Lewis Acid-Catalyzed Benzannulation of Vinyloxiranes with 3-Formylchromones or 1,4-Quinones for Diversely Functionalized 2-Hydroxybenzophenones, 1,4-Naphthoquinones, and Anthraquinones.

A facile and convenient protocol for the regioselective construction of functionalized 2-hydroxybenzophenones is described. This protocol involves the Sc(OTf)3/BF3·OEt2-catalyzed benzannulation of 2-vinyloxirans with 3-formylchromone, which involves cascade in situ diene formation, [4 + 2] cycloaddition, elimination, and ring-opening strategies. Moreover, it provides an expedited synthetic pathway to access biologically intriguing 1,4-naphthoquinones and anthraquinones including vitamin K3 and tectoquinone. The synthesized compounds also hold potential for use as UV filters and show promise as chemosensors for Cu2+ and Mg2+ ions.

Silver nanoparticles loaded graphene-poly-vinylpyrrolidone composites as an effective recyclable antimicrobial agent.

Silver nanoparticles (AgNPs) are often used as antibacterial agents. Here, graphene-silver nanoparticles (G-Ag) and graphene-silver nanoparticles poly-vinylpyrrolidone (G-AgPVPy) were prepared by chemical reduction and in-situ polymerization of vinylpyrrolidone (VPy). The prepared G-Ag and G-AgPVPy composites were characterized using various techniques. The size of the AgNPs on the graphene surface in the prepared G-Ag and G-AgPVPy composites was measured as ∼20 nm. The graphene sheets size in the G-Ag and G-AgPVPy composites were measured as 6.0-2.0 µm and 4.0-0.10 µm, respectively, which are much smaller than graphene sheets in graphite powder (GP) (10.0-3.0 µm). The physicochemical analysis confirmed the formation of G-Ag and G-AgPVPy composites and even the distribution of AgNPs and PVPy on the graphene sheets. The synthesized composites (G-AgPVPy, G-Ag) exhibited a broad-spectrum antibacterial potential against both Gram-negative and Gram-positive bacteria. The lowest minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were calculated as >40 µg/mL using G-Ag and GP, while G-AgPVPy showed as 10 µg/mL against Staphylococcus aureus. Among GP, G-Ag, and G-AgPVPy, G-AgPVPy disturbs the cell permeability, damages the cell walls, and causes cell death efficiently. Also, G-AgPVPy was delivered as a significant reusable antibacterial potential candidate. The MIC value (10 µg/mL) did not change up to six subsequent MIC analysis cycles.

Multiple heteroatom dopant carbon dots as a novel photoluminescent probe for the sensitive detection of Cu2+ and Fe3+ ions in living cells and environmental sample analysis.

Heavy metal ion pollution harms human health and the environment and continues to worsen. Here, we report the synthesis of boron (B), phosphorous (P), nitrogen (N), and sulfur (S) co-doped carbon dots (BP/NS-CDs) by a one-step facile hydrothermal process. The optimum synthetic parameters are of 180 °C temperature, 12 h reaction time and 15% of PBA mass. The as-synthesized BP/NS-CDs exhibits excellent water solubility, strong green photoluminescence (PL) at 510 nm, and a high quantum yield of 22.4%. Moreover, BP/NS-CDs presented high monodispersity (7.2 ± 0.45 nm), excitation-dependent emission, PL stability over large pH, and high ionic strength. FTIR, XRD, and XPS are used to confirm the successful B and P doping of BP/NS-CDs. BP/NS-CD photoluminescent probes are selectively quenched by Cu2+ and Fe3+ ions but showed no response to the presence of other metal cations. The PL emission of BP/NS-CDs exhibited a good linear correlation with Cu2+ and Fe3+ concentrations with detection limits of 0.18 µM and 0.27 µM for Cu2+ and Fe3+, respectively. Furthermore, the HCT116 survival cells kept at 99.4 ± 1.3% and cell imaging capability, when the BP/NS-CDs concentration is up to 300 µg/mL by MTT assay. The proposed sensor is potential applications for the detection of Cu2+ and Fe3+ ions in environmental water samples.

