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Synthesis of a novel binuclear Cu(II) carboxylate complex under ambient laboratory conditions is presented. The complex exhibits a paddle wheel structure in which the axial positions are occupied by two copper atoms instead of two water molecules. The synthesized complex was characterized by single-crystal X-ray crystallography, FT-IR, X-ray diffraction, and UV-visible spectroscopy techniques. The thermal stability of the metal complex was studied by the thermogravimetric analysis study. The synthesized metal complex was employed for the synthesis of metal complex-coated polyether sulfone (PES) membranes which were characterized before and after filtration using the FESEM technique. The photocatalytic efficiency of the metal complex was studied for the degradation of methylene blue dye under UV irradiation in the presence of H2O2 and was compared with the photodegradation efficiency of the metal complex-coated polyether sulfone (PES) membrane. [ABSTRACT FROM AUTHOR]

Anion-induced self-assembly is one of the growing research fields as it provides a better understanding of natural self-assemblies such as DNA, proteins, peptides, etc. Peptides are well known for their aggregation properties owing to their hydrogen bonding interactions. Herein, nanohybrids of the glutathione tripeptide and naphthalimide based compounds were fabricated, in order to explore their self-assembly behaviour. The naphthalimide based compounds were processed into organic nanoparticles using a re-precipitation method and then into nanohybrids with a tripeptide under ultrasonication conditions to get nanohybrids NH-1, NH-2 and NH-3. The morphology of prepared nanohybrids was studied by HRTEM analysis. The photophysical studies of these nanohybrids were carried out by adding various anions. NH-1 shows enhanced fluorescence intensity with bisulphate anions and the rest of the anions do not induce any change in the fluorescence intensity. Furthermore, the morphology of these nanohybrids was monitored using HRTEM and STEM. With bisulphate anions, a beautiful butterfly shaped self-assembly was observed for NH-1. The increase in intensity was a result of the aggregation induced enhanced emission mechanism. These self-assemblies have potential applications in the recognition of bisulphate with a limit of detection (LOD) of 3 nM and a limit of quantification of 10 nM respectively. [ABSTRACT FROM AUTHOR]

A chitosan–poly(vinyl alcohol)–ionic liquid-grafted hydrogel was prepared for water purification. The hydrogel was characterized using various techniques, including nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The swelling properties of the hydrogels were optimized by varying the solvent, pH, time, and temperature. The maximum swelling of the hydrogel was 330%. The hydrogel absorbed dye, nitrite, and Pb2+, with removal rates of up to 97% for dye and 88% for Pb2+. The hydrogel could effectively recover oil from an oil–water mixture, where the removal mechanism was predominantly attributed to electrostatic interactions between the cationic hydrogel and the dye, Pb2+, and nitrite anions. The hydrogel was biodegradable, making it environmentally friendly. [ABSTRACT FROM AUTHOR]

4H-Chromene derivatives are promising anticancer compounds known to bind within the colchicine binding site of the tubulin protein. Among these, the 2-amino-4-phenyl-4H-benzo[h]chromene-3-carbonitrile-based 4H-chromenes scaffold is known to produce a significant impact on tubulin proteins. Other molecules with similar pharmacophores are also known for their colchicine binding site targeting abilities. However, tubulin is not a single protein; multiple isoforms have been reported, and some are comparatively more important under malignant conditions. Therefore, the research findings presented herein include a detailed understanding of the interaction pattern of the 2-amino-4-phenyl-4H-benzo[h]chromene-3-carbonitrile series for their colchicine binding ability against various tubulin isoforms proteins. We have established the current series anticancer potential and structural activity relationship. The series revealed promising anticancer potential, and MNC-1 was the best among all. However, a serious side effect of this scaffold is a major problem, as these derivatives indiscriminately bind to the tubulin of malignant and normal cells. However, the expression profile of tubulin isoforms was found to be different in normal and malignant cell types. Therefore, selective killing of the malignant cell seems possible by designing a 4H-chromenes derivative selective against particular tubulin isoforms. The insights provided herein clearly indicate the differences in the binding pattern of different 4H-chromenes derivatives against different tubulin isoforms. Therefore, with precise structural modification, these molecules' selective targeting against cancer cells seems quite possible. [ABSTRACT FROM AUTHOR]

