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The urease enzyme has been an important target for the discovery of effective pharmacological and agricultural products. Thirteen regio-selectively alkylated benzimidazole-2-thione derivatives have been designed to carry the essential features of urease inhibitors. The urease enzyme was isolated from Helicobacter pylori as a recombinant urease utilizing the His-tag method. The isolated enzyme was purified and characterized using chromatographic and FPLC techniques showing a maximal activity of 200 mg/mL. Additionally, the commercial Jack bean urease was purchased and included in this study for comparative and mechanistic investigations. The designed compounds were synthesized and screened for their inhibitory activity against the two ureases. Compound 2 inhibited H. pylori and Jack bean ureases with IC50 values of 0.11; and 0.26 mM; respectively. While compound 5 showed IC50 values of 0.01; and 0.29 mM; respectively. Compounds 2 and 5 were docked against Helicobacter pylori urease (PDB ID: 1E9Y; resolution: 3.00 Å) and exhibited correct binding modes with free energy (ΔG) values of −9.74 and −13.82 kcal mol−1; respectively. Further; the in silico ADMET and toxicity properties of 2 and 5 indicated their general safeties and likeness to be used as drugs. Finally, the compounds’ safety was authenticated by an in vitro cytotoxicity assay against fibroblast cells.

Hemin as the organic linker ligand and Cu (II) as the metal center were applied to prepare a copper-metal-organic framework (Cu-hemin-MOF) via one-step hydrothermal method. Characterization using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD) demonstrate that the acquired Cu-hemin-MOF possesses the appearance of 3D ball-flower shape with the existence of C, N, O, Fe, and Cu on the surface. Further study found that this 3D ball-flower shaped Cu-hemin-MOF exhibits peroxidase-like activity, which can catalyze the peroxidase substrate of o-phenylenediamine (OPD) to generate 2,3-diaminophenazine (DAP) in the presence of H2O2. DAP has a yellow color and also emits a strong fluorescence when excited by ultraviolet light. Interestingly, Cu-hemin-MOF’s peroxidase-like activity can be strongly inhibited by glutathione (GSH). In view of this, a dual readout (fluorescence and colorimetry) was proposed to detect GSH for the first time. Under optimal conditions, the proposed method exhibits good linear relationship between the signal response (fluorescence and colorimetry) and the concentration of GSH, and low limits of detection (LOD) of 2.3 and 26.6 nM, respectively. Graphical abstract [ABSTRACT FROM AUTHOR]

Sulfoxonium ylides as safe carbene precursors are described for iridium‐catalyzed carbene insertions and annulation, providing a facile and green approach to access a variety of quinoxaline derivatives in water. This water‐mediated method also allows the preparation of β‐keto thioethers under mild condition. [ABSTRACT FROM AUTHOR]

The mycotoxin zearalenone (ZEA) prompts reproductive toxicity due to its strong estrogenic effects. In this work, an electrochemical sensor for determination of ZEA was developed by electropolymerization of a molecularly imprinted poly (o‐phenylenediamine) (PPD) film on screen‐printed gold electrode (SPGE) surface. The sensor was examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using K3[Fe(CN)6]/K4[Fe(CN)6] as redox probe. The molecularly imprinted polymer (MIP) sensor showed a wide determination range from 2.50 to 200.00 ngmL−1 for ZEA. The Limit of detection (LOD) was calculated to be 0.20 ngmL−1, based on the signal to noise (S/N) ratio equal to 3.0. The sensor displayed good repeatability, with RSD values≤4.6 %, and maintained 93.2 % of its initial response after storage for 10 days in air at room temperature. The developed method was successfully applied for the determination of ZEA in corn flakes with mean recoveries ranged from 96.2 % to 103.8 % and RSDs within the interval of 2.1 % to 3.8 %. [ABSTRACT FROM AUTHOR]

A simple Schiff base (L) based on 2-hydroxyacetophenone and o-phenylenediamine was prepared which acts as an effective fluorescent sensor for Al3+ with ca. 9.0 fold enhancement in fluorescence intensity and detection limit 10–4.3 M. L can quite clearly distinguish Al3+ over other metal ions Zn2+, Hg2+, Cd2+, Pb2+, Mn2+, Mg2+, Co2+, Ni2+, Cu2+, Ca2+, K+, Li+, Na+ and Fe3+. Cyclic voltammogram and square wave voltammogram of L shows a significant change on interaction with Al3+. Spectroscopic data and DFT calculations confirm 1:1 interaction between L and Al3+ which is reversible with respect to Na2EDTA. [ABSTRACT FROM AUTHOR]

