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.

Bright Luminescence of Free Radical TEMPO Enabled by Electrochemiluminescence Technique.

Radicals can feature theoretically 100% light utilization owing to their nonelectron spin-forbidden transition and represent the most advanced luminescent materials at present. 2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMPO) acts as a typically stable radical with very broad applications. However, their luminescent properties have not been discovered to date. In the present work, we observed the bright electrochemiluminescence (ECL) emission of TEMPO with a higher efficiency (72.3%) via the electrochemistry and coreactant strategies for the first time. Moreover, the radical-based ECL achieved high detection toward boron acid with a lower limit of detection (LOD) of 1.9 nM. This study offers a new approach to generate emissions for some unconventional luminophores and makes a major breakthrough in the field of new luminescent materials as well.

Enhancing the Electrochemiluminescence of Porphyrin via Crystalline Networks of Metal-Organic Frameworks for Sensitive Detection of Cardiac Troponin I.

Porphyrins easily aggregate due to unfavorable π-π accumulation, causing luminescent quenching in the aqueous phase and subsequently reducing luminescent efficiency. It is a feasible way to immobilize porphyrin molecules through metal-organic framework materials (MOFs). In this study, 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) was introduced into the metal-organic skeleton (PCN-224) as a ligand. The result showed that the electrochemiluminescence (ECL) and photoluminescence (PL) efficiency of the MOF skeleton was 8.2 and 6.5 times higher than TCPP, respectively. Impressively, the periodic distribution of porphyrin molecules in the MOF framework can overcome the bottleneck of porphyrin aggregation, resulting in the organic ligand TCPP participating in the electron transfer reaction. Herein, based on the PCN-224, a sandwich-type ECL immunosensor was constructed for the determination of cardiac troponin I (cTnI). It provided sensitive detection of cTnI in the range of 1 fg/mL to 10 ng/mL with a detection limit of 0.34 fg/mL. This work not only innovatively exploited a disaggregation ECL (DIECL) strategy via the crystalline framework of MOF to enhance the PL and ECL efficiency of porphyrin but also provided a promising ECL platform for the ultrasensitive monitoring of cTnI.

Viscosity-Responsive Electrochemiluminescence of Diphenylbenzofulvene Derivatives.

The development of superior probes is highly desirable and valuable for viscosity measurement. Herein, we designed and reported a series of diphenylbenzofulvene (DPBF)-based organic luminophores according to the molecular regulation strategy. There are two free-rotating phenyl groups attached to the rigid fluorene skeleton in the DPBF, enabling its unique propeller-like noncoplanar chemical structure. Benefiting from this, DPBFs could feature outstanding PL and ECL emissions with intriguing aggregation-induced characteristics. Experimental and theoretical investigations revealed that substituent, spatial structure, and molecular orbital energy profoundly affected their luminescent behaviors. It was disclosed that fluoro-substituted DPBF(F)2 with a smaller LUMO-HOMO band gap demonstrated the strongest ECL emission and was selected as the optimal ECL emitter. Finally, DPBF(F)2 featured a linear response to the viscosity and VC content with lower limits of detection (LOD) of 5.69 µcP and 38.2 nM, respectively. This study represents the first example of the ECL probe toward viscosity and will be of great significance for both ECL application and viscosity measurement.

Study on the Electrochemiluminescence of Pentaphenylpyrrole in the Aqueous Phase Based on Structure-Regulated Strategy.

Heterocyclic nitrogen compounds play a vital role in luminescent materials, but most of them face the challenges of aggregation-caused quenching (ACQ) and poor water solubility. In this work, we present the nitrogen heterocyclic pentaphenylpyrrole (PentaPP) with an excellent aggregation-induced electrochemiluminescence (AIE-ECL) performance in the aqueous phase through the comparison of the elegant ECL luminophore 5,10,15,20-tetraphenylporphyrin (TPP). Further studies suggest that such unique AIE-ECL arises from its propeller-like noncoplanar structure and the large conjugation from the phenyl groups on the ring. In addition, the new ECL analysis could feature some advantages of AIE characteristic, water compatibility, and strong signal and finally achieve the ultrasensitive detection toward the explosive 2,4,6-trinitrophenol (TNP) with a lower detection limit (1.1 nM). This study does not only benefit to solve the two key problems mentioned before but also enriches the fundamentals and applications for ECL and pyrrole research.

