2-(Dibutylamino)ethyl acrylate as a highly efficient co-reactant of Ru(bpy)32+ electrochemiluminescence for selective detection of cysteine

Confinement-enhanced electrochemiluminescence by Ru(dcbpy)32+-functionalized γ-CD-MOF@COF-LZU1 porous hybrid material as micro-reactor for CYFRA 21-1 detection

The improvement of electrochemiluminescence (ECL) performance relies on the electron transfer efficiency between luminophore and coreactant. An ultrasensitive ECL micro-reactor with confinement-enhanced performance was prepared by using the covalent organic framework-LZU1-functionalized metal-organic framework (MOF@COF-LZU1) as a platform to assemble enormous N,N-dibutyl-2-hydroxyethylamine (DBAE) and tris(4,4'-dicarboxylic acid-2,2'-bipyridyl) ruthenium(II) [Ru(dcbpy)32+] into its pore channels. Compared to individual substances of γ-CD-MOF and COF-LZU1, the synergistic effects can conduce to the enhancement of the intensity, durability and sensitivity of the micro-reactor. Besides, COF-LZU1 can provide a mild environment to accommodate a certain amount of DBAE by concentrating them from the aqueous solution into its hydrophobic cavities and boost the oxidation efficiency of DBAE to generate more DBAE●+ and profited the survival of DBAE●, leading to an improved reaction efficiency with the Ru(dcbpy)32+ intermediate. Thanks to the confinement-enhanced strategy, engineered as high-functioning luminescent materials, Ru@γ-CD-MOF@COF-LZU1 micro-reactors decorated with Au NPs can facilitate electron transfer and capture primary antibodies (Ab1). Moreover, Au-Pd-Pt noble metal aerogels (NMAs) functionalized MoS2 NFs (Au-Pd-Pt NMAs@MoS2 NFs) were chosen as base material due to its large specific surface areas, high porosity, and excellent electrical conductivity. Based on above merits, the sensor demonstrated a sensitive response to CYFRA 21-1 detection in a linear concentration gradient from 10 fg/mL to 50 ng/mL with a detection limit of 0.0055 pg/mL (S/N = 3). The COF-LZU1 decorated ECL micro-reactors were constructed based on the signal amplification strategies to realize accurate CYFRA 21-1 detection.

Precise Modulation of Intramolecular Aggregation-induced Electrochemiluminescence by Tetraphenylethylene-based Supramolecular Architectures

The precisely modulated synthesis of programmable light-emitting materials remains a challenge. To address this challenge, we construct four tetraphenylethylene-based supramolecular architectures (SA, SB, SC, and SD), revealing that they exhibit higher electrochemiluminescence (ECL) intensities and efficiencies than the tetraphenylethylene monomer and can be classified as highly efficient and precisely modulated intramolecular aggregation-induced electrochemiluminescence (PI-AIECL) systems. The best-performing system (SD) shows a high ECL cathodic efficiency exceeding that of the benchmark tris(2,2'-bipyridyl)ruthenium(II) chloride in aqueous solution by nearly six-fold. The electrochemical characterization of these architectures in an organic solvent provides deeper mechanistic insights, revealing that SD features the lowest electrochemical band gap. Density functional theory calculations indicate that the band gap of the guest ligand in the SD structure is the smallest and most closely matched to that of the host scaffold. Finally, the SD system is used to realize ECL-based cysteine detection (detection limit=14.4 nM) in real samples. Thus, this study not only provides a precisely modulated supramolecular strategy allowing chromophores to be controllably regulated on a molecular scale, but also inspires the programmable synthesis of high-performance aggregation-induced electrochemiluminescence emitters.

A photoluminescent and electrochemiluminescent probe based on an iridium(III) complex with a boronic acid-functionalised ancillary ligand for the selective detection of mercury(II) ions

Exposure to mercury(II) ions (Hg2+) can cause various diseases such as Minamata disease, acrodynia, Alzheimer's disease, and Hunter-Russell syndrome, and even organ damage. Therefore, real-time and accurate monitoring of Hg2+ in environmental samples is crucial. In this study, we report a photoluminescent (PL) and electrochemiluminescent (ECL) probe based on a cyclometalated Ir(III) complex for the selective detection of Hg2+. The introduction of a reaction site, o-aminomethylphenylboronic acid, on the ancillary ligands allowed a prompt transmetalation reaction to take place between Hg2+ and boronic acid. This reaction resulted in significant decreases of the PL and ECL signals due to the photo-induced electron transfer from the Ir(III) complex to the Hg2+ ions. The probe was applied to the selective detection of Hg2+, and the signal changes revealed a linear correlation with Hg2+ concentrations in the range of 0-10 μM (LOD = 0.72 μM for PL, 8.03 nM for ECL). The designed probe allowed the successful quantification of Hg2+ in tap water samples, which proves its potential for the selective detection of Hg2+ in environmental samples.