Benzimidazole structure contains imidazole ring fused with phenyl ring at 4‐ and 5‐position. The mono and disubstituted derivatives of benzimidazole are very interesting heterocyclic organic molecules, synthesized by a simple nucleophilic substitution reaction and condensation method between o‐phenylenediamine with carbonyl compound under different conditions are reported, and as time passed away, the method also be reported in favor of the environment‐friendly with good yield product. We cover the literature up to the end of 2019 in which very recently reported synthetic route to access benzimidazole scaffolds are discussed. We are focus on the evaluation of synthetic route to construct monosubstituted‐benzimidazole (MSBs) and disubstituted‐benzimidazoles (DSBs), via various methods involving condensation, cyclization or employing green chemistry aspect such as utilizing solvent‐free conditions, metal‐free conditions, or using nanoparticle catalyst etc. Benzimidazoles found in the natural system display a wide range of pharmaceutical properties have been reported. The scaffolds are characterized as structurally potential ligands which can bind to different receptor sites for the discovery of various immerging drugs. Therefore, benzimidazole is recognized as a potent scaffold in the pharmaceutical industry and diverse synthetic pathways have been developed to prepare its functionalized derivatives which are described in this review. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus (S. aureus) is an important foodborne pathogen that causes food poisoning and severe infections. Herein, we design a novel and sensitive colorimetric immunoassay for the detection of S. aureus based on the formation of a magnetic bead-based sandwich complex and signal amplification via an enzyme mimic. Magnetic nanoparticles decorated with carbon dots offer rapid enrichment and separation of target bacteria in complex matrices. Sliver nanoclusters are used as an artificial enzyme that can oxidize o-phenylenediamine to form a yellow product with a maximum absorption peak at 421 nm. This method can visually detect S. aureus ranging from 10 to 106 cfu mL−1. Its limit of detection reaches down to 4.9 cfu mL−1. By analyzing food samples, the recovery is from 85.6 to 103.7%. [ABSTRACT FROM AUTHOR]

In this paper, a simple and feasible immunoassay protocol with signal amplification for sensitive determination of alpha fetoprotein (AFP, used as a model) by using new enzyme-induced Fenton reaction (EIFR) accompanying the oxidation of o-phenylenediamine (OPD) system. We discovered that glucose oxidase (GOx) has the ability to stimulate in situ Fenton reaction coupling the oxidation of OPD. GOx-catalyze of glucose results in the formation of hydrogen peroxide (H2O2). It can catalytically oxidize Fe2+to Fe3+, meanwhile producing hydroxyl radicals (•OH). The latter effectively initiated the catalytic oxidation of o-phenylenediamine (OPD) to 2,2-aminoazobenzene (DAP), resulting in the production of an electrochemical signal. On the basis of EIFR-OPD system, a new immunoassay protocol with GOx/anti-pAb2-conjugated gold nanoparticle (Ab2-AuNP-GOx) detection antibody can be designed for the detection of target AFP on capture antibody–functionalized transparent 96-well polystyrene microplate, monitored by recording the current peak of the generated DAP. The electrochemical current shows to be positively correlated with the concentration of target AFP. Under optimal conditions, the proposed assay exhibited good electrochemical responses for detecting target AFP in the range of 1.0 pg mL−1 to 100 ng mL−1 with a detection limit (LOD) of 0.5 pg mL−1 (0.5 ppt) estimated at the 3Sblank level. Additionally, the precision, reproducibility, specificity, and method accuracy were also investigated with acceptable results. Importantly, the EIFR-OPD system can be further extended for the determination of other protein or biomarkers by controlling the specific recognition system (antibody or aptamer). [ABSTRACT FROM AUTHOR]

As benzodiazepines occupy an important place in the realm of medicinal and material chemistry, a facile, ecofriendly, one-pot protocol for the synthesis of 4-substituted-1,5-benzodiazepine derivatives has been described through the one-pot three-component reaction of o-phenylenediamine, dimedone, and aldehydes in the presence of tris(hydrogensulfato) boron [B(HSO4)3] under reflux conditions in aqueous ethanol. The operational simplicity without column chromatographic purification and the avoidance of using hazardous and expensive solvents and catalysts are the most advantages of this method. [ABSTRACT FROM AUTHOR]

In this study, we report a novel magnetic biomimetic nanozyme (Fe 3 O 4 @Cu/GMP (guanosine 5′-monophosphate)) with high laccase-like activity, which could oxidize toxic o -phenylenediamine (OPD) and remove phenolic compounds. The magnetic laccase-like nanozyme was readily obtained via complexed Cu2+ and GMP that grew on the surface of magnetic Fe 3 O 4 nanoparticles. The prepared Fe 3 O 4 @Cu/GMP catalyst could be magnetically recycled for at least five cycles while still retaining above 70% activity. As a laccase mimic, Fe 3 O 4 @Cu/GMP had more activity and robust stability than natural laccase for the oxidization of OPD. Fe 3 O 4 @Cu/GMP retained about 90% residual activity at 90°C and showed little change at pH 3–9, and the nanozyme kept its excellent activity after long-term storage. Meanwhile, Fe 3 O 4 @Cu/GMP had better activity for removing phenolic compounds, and the removal of naphthol was more than 95%. Consequently, the proposed Fe 3 O 4 @Cu/GMP nanozyme shows potential for use as a robust catalyst for applications in environmental remediation. Unlabelled Image [ABSTRACT FROM AUTHOR]

Infections caused by foodborne microorganisms are a great threat to the global environment and public healthcare today. Thus, rapid, portable and sensitive assays that can realize the identification of foodborne bacteria are highly desired. In this study, a smart fluorescent and colorimetric dual-readout sensing system has been established for simple and rapid E. coli determination by utilizing the Cu2+-triggered oxidation of o-phenylenediamine (OPD). Initially, Cu2+ can oxidize OPD to OPDox, resulting in an orange-yellow fluorescence and visible pale-yellow color. However, E. coli can effectively reduce Cu2+ into Cu+, inhibiting the Cu2+-triggered oxidation of OPD to OPDox. Consequently, the introduction of E. coli can turn off both the fluorescence and the UV-vis absorbance signals of the OPD-Cu2+ system, illustrating an original mechanism for fluorescent and colorimetric dual-channel detection of E. coli. Moreover, a filter paper-based visual sensor was built and coupled with OPD-Cu2+ solution under the assistance of a UV lamp. The as-prepared sensor can detect E. coli quantitatively with the help of a typical smartphone color-scanning application (APP). Thus, this study offers a valid dual-mode assay for sensitive and on-site visible detection of E. coli, guaranteeing the reliability of the results and is more attractive for practical use. [ABSTRACT FROM AUTHOR]

