 times and 18.8 times, respectively, which demonstrated that the increase in conductivity induced the ECL enhancement of the MOF-based ECL materials. What's more, the hydrophobic and porous Ni3(HITP)2 can not only effectively enrich the lipophilic tripropylamine (TPrA) coreactants in its channels to enhance the electrochemical oxidation efficiency of TPrA, but also provide a conductive reaction micro-environment to boost the ECL reaction between Ru(bpydc)33- intermediates and TPrA• in confined spaces, thus realizing a remarkable confinement-enhanced ECL. Considering the excellent ECL performance of Ru@Ni3(HITP)2, an ultrasensitive ECL biosensor was prepared based on the Ru@Ni3(HITP)2 ECL indicator combining an exonuclease I-aided target cycling amplification strategy for thrombin determination. The constructed ECL biosensor showcased a wide linear range from 1 fM to 1 nM with a low detection limit of 0.62 fM. Overall, the conductivity- and confinement-enhanced ECL based on Ru@Ni3(HITP)2 provided effective and feasible strategies to enhance ECL performance, which paved a promising avenue for exploring high-efficient MOF-based ECL materials and thus broadened the application scope of conductive MOFs.

Recent Progress in Plasmonic based Electrochemiluminescence Biosensors: A Review

Electrochemiluminescence (ECL) analysis has become a powerful tool in recent biomarker detection and clinic diagnosis due to its high sensitivity and broad linear range. To improve the analytical performance of ECL biosensors, various advanced nanomaterials have been introduced to regulate the ECL signal such as graphene, gold nanomaterials, and quantum dots. Among these nanomaterials, some plasmonic nanostructures play important roles in the fabrication of ECL biosensors. The plasmon effect for the ECL signal includes ECL quenching by resonant energy transfer, ECL enhancement by surface plasmon resonance enhancement, and a change in the polarized angle of ECL emission. The influence can be regulated by the distance between ECL emitters and plasmonic materials, and the characteristics of polarization angle-dependent surface plasmon coupling. This paper outlines the recent advances of plasmonic based ECL biosensors involving various plasmonic materials including noble metals and semiconductor nanomaterials. The detection targets in these biosensors range from small molecules, proteins, nucleic acids, and cells thanks to the plasmonic effect. In addition to ECL biosensors, ECL microscopy analysis with plasmonic materials is also highlighted because of the enhanced ECL image quality by the plasmonic effect. Finally, the future opportunities and challenges are discussed if more plasmonic effects are introduced into the ECL realm.

Paper-based electrodes with nitrogen-doped graphene quantum dots for detection of copper ions via electrochemiluminescence

Nitrogen-doped graphene quantum dots (N-GQDs) were prepared using pyrolysis, with citric acid and urea as the carbon and nitrogen sources, respectively, to be used for Cu2+ ion detection in a paper-based ECL sensor. Existing methods for Cu2+ detection require expensive equipment, specialized experimental chambers, or complex sample pretreatment procedures, which limit their functionality. Using first principles, the electronic and optical properties of graphene quantum dots (GQDs) and N-GQDs were calculated and analyzed. The N-GQDs showed clearer green fluorescence under long-wave ultraviolet light and a better, more stable electrochemiluminescence (ECL) performance. Using first principles, the electronic and optical properties of the GQDs and N-GQDs were calculated and analyzed, and A theoretical mechanism for the observed ECL enhancement in the N-GQDs was proposed. A paper-based ECL sensor with N-GQDs was then developed, using a screen-printing technique, to detect Cu2+ ions. The results showed that the ECL intensity of the sensor increased as the Cu2+ ion concentration increased, and the sensor demonstrated a linear detection range of 0.01–1000 μM. Overall, the sensor exhibited excellent ECL stability, reproducibility, and selectivity. This simple, inexpensive, and effective monitoring technique can be used to detect Cu2+ to prevent negative effects on human health and the environment.

Performance Enhancement of Electrochemiluminescence with the Immunosensor Controlled Using Magnetized Masks for the Determination of Epithelial Cancer Biomarker EpCAM.

The performance of an electrochemiluminescence (ECL) immunosensor was improved with a particle gradient. SiO2-coated magnetic beads were adopted as nanocarriers for gradient manipulation and immobilized with the primary antibody. Cadmium telluride quantum dots were coated with a layer of protein G for conjugation and orientation of the secondary antibody as signal labels. ECL immunosensor gradients on the electrode were formed by magnetolithography (ML) with magnetized nickel masks of column and stripe arrays. The immunosensor generally aggregated as an island on the substrate, leading to a decrease of efficiency in the characteristic signals. Stripe arrays of magnetized nickel were designed to generate cylindrical magnetic flux on the substrate to improve the particle manipulation with the gradient. Various gradients of the sandwich-structured immunosensor substantially affected the electrochemical performance. Compared to the gradient-free immunosensor, the gradient of the immunosensor generated by ML using a 3 μm stripe array mask enhanced the ECL intensity ∼2.2 times. The results of quantification of epithelial cell adhesion molecules (EpCAM) with the gradient immunosensor showed a broad linear range (15-420 pg mL-1), a low limit of detection (5.5 pg mL-1), and high reliability for EpCAM-spiked serum samples, indicating that the immunosensor gradient substantially enhances the performance of the ECL assay.