Signal "On-Amplified-Off" Strategy Based on Hafnium Dioxide Nanomaterials as Electrochemiluminescence Emitters for Progesterone Detection

When consumed, excess progesterone (P4)─found in food and the environment─can lead to severe illnesses in humans. Therefore, quantitative analysis of P4 is critical for identifying its hazardous levels. In this study, a novel signal "on-amplified-off" P4 detection mode was proposed, which was based on the utilization of hafnium oxide (HfO2) as a unique electrochemiluminescence (ECL) emitter, produced by calcining UiO-66(Hf). This is the first time that HfO2 has been used as an ECL emitter. HfO2 displayed excellent conductivity and a high specific surface area, allowing it to connect with numerous aptamers and produce a "signal-on" effect. Ni-doped ZnO (Ni-ZnO) acted as a coreaction accelerator, enhancing the ECL strength of HfO2 by generating more tripropylamine radicals. cDNA was labeled with Ni-ZnO, and Ni-ZnO was linked to the aptamer via base complementary pairing, affording "signal-amplified". The presence of the target molecule P4 instigated a specific binding process with the aptamer, triggering the shedding of cDNA-Ni-ZnO and resulting in "signal-off". This novel "on-amplified-off" strategy effectively improved the sensitivity and specificity of P4 analysis, introducing a practical method for detecting biomolecules beyond the scope of this study, which holds immense potential for future applications.

Polymer Carbon Nanodots: A Novel Electrochemiluminophore for Dual Mode Detection of Ferric Ions

The development of simple and effective dual-mode analytical methods plays crucial regulatory roles in the discrimination of relevant target species, because of their built-in cross reference correction and high accuracy. In this work, a novel polymer carbon nanodots (PCNDs) prepared from a facile one-pot hydrothermal procedure using readily available l-tryptophan and l-phenylalanine as precursors, showed excellent aqueous solubility and blue fluorescence property with a high quantum yield of 29%. Moreover, the PCNDs was demonstrated to be a robust luminophore with electrochemiluminescence (ECL) efficiency of 43% was achieved by using K₂S₂O₈ as a coreactant. The spooling ECL spectroscopy was employed to take insight into excited states responsible for the potential-dependent ECL emissions. Most importantly, when introduced into construction of the fluorescence and ECL dual mode sensing platform, for the first time, the PCNDs displayed prominent performance for the detection of ferric ions (Fe³⁺). The ferric ions could be quantified ranging from micromolar to millimolar with a detection limit of 0.22 and 5.3 μM, respectively. Such a dual-functional sensing platform also exhibits excellent selectivity, reproducibility and stability. Results from this work indicate that PCNDs showing great promise as a bright luminophore for the fabrication of low-cost, high-performance dual-signal readout platforms for ferric ions determination.

Synthesis of a Novel Electrochemical Probe for the Sensitive and Selective Detection of Biothiols and Its Clinical Applications

The ability to estimate and quantify biothiols in biological fluids is very significant for attaining a detailed understanding of biothiols-related pathological diseases. Most of the developed methods for biothiols detection are not suitable for this purpose owing to their low sensitivity, poor selectivity, and long experimental procedures. In this study, a novel and simple structure electrochemical probe has been synthesized for the first time for the selective determination of biothiols. The developed probe is based on using 2,4-dinitrobenzenesulfonyl moiety (DNBS) as a selective recognition moiety for biothiols. The electrochemical probe was successfully fabricated through a facile one-step reaction between 2,4-dinitrobenzenesulfonyl chloride (DNBS-Cl) and p-aminophenol. The successful synthesis of the probe was confirmed by using different characterization techniques such as an NMR spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and mass spectrometry. Biothiols can selectively cleave the DNBS moiety through an aromatic nucleophilic substitution (ANS) reaction within 10 min to release p-aminophenol, which is a highly electrochemical active molecule that can be selectively detected easily by cyclic voltammetry at low potential. The probe has been employed for the quantification of cysteine, glutathione, and homocysteine with a LOD of 1.50, 3.48, and 4.67 μM, respectively. Excellent recoveries have been achieved in the range of 95.44-98.71% for the determination of the total biothiols in the human plasma sample.

Smartphone-based label-free photoelectrochemical sensing of cysteine with cadmium ion chelation

As an important amino acid, cysteine is related to the development of various diseases. The quantitative detection of cysteine is of great significance for both disease diagnosis and treatment. The current labeling methods mainly rely on fluorescent probes, making it difficult for quantitative cysteine detection in point-of-care testing (POCT). In this study, we proposed a label-free method for cysteine quantification by novel photoelectrochemical (PEC) sensing using a specific ion chelation probe. An indium tin oxide electrode loaded with nanoscale graphitic carbon nitride (g-C₃N₄) was used as the PEC electrode and gold nanoparticle modification was performed to further promote the charge transfer efficiency for enhanced photocurrent detection. Cadmium ions (Cd²⁺) were employed as the specific ion chelation probe for cysteine detection, and the formed Cd²⁺/cysteine chelate complex served as the electron acceptor for sensitive PEC sensing under low-power LED illumination. A portable PEC system was developed for quantitative detection of cysteine by integrating the PEC sensor, a self-designed detection circuit and a smartphone. The detected photocurrents changed linearly with the cysteine concentrations ranging from 0 μM to 40 μM, and the limit of detection is calculated to be 9.2 μM. To demonstrate the capability of this system, cysteine in spiked urine samples was quantified with a recovery rate of 96.1%-100.57%. This system provides high portability, sufficient accuracy and sensitivity, and greatly reduces the complexity and cost of point-of-care cysteine detection.