By combining molecular modelling and electrochemistry we envision the creation of modified electrodes tailored for a more sensitive and selective detection of a single analyte. In this study we report on a graphite screen printed electrode modified with electropolymerized o‐phenylenediamine, selected by rational design, which promotes the detection of nafcillin (NAF), an antibiotic. Parameters such as monomer concentration, pH and number of electropolymerization cycles were optimized to obtain the highest current signal for the target upon amperometric detection. NAF identification was based on the redox process at +1.1 V (vs pseudo Ag), ascribed to the oxidation of the C‐7 side chain. With the optimized modification protocol, a two‐fold increase in nafcillin signal could be obtained: the calibration plot in 0.1 M Britton‐Robinson buffer pH 4 showed a limit of detection of 80 nM with improved sensitivity and reproducibility (RSD<5 %) compared to the detection at non‐modified electrodes. [ABSTRACT FROM AUTHOR]

A simple and highly selective electrochemical method for the investigation of catechol (CC) and hydroquinone (HQ) was developed on the surface bare carbon paste electrode (BCPE) modified with electropolymerized thin film of o-Phenylenediamine (o-PD) by using cyclic voltammetric technique. Electrochemical measurements were carried by using both cyclic voltammetric (CV) and differential pulse voltammetric (DPV) techniques at poly(o-PD) modified carbon paste electrode (MCPE). The proposed modified electrode shows adsorption-controlled process and exhibited a good limit of detection for CC and HQ was 1.1 and 2.1 µM respectively. In order to study the selectivity of the electrode, interference study was carried out by using DPV technique. Therefore, poly(o-PD)/MCPE showed excellent electrocatalytic behavior for the simultaneous electrochemical investigation of CC and HQ. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) were prepared by a solvent-involved molecular fusion strategy using o-phenylenediamine (OPD) as the carbon source and formamide as the reaction solvent. The CDs possessed not only the functional groups inherited from the carbon source and the reaction solvent, but also numerous C=N groups in the structure, resulting from the Schiff base reaction between –NH 2 of OPD and C=O of formamide. These functional groups endowed the final CDs with a favorable soft-base property, leading to the high tolerance level toward hard-acid type metal ions and prominent detection selectivity toward Ag+. Moreover, the obtained CDs displayed outstanding biocompatibility and low cytotoxicity, and demonstrated potential as an effective photoluminescence probe for intercellular Ag+ and Cys imaging, preventing the interference of autofluorescence from living tissues. This study focused on the solvent-involved molecular fusion strategy could provide new insights into the design of novel carbon-based nanostructures and optimization of the structure-property relationship of CDs. CDs prepared via a solvent-involved molecular fusion strategy using formamide as reaction solvent exhibits prominent detection selectivity toward Ag+. Image 1 • A solvent-involved molecular fusion strategy is adopted for the CDs preparation. • The CDs exhibits prominent detection selectivity toward Ag+. • The obtained CDs can be used as an effective photoluminescence probe for intercellular Ag+ and Cys imaging. [ABSTRACT FROM AUTHOR]

This paper reports on a sensitive and selective electrochemical sensor for lactic acid. The sensor is based on molecularly imprinted polymers (MIP), obtained on glassy carbon electrode (GCE) modified with reduced graphene oxide and gold nanoparticles. The MIP was obtained by electropolymerization of the o-phenylenediamine (o-PD) on the modified surface of the GCE in the presence of lactic acid. The steps involving the GCE modification and MIP construction were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy and atomic force microscopy. The results were evaluated using differential pulse voltammetry, using the hexacyanoferrate redox system as an electrochemical probe. Under optimized experimental conditions, the imprinted sensor has a linear response in the 0.1 nM to 1.0 nM lactic acid concentration range, with detection limit of 0.09 nM. The sensor exhibits excellent selectivity in the presence of molecules of similar chemical structure. It was applied for the selective determination of lactic acid in sugarcane vinasse. The recovery values ranged from 97.7 to 104.8%. [ABSTRACT FROM AUTHOR]

The authors describe a dual-signal colorimetric and ratiometric fluorescent probe for uric acid (UA). It is based on cascade catalysis and an inner filter effect. The method involves uricase-catalyzed oxidation of UA and iodide-catalyzed oxidation of the colorless peroxidase substrate o-phenylenediamine (OPD) to form yellow 2,3-diaminophenazine (oxOPD). This can be visually observed or monitored by measuring absorbance at 417 nm. Furthermore, oxOPD quenches the fluorescence of silicon nanoparticles (SiNPs) (with peaks at 450 and 565 nm) via an inner filter effect. The change in the ratio of emissions peaking 565 and 450 (at excitation wavelength of 380 nm) increases linearly in the 0.01–0.8 mM UA concentration range). The lower detection limits are 8.4 and 0.75 μM when using the colorimetric and ratiometric fluorometric method, respectively. The assay was successfully applied to the quantitation of UA in spiked serum samples. [ABSTRACT FROM AUTHOR]