WITHDRAWN: Heavy metal ions and dyes removal from aqueous solution using Aloevera-based biosorbent: A systematic review.

This article has been withdrawn: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been withdrawn at the request of the authors, editor and publisher. The publisher regrets that an error occurred which led to the premature publication of this paper. The publisher apologizes to the readers for this unfortunate erro

Nitrogen and sulfur co-doped photoluminescent carbon dots for highly selective and sensitive detection of Ag+ and Hg2+ ions in aqueous media: Applications in bioimaging and real sample analysis.

In this study, we report the synthesis of photoluminescent (PL) nitrogen (N) and sulfur (S) co-doped carbon dots (NS-CDs) from nitazoxanide and 3-mercaptopropionic acid as a precursors via a one-pot hydrothermal methods. N and S co-doped materials allows more active sites in the CDs surface resulting in an enhancement of their PL properties. NS-CDs show bright blue PL, excellent optical properties, good water solubility, and a high quantum yield (QY) of 32.1%. The as-prepared NS-CDs were confirmed by UV-Visible, photoluminescence, FTIR, XRD and TEM analysis. An optimized excitation at 345 nm, the NS-CDs exhibited strong PL emission at 423 nm with an average size of 3.53 ± 0.25 nm. Under optimized conditions, the NS-CDs PL probe shows high selectivity with Ag+/Hg2+ ions detected, while other cations no significant changes the PL signal. The PL intensity of NS-CDs linearly quenching and enhancement with Ag+ and Hg2+ ions from 0 to 50 × 10-6 M, with the detection limit of 2.15 × 10-6 M and 6.77 × 10-7 M (S/N = 3). More interestingly, as-synthesized NS-CDs shows a strong binding to Ag+/Hg2+ ions with the PL quenching and enhancement to precise and quantitative detection of Ag+/Hg2+ ions in living cells. The proposed system was effectively utilized for the sensing of Ag+/Hg2+ ions in real samples resulting in high sensitivity and good recoveries (98.4-109.7%).

Natural Nitrogen-Doped Carbon Dots Obtained from Hydrothermal Carbonization of Chebulic Myrobalan and Their Sensing Ability toward Heavy Metal Ions.

Chebulic Myrobalan is the main ingredient in the Ayurvedic formulation Triphala, which is used for kidney and liver dysfunctions. Herein, natural nitrogen-doped carbon dots (NN-CDs) were prepared from the hydrothermal carbonization of Chebulic Myrobalan and were demonstrated to sense heavy metal ions in an aqueous medium. Briefly, the NN-CDs were developed from Chebulic Myrobalan by a single-step hydrothermal carbonization approach under a mild temperature (200 °C) without any capping and passivation agents. They were then thoroughly characterized to confirm their structural and optical properties. The resulting NN-CDs had small particles (average diameter: 2.5 ± 0.5 nm) with a narrow size distribution (1-4 nm) and a relatable degree of graphitization. They possessed bright and durable fluorescence with excitation-dependent emission behaviors. Further, the as-synthesized NN-CDs were a good fluorometric sensor for the detection of heavy metal ions in an aqueous medium. The NN-CDs showed sensitive and selective sensing platforms for Fe3+ ions; the detection limit was calculated to be 0.86 µM in the dynamic range of 5-25 µM of the ferric (Fe3+) ion concentration. Moreover, these NN-CDs could expand their application as a potential candidate for biomedical applications and offer a new method of hydrothermally carbonizing waste biomass.

Supramolecular ß-Cyclodextrin-Quercetin Based Metal-Organic Frameworks as an Efficient Antibiofilm and Antifungal Agent.