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.

Charge-Dependent Signal Changes for Label-Free Electrochemiluminescence Immunoassays.

Label-free electrochemiluminescence (ECL) immunoassays (lf-ECLIA), based on biomarker-induced ECL signal changes, have attracted increasing attention due to the simple, rapid, and low-cost detection of biomarkers without secondary antibodies and complicated labeling procedures. However, the interaction rule and mechanism between analytical interfaces and biomarkers have rarely been explored. Herein, the interactions between biomarkers and analytical interfaces constructed by assembly of a nanoluminophore and antibody-functionalized gold nanoparticles on an indium tin oxide electrode were studied. The nanoluminophore was synthesized by mixing Cu2+/l-cysteine chelate and N-(4-Aminobutyl)-N-ethylisoluminol-bifunctionalized gold nanoparticles with chitosan. It was found that positively charged biomarkers increased the ECL intensity, whereas negatively charged biomarkers decreased the ECL intensity. The assembly pH influenced the biomarker charges, which determined the ECL enhancement or inhibition. The detection pH only affected the ECL intensity but not the ECL changing trends. Based on the ECL signal changes, a charge-dependent lf-ECLIA was established, which exhibited inhibition responses to negatively charged human immunoglobulin G and copeptin and enhancement responses to positively charged cardiac troponin I, heart-type fatty acid binding protein, brain natriuretic peptide, and SARS-CoV-2 N protein. The linear range was 0.1-1000 pg/mL, and the detection limits were distributed in 0.024-0.091 pg/mL. Besides, a mechanism of the charge-dependent ECL enhancement and inhibition effects is proposed, which is very important for the development of new lf-ECLIA methodologies.

Pyrene-Based Hydrogen-Bonded Organic Frameworks as New Emitters with Porosity- and Aggregation-Induced Enhanced Electrochemiluminescence for Ultrasensitive MicroRNA Assay.

Exploring new electrochemiluminescence (ECL) luminophores with strong ECL emission is highly desirable for developing ultrasensitive ECL sensors. Herein, a pyrene-based hydrogen-bonded organic framework (Py-HOF) featuring prominent ECL performance was prepared by utilizing 1,3,6,8-tetrakis(p-benzoic acid) pyrene (H4TBAPy) with an aggregation-induced enhanced emission (AIEE) property as a building block, exhibiting a stronger ECL emission than those of H4TBAPy monomers, H4TBAPy aggregates, the low-porosity Py-HOF-210 °C and Py-HOF-180 °C. We have coined the term "the porosity- and aggregation-induced enhanced ECL (PAIE-ECL)" for this intriguing phenomenon. The Py-HOF displayed superb and stable ECL intensity, not only because the luminophore H4TBAPy was assembled into the Py-HOF via four pairs of O-H···O hydrogen bonds, which constrained the intramolecular movements to reduce nonradiative transition, but also because the H4TBAPy in Py-HOF was stacked in a slipped face-to-face mode to form J-aggregates that benefited the ECL enhancement. Furthermore, the high porosity of Py-HOF allowed the enrichment of coreactants and facilitated the migration of ions, electrons, and coreactants, which made it possible for the inner and outer H4TBAPy to be electrochemically excited. Considering the remarkable ECL performance, Py-HOF was first employed as an ECL probe combined with a 3D DNA nanomachine amplification strategy to assemble a hypersensitive "on-off" ECL sensor for the microRNA-141 assay, presenting a satisfactory linear range (100 aM to 1 nM) with a detection limit of 14.4 aM. The PAIE-ECL manifested by Py-HOF provided a bright avenue for the design and synthesis of outstanding HOF-based ECL materials and offered new opportunities for the development of ECL biosensors with excellent sensitivity.

Electrochemistry and electrochemiluminescence of resorufin dye: Synergetic reductive-oxidation boosted by hydrogen peroxide

To develop robust field diagnostic systems capable of responding to medical needs, miniaturization of devices and high target sensitivity remain significant challenges. Electrochemiluminescence (ECL) is an ideal analysis tool to meet these challenges, and developing novel ECL materials is essential. Here we report the reversible electrochemical properties of resorufin, a commercial fluorescent dye, and its highly stable cathodic ECL. We find the cathodic ECL emission from the resorufin quantitatively changes upon the H2O2 content and propose the selective ECL molecular sensor against it. Resorufin undergoes reversible two-electron-transfer electrochemical reduction, and it generates cathodic ECL via a reductive-oxidation pathway with the S2O82− co-reactant. Interestingly, highly enhanced, synergetic ECL is produced in the dual K2S2O8–H2O2 co-reactant system, and especially, it can be used for selective molecular recognition of H2O2. Via the chronoamperometric application, the resorufin ECL signal reveals the linear correlation with the H2O2 concentration range of 0–150 µM with a detection limit of 6.8 µM. Resorufin exhibits strong potential as a new ECL luminophore. Also, selective enhancement of ECL suggests potential applicability to various immunoassays using H2O2.