Highly Selective Electrochemiluminescence Chemosensor for Sulfide Enabled by Hierarchical Reactivity

Hydrogen sulfide (H₂S) is a well-known toxic gas with the odor of rotten eggs. Several reaction-based electrochemiluminescence (ECL) chemosensors for H₂S have been developed; however, no homogeneous ECL probe with high selectivity toward H₂S in aqueous media has been reported. Herein, we report an iridium(III) complex-based ECL chemodosimetric probe employing two 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) groups known as a photo-induced electron transfer quencher and a reaction site for the selective detection of H₂S; the detection mechanism involves H₂S being clearly distinguished from biothiols based on the different cleavage rates of the two NBD groups and extremely weak ECL interferences caused by reaction by-products. The probe was rationally designed to improve selectivity toward H₂S within the ECL analysis platform by enabling the removal of nonspecific background signals observed via fluorescence analysis. This analytical system exhibited remarkable selectivity toward H₂S, a rapid reaction rate, and high sensitivity (LOD = 57 nM) compared to conventional fluorescence methods. Furthermore, the probe could successfully quantify H₂S in tap water samples and commercial ammonium sulfide solutions, which demonstrates the effectiveness of this probe in field monitoring.

Rational Design of Electrochemiluminescent Devices

Electrochemiluminescence (ECL) is a light-emitting process which combines the intriguing merits of both electrochemical and chemiluminescent methods. It is an extensively used method especially in clinical analysis and biological research due to its high sensitivity, wide dynamic range, and good reliability. ECL devices are critical for the development and applications of ECL. Much effort has been expended to improve the sensitivity, portability, affordability, and throughput of new ECL devices, which allow ECL to adapt broad usage scenarios.In this Account, we summarize our efforts on the recent development of ECL devices including new electrodes, ECL devices based on a wireless power transfer (WPT) technique, and novel bipolar electrochemistry. As the essential components in the ECL devices, electrodes play an important role in ECL detection. We have significantly improved the sensitivity of luminol ECL detection of H₂O₂ by using a stainless steel electrode. By using semiconductor materials (e.g., silicon and BiVO₄), we have exploited photoinduced ECL to generate intense emission at much lower potentials upon illumination. For convenience, portability, and disposability, ECL devices based on cheap WPT devices have been designed. A small diode has been employed to rectify alternating current into direct current to dramatically enhance ECL intensity, enabling sensitive ECL detection using a smart phone as a detector. Finally, we have developed several ECL devices based on bipolar electrochemistry in view of the convenience of multiplex ECL sensing using a bipolar electrode (BPE). On the basis of the wireless feature of BPE, we have employed movable BPEs (e.g., BPE swimmers and magnetic rotating BPE) for deep exploration of the motional and ECL properties of dynamic BPE systems. To make full use of the ECL solution, we have dispersed numerous micro-/nano-BPEs in solution to produce intense 3D ECL in the entire solution, instead of 2D ECL in conventional ECL devices. In addition, the interference of ECL noise from driving electrodes was minimized by introducing the stainless steel with a passivation layer as the driving electrode. To eliminate the need for the fabrication of electrode arrays and the interference from the driving electrode and to decrease the applied voltage, we develop a new-type BPE device consisting of a single-electrode electrochemical system (SEES) based on a resistance-induced potential difference. The SEES is fabricated easily by attaching a multiperforated plate to a single film electrode. It enables the simultaneous detection of many samples and analytes using only a single film electrode (e.g., screen-printed electrode) instead of electrode arrays. It is of great potential in clinical analysis especially for multiple-biomarker detection, drug screening, and biological studies. Looking forward, we believe that more ECL devices and related ECL materials and detection methods will be developed for a wide range of applications, such as in vitro diagnosis, point-of-care testing, high-throughput analysis, drug screening, biological study, and mechanism investigation.

Electrochemiluminescent Chiral Discrimination with a Pillar[5]arene Molecular Universal Joint-Coordinated Ruthenium Complex

A bicyclic pillar[5]arene derivative fused with a bipyridine side ring, a so-called molecular universal joint (MUJ), was synthesized, and the pair of enantiomers was resolved by high-performance liquid chromatography enantioresolution. The electrochemiluminescent detection based on the ruthenium complex of the enantiopure MUJ showed excellent chiral discrimination toward certain amino acids.