The loading of drugs or medicinally active compounds has recently been performed using metal-organic frameworks (MOFs), which are thought to be a new type of porous material in which organic ligands and metal ions can self-assemble to form a network structure. The quercetin (QRC) loading and biofilm application on a cyclodextrin-based metal-organic framework via a solvent diffusion approach is successfully accomplished in the current study. The antibacterial plant flavonoid QRC is loaded onto ß-CD-K MOFs to create the composite containing inclusion complexes (ICs) and denoted as QRC:ß-CD-K MOFs. The shifting in the chemical shift values of QRC in the MOFs may be the reason for the interaction of QRC with the ß-CD-K MOFs. The binding energies and relative contents of MOFs are considerably changed after the formation of QRC:ß-CD-K MOFs, suggesting that the interactions took place during the loading of QRC. Confocal laser scanning microscopy (CLSM) showed a reduction in the formation of biofilm. The results of the cell aggregation and hyphal growth are consistent with the antibiofilm activity that is found in the treatment group. Therefore, QRC:ß-CD-K MOFs had no effect on the growth of planktonic cells while inhibiting the development of hyphae and biofilm in C. albicans DAY185. This study creates new opportunities for supramolecular ß-CD-based MOF development for use in biological research and pharmaceutical production.

Tenofovir antiviral drug solubility enhancement with ß-cyclodextrin inclusion complex and in silico study of potential inhibitor against SARS-CoV-2 main protease (Mpro).

Tenofovir (TFR) is an antiviral drug commonly used to fight against viral diseases infection due to its good potency and high genetic barrier to drug resistance. In physiological conditions, TFR is less water soluble, more unstable, and less permeable, limiting its effective therapeutic applications. In addition to their use in treating the Coronavirus disease 2019 (COVID-19), cyclodextrins (CDs) are also being used as a molecule to develop therapies for other diseases due to its enhance solubility and stability. This study is designed to synthesize and characterization of ß-CD:TFR inclusion complex and its interaction against SARS-CoV-2 (MPro) protein (PDB ID;7cam). Several techniques were used to characterize the prepared ß-CD:TFR inclusion complex, including UV-Visible, FT-IR, XRD, SEM, TGA, and DSC, which provided appropriate evidence to confirm the formation. A 1:1 stoichiometry was determined for ß-CD:TFR inclusion complex in aqueous medium from UV-Visible absorption spectra by using the Benesi-Hildebrand method. Phase solubility studies proposed that ß-CD enhanced the excellent solubility of TFR and the stability constant was obtained at 863 ± 32 M-1. Moreover, the molecular docking confirmed the experimental results demonstrated the most desirable mode of TFR encapsulated into the ß-CD nanocavity via hydrophobic interactions and possible hydrogen bonds. Moreover, TFR was validated in the ß-CD:TFR inclusion complex as potential inhibitors against SARS-CoV-2 main protease (Mpro) receptors by using in silico methods. The enhanced solubility, stability, and antiviral activity against SARS-CoV-2 (MPro) suggest that ß-CD:TFR inclusion complexes can be further used as feasible water-insoluble antiviral drug carriers in viral disease infection.

Fe(III)-Catalyzed Tandem Cyclization of Phenylpropiolamides with 3-Formylchromones for the Construction of 2-Pyridones.

A highly efficient and atom-economic iron(III)-catalyzed three-component heteroannulation reaction between phenylpropiolamides, 3-formylchromones, and water is described for the construction of diversely multifunctionalized 2-pyridones. This protocol allows rapid access to a variety of 2-pyridones bearing an ortho-hydroxybenzoyl and a benzoyl scaffold under operationally simple conditions. The synthetic utility of the synthesized 2-pyridone scaffolds is demonstrated by transformation into biologically interesting complex heterocycles.

Annulation strategies for diverse heterocycles via the reductive transformation of 2-nitrostyrenes.