Regardless of the significant use of 5-bromo-2′-deoxyuridine (BrdU) as a radiosensitizer and diagnostic tool in cancer patients, some severe side effects and health issues have been reported, such as genetic mutations, birth defects, and other inheritable genetic effects. Thus, it has become more important to quantify the amount of BrdU during its usage. With reference to this, Ni@4H-chromene (Ni@G1)-based core–shell nanoparticles have been fabricated and these show a great response for the selective and sensitive detection of BrdU. The formed Ni@G1 exhibits no significant response with interfering thymidine analogs like iododeoxyuridine (EI) and ethynyl deoxyuridine (EdU) in competitive binding studies. Ni@G1 shows the ability to sense BrdU up to a detection limit of 9 nM and no significant interference is shown by pH, salt and temperature. A comparison of studies in aqueous and organic media further reveals that the sensor reported here shows an excellent response in an aqueous medium. [ABSTRACT FROM AUTHOR]

Novel and efficient TiO2@Ag@LaFeO3 core–shell nanorods (hereafter referred as TiO2@Ag@LaFeO3 NRs) were rationally constructed via a facile hydrothermal method. Optical absorption and emission spectra, HRTEM, and XRD investigations were used to ensure the development of nanostructures. The element composition of the composite was further validated by XPS analysis. The energy harvesting efficiency of TiO2@Ag@LaFeO3 NRs is higher than that of bare TiO2, TiO2@Ag, and TiO2@LaFeO3 NRs. The photocurrent value of TiO2@Ag@LaFeO3 NRs is greatly increased by coating with Ag and LaFeO3 shell on the TiO2 NRs core. Under illumination of simulated solar light, the charge transfer resistance of TiO2@Ag@LaFeO3 NRs is significantly reduced. Due to perfect band matching, efficient charge carrier generation, and effective separation within the nanostructure, the maximum catalytic activity of TiO2@Ag@LaFeO3 NRs was obtained. The photocatalytic activity was also investigated for poisonous chemical disintegration and water-soluble harmful Cu2+ ion reduction. The TiO2@Ag@LaFeO3 NRs demonstrated effective photocatalytic reproducibility, universality, and stability for the disintegration of hazardous organic/inorganic compounds. [ABSTRACT FROM AUTHOR]

In today's world, toxic nerve agents pose a significant threat to humankind, and their detection methodology requires an advanced, facile method with a rapid response that is also handy and economical. For the first time, we fabricated bimetallic CdAg alloy over a Biginelli-based non-conjugated polymer dot (Pdot) surface, with chemical reduction in water. The fabricated CdAgAlloy@Pdots were then fully characterized by the use of physicochemical techniques. The modified surface of the Pdots resulted in increased activity and selectivity, and decreased inter-Pdot distance, with generated surface conductivity towards polar organophosphates. The conductive surface was able to selectively bind polar diethylchlorophosphate (DCP) and diethylcyanophosphonate (DCNP), which are nerve agent mimics, through weak interactions such as dipole–dipole or H-bonding interaction. The sensing mechanism was demonstrated by transmission electron microscopy (TEM), FT-IR, 31P NMR images, and cyclic voltammetry (CV) studies. The limit of detection of the sensor for DCP and DCNP was 0.85 nM and 1.2 nM, respectively. In the presence of DCP, the blue color of CdAgAlloy@Pdots changed to fluorescent greenish-yellow under UV light at 365 nm. Based on these results, we fabricated economic test paper strips for an instant, rapid, and sensitive vapor phase detection of DCP that occurred within a few seconds. Hence, we incorporated many key innovations for DCP detection into the formation of bimetallic CdAg alloy@Pdots, which possess long-term economic and sustainable features for real-world sensing applications. [ABSTRACT FROM AUTHOR]

Au@tin and fluorine-doped In2O3 core–shell nanoparticles with different shell thicknesses have been prepared by a simple, cost-effective, and versatile hydrothermal process. The successful formation of the nanocomposites was confirmed by using UV-vis absorption spectra, TEM, XRD, and XPS analysis. The nanoparticles exhibited a highly versatile and repeatable behavior for the decomposition of different toxic organic dyes. The optical, catalytic, and photoelectrochemical properties of tin and fluorine-doped In2O3 were greatly improved by the surface plasmon of Au nanoparticles. The Au@tin and fluorine-doped In2O3 core–shell nanoparticles with low shell thickness, demonstrated 2 times higher photocatalytic activity to decompose poisonous organic dye and around 2.5 times higher catalytic decomposition of toxic Cr(VI) ions present in the aqueous medium. The scavengers and pH of the aqueous solution significantly influenced the catalytic activity of the core–shell nanocomposite. The enhanced catalytic activity of the core–shell nanoparticles was due to the successful use of surface plasmon-generated hot electrons and their effective separation at the metal-semiconductor interface. The photocurrent density of the core–shell nanoparticles was observed to be around 13-fold higher than that of tin and fluorine-doped In2O3 nanoparticles. [ABSTRACT FROM AUTHOR]