Considering the biological properties of the compounds containing quinoxaline and indandione skeleton, a new thiolate salt was synthesized via the reaction between ninhydrin and phenacyl thiocyanate in the presence of triethylamine and in continuous, from the reaction of this thiolate with methyl iodide and o-phenylenediamine in absolute ethanol, quinoxaline containing indandione substituent was obtained. [ABSTRACT FROM AUTHOR]

Multicolor carbon dots (CDs) with high stability are desired for various light emitting devices and bio-images. In this paper, the green and red emitting CDs were created by o -phenylenediamine and terephthalic acid (TA) as precursors at different temperatures via a solvothermal reaction. An efficient response surface methodology is developed to analyze the formation mechanism. Using optimized conditions, the green and red emitting CDs reveal photoluminescence quantum yields (PLQYs) of 34.0 % and 26.8 %, respectively. The result of response surface method indicates that temperature, precursor concentration, and TA amount significantly influence the PLQYs of the CDs. The formation mechanism of the CDs was proposed by analyzing solvatochromism phenomena, oxidation processes, and fluorescence lifetimes. Initially, green CDs with surface state luminescence were formed followed by the subsequent generation of red CDs exhibiting molecular and carbon core state emission during oxidation. These CDs reveal high stability, in which the PL intensity almost remained unchanged after 7 months. Furthermore, three-color CDs/polymer films (λ em = 500, 536, and 568 nm) were successfully fabricated by using these two types of CDs. Sample 180-CDs/polystyrene film had photochromic properties, while other films had good photostability. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A cellulosic gold nanocluster multi-emission probe was designed for hROS detection. • The hROS responsive property of gold nanocluster is regulated by ligands structure. • Cellulose nanocrystal could extend the storage times of the probe to 12 months. • Au(Ⅲ) expedited fluorescence opening of o-phenylenediamine during hROS detection. • The probe could visually identify •OH, ClO−, ONOO− and intracellular hROS. The distinction of high reactive oxygen species (hROS) types has positive significance for disease diagnosis. Here, to visibly assess hROS types and levels, a cellulosic multi-emission fluorescence probe was designed by incorporating proline-protected gold nanoclusters (Em: 450 nm), glutathione-protected gold nanoclusters (Em: 680 nm) and o-phenylenediamine (Em: 565 nm) onto cellulose nanocrystal. Ingeniously, the probe displayed the stabilized, quenched and activated fluorescence signals corresponding to hROS at 450 nm, 680 nm, and 565 nm, respectively. The response time of the probe for hROS was greatly reduced from 29 min to 7 min through gold nanoclusters releasing Au(Ⅲ) during the fluorescence quenching process to accelerate the fluorescence opening of o-phenylenediamine. Therefore, the probe with long-term stability (12 months) possessed excellent sensitivity and selectivity to distinguish hROS types, and exhibited visually yellow, white, and green fluorescence for •OH, ClO−, and ONOO−, respectively, and the corresponding detection limits were 0.56 μM, 0.73 μM and 0.81 μM within 5 min, 6 min and 7 min, respectively. The design strategy provides the ideas for constructing multi-emission probe to distinguish multiple analytes at similar levels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bifunctional Fe-MOF@Fe 3 O 4 NPs was first prepared by a one-step encapsulation method. • Fe-MOF@Fe 3 O 4 NPs acts as fluorescent indicators as well as peroxidase mimics. • A dual-mode assay for UA was proposed based on Fe-MOF@Fe 3 O 4 NPs combined with OPD. • Accurate and reliable assays of UA in urin samples were achieved. Nanozymes as a substitute for natural enzymes have attracted many attention owing to their high stability, low cost, and satisfactory catalytic activity. In this study, a new dual-readout detection strategy was proposed for colorimetric and ratiometric fluorescence detection of uric acid (UA) based on bifunctional metal–organic framework nanocomposite (Fe-MOF@Fe 3 O 4 NPs), which functions as fluorescent indicators as well as peroxidase mimics. In the presence of uricase, the decomposition of UA can produce H 2 O 2 , and Fe-MOF@Fe 3 O 4 NPs catalyzed H 2 O 2 into the OH radicals, which could oxidize o -phenylene-diamine to 2,3-diaminophenazine, accompanied by a fluorescence emission at 600 nm and a UV–vis absorption peak at 450 nm. At the same time, the fluorescence of Fe-MOF@Fe 3 O 4 NPs at 460 nmcould be quenched by 2,3-diaminophenazine via Förster resonance energy transfer. Therefore, the fluorescence intensity ratio (I 600 / I 460) and UV–vis absorption intensities are employed to construct the dual-readout biosensor for the determination of UA. The linear range was 0.2–200 μM and the limit of detection for the fluorometric and colorimetric detection were 0.03 μM and 0.18 μM, respectively. Finally, the biosensor was employed to determine UA in urine samples, and satisfactory results were obtained. [ABSTRACT FROM AUTHOR]

In this article, a zirconia-based nano-catalyst (Nano-ZrO2), with intermolecular C-N bond formation for the synthesis of various benzimidazole-fused heterocycles in a concise method is reported. The robustness of this reaction is demonstrated by the synthesis of a series of benzimidazole drugs in a one-pot method. All synthesized materials were characterized using 1HNMR, 13CNMR, and LC-MS spectroscopy as well as microanalysis data. Furthermore, the synthesis of nano-ZrO2 was processed using a standard hydrothermal technique in pure form. The crystal structure of nano-ZrO2 and phase purity were studied, and the crystallite size was calculated from XRD analysis using the Debye–Scherrer equation. Furthermore, the antimicrobial activity of the synthesized benzimidazole drugs was evaluated in terms of Gram-positive, Gram-negative, and antifungal activity, and the results were satisfactory.