Reduction of the stable nitro group is a fundamental and widely used transformation for the construction of complex and functionalized heterocyclic architectures. The unfolding of the reactivity of the nitro group in the 2-nitrostyrene moiety not only triggers the formation of carbon-nitrogen bonds, but also offers the opportunity for annulation and heteroannulation, thereby providing a cascade process for the synthesis of highly conjugated natural and unnatural molecules. In this review, we comprehensively discuss the use of 2-nitrostyrene motifs in the synthesis of various N-heterocycles. We offer readers an overview of the synthetic achievements achieved to date, highlighting their important features, reactivities, and mechanisms.

Microwave-assisted annulation for the construction of pyrido-fused heterocycles and their application as photoluminescent chemosensors.

A catalyst-free microwave-assisted annulation protocol for the preparation of biologically interesting pyrido-fused quinazolinones and pyrido[1,2-a]benzimidazoles is developed. This reaction involves the [3 + 3] annulation of various quinazolinones or benzimidazoles with 3-formylchromones to yield functionalized 11H-pyrido[2,1-b]quinazolin-11-one and pyrido[1,2-a] benzimidazole derivatives. This approach is successfully extended to the construction of various pyrazolo[4,3-d]pyrido[1,2-a]pyrimidin-10(1H)-ones. The present approach is complementary to the existing synthetic methodologies and offers a rapid and facile approach with a broad substrate scope, good yields, catalyst-free conditions, and a high functional group tolerance. The optimal synthesized compound is also employed as an "on-off" photoluminescent probe for the selective detection of Fe3+ and Ag+ metal ions.

Transition metal-catalyzed regioselective functionalization of carbazoles and indolines with maleimides.

The directing group-assisted regioselective C-H activation of carbazoles and indolines is achieved via transition metal-catalyzed reactions. This C-H functionalization protocol provides a rapid approach to install diversely functionalized succinimide groups at the C-1 position of the carbazole moiety. In addition, this protocol demonstrates the intrinsic reactivity of indolines in providing C-2 succinimide-substituted indoles via cascade direct oxidation and C-H functionalization. This protocol also provides C-7 succinimide-substituted indolines under mild reaction conditions. The features of this reaction include a wide substrate scope and excellent regioselectivity for the installation of the succinimide moiety on biologically interesting molecules.

Immobilization of enzymes for bioremediation: A future remedial and mitigating strategy.

Over the years, extensive urbanization and industrialization have led to xenobiotics contamination of the environment and also posed a severe threat to human health. Although there are multiple physical and chemical techniques for xenobiotic pollutants management, bioremediation seems to be a promising technology from the environmental perspective. It is an eco-friendly and low-cost method involving the application of microbes, plants, or their enzymes to degrade xenobiotics into less toxic or non-toxic forms. Moreover, bioremediation involving enzymes has gained an advantage over microorganisms or phytoremediation due to better activity for pollutant degradation with less waste generation. However, the significant disadvantages associated with the application of enzymes are low stability (storage, pH, and temperature) as well as the low possibility of reuse as it is hard to separate from reaction media. The immobilization of enzymes without affecting their activity provides a possible solution to the problems and allows reusability by easing the process of separation with improved stability to various environmental factors. The present communication provides an overview of the importance of enzyme immobilization in bioremediation, carrier selection, and immobilization methods, as well as the pros and cons of immobilization and its prospects.

Lotus-biowaste derived sulfur/nitrogen-codoped porous carbon as an eco-friendly electrocatalyst for clean energy harvesting.