Due to the high affinity of imidazolium and benzimidazolium cations to interact with phosphate and sulfate-based anionic surfactants, micelles of different shapes and properties have been constructed by tailoring the design of organic cations and anionic surfactants. Accumulation of a conjugated aromatic system to such kinds of cationic receptors introduces interesting photophysical properties such as aggregation-induced emission (AIE), and aggregation caused quenching (ACQ), which allows them to be used as a sensor and for catalytic degradation of environmental contaminants. The current review will be focused on the design, synthesis, and characterization of micellar structures with various spectroscopic and electrochemical techniques. The applications of the micellar system to the potential future development of sensors are discussed in the context of recent findings of catalytic and sensing activity of cationic receptors. Additionally, the resemblance of these micelles with lipid bilayer structures (phospholipids), and their interaction with the cell wall of bacteria to eradicate the bacteria, is also discussed. [ABSTRACT FROM AUTHOR]

Okadaic acid (OA) is one of the known marine biotoxins produced by various dinoflagellates and exists in seafood such as shellfish. The consumption of contaminated shellfish with OA leads to diarrheic shellfish poisoning (DSP), which results in the inhibition of protein phosphatase enzymes in humans. This poisoning can cause immunotoxicity and tumor promotion due to the accumulation of okadaic acid in more than the allowed limit in bivalve molluscs. The reported methods for the detection of okadaic acid include mouse bioassays, immunoassays, chromatography coupled with spectroscopic techniques, electrochemical sensors and immunosensors. We have developed a naphthalimide-gold-based nanocomposite for the detection of okadaic acid. Individually, the organic nanoparticles (ONPs) of synthesized naphthalimide-based receptors and gold-coated ONPs are less sensitive for detection. However, fabrication of the composite of Au@ONPs and ONPs enhance the sensing properties and selectivity. The composite shows a ratiometric response in the UV-Vis absorption spectrum and quenching in the fluorescence profile with a detection limit of 20 nM for OA in aqueous medium. In cyclic voltammetry, a shift was observed in the cathodic peak (−0.532 V to −0.618 V) as well as in the anodic peak (−0.815 V to −0.847 V) with the addition of okadaic acid. To study the quick binding of the composite with OA, a time response experiment was performed. Also, the developed sensor retains its sensing ability in the pH range of 5–9 and in high salt conditions. Our developed composite can be used for the detection of OA in real applications. [ABSTRACT FROM AUTHOR]

Environmental contamination due to increase in drug levels is reaching an alarming stage. An array of drugs, such as antibiotics, antidepressants, analgesics, and chemotherapy drugs, have been found to be polluting agriculture soils and rivers. Here we developed optical sensors based on terbium(III)-coated carbon quantum dots (Tb-CQDs) synthesized by carrying out a single-step one-pot hydrothermal process in an aqueous medium and characterized by using UV-visible, fluorescence, DLS, HRTEM and XRD measurements. Photophysical studies showed the ability of CQD-Tb to act as a chemosensor of the antidepressant drug clomipramine in aqueous medium. A competitive binding assay using CQD-Tb and clomipramine was carried out in the presence of other drugs. No interference resulted from the presence of the other drugs; and hence, the developed chemosensor can be used for selective detection of clomipramine. A functional group analysis was done using FTIR spectroscopy and a mechanism for drug binding with the chemosensor was derived. To target the interfacial behavior with different drugs, vibrational sum-frequency generation (VSFG) spectroscopy was carried out and further confirmed the ability of the synthesized CQD-Tb to act as a chemosensor for the selective detection of clomipramine in the presence of other drugs. [ABSTRACT FROM AUTHOR]

Carbon Quantum Dots (CQDs) have been extensively employed in various fields of science such as sensing, catalysis, and drug delivery. In this work, ionic liquid coated CQDs (IL@CQDs) have been used as catalysts for the rearrangement of a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) amide coupling intermediate. The rearranged product was confirmed by single crystal structure analysis and it was processed into organic nanoparticles (ONPs). An optical detection method was used to scrutinize the anion sensing properties. The ONPs were found to be sensitive and selective for the recognition of highly toxic cyanide ions through enhancement in the fluorescence intensity. The cyanide ion co-ordinates with the –NH groups of the product and restricts the rotation of molecules around the single bond. The ONPs coated over silica-beads were also showing CN− recognition in the solid state. The detection limit for CN− sensing was found to be 3.8 nM, and real sample analysis depicts more than 90% accuracy in detection. [ABSTRACT FROM AUTHOR]