Tuned-Potential Covalent organic framework Electrochemiluminescence platform for lutetium analysis

Mechanism diagram. Through the structural design at the molecular level, the ECL-COF with electrocatalytic performance and excellent electronic structure was obtained, which display an adjustable easily potential ECL platform. Meanwhile, the advanced COF’ECL platform was developed for accurate monitoring of Lu 3+ , indicating the inestimable application potential of COFs in environment field. • The azine-linked COFs are prepared for precise ECL performance regulation. • COFs display decrease of reduction potential and increase of intensity in ECL. • Introducing nitrogen into COFs bring electrocatalysis for ECL enhancement. • COFs show efficiently carrier transport for improving ECL. • A novel COF-ECL platform is structured for Lu 3+ detection. Covalent organic frameworks (COFs) have emerged as a novel class of electrochemiluminescence (ECL) materials on account of its highly tunable structure and versatile properties. However, decoding the ECL property and its luminophor structure to improve the luminous performance remains challenging, which hinders its deeper development and wider application. Herein, by condensing triphenylarene aldehydes with varying number of nitrogen atoms with 2,4,6-trimethylbenzene-1,3,5-tricarbonitrile, a series of COFs were prepared to regulate the ECL potential, opening up a new way to precisely improve ECL performance. The electron and spatial changes in the precursor are transferred to the generated COFs skeleton, resulting in a progressively decrease in the reduction potential and a gradual increase intensity in ECL with the precise increase of nitrogen content in the skeleton. Introduction of nitrogen into COFs brings electrocatalysis and planarization of the framework for more efficiently carrier transport. The conclusion is confirmed by optical, electrical tests, as well as density functional theory calculations. As a proof-of-methodology, an ECL method was developed for the selective determination of lutetium ion with a detection limit as low as 1.6 nM (S/N = 3). This work exhibits that the advanced potential-tunable ECL-COFs can be obtained accurately and easily through design structure at the molecular level, which is expected to promote the exploration of the relationship between ECL potential and framework structure, and further apply to environment-related sensing analysis.

Insights into the electrochemiluminescence process of a hydrogen bonding iridium(III) complex

• An Ir III complex ( 1 ) and pyrimido-[4,5-c]isoquinolin-3-amine ( 3 )complex 1•3 based on the hydrogen-bonding interaction was investigated. • It was discovered that the complex 1•3 displayed a new reduction upon the mixture of 1 and 3 . • The hydrogen-bonding complex 1•3 demonstrated an ECL enhancement. • Our report provides insights into the ECL processes of this hydrogen-bonding complex. Hydrogen-bonding has been reported as a smart strategy in electrochemiluminescence (ECL) mechanism studies and sensing applications. However, the insights into the hydrogen-bonding effect on ECL behavior have never been clearly demonstrated. This work reports ECL of complex 1•3 based on the hydrogen-bonding interaction between an Ir III complex ( 1 ) and pyrimido-[4,5-c]isoquinolin-3-amine ( 3 ). In their cyclic voltammograms (CVs), both complex 1 and compound 3 did not show any reductions; however, the hydrogen-bonding complex 1•3 displayed a new reduction upon the mixture of 1 and 3 , which could be significantly weakened by the addition of DMF. In a co-reactant ECL pathway with BPO, exciplex [PhCO 2 •1] and excimer [3•3] were produced, which were demonstrated by PL and ECL spectroscopies. Furthermore, benzoate radical PhCO 2 could also react with the hydrogen-bonding complex 1•3 to form [PhCO 2 •1•3] and generate the same ECL emission as [PhCO 2 -1] . Our report provides insights into the ECL processes of this hydrogen-bonding complex.

Shell-Isolated Nanoparticle-Enhanced Electrochemiluminescence.

Enhanced electrochemiluminescence (ECL) aims to promote higher sensitivity and obtain better detection limit. The core-shell nanostructures, owing to unique surface plasmon resonance (SPR) enabling distance-dependent strong localized electromagnetic field, have attracted rising attention in enhanced ECL research and application. However, the present structures usually with porous shell involve electrocatalytic activity from the metal core and adsorption effect from the shell, which interfere with practical SPR enhancement contribution to ECL signal. Herein, to exclude the interference and unveil exact SPR-enhanced effect, shell-isolated nanoparticles (SHINs) whose shell gets thicker and becomes pinhole-free are developed by modifying pH value and particles concentration. Furthermore, allowing for the distribution of hotspots and stronger enhancement, excitation intensity and ECL reaction layer thickness are mainly investigated, and several types of SHINs-enhanced ECL platforms are prepared to fabricate distinct hotspot distribution via electrostatic attraction (submonolayer) and a layer-by-layer deposition method (monolayer). Consequently, the strongest enhancement up to ≈250-fold is achieved by monolayer SHINs with 10nm shell, and the platform is applied in a "turn-off" mode sensing for dopamine. The platform provides new guidelines to shell preparation, interface engineering and hotspots fabrication for superior ECL enhancement and analytical application with high performance.