In this research, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has been used in the condensation reaction between o-phenylenediamine and various arylaldehydes as oxidants under microwave irradiation. In this clean reaction, the benzimidazole derivatives were synthesized as benefit target products. The advantages to this procedure include high yields, easy work-up procedure, no chromatographic separation, and short reaction times. The obtained pure products were characterized by physical and spectral data such as IR, 1H NMR and 13C NMR techniques.

The methods for the synthesis of benzimidazoles have become a focus of synthetic organic chemists, as they are useful building blocks for the development of important therapeutic compounds in medicine. Benzimidazole nucleus plays a very important role as a therapeutic agent e.g. antiulcer and anthelmintic drugs. Other benzimidazole derivatives exhibit pharmacological activities such as antimicrobial, antiviral, anticancer, anti-inflammatory and analgesic.

The development of various enzyme-linked immunosorbent assays (ELISAs) coupled with surface-enhanced Raman scattering (SERS) detection is a growing area in analytical chemistry due to their potentially high sensitivity. A SERS-based ELISA with horseradish peroxidase (HRP) as an enzymatic label, an o -phenylenediamine (oPD) substrate, and a 2,3-diaminophenazine (DAP) enzymatic product was one of the first examples of such a system. However, the full capabilities of this long-known approach have yet to be revealed. The current study addresses a previously unrecognized problem of SERS detection stage performance. Using silver nanoparticles and model mixtures of oPD and DAP, the effects of the pH, the concentration of the aggregating agent, and the particle surface chloride stabilizer were extensively evaluated. At the optimal mildly acidic pH of 3, a 0.93 to 1 M citrate buffer, and AgNPs stabilized with 20 mM chloride, a two orders of magnitude advantage in the limits of detection (LODs) for SERS compared to colorimetry was demonstrated for both DAP and HRP. The resulting LOD for HRP of 0.067 pmol/L (1.3 amol per assay) underscores that the developed approach is a highly sensitive technique. We suppose that this improved detection system could become a useful tool for the development of SERS-based ELISA protocols.

This review article discusses the recent progress in synthesizing seven-membered ring 1,3,5-triazepine and benzo[ f ][1,3,5]triazepine derivatives. These derivatives can be either unsaturated, saturated, fused, or separated. This review covers strategies and procedures developed over the past two decades, including cyclo-condensation, cyclization, methylation, chlorination, alkylation, addition, cross-coupling, ring expansions, and ring-closing metathesis. This review discusses the synthesis of 1,3,5-triazepine derivatives using nucleophilic or electrophilic substitution reactions with various reagents such as o -phenylenediamine, 2-aminobenzamide, isothiocyanates, pyrazoles, thiazoles, oxadiazoles, oxadiazepines, and hydrazonoyl chloride. This article systematically presents new approaches and techniques for preparing these compounds. It also highlights the biological importance of benzo[ f ][1,3,5]triazepine derivatives, which have been used as drugs for treating nervous system diseases. This review aims to provide researchers with the necessary information to create and develop new derivatives of these compounds as quickly as possible.

Herein, an adenosine triphosphate (ATP)-induced enzyme-catalyzed cascade reaction system based on metal-organic framework/alkaline phosphatase (MOF/ALP) nanocomposites was designed to establish a surface-enhanced Raman spectroscopy (SERS) biosensor for use in rapid, sensitive ATP detection. Numerous ALP molecules were first encapsulated using ZIF-90 to temporarily deactivate the enzyme activity, similar to a lock. Au nanostars (AuNSs), as SERS-enhancing substrates, were combined with o -phenylenediamine (OPD) to form AuNSs@OPD, which could significantly improve the Raman signal of OPD. When the target ATP interacted with the MOF/ALP nanocomposites, ATP could act as a key to open the MOF structure, releasing ALP, which should further catalyze the conversion of OPD to oxOPD with the aid of ascorbic acid 2-phosphate. Therefore, with the increasing concentrations of ATP, more ALP was released to catalyze the conversion of OPD, resulting in the reduced intensity of the Raman peak at 1262 cm -1 , corresponding to the level of OPD. Based on this principle, the ATP-induced enzyme-catalyzed cascade reaction SERS biosensor enabled the ultrasensitive detection of ATP, with a low detection limit of 0.075 pM. Consequently, this study provides a novel strategy for use in the ultrasensitive, rapid detection of ATP, which displays considerable potential for application in the fields of biomedicine and disease diagnosis.