Selective affinity of a novel coumarin-functionalized fluorescent sensor, 8-((E)-((thiophen-2-yl)methylimino)methyl)-7-hydroxy-4-methyl-2H-chromen-2-one (L), to copper(II) ions via fluorescence quenching in HEPES buffer at pH 7.4 has been demonstrated. This coordination chemistry between the coumarin-based ligand L and copper(II) ions has been subsequently exploited for the generation of a unique chemical ensemble, L·Cu2+, which qualifies the former as a sensitive and selective fluorogenic sensor for the toxic organophosphate pesticide azamethiphos in aqueous medium. The sequestering of the native fluorescence of receptor probe L upon entrapment of copper(II) within the former was altered upon sequential administration of azamethiphos into the environment of the host complex, L·Cu2+. The physico-chemical interactions between the sensor complex L·Cu2+ and azamethiphos, as corroborated by 31P NMR studies and fluorescence spectroscopy, serve as the basis for ideal chemical discrimination of azamethiphos, amongst a pool of several ecotoxic organophosphate pesticides. [ABSTRACT FROM AUTHOR]

As a way to investigate new antiviral leads against Zika virus (ZIKV), we have targeted the NS3 helicase (NS3H) protein with biscoumarin derivatives. The NS3H protein from ZIKV is important, as it plays a significant role in the viral genome replication process. We have assessed the NTPase modulatory effects of biscoumarin derivatives against the NTPase activity of NS3H through in vitro enzymatic studies. Subsequently, to explore the mechanism, detailed computational studies were conducted. The NS3H protein has two binding cavities: one is the NTPase binding cavity where ATP binds, and the other is an RNA binding cavity for the binding of RNA molecules. Biscoumarin derivatives were found to be efficient in binding to both cavities, i.e., the NTPase and RNA binding cavities of the NS3H protein. A biscoumarin derivative with the best binding affinity for the NTPase binding cavity and the lowest binding affinity for the RNA binding groove revealed the best in vitro NTPase inhibitory activity. Also, the biscoumarin derivative with the lowest binding affinity for the NTPase binding cavity and higher binding affinity for the RNA binding cavity revealed the worst NTPase inhibitory activity under the same in vitro assay conditions. Here, we concluded that biscoumarin derivatives are modulators of the NS3H protein and they can be considered as promising anti-viral lead molecules. The structural activity relationships (SARs) of the biscoumarin derivatives in relation to their NTPase inhibitory activities were established, and we reported two derivatives, namely MN-9 and MN-10, as potential NS3H–NTPase inhibitor molecules. [ABSTRACT FROM AUTHOR]

This work is focused on the development of an efficient and green protocol for the one-pot multicomponent synthesis of a series of 4H-pyran derivatives. Herein, a protein–peptide conjugate (SS1–Cyt. c) is synthesized and characterized using Circular Dichroism (CD), UV-Visible absorption spectroscopy, and docking studies. The whole assembly is used as an efficient catalytic system by incorporating a derivatized dipeptide molecule in the hydrophobic cavities of the protein Cytochrome c (Cyt. c) that leads to the activation of Hydrogen Bond Donating (HBD) units of a urea derivative of a dipeptide (SS1). The HBD units tend to show non-covalent interactions with the reactant species responsible for triggering the occurrence of an organic transformation. Also, the stability and binding interactions of SS1–Cyt. c with the multicomponent reactants involved in the organic transformation are studied in detail using MD-simulation studies. It is a metal-free catalyst and provides higher yield in relatively short reaction times. As per green chemistry principles, the catalyst has provided us ideal Eco-scale and E factor scores of 79 and 0.089, respectively. [ABSTRACT FROM AUTHOR]

The labelling and imaging of mitochondria and nucleolus have attracted great attention because of the involvement of these cellular organelles in critical cellular activities. Therefore, a large number of mitochondria- or nucleolus-labelling probes have been developed throughout the world. However, in the current study, we successfully developed two pyrazole-based, copper-linked triphenylphosphine-coupled emissive metallo-complexes (C1 and C2) for the simultaneous visualization of mitochondria and nucleolus in a single run. These complexes were very inexpensive and could be synthesized by a simple one-pot multicomponent reaction scheme. The complexes were very specific, and only a small concentration of 5 μM was found to be sufficient to probe both the organelles efficiently. Additionally, even under a shorter incubation period (half hour), the fluorescence intensity from the cells was appreciable. Also, both the compounds were found to be photostable when torched with 10% of a 100 mW laser for up to 10 min. All these results indicate that both the complexes may contribute towards the future development of cell imaging tools. To the best of our knowledge, this is the first report on the development of multifunctional live cell imaging tools for simultaneous mitochondria and nucleolus imaging and within the shortest incubation time of about 30 minutes. [ABSTRACT FROM AUTHOR]