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.

Highly Facile Strategy for Detecting D2O in H2O by Porphyrin-Based Luminescent Probes.

Owing to their almost similarities in size, shape, and chemical reactivity, effectively distinguishing deuteroxide (D2O) in water (H2O) remains an ongoing challenge, and the examples of a D2O probe are still quite scarce. Herein, since H2O can decrease the lifetime of a singlet oxygen as a vital intermediate and an H/D exchange in the luminescence process of porphyrins, we systematically investigated the enhanced ultraviolet-visible (UV-vis), photoluminescence (PL), and electrochemiluminescence (ECL) of water-soluble tetrakis(carboxphenyl)porphyrin (TCPP) in D2O. The findings showed that these luminescent properties had been greatly enhanced with the increase of the D2O fraction in water. Consequently, we first developed the highly facile methods of detecting D2O in H2O by the UV-vis, PL, and ECL of TCPP, respectively. Impressively, the ECL analysis exhibited a great superiority with a lower detection limit of 0.29 nM. The work not only achieves the challenging task of distinguishing between H2O and D2O but also provides a unique strategy to enhance the luminescent performance of porphyrin.

Significantly Promoting the Photogenerated Charge Separation by Introducing an Oxygen Vacancy Regulation Strategy on the FeNiOOH Co-Catalyst.

Semiconductor/co-catalyst coupling is considered as a promising strategy to enhance the photoelectrochemical (PEC) conversion efficiency. Unfortunately, this model system is faced with a serious interface recombination problem, which limits the further improvement of PEC performances. Here, a FeNiOOH co-catalyst with abundant oxygen vacancies on BiVO4 is fabricated through simple and economical NaBH4 reduction to accelerate hole transfer and achieve efficient electron-hole pair separation. The photocurrent of the BV (BiVO4 )/Vo-FeNiOOH system is more than four times that of pure BV. Importantly, the charge transfer kinetics and charge carrier recombination process are studied by scanning photoelectrochemical microscopy and intensity modulated photocurrent spectroscopy in detail. In addition, the oxygen vacancy regulation proposed is also applied successfully to other semiconductors (Fe2 O3 ), demonstrating the applicability of this strategy.

Aromaticity-Enhanced pH-Responsive Electrochemiluminescence of Cyclopentadienols.

Due to significantly tackling the problems of aggregation-caused quenching and water insolubility, aggregation-induced emission electrochemiluminescence (AIE-ECL) has emerged as a research highlight in aqueous detection and sensing. Herein, we reported a series of cyclopentadienols featuring excellent AIE-ECL properties on the basis of an enhanced aromaticity strategy. In detail, substituents profoundly determined ECL emission by affecting the characteristic absorption peak intensity ratio in UV-vis spectra and lowest unoccupied molecular orbital (LUMO)-highest occupied molecular orbital (HOMO) energies. It was found that 1,2,3,4,5-pentafluorophenyl cyclopentadienol (PFCD) containing an electron-withdrawing fluorine substituent, the maximum R/B band ratio, and a smaller LUMO-HOMO band gap demonstrated the best ECL performance. Meanwhile, such an AIE-ECL system displayed a wide response range toward pH (4-12) with a good linear relationship. Our research not only enriched polycyclic aromatic hydrocarbon-based AIE-ECL systems but also established an efficient pH sensor in the aqueous phase.

Insight into the Transition-Metal Hydroxide Cover Layer for Enhancing Photoelectrochemical Water Oxidation.

