Aromaticity-Enhanced pH-Responsive Electrochemiluminescence of Cyclopentadienols

Artemisinin: a novel chiral electrochemiluminescence luminophore-assisted enantiospecific recognition and mechanism identification

Exploring novel electrochemiluminescence (ECL) molecules with high efficiency and good stability in aqueous solutions is crucial for achieving highly sensitive detection of analytes. However, developing chiral luminophores with efficient ECL performance is still a challenge. Herein, we first uncover that artemisinin (ART), a well-known chiral antimalarial drug, features a strong ECL emission at 726 nm with the assistance of a co-reactant potassium persulfate (K2S2O8), and an ECL efficiency of 195.3%, compared to that of standard Ru(bpy)3Cl2/K2S2O8. Mechanistic studies indicate that the strong ECL signal of ART is generated when the excited state formed by the reduction of ART peroxide bonds and combination with persulfate returns to the ground state. Significantly, we found that the ECL sensor based on chiral ART could efficiently identify and detect chiral cysteine (Cys) through ECL signals, with a lower limit of detection of 3.7 nM for l-Cys. Density functional theory calculations and scanning electrochemical microscopy technology further confirm that the disparity in the ECL signals is attributed to the different affinity between chiral ART and d/l-Cys, resulting in distinct electron transfer rates. The study demonstrates a new role of ART in ECL investigation and for the first time, achieves the development of ART for the enantioselective recognition and sensitive detection of chiral substances. This will be of vital significance for ECL and chirality research.

A novel and efficient electrochemiluminescence sensing strategy for the determination of trimethylamine oxide in seafood

A novel and efficient electrochemiluminescence (ECL) sensing strategy and a solid-state ECL sensor was proposed to detect trimethylamine oxide (TMAO), which is widely presented in marine species and has important physiological functions. TMAO was reduced by Fe(II)-EDTA complex to trimethylamine, acting as coreactant, to amplify the ECL response of the Ru (bpy)32+ system. To improve the detection sensitivity and efficiency, a robust solid-state ECL probe was prepared and a flow injection ECL detection system was established with a specially designed flow ECL unit, under the excitation of stepping pulse potentials. Under optimized experimental conditions, the developed ECL sensor worked well for TMAO detection in a wide linear range of 10.00 μM to 1.00 mM with a limit of detection of 3.41 μM. It was successfully applied to determine TMAO in various species of seafood samples. This work provides a promising strategy for TMAO detection.

Dual-Signal Integrated Aptasensor for Microcystin-LR Detection via In Situ Generation of Silver Nanoclusters Induced by Circular DNA Strand Displacement Reactions

Inspired by the signal accumulation of circular DNA strand displacement reactions (CD-SDRs) and the in situ generation of silver nanoclusters (AgNCs) from signature template sequences, a dual-signal integrated aptasensor was designed for microcystin-LR (MC-LR) detection. The aptamer was programmed to be included in an enzyme-free CD-SDR, which utilized MC-LR as the primer and outputted the H1/H2 dsDNA in a continuous manner according to the ideal state. Ingeniously, H1/H2 dsDNA was enriched with signature template sequences, allowing in situ generation of AgNCs signal probes. To enhance the signal amplification performance, co-reaction acceleration strategies and CRISPR-Cas12a nucleases were invoked. The H1/H2 dsDNA could trigger the incidental cleavage performance of CRISPR-Cas12a nucleases: cis-cleavage reduced signature template sequences for the synthetic AgNCs, while trans-cleavage enabled fluorescence (FL) analysis. Meanwhile, AuPtAg was selected as the substrate material to facilitate the S2O82- reduction reaction for enhancing the electrochemiluminescence (ECL) basal signals. ECL and FL detection do not interfere with each other and have improved accuracy and sensitivity, with limits of detection of 0.011 and 0.023 pmol/L, respectively. This widens the path for designing dual-mode sensing strategies for signal amplification.

Advances in electrochemiluminescence luminophores based on small organic molecules for biosensing

Electrochemiluminescence (ECL) has several advantages, such as a near-zero background signal, high sensitivity, wide dynamic range, simplicity, and is widely used for sensing, imaging, and single cell analysis. ECL luminophores are the key factors in the performance of various applications. Among various luminophores, small organic luminophores exhibit many intriguing features including good biocompatibility, facile modification, well-defined molecular structure, and sustainable raw materials, making small organic luminophores attractive for the use in the ECL field. Although many great achievements have been made in the synthesis of new small organic luminophores, solving various challenges, and expanding new applications, there are almost no comprehensive reviews on small organic ECL luminophores. In this review, we briefly introduce the advantages and emission mechanisms of small organic ECL luminophores, summarize the main types, molecular characteristics, and ECL properties of most existing small organic ECL luminophores, and present the important applications and design principles in sensors, imaging, single cell analysis, sterilization, and other fields. Finally, the challenges and outlook of organic ECL luminophores to be popularized in biosensing applications are also discussed.

Studies on Annihilation and Coreactant Electrochemiluminescence of Thermally Activated Delayed Fluorescent Molecules in Organic Medium

Very recently, there is a great research interest in electrochemiluminescence (ECL) featuring thermally activated delayed fluorescence (TADF) properties, i.e., TADF-ECL. It is appealing since the earlier reports in this topic well-confirmed that this strategy has a great potential in achieving all-exciton-harvesting ECL efficiency under electrochemical excitation, which is a breakthrough in the topic of organic ECL. However, organic phase electrochemistry and ECL studies surrounding TADF-ECL are still extremely rare. Especially, the ECL spectra of previous reported TADF emitters are still very different from their PL spectra. In this work, we systematically measure and discuss the liquid electrochemistry and ECL behavior of two typical TADF molecules in organic medium. Most importantly, we verify for the first time that the ECL spectra of them (coreactant ECL mode) are identical to their PL spectra counterparts, which confirms the effectiveness of TADF photophysical properties in the coreactant ECL mode in practice.

Rigid Enhanced Electrochemiluminescence of 1,2,3-Triaryl Indenes as an Ultrasensitive Sensor for D2O in H2O

The intriguing aggregation-induced emission has recently been applied in the electrochemiluminescence, called aggregation-induced electrochemiluminescence (AIE-ECL), which is conducive to solving the water insolubility and aggregation-caused quenching for most organic luminescence probes. However, AIE-ECL still has the problems of low luminous efficiency and limited practical application. In this work, we disclosed the AIE-ECL properties of 1,2,3-triaryl-substituted indenes containing rigid structures. Experimental and theoretical investigations demonstrated that such a rigid structure could significantly enhance the aromaticity and stability and thereby the luminescence performance of these indenes. Moreover, according to the finding of hydrogen/deuterium exchange for active hydrogen in indene under electrical excitation, ultrasensitive detection for D₂O in H₂O was realized by such an indene-based AIE-ECL system. Our research not only provided an attractive strategy to enhance the luminescence property for an AIE-active luminophore but also established a superior sensor toward D₂O.