Hyperglycaemia is a condition of metabolic disorder in which glycation of human serum albumin (HSA) protein occurs. Upon glycation, the α-helical region of the protein undergoes characteristic changes in its structural features. In this study, we designed a fluorescence probe that can distinguish HSA proteins from glycated HSA (GHSA) proteins. The developed probe contains an oxazolonapthoimidazo[1,2-a]pyridine-based moiety (ONIP1) and was designed using rational computational techniques. The compound exhibits aggregation-induced enhanced emission (AIEE) along with the excited-state intermolecular proton transfer (ESIPT) phenomenon. Density functional theory (DFT) calculations have provided data on ground- and excited-state energy-optimized structures and properties of the proposed enol (N*) and keto (T*) form, which is also in agreement with the solution-state experimental findings and supports the occurrence of the ESIPT phenomenon. Using ONIP1, we were able to distinguish HSA and GHSA proteins via typical modulation of AIEE and ESIPT events. [ABSTRACT FROM AUTHOR]

The extreme toxicity of mercury and its derivatives results from its high affinity for thiol groups in proteins and enzymes, leading to the dysfunction of cells and consequent health problems. Thus, developing a rapid, cheap and colorimetric sensor for detecting mercury ions at very low levels remains a challenge. Herein, we have developed a new chromogenic azophenol-based probe which allows the colorimetric detection of Hg(ii) metal ions and subsequently, showed suitability as a RGB chemodosimeter for the selective sensing of Hg(ii) in aqueous medium. The UV-vis absorption and colorimetric study showed that the azophenol-based sensor is highly selective towards Hg(ii) detection without the interference of other analytes. The color change from deep red to yellow in the complex solution after treating with mercury metal ions, which is visible by the naked-eye, makes this probe more convenient and simple to use in real sample analysis. Furthermore, for practical application of the sensor system in real time sample analysis, solid state silica based sensor chips have been developed which are impregnated with probe 1 displaying colorimetric changes for different concentrations of Hg2+, where the intensity of the red color decreased gradually towards a yellow color after the addition of Hg2+, apparently, makes them as potential candidate to conveniently monitor the concentration of Hg2+ in aqueous test solutions. [ABSTRACT FROM AUTHOR]

Tyrosinase is polyphenolic oxidase enzyme associated with the progression of various diseases. Therefore, for the recognition of tyrosinase, naphthalimide-based ratiometric fluorescent sensor probe was designed and synthesized. 3-Hydroxyphenyl, as the substrate unit for the enzyme, is an important feature of this design, which avoids the interference of other bio-analytes for the recognition of tyrosinase. When the sensor probe was excited at 425 nm, an intense blue emission band emerged at 467 nm. However, upon the addition of tyrosinase to the probe solution, the monophenolic unit oxidized to o-dihydroxy and consequently released the 4-aminonaphthalimide unit. As the oxidation reaction proceeded, the fluorescence emission at 535 nm started to increase gradually with an increase in the concentration of enzyme. Therefore, the sensor probe gives the ratiometric changes via fluorescence spectroscopy. The probe affords high selectivity and sensitivity to tyrosinase with a detection limit of 0.2 U mL−1. Furthermore, live cell images were recorded to assay the endogenous enzyme in A375 cells, which also show a dual color change in the presence of the L3 probe. [ABSTRACT FROM AUTHOR]

There is burgeoning interest among supramolecular chemists to develop novel molecular systems to detect biogenic amines and bio-thiols in aqueous and non-aqueous media due to their potential role in biological processes. Biogenic amines are biologically important targets because of their involvement in the energy metabolism of human biological systems and their requirement is met through food and nutrition. However, the increasing instances of serious health problems due to food toxicity have raised the quality of food nowadays. Biogenic amines have been frequently considered as the markers or primary quality parameters of foods like antioxidant properties, freshness and spoilage. For instance, these amines such as spermine, spermidine, cadavarine, etc. may originate during microbial decarboxylation of amino acids of fermented foods/beverages. These amines may also react with nitrite available in certain meat products and concomitantly produce carcinogenic nitrosamine compounds. On the other hand, it is also well established that biothiols, particularly, thiol amino acids, provide the basic characteristics to food including flavor, color and texture that determine its acceptability. For instance, the reduction of thiol groups produces hydrogen sulfide which reduces flavour as in rotten eggs and spoiled fish, and the presence of hydrogen sulfide in fish is indicative of spoilage. Thus, biogenic amines and bio-thiols have attracted the profound interest of researchers as analytical tools for their quantification. Much scientific and technological information is issued every year, where the establishment of precise interactions of biogenic amines and bio-thiols with other molecules is sought in aqueous and non-aqueous media. This review summarizes the optical chemosensors developed for the selective detection of biogenic amines and bio-thiols. [ABSTRACT FROM AUTHOR]