Benzimidazoles have a broad spectrum of biological and pharmacological properties, including anticancer activity. This study reports the facile synthesis and cytotoxic evaluation of twenty-eight 1,2-disubstituted benzimidazoles (6a-β), based on condensation reactions between N-benzyl o-phenylenediamine and benzylamine. The reactions were solvent-free, with the use of Na 2 S 2 O 5 as an inexpensive and environmentally friendly oxidizing agent, and progressed rapidly. Cytotoxicity assessments using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were performed against the A549, HeLa, and MCF-7 cell lines for all synthesized compounds (6a-β). Among them, 6j, 6k, 6l, and 6n displayed good activities against the A549 and MCF-7 cell lines. These compounds possessed IC 50 values ranging from 2.55 to 4.50 µM, corresponding to 1.4-fold to 2.4-fold stronger potencies than that of the positive control 5-fluorouracil (5-FU) (IC 50  = 6.08 µM) against MCF-7 cells, while 6k (IC 50  = 3.22 µM) was consistent with 5-FU on the A549 cell line (IC 50  = 3.77 µM). Structure-activity relationship analyses revealed the 3-pyridinyl moiety at C-2 and the CH 3 , OCH 3 , or 1,3-dioxolyl groups on the benzene ring at the N-1 position of the benzimidazole heterocycle as key structural features effectuating the observed cytotoxicities.

This study was aimed to reveal the binding mechanism between bovine hemoglobin and o-phenylenediamine by using molecular spectroscopy techniques and molecular modeling methods. The experimental results revealed that the fluorescence quenching mechanism was a combined dynamic and static quenching. The binding constant was (1.17 ± 0.02)×104 L/mol, and only a single binding site exists. The binding distance was 2.46 nm. The binding process was a spontaneous reaction, dominated by hydrophobic forces. The molecular docking simulations have also confirmed the results of the spectroscopic methods. The results reported here may significantly help understanding the interaction mechanism of o-phenylenediamine and hemoglobin. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hexahydrofarnesol is the main contaminant of aviation biokerosene. • The determination of hexahydrofarnesol is of great importance for the aviation and biokerosene industries. • The first electrochemical sensor for the determination of hexahydrofarnesol was developed in this work. • The first electroanalytical method for the analysis of aviation biokerosene was proposed. Abstract In this work, the first electrochemical sensor for determination of hexahydrofarnesol in aviation biokerosene was developed by electropolymerization of a molecularly imprinted ortho-phenylenediamine film on a glassy carbon electrode. The modified electrode was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, RAMAN spectroscopy and atomic force microscopy. Parameters that influence the performance of the imprinted sensor, such as the molar ratio between functional monomer and template molecule, number of cycles and pH used in the electropolymerization, extraction time of the template molecule, and time of rebinding of the hexahydrofarnesol molecules in the imprinted cavities were optimized. The developed sensor presented the following linear ranges: 4.0 × 10−8 to 1.5 × 10-7 mol L-1 and 1.5 × 10-7 to 1.5 × 10-6 mol L-1. The apparent dissociation constant (K D) for the first linear range of this device calculated by the isothermal Langmuir adsorption model was 4.8 × 10-7 mol L-1. The limit of detection, limit of quantification and sensitivity were 1.2 × 10−8 mol L-1, 4.1 × 10−8 mol L-1 and 67 A L mol-1 (n = 3) respectively. The sensor showed considerable inter-day and intra-day repeatability, with RSD values ≤ 4.8%, and had 96% of its initial current preserved after being stored for 10 days in contact with air at room temperature. The developed method was successfully applied toward the determination of hexahydrofarnesol in aviation biokerosene. Mean recoveries ranged from 97.6% to 105.8%, with RSDs within the interval of 1.7% to 3.9%. These results indicate that the method developed has a good accuracy for the determination of hexahydrofarnesol. [ABSTRACT FROM AUTHOR]