Recent research is focused on biomass-derived porous carbon materials for energy harvesting (hydrogen evolution reaction) because of their cost-effective synthesis, enriched with heteroatoms, lightweight, and stable properties. Here, the synthesis of porous carbon (PC) materials from lotus seedpod (LP) and lotus stem (LS) is reported by the pyrolysis method. The porous and graphitic structure of the prepared LP-PC and LS-PC materials were confirmed by field emission scanning electron microscopy, transmission electron microscopy with selected area electron diffraction, X-ray diffraction, and nitrogen adsorption-desorption measurements. Heteroatoms in LP-PC and LS-PC materials were investigated by attenuated total reflection-Fourier transform infrared and X-ray photoelectron spectroscopy. The specific surface area of LP-PC and LS-PC were calculated as 457 and 313 m2 g-1, respectively. Nitrogen and sulfur enriched LP-PC and LS-PC materials were found to be effective electrocatalysts for hydrogen evolution reactions. LP-PC catalyst showed a very low overpotential of 111 mV with the Tafel slope of 69 mV dec-1, and LS-PC catalyst achieved a Tafel slope of 85 mV dec-1 with a low overpotential of 135 mV. This work is expected to be extended for the development of biomass as a sustainable porous carbon electrocatalyst with a tunable structure, elements, and electronic properties. Furthermore, preparing carbon materials from the biowaste and applying clean energy harvesting might reduce environmental pollution.

Tunable fluorescent carbon dots from biowaste as fluorescence ink and imaging human normal and cancer cells.

Growing global biowaste and its environmental issues challenge the need for converting biowastes into a beneficial product. Among the biowaste, here kiwi fruit (Actinidia Deliciosa) peels are considered for the preparation of carbon dots (CDs). Using a green one-pot hydrothermal-carbonization method, kiwi fruit peels were effectively converted into valuable kiwi fruit peel carbon dots (KFP-CDs). The morphology, physio-chemical and optical properties of as-synthesized KFP-CDs were analyzed using various analytical techniques such as X-ray powder diffraction, Raman spectroscopy, attenuated total reflection-Fourier transform infrared spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Ultraviolet-visible, and fluorescence spectroscopy. The KFP-CDs revealed a homogeneous spherical shape, monodispersed with an average size of 5 nm. The characterization confirms that KFP-CDs have functional groups such as -CN, -COOH, and -OH which are responsible for the easy dispersion of KFP-CDs in aqueous media. Without any preprocessing, KFP-CDs exhibit strong fluorescence upon exposure to UV light. Further, KFP-CDs displayed excitation-dependent fluorescence emission with a good quantum yield of about 18%. Thus by considering the excellent properties of KFP-CDs, KFP-CDs were used as fluorescent ink for drawing and writing without any capping/passivation agent. The pictures and words were instantaneously viewed when exposed to UV light. In addition, KFP-CDs tested for cell imaging in four human cell lines (normal and cancer cells) bestowed excellent biocompatibility and low cytotoxicity, which is important for the safe and long-term development of cellular imaging. The findings imply that KFP-CDs can be utilized as a cell labeling agent for mesenchymal stem cells, breast cancer, and thyroid cancer cells in vitro imaging. Thus, these observations revealed that investigating sustainable resource-based CDs can open up new avenues for tackling environmental issues.

Sustainable Synthesis of Bright Fluorescent Nitrogen-Doped Carbon Dots from Terminalia chebula for In Vitro Imaging.

In this study, sustainable, low-cost, and environmentally friendly biomass (Terminalia chebula) was employed as a precursor for the formation of nitrogen-doped carbon dots (N-CDs). The hydrothermally assisted Terminalia chebula fruit-derived N-CDs (TC-CDs) emitted different bright fluorescent colors under various excitation wavelengths. The prepared TC-CDs showed a spherical morphology with a narrow size distribution and excellent water dispensability due to their abundant functionalities, such as oxygen- and nitrogen-bearing molecules on the surfaces of the TC-CDs. Additionally, these TC-CDs exhibited high photostability, good biocompatibility, very low toxicity, and excellent cell permeability against HCT-116 human colon carcinoma cells. The cell viability of HCT-116 human colon carcinoma cells in the presence of TC-CDs aqueous solution was calculated by MTT assay, and cell viability was higher than 95%, even at a higher concentration of 200 µg mL-1 after 24 h incubation time. Finally, the uptake of TC-CDs by HCT-116 human colon carcinoma cells displayed distinguished blue, green, and red colors during in vitro imaging when excited by three filters with different wavelengths under a laser scanning confocal microscope. Thus, TC-CDs could be used as a potential candidate for various biomedical applications. Moreover, the conversion of low-cost/waste natural biomass into products of value promotes the sustainable development of the economy and human society.