Non-covalent bonding viaπ–π stacking is in demand these days because it does not affect the structure of the carbon nanotube (CNT). Herein, a hybrid material was fabricated viaπ–π stacking between the aromatic rings of carbon nanotubes and a dihydropyrimidone-based pyrene derivative. The developed CNT@pyrene hybrid material was fully characterized using SEM, EDX, TEM, XRD, and FTIR techniques. The hybrid was developed to improve the heat transport in the hybrid solution by anion addition. The emission profile of the developed hybrid was screened against TBA salts of different anions in EtOH–H2O (10–90% v/v) solvent system to identify the anion that can interact with the hybrid. The hybrid exhibited high sensitivity and selectivity towards NO3− ions with 1.5-fold enhancement in fluorescence intensity, while other anions neither showed significant responses nor interfered in the sensor's response. The limit of NO3− ions detection was found to be 8.1 nM, calculated using the 3-sigma method. It was observed that the proposed hybrid sensor showed stable response at different pH and diverse salt concentrations. The binding mechanism was elucidated by DFT-based theoretical calculations. Real sample analysis was performed for the detection of NO3− concentrations in local water bodies with accuracy as high as 95%. Viscosity and thermal conductivity experiments were performed to measure the effect of concentration, temperature, and pH on the NO3− response. [ABSTRACT FROM AUTHOR]

A dual mechanistic FRET and PET paired ratiometric fluorescence sensor probe has been prepared using carbon dots and naphthalimide fluorophores. The carbon dots are covalently joined with a naphthalimide moiety to develop the FRET phenomenon, which emits at two different wavelengths (i.e., λmax = 440 and 540 nm). However, on catalytic reaction of tyrosinase, the fluorescence emission intensity of the acceptor unit at 540 nm is quenched gradually, owing to the switching on of the PET mechanism; while emission of the donor unit remains significantly unaffected. The probe exhibits high selectivity and specificity towards tyrosinase in complex biological medium with a detection limit of 1.2 U mL−1. Moreover, endogenous images of tyrosinase in B16 cells have been observed under a confocal laser-scanning microscope. [ABSTRACT FROM AUTHOR]

The unregulated use of organophosphates (OPs) as pesticides and toxic chemical warfare agents demands their continuous monitoring from a human health perspective. This study describes a fluorescence turn-on sensing assay for the selective quantification of OPs in aqueous medium. Metal complexes of two different Biginelli derivatives were processed in water through a reprecipitation technique. The engineered self-assembly of the pyridyl-2-cobalt complex (L1·Co(II)) was employed to selectively detect malathion while the pyridyl-4-cobalt complex (L2·Co(II)) could estimate azamethiphos fluorimetrically up to a detection limit of 9.2 nM and 11 nM, respectively. Furthermore, the pesticide degradation ability of OPs was assessed using a 31P-NMR technique. This new paradigm expands the versatility of Biginelli derivatives as promising sensing platforms via metal complexation which may further be explored for estimation of analytes. [ABSTRACT FROM AUTHOR]

Thioredoxin Reductase (TrxR) is a redox regulating enzyme which is predestined for the maintenance of redox homeostasis of mammalian cells. However, the elevated level of TrxR is associated with the progress of various types of tumors and therefore, this is a significant target for the detection of cancer cells. Herein, an easily engineered ‘Turn ON’ fluorescent sensor probe has been synthesized for the detection of TrxR and cell imaging using carbon dots. The emission intensity of fCDs on complexation with Cu2+ ions was drastically quenched. Subsequently, the addition of TrxR to the solution of the fCDs-Cu2+ complex leads to the cleavage of the disulfide bond of the fCDs, which acclaim the release of 3-mercaptopropionic acid. 3-Mercaptopropionic acid, being a strong bi-dentate chelating agent for Cu2+ ions, extracted Cu2+ from the coordination sphere of fCDs and restored the original fluorescence intensity of fCDs. Thus, the probe is operating with a simple process of “ON–OFF” emission switching due to Cu2+ and “OFF–ON” switching with TrxR. The probe has been successfully used for real-time application to monitor TrxR activities in the complex biological system. The fluorescence images of MCF-7 and HeLa cells after incubation with the fCDs-Cu2+ complex were recorded under a confocal laser scanning microscope (CLSM) as a function of time. Enhancement in the emission intensity of cancer cells after 2 h of treatment demonstrates the potential application of the sensor probe for the bioimaging of endogenous TrxR in living cells and screening of cancer cells. Such fluorescent probes will open the door for the development of promising clinical devices for the diagnosis of cancer cells. [ABSTRACT FROM AUTHOR]