Depositing a transition-metal hydroxide (TMH) layer on a photoanode has been demonstrated to enhance photoelectrochemical (PEC) water oxidation. However, the controversial understanding for the improvement origin remains a key challenge to unlock the PEC performance. Herein, by taking BiVO4 /iron-nickel hydroxide (BVO/Fx N4-x -H) as a prototype, we decoupled the PEC process into two processes including charge transfer and surface catalytic reaction. The kinetic information at the BVO/Fx N4-x -H and Fx N4-x -H/electrolyte interfaces was systematically evaluated by employing scanning photoelectrochemical microscopy (SPECM), intensity modulated photocurrent spectroscopy (IMPS) and oxygen evolution reaction (OER) model. It was found that Fx N4-x -H acts as a charge transporter rather than a sole electrocatalyst. PEC performance improvement is mainly ascribed to the efficient suppression of charge recombination by fast hole transfer kinetics at BVO/Fx N4-x -H interface.

Encapsulation of Porphyrin-Fe/Cu Complexes into Coordination Space for Enhanced Selective Oxidative Dehydrogenation of Aromatic Hydrazides.

The encapsulation of specific nanoentities into hollow nanomaterials derived from metal organic frameworks has attracted continuous and growing research attentions owing to their unique structural properties and unusual synergistic functions. Herein, using the phase transformation of uniform rhombi dodecahedron ZIF-67, hollow nano-shell with a well-defined morphology is successfully prepared. Particularly, the iron-oxygen complex, that is formed by the interaction between TCPP-Fe/Cu (TCPP = tetrakis(4-carboxyphenyl)-porphyrin) and oxygen, can be acted as an ideal proton acceptor for practical organic reactions. Considering the unique adaptability of hollow ZIFs (named HZ) to the transformation of encapsulated TCPP-Fe/Cu bimetallic catalytic active sites, a heterogeneous catalyst (defined as HZ@TCPP-Fe/Cu) through morphology-controlled thermal transformation and rear assemble processes is designed and constructed. Under heterogeneous conditions, HZ@TCPP-Fe/Cu serves as a multifunctional molecular selector to promote the oxidative dehydrogenation of different aromatic hydrazide derivatives with high selectivity toward primary carbon among primary, secondary, and tertiary carbons that are unachievable by other traditional homogeneous catalysts. The high catalytic activity, selectivity, and recyclability of the catalyst proposed here are attractive advantages for an alternative route to the environmentally benign transformation of aromatic hydrazides to aromatic azobenzene.

Switching the Photoluminescence and Electrochemiluminescence of Liposoluble Porphyrin in Aqueous Phase by Molecular Regulation.

By a facile peripheral decoration of 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (ATPP) with inherent aggregation-induced emission (AIE) active tetraphenylethene (TPE), a versatile AIEgenic porphyrin derivative (ATPP-TPE) was obtained, which greatly abolishes the detrimental π-π stacking and thus surmounts the notorious aggregation-caused quenching (ACQ) effect of ATPP in aqueous phase. The photoluminescence of ATPP-TPE is 4.5-fold stronger than ATPP at aggregation state. Moreover, an unequivocal aggregation induced electrochemiluminescence (AIECL) of ATPP-TPE was found to be seriously dependent on its aggregation property in aqueous solution with efficiency of 34 %, which is 6 times higher than pure ATPP. The versatility of this molecular structure modulation strategy along with the ACQ-to-AIE transformation in this work provides direction to guide for applying liposoluble porphyrins in aqueous phase by designs of synthetic porphyrin AIEgens.

Dual-Channel Luminescent Signal Readout Strategy for Classifying Aprotic/Protic Polar Organic Medium and Naked-Eye Monitoring of Water in Organic Solvents.