Abstract In this work, a simple, selective and stable strategy for encapsulation of triangular ruthenium nanoplates (RuNPs) through o-Phenylenediamine (oPD) polymerization on graphene modified screen-printed carbon electrode (SPEGPH) was demonstrated. o-Phenylenediamine polymer (PoPD) film provided a suitable microenvironment for RuNPs immobilization. Synthesis of RuNPs was characterized by transmission electron microscope (TEM) and electrochemical methods including cyclic voltammetry (CV) and linear sweep voltammetry (LSV). Encapsulation or incorporation of RuNPs through PoPD were carried out following three different strategies and the resulting platforms were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The electrocatalytic performance of RuNPs-PoPD-GPH platform was demonstrated using the NADH oxidation as model electrochemical reaction. The incorporation of 18 ± 3 nm RuNPs onto PoPD decreased the NADH oxidation potential by ca. 350 ± 5 mV in comparison to bare SPEGPH as well as a remarkable enhance of sensitivity to NADH detection. Therefore, RuNPs have provided electron transfer with a strong catalytic effect for NADH oxidation representing a promising application in sensors. Graphical abstract Image 100 Highlights • A new NADH sensing GPH platform based on Ru nanoplates and several RuNPs/PoPD composite strategies are reported. • RuNPs shows high catalytic effect on NADH oxidation. • PoPD polymer film improves the stability of the RuNPs/PoPD composite on the electrode surface. • Excellent sensitivity and selectivity for detection of NADH. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A ratiometric fluorescent strategy for alkaline phosphatase (ALP) activity assay was proposed. • g-C3N4 and CoOOH nanoflakes were used to develop the sensing platform. • The assay system based on the g-C3N4/CoOOH hybrid responded to ALP sensitively. • Competitive redox reaction was responsible for the ratiometric fluorescence response. • The ratiometric method was applied to quantitative analysis of ALP activity in serum samples. Abstract The development of ratiometric fluorescent strategy is very significant and challenging in bioanalysis. Herein, graphitic carbon nitride (g-C 3 N 4) nanosheets and cobalt oxyhydroxide (CoOOH) nanoflakes are exploited for ratiometric fluorescence assay of alkaline phosphatase (ALP) activity. In the g-C 3 N 4 /CoOOH nanohybrid, g-C 3 N 4 nanosheets serve as a signal unit and the CoOOH nanoflakes function as a recognition element, and initially, the fluorescence of g-C 3 N 4 is quenched by the CoOOH nanoflakes. In the absence of target, the CoOOH nanoflakes of the nanohybrid system are able to oxidize o-phenylenediamine (OPD), and the resultant oxidation product (OxOPD) quenches the blue emission of g-C 3 N 4 and meanwhile emits orange fluorescence which acts as another signal element. However, an efficient redox reaction between ascorbic acid (AA) and CoOOH can cause decomposition of the CoOOH nanoflakes, and additionally, ALP can catalytically hydrolyze L-ascorbic acid-2-phosphate (AAP) to generate AA. Thus, in the presence of target, the CoOOH nanoflakes are destroyed by AA preferentially and the OPD is rarely oxidized to OxOPD, accompanied with strong blue emission of g-C 3 N 4 and weak orange fluorescence from OxOPD. Target-dependent dual-signal change made the ratiometric assay possible, and also AA-induced signal variation was investigated and attributed to the stronger reducing capacity of AA than OPD. The ratiometric sensing platform for ALP activity assay provides a new perspective for the applications of two-dimensional nanomaterials to develop novel and sensitive biosensors. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel dual-ratio fluorescence and colorimetric dual-readout assay for ascorbic acid (AA) was developed. • The dual-readout assay was based on non-oxidation reduction regulation (NRR) strategy. • The NRR strategy remarkably improved the selectivity and sensitivity. • The sensing system with clear response mechanism gives new insight into design of selective detection of AA. • The proposed method has been applied to the analysis of AA in real sample with satisfactory results. Abstract Ascorbic acid (AA), one of the most important vitamins, acts a critical role in various physiological reactions and is involved in many diseases. Thus, the development of highly selectivity methods for detecting AA level with the presence of different reducing substances is of great significance in complicated serum matrix. In this paper, a non-oxidation reduction regulation (NRR) strategy was designed to construct a novel dual-ratio fluorescence and colorimetric dual-readout assay for highly selective detection of AA. The strategy involves three processes: Ag+ oxidated o -phenylenediamine (OPD) to 2,3-diaminophenazine (OPDox), AA inhibited the generation of OPDox and the AA was oxidized to dehydroascorbic acid (DHAA). The specific performance of DHAA NRR, due to the condensation reaction between dicarbonyl group of DHAA and diamine group of OPD, that is confirmed by ESI-MS and 1H NMR spectra analysis, can remarkably enhance the selectivity of AA detection. Additionally, the proposed method based on NRR strategy not only provides a sensing platform for probing AA but also shows promising outlook in biomedical studies. [ABSTRACT FROM AUTHOR]

Abstract To further improve the capacitive performances of reduced graphene oxide-based materials is still crucial although N-doped reduced graphene oxide hydrogels (NrGOHs) exhibit fairly good performance. Here the purified NrGOHs (NrGOHs-SA) are obtained by treating the NrGOHs which are hydrothermally synthesized in the presence of o-phenylenediamine (oPDA) with concentrated sulfuric acid. The effect of preparation conditions on the hydrogels' electrochemical behavior has been systematically investigated. The results reveal that the capacitive performances of NrGOHs-SA are remarkably enhanced compared with the samples of NrGOHs. The optimal NrGOH-SA shows specific capacitance about 519.8 F g−1 at low scan rate, and excellent rate capability. The cells assembled by the optimal hydrogels exhibit the maximum energy density of 11.1 Wh kg−1 and power density of 14.1 kW kg−1, and can retain 93.3% of its initial capacitance after 15,000 cycles. This method can be developed to prepare high-performance NrGOHs materials for energy storage applications. Graphical abstract Unlabelled Image Highlights • Synthesizing NrGOHs by using oPDA and GO as precursors under hydrothermal conditions • Purifying the NrGOHs by using concentrated sulfuric acid • The NrGOHs-SA shows better specific capacitance and rate capacitance than NrGOHs. • The cells assembled by the NrGOHs-SA show high power density and cycling performance. [ABSTRACT FROM AUTHOR]

Background: Aniline compounds are widely applied as important chemical raw materials. However, they are so toxic and harmful to humans and environment that they need to be removed by an effective and economic approach, such as enzymatic reaction, which is in line with contemporary green development concepts. Methods: The effects of major factors, such as temperature, reaction time, concentration of laccase and the initial concentration of substrate on the removal of substrate were investigated by OFAT approach. After simulated wastewater is treated with enzymes, aniline concentration was determined by N-(1-Naphthyl)ethylene-diamine dihydrochloride spectrophotometric method. Concentration of o-phenylenediamine was determined by ferric ammonium alum spectrophotometric method. Results: For the removal of aniline, the optimum conditions were as follows: 50 °C, initial aniline concentration of 80 mg/L and laccase concentration of 1 g/L. In this case, the total removal of aniline reached 97.1% after 8 h, this also involves the volatilization of aniline itself. The optimum conditions of o-phenylenediamine were as follows: 50 °C, initial concentration of 100 mg/L and laccase concentration of 1 g/L. Under the above condition, the o-phenylenediamine could be removed completely after 60 min. Conclusion: The results show that the removal of aniline compounds by laccase from white-rot fungi has good effect and potential application prospect. [ABSTRACT FROM AUTHOR]