A convenient, solvent free strategy for the synthesis of bis-coumarins has been developed using zwitterionic liquid (ZIL) coated copper oxide (CuO) and mechanical ball milling. The ZIL were fabricated from imidazolium/benzimidazolium and sulfonate/carboxylate based moieties. Use of the ZIL offers an interesting multifunctional opportunity to immobilize them over CuO using the anionic part and the cationic part is left freely available for use in catalytic applications. The hybrid catalysts were fully characterized using scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, powder X-ray diffraction, cyclic voltammetry, solid state ultraviolet-visible absorption and spectroscopic emission methods. The three ZIL-based and CuO coupled hybrid catalysts (ZIL@CuO1–3) generated were found to have diverse sizes, shapes, photophysical signatures and electrochemical properties. The supramolecular assembly of ZIL and CuO in ZIL@CuO1 has extensively enhanced catalytic activity compared to their individual parent components as well as to the two other hybrid materials, ZIL@CuO2–3. The reaction conditions were optimized by varying the number of balls used, the milling time and the milling speed. The reaction mechanism was elucidated using proton–nuclear magnetic spectroscopy and all the final products were fully characterized using spectroscopic methods. Finally, the performance of the reaction at the multigram scale is also detailed and a high EcoScale score and a low E-factor are the most pleasing features of this methodology, and thus, authenticate its use for eco-friendly synthesis of bis-coumarins and offer advancements over other catalysts described in the literature. [ABSTRACT FROM AUTHOR]

Nanostructures possess interesting particle dimensions, high surface areas, improved solubility, biological adsorption and improved electrochemical behavior. Based on the properties of nanostructures compared to their bulk counterparts, a hybrid material has been developed using carbon nanotubes (CNTs) and silver (Ag) nanoparticles. CNTs were grown using a chemical vapor deposition (CVD) method and then purified and functionalized using an acidic mixture. Silver nanoparticles were generated through the reduction of AgNO3 using NaBH4 and during the progression of reaction, Ag ions were trapped in the COOH linkage of an acid functionalized CNT, which resulted in decoration of Ag nanoparticles on the surface of the CNT. Three different concentrations of nano-hybrids were developed by varying the amount of Ag nanoparticles. The CNT@Ag nano-hybrids were successfully characterized using SEM, TEM, EDX, BET, XRD and FTIR. It was observed from SEM micrographs that the variation in concentrations of reactants resulted in modulation of the morphology of CNT@Ag nano-hybrid. Electrochemical and photo-physical behaviours were tested for the developed nano-hybrids. The synthesized CNT@Ag nano-hybrid was used to monitor and control toxic gases, where an attempt was made to detect CO2 in an aqueous medium using developed nano-hybrids via an electrochemical route. Results showed that the proposed sensor exhibited a significant response towards the detection of CO2 with a detection limit of 52 nM, and it also converted CO2 to oxalates. [ABSTRACT FROM AUTHOR]

Two copper complexes C1 and C2 have been designed and developed for selective sensing of organophosphates. It is important to develop an efficient method for the detection of these agents for environmental analysis because the overuse of these agents in the environment causes harmful effects on living systems. Our attempts to utilize the copper complexes for the detection of organophosphates remained successful: the C1 complex has shown selective binding for the azamethiphos with a detection limit of 19 nM; while the C2 complex has not revealed any selectivity for any of the tested organophosphates. The results indicated that the coordination sphere of the C1 complex is proficiently engineered in such a way that it offers judicial binding sites for guest molecules. [ABSTRACT FROM AUTHOR]

The detrimental effects caused by the presence of biogenic amines in food samples render them an important parameter for evaluating food quality. In the current report, a facile fluorescent Biginelli based receptor 1 has been prepared through a multicomponent reaction between pyridine-2-carbaldehyde, methyl acetoacetate and 2-aminobenzimidazole in a single pot using a zinc perchlorate catalyst. Subsequently, the receptor 1 was processed to obtain aqueous phase organic nanoparticles, N1, which were characterized using DLS and TEM. Fluorescence spectroscopy studies in aqueous media revealed that the organic nanoparticles show interesting potential for Ag(i) recognition with a fluorescence “turn-off” mechanism. The resultant Ag–receptor complex, N1.Ag(i), was further found to bind with tyramine (limit of detection: 3.91 nM) and 1,2-diaminopropane (limit of detection: 4.21 nM) through unquenching of fluorescence. [ABSTRACT FROM AUTHOR]