Developing a convenient and rapid detection method for water is greatly desirable in the field of chemical industry. Herein, we present a simple and effective strategy combining a fluorescence sensor and a one-to-two fluorescence colorimetric logic operation to monitor water in a wide range of organic media and classify aprotic/protic polar solvents. The dual-emitting luminescent detector was prepared by incorporating a fluorescent dye Rhodamine 6G (R6G) with strong green light emission within a red light-emitting Eu-metal-organic framework (MOF) through the "bottle around ship" method. R6G@Eu-MOF displays completely different fluorescence response behaviors to various organic solvents. Thus, when one made use of the intensity ratio of different fluorescence emission centers, a 3D decoded map was proposed to reliably and effectively distinguish different aprotic/protic polar solvents. Moreover, R6G@Eu-MOF exhibited two different ratiometric sensing modes when detecting water in aprotic/protic polar solvents due to the hydrogen bonding interaction, that is ratiometry with one reference signal or two reversible signal changes. Furthermore, using water content as the input signal and two kinds of fluorescence emission as the output signals, a one-to-two logic gate system was constructed, making it possible to develop an intelligence system for water detection. Overall, we demonstrated for the first time that R6G@Eu-MOF could serve as an efficient platform for tracing water in organic media and distinguishing protic/aprotic polar organic solvents.

Cross-Linked Surface Engineering to Improve Iron Porphyrin Catalytic Activity.

Quasi-two-dimensional (QTD) structural heterogeneous catalysts have attracted a broad interest in multidisciplinary research due to their unique structure, preeminent surface properties and outstanding catalytic performance. Herein, a HZIF@TCPP-Fe/Fe heterogeneous catalyst based on cross-linked surface engineering is constructed by supporting QTD TCPP-Fe/Fe ultra-thin metallized film (≈2 nm) on hollow skeleton of zeolite imidazolate frameworks. The designed QTD structure exhibits high efficiency for the catalytic oxidative dehydrogenation of aromatic hydrazides reactions which is the key technology in various industrial processes. Taking advantage of QTD structure with excellent accessibility, the metallized film with irregular defects not only enhances electron transfer during the reaction but also exposes more surface-active sites. Furthermore, the prepared HZIF@TCPP-Fe/Fe heterogeneous catalyst can be recycled and reused, which is of great significance in the field of green chemistry.

Depolymerization-Induced Electrochemiluminescence of Insoluble Porphyrin in Aqueous Phase.

Exploring efficient and robust electrochemiluminescence (ECL) performance of liposoluble porphyrins in aqueous phase for analytical purposes especially for important biological targets is still very challenging. In this work, a novel depolymerization-induced electrochemiluminescence (DIECL) of porphyrin and ß-cyclodextrin (ß-CD) self-assembly through a coreactant route was discovered. Among the studied meso-tetrasubstituted porphyrins, self-assembly of 5,10,15,20-tetrakis(4-hydroxyphenyl) porphyrin (THPP) and ß-CD (THPP@ß-CD) exhibits the best DIECL behavior with high efficiency (21.8%) as well as good reproducibility and stability. A mechanistic study suggests that the facile complexation of porphyrins with amphiphilic ß-CD via hydrogen bonding interaction greatly improves the water insolubility and the aggregation-caused deficient ECL of liposoluble porphyrins in aqueous solution. Furthermore, because of the strong hydrogen bonding between the hydroxyl groups on THPP@ß-CD and a highly electronegative substrate, such THPP@ß-CD is found to serve as an efficient luminophore for recognition of most electronegative fluoride (F-) in the aqueous phase with high sensitivity and selectivity, together with a low limit of detection (0.74 µΜ). The simplicity of this THPP@ß-CD and its unique DIECL property in current work provides a new guide for the ECL applications of liposoluble porphyrins in aqueous phase.

Substituent-Induced Aggregated State Electrochemiluminescence of Tetraphenylethene Derivatives.

The development of highly active, eco-friendly, and structurely fine-tunable organic luminophores is currently desirable for electrochemiluminescence (ECL). Tetraphenylethene (TPE) derivatives are the most representative aggregation-induced emission characteristic (AIEgens). In contrast, their aggregation-induced ECLs have not been detail studied. Herein, we report the bright cathodic aggregated state ECL of TPE derivatives by a coreactant approach. In this system, the substituents profoundly affect ECL emissions by changing the relative intensities of R and B band intensity ratios in their UV-vis spectra as well as the HOMO and LUMO energies. It was discovered that electron-withdrawing nitro-substituted TPE-(NO2)4 with a smaller LUMO/HOMO band gap and stronger R band featured the strongest ECL emissions and became the best luminophore for the highly efficient detection of iodide (I-) in the aqueous phase. This work not only reveals the influence of R and B bands in TPE derivative UV-vis spectra on their optical properties but also constructs a novel aggregation-induced ECL sensing.