A one-pot microwave-assisted hydrothermal approach was developed to quickly synthesize yellow fluorescent carbon dots (CDs) using o-phenylenediamine and urea as raw materials. The optimized reaction temperature of 140°C and reaction time of 10 min were adopted to synthesize the CDs with photoluminescence quantum yield of 4.23%. The as-prepared CDs exhibit yellow fluorescence (λem ∼ 563 nm) and an excitation-independent PL emission in the region of 440-700 nm. The CDs were combined with a blue chip (λex = 420 nm) to fabricate white light-emitting diodes (WLEDs) and realize white light emission. The WLED has the color coordinates of (0.30, 0.30) and the correlated color temperature of 7915 K, which is suitable for office and outdoor illumination. The results demonstrate that as-obtained CDs can be a promising candidate as yellow-emitting phosphors for WLEDs. [ABSTRACT FROM AUTHOR]

We investigated the catalytic efficacy of supported gold nanoparticles (AuNPs) towards the selective reaction between o-phenylenediamine and aldehydes that yields 2-substituted benzimidazoles. Among several supported gold nanoparticle platforms, the Au/TiO2 provides a series of 2-aryl and 2-alkyl substituted benzimidazoles at ambient conditions, in the absence of additives and in high yields, using the mixture CHCl3:MeOH in ratio 3:1 as the reaction solvent. Among the AuNPs catalysts used herein, the Au/TiO2 containing small-size nanoparticles is found to be the most active towards the present catalytic methodology. The Au/TiO2 can be recovered and reused at least five times without a significant loss of its catalytic efficacy. The present catalytic synthetic protocol applies to a broad substrate scope and represents an efficient method for the formation of a C–N bond under mild reaction conditions. Notably, this catalytic methodology provides the regio-isomer of the anthelmintic drug, Thiabendazole, in a lab-scale showing its applicability in the efficient synthesis of such N-heterocyclic molecules at industrial levels.

Polymer supported sulphanilic acid was synthesized and used as green, reusable and heterogeneous catalyst and duly characterized using chemical methods like determination of free hydroxyl content, epoxy equivalent weight and free sulphonic acid content as well as infrared spectroscopy and thermogravimetric analysis. The prepared catalyst was applied for one-pot synthesis of 2-substituted benzimidazoles from o-phenylenediamine and various aromatic aldehydes in absolute ethanol under thermal condition. Catalyst was separated from the product by simple filtration and could be reused for at least five times with almost retention in its efficiency. Due to three dimensional network structures, it shows high thermal stability and can be reused without any further purification.

A novel method was developed for synthesizing a series of new three dentate Schiff base ligands starting from hydroxynaphthalidene pyrimidinyl amines with o-phenylenediamines or o-aminophenol or 2-amino-3-hydroxy-pyri-dine in the presence of formic acid catalyst under solvent-free conditions. In these reactions [1+1] condensation product as half-unit ligand was obtained. Moreover, the reaction of hydroxynaphthalidene pyrimidinyl amines with 3,4-diamino-pyridine and 1,8-naphthalenediamine lead to the formation of C2-naphthylated imidazopyridine and dihydropyrimidine, respectively. The attractive features of this protocol are: use of inexpensive catalyst, operationally simple, short reaction times, easy handling, and good yields.

The rapid, sensitive, and selective detection of pathogenic bacteria is of utmost importance in ensuring food safety and preventing the spread of infectious diseases. Here, we present a novel, reusable, and cost-effective impedimetric sensor based on a dual bacteria-imprinted polymer (DBIP) for the specific detection of Escherichia coli O157:H7 and Staphylococcus aureus . The DBIP sensor stands out with its remarkably short fabrication time of just 20 min, achieved through the efficient electro-polymerization of o-phenylenediamine monomer in the presence of dual bacterial templates, followed by in-situ template removal. The key structural feature of the DBIP sensor lies in the cavity-free imprinting sites, indicative of a thin layer of bacterial surface imprinting. This facilitates rapid rebinding of the target bacteria within a mere 15 min, while the sensing interface regenerates in just 10 min, enhancing the sensor's overall efficiency. A notable advantage of the DBIP sensor is its exceptional selectivity, capable of distinguishing the target bacteria from closely related bacterial strains, including different serotypes. Moreover, the sensor exhibits high sensitivity, showcasing a low detection limit of approximately 9 CFU mL -1 . The sensor's reusability further enhances its cost-effectiveness, reducing the need for frequent sensor replacements. The practicality of the DBIP sensor was demonstrated in the analysis of real apple juice samples, yielding good recoveries. The integration of quick fabrication, high selectivity, rapid response, sensitivity, and reusability makes the DBIP sensor a promising solution for monitoring pathogenic bacteria, playing a crucial role in ensuring food safety and safeguarding public health.

An expeditious one‐pot, metal‐free multicomponent synthesis of quinoxalines has been developed, from easily available starting materials as α‐aminocarbonyl compounds and o‐phenylenediamine instead of complex catalyst systems. The reaction has a broad substrate scope and displays excellent functional‐group tolerance. This method could be easily applied to many fields. An expeditious one‐pot, metal‐free multicomponent synthesis of quinoxalines has been developed, from easily available starting materials as a‐Aminocarbonyl compounds and o‐phenylenediamine instead of complex catalyst systems. The reaction has a broad substrate scope and exhibits excellent functional‐group tolerance. [ABSTRACT FROM AUTHOR]