Palladium-catalyzed synthesis of α-aryl acetophenones from styryl ethers and aryl diazonium salts via regioselective Heck arylation at room temperature.

Preparation of α-aryl acetophenones from styryl ethers and aryldiazonium salts is described. The reaction is catalyzed by palladium acetate at room temperature in the absence of ligand and base. The developed method is highly attractive in terms of reaction conditions, substrate scope, functional group tolerance and yields. Synthetic applications of the present method are demonstrated by preparing α-aryl indoles and 3-aryl isocoumarin from styryl ethers.

Exfoliation and Noncovalent Functionalization of Graphene Surface with Poly-N-Vinyl-2-Pyrrolidone by In Situ Polymerization.

Heteroatom functionalization on a graphene surface can endow the physical and structural properties of graphene. Here, a one-step in situ polymerization method was used for the noncovalent functionalization of a graphene surface with poly-N-vinyl-2-pyrrolidone (PNVP) and the exfoliation of graphite into graphene sheets. The obtained graphene/poly-N-vinyl pyrrolidone (GPNVP) composite was thoroughly characterized. The surface morphology of GPNVP was observed using field emission scanning electron microscopy and high-resolution transmission electron microscopy. Raman spectroscopy and X-ray diffraction studies were carried out to check for the exfoliation of graphite into graphene sheets. Thermogravimetric analysis was performed to calculate the amount of PNVP on the graphene surface in the GPNVP composite. The successful formation of the GPNVP composite and functionalization of the graphene surface was confirmed by various studies. The cyclic voltammetry measurement at different scan rates (5-500 mV/s) and electrochemical impedance spectroscopy study of the GPNVP composite were performed in the typical three-electrode system. The GPNVP composite has excellent rate capability with the capacitive property. This study demonstrates the one-pot preparation of exfoliation and functionalization of a graphene surface with the heterocyclic polymer PNVP; the resulting GPNVP composite will be an ideal candidate for various electrochemical applications.

Organocatalyzed Synthesis of Highly Functionalized Phthalimides via Diels-Alder Reaction Employing Two Dienophiles.

An efficient and facile protocol for the synthesis of biologically and pharmaceutically important phthalimides is developed by l-proline-catalyzed reaction between two dienophiles of α,ß-unsaturated aldehydes and maleimides. The reaction involves an efficient benzannulation that proceeds via a formal [4 + 2] cycloaddition of azadiene intermediates generated in situ from enals and N-substituted maleimides. This protocol provides a variety of functionalized phthalimide derivatives, including a potent COX-2 enzyme inhibitor.

Support-Free Pd3 Co NCs as an Efficient Heterogeneous Nanocatalyst for New Organic Transformations of C-C Coupling Reactions.

A support-free heterogeneous Pd3 Co nanostructured composite (NC), synthesized through a hydrothermal route, acted as an effective catalytic system in multivariate Heck-, Sonogashira-, and Suzuki-type coupling reactions of iodonium ylides. The XPS analysis of the bimetallic Pd3 Co NCs confirmed the elemental composition as 75 % palladium and 25 % cobalt. Furthermore, high-resolution (HR) TEM analysis confirmed the spherical morphology of the Pd3 Co bimetallic nanoparticles. The average diameter of the NCs is 14.8 nm. The coupling reaction proceeded through the generation of α-iodoenones with simultaneous migration of the phenyl group, thereby giving a scaffold with higher atom economy. The heterogeneous Pd3 Co NCs were recycled and reused without any significant change in catalytic ability for up to five reaction cycles. The high concentration of Pd and association of cobalt into the lattice of palladium appears to enhance its catalytic ability for the diverse coupling reactions in comparison with its monometallic counterparts as well as with bimetallic NCs with a comparatively lesser amount of Pd.