Molecular recognition is an emerging field of Supramolecular Chemistry. The major challenge for supramolecular chemists is detection in an aqueous medium. However, most biological and environmental processes happen in an aqueous medium; therefore, chemosensors that can operate in water are highly demanded. This review mainly focuses on the recognition of analytes (metal, anion and biomolecules) in an aqueous medium (≥90% water) and demonstrates that sensing in an aqueous medium can be achieved without compromising the selectivity and sensitivity. The detail discussion on the design of chemosensors and the mechanism of action for detection of metal ions, anions and biomolecules in an aqueous medium has been provided, reported in the period of 2001–2015. [ABSTRACT FROM AUTHOR]

We have developed a novel isonicotiamide-based fluorescent “turn-on” chemosensor 1 for the selective detection of Zn2+ and HSO4−. The sensor 1 can detect Zn2+ and HSO4− with a detection limit down to the nanomolar level by forming a complex in 1 : 1 stoichiometry in the presence of other anions and 2 : 1 in presence of cations in aqueous solution. Density functional theory calculations on 1 and the 1-Zn2+/HSO4− complexes are consistent with the experimental results. We have successfully utilized the above cation and anion for the fabrication of INHIBIT molecular logic gates. Furthermore the receptor 1 successfully detected the Zn2+ and HSO4− ions in HeLa cells cultured in Zn2+ and HSO4− enriched medium. [ABSTRACT FROM AUTHOR]

ZnO nanoparticles decorated with organic receptor 1 (R1) have been prepared and the resultant compound (N1) was investigated for its metal recognition ability. N1 was found to be selective for mercury ions (Hg2+) in a DMSO/water mixture in a ratio of 7 : 3 and possessed no interference from any of the potential interferent metal ions. The crystal size and morphology of ZnO is characterized using various spectroscopic and diffraction techniques like scanning electron microscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), etc. Surface decoration of the ZnO with receptor 1 is confirmed using NMR spectroscopy. On successive additions of Hg2+ ions, the fluoresence intensity of the compound was quenched at 427 nm with enhancement of the peak at 482 nm, which led to ratiometric sensor development for the recognition of mercury ions having a detection limit of 0.19 nM. The prepared receptor was also tested for real sample application by preparing a known concentration of Hg2+ solution and it was found to respond well with an accuracy more than 90%. [ABSTRACT FROM AUTHOR]

A solvent-free selective green synthesis of 1,2-disubstituted benzimidazoles was developed using a ball-milling technique. Recyclable ionic liquid-coated ZnO-nanoparticles (ZnO-NPs, catalyst 5) were employed as a catalyst, which produced high yields, turnover number and turnover frequency because of the synergetic catalytic properties of the ionic liquid and ZnO-NPs. The present method was successfully employed in the synthesis of various 1,2-disubstituted benzimidazole derivatives in excellent yields with high selectivity. The reaction could also be performed on a multi-gram scale with the same efficiency. A high eco-scale score and a low E-factor emphasize the ecofriendly nature of the present method. [ABSTRACT FROM AUTHOR]

A Schiff base based tripodal receptor was synthesized and complexed with a zinc metal ion (n17) using a very easy single step process. The resulting complex was fully characterized by CHN and single crystal XRD. The real time application of the complex in aqueous media was devised by preparing its organic nanoparticles (ONPs) and their sensor activity was tested with various anions by observing changes in the fluorescence profile of n17. It was observed that ONPs of n17 responded excellently for fluoride and sulfate, producing two different signals, with detection limits of 4.84 × 10−12 M and 5.67 × 10−9 M respectively, without having any interference from each other. The real time application of the sensor was also tested using various samples collected from various daily utility items and found to respond exceptionally well. [ABSTRACT FROM AUTHOR]

Luminescent sensors and switches continue to play a key role in shaping our understanding of key biochemical processes, assist in the diagnosis of disease and contribute to the design of new drugs and therapies. Similarly, their contribution to the environment cannot be understated as they offer a portable means to undertake field testing for hazardous chemicals and pollutants such as heavy metals. From a physiological perspective, the Group I and II metal ions are among the most important in the periodic table with blood plasma levels of H+, Na+ and Ca2+ being indicators of several possible disease states. In this review, we examine the progress that has been made in the development of luminescent probes for Group I and Group II ions as well as protons. The potential applications of these probes and the mechanism involved in controlling their luminescent response upon analyte binding will also be discussed. [ABSTRACT FROM AUTHOR]