High-level secretive expression of a novel achieved Talaromyces cellulolyticus endo-polygalacturonase in Pichia pastoris by improving gene dosage for hydrolysis of natural pectin.

Pectin is a type of complex hydrophilic polysaccharide widely distributed in plant resources. Thermal stable pectinase has its advantage in bioapplication in the fields of food processing, brewing, and papermaking, etc. In this study, we enzymatically characterized a putative endo-polygalacturonase TcPG from a Talaromyces cellulolyticus, realized its high-level expression in Pichia pastoris by in vitro constructing of a series of multi-copy expression cassettes and real time quantitative PCR screening. The secretive expression level of TcPG was nonlinear correlated to the gene dosage. Recombinants with five-copy TcPG gene in the host genome showed the highest expression. After cultivation in a bioreactor for about 96 h, the enzyme activity reached 7124.8 U/mL culture. TcPG has its optimal temperature of 70 °C. Under the optimized parameters, the pectin could be efficiently hydrolyzed into oligosaccharides.

Electrochemiluminescence Platforms Based on Small Water-Insoluble Organic Molecules for Ultrasensitive Aqueous-Phase Detection.

Highly efficient detection in the aqueous phase for water-insoluble organic molecule probes is challenging. The bright aggregated-state electrochemiluminescence (ECL) of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles by a co-reactant approach was discovered, and a heterogeneous aggregation-induced emission ECL (HAIE-ECL) was constructed at the electrode surface, showing very high ECL efficiency (37.8 %) and selective recognition for industrially important DNBP plasticizer with a low detection limit of 0.15 nm in the water phase. A mechanistic study indicates that ECL is mainly generated due to the high electron affinity of siloles and restriction of the intramolecular motions caused by their propeller-like noncoplanar structures. This system realizes the sensing of organic-based ECL in the water phase by solving the crucial problems of water insolubility and aggregation-caused quenching (ACQ), and demonstrates potential for further application because of its design and high efficiency.

Recyclable magnetic carbonaceous porous composites derived from MIL-100(Fe) for superior adsorption and removal of malachite green from aqueous solution.

Development of novel porous materials for efficient adsorption and removal of environmental pollutants from aqueous solution is of great importance and interest in environmental science and chemistry. Herein, we reported a facile synthesis of recyclable magnetic carbonaceous porous composite derived from iron-based metal-organic framework MIL-100(Fe) for superior adsorption and removal of malachite green (MG) from aqueous solution. Because of large surface area and high porosity, the synthesized magnetic carbonaceous porous material presented a superior adsorption capacity of 2090 mg g-1 for MG. The adsorption of MG on magnetic carbonaceous porous composite is endothermic and spontaneous. The prepared magnetic carbonaceous porous composite could be separated easily and rapidly from the solution matrix by an external magnet. The rapid adsorption, large adsorption capacity and good reusability make it attractive for practical use in the adsorption and removal of dyes from aqueous solutions.

Isolable 1,1-disubstituted silole dianion: a homogeneous two-electron-transfer reducing reagent.

The 1,1-disubstituted silole dianion 2 has been isolated and characterized by single-crystal X-ray analysis for the first time. 2 can be used as a two-electron-transfer reducing reagent for the reduction of organic compounds and inorganic salts with regeneration of the corresponding neutral silole in nearly quantitative yields, indicating that it is an excellent reducing reagent. Reduction of (Mes)2SiCl2 with 2 selectively yielded the cyclotrisilane (Mes2Si)3 in high yield, which has not been isolated in pure form with the existing methods.