Nayim Sepay

Improving the thermal stability, electroactive β phase crystallization and dielectric constant of NiO nanoparticle/C–NiO nanocomposite embedded flexible poly(vinylidene fluoride) thin films

Using a simple chemical precipitation process followed by sintering at 400 °C, NiO nanoparticles (NPs) and C–NiO nanocomposites (NCs) have been synthesized and characterized by X-ray diffraction, UV-visible spectroscopy, zeta potential measurement, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. Then, NiO NP or C–NiO NC loaded PVDF thin films were fabricated via a simple solvent casting or solution casting method. Thermogravimetric analysis confirmed good thermal stability of the nanocomposite films. Strong ion–dipole interaction between the negative surfaces of NiO NPs or C–NiO NCs and –CH2 dipoles of polymer chains leads to the formation of a long stabilized TTTT conformation, i.e. formation of large number of electroactive β polymorphs in the modified PVDF thin films. Detailed study of the dependency of the dielectric properties on filler content (NiO NPs/C–NiO NCs) and frequency illustrates significant increase in the dielectric constant in the three phase C–NiO NCs–PVDF system than in the two phase NiO NPs–PVDF system. The dielectric constant is found to be as large as 317.4 at 20 Hz with a relatively low tangent loss value, and good flexibility when 20 mass% C–NiO NCs is incorporated in the PVDF matrix. These results have been explained in terms of Maxwell–Wagner–Sillars interfacial polarization at the NiO NPs/C–NiO NCs and insulating polymer matrix interface, evolution of a conductive network and formation of a microcapacitive structure in the NiO NPs or C–NiO NCs modified PVDF thin films.

Multispectroscopic analysis and molecular modeling to investigate the binding of beta lactoglobulin with curcumin derivatives

Bovine beta lactoglobulin (β-lg), the major whey protein, has a great affinity for a wide range of organic compounds like fatty acids, retinol etc. Curcumin, a polyphenolic antioxidant present in turmeric and its isoxazole (IOC) and pyrazole (PY) derivatives have been elicited worldwide for their therapeutic activities. However, the nature of interaction of β-lg with these derivatives remains unexplored. Fluorescence quenching studies suggest a static quenching mechanism for both the compounds. The average distances of 7.28 nm and 7.33 nm have been determined for IOC and PY respectively for energy transfer based on FRET which have application in many biological and biophysical fields. Circular dichroism spectra (CD) and Fourier transform infrared spectroscopy (FTIR) have been utilized to analyze the influence on the secondary structure of the protein. Docking simulation reveals a possible mechanism for different quenching behaviours and modes of binding preferred by the two compounds. Our findings will be helpful in the design of the drugs and other biologically active molecules that bind more strongly to β-lg and have the ability to show FRET.

The structural characterization and biological activity of sulfamethoxazolyl-azo-p-cresol, its copper(II) complex and their theoretical studies

(E)-4-((2-Hydroxy-5-methylphenyl)diazenyl)-N-(5-methylisoxazole-3-yl)benzene sulfonamide (SMX-NN-C6H3(p-Me)-OH, 1) and its Cu(II) complex, [Cu(SMX-NN-C6H3(p-Me)-O)2]n (2), have been characterized by spectroscopic data and single crystal X-ray diffraction studies. The supramolecular 1D chain of 1 is constituted by inter- and intra-molecular hydrogen bonds and also by π⋯π interactions of aromatic rings. Complex 2 has a tetragonally distorted octahedral structure in which ligand 1 serves as an N,O chelator and forms a planar Cu(N,O)2 motif; two axial positions are occupied by the oxazolyl-N of neighbouring units and a 3D structure is formed. The biological activities of these compounds have been evaluated against Gram positive (B. subtilis; IC50: 105 μg ml−1 (1) and 105 μg ml−1 (2)) and Gram negative bacteria (E. coli; IC50: 66.36 μg ml−1 (1) and 62.2 μg ml−1 (2)) and the complexes exhibit better efficiency. Interactions of DNA with 1 and 2 have been examined and the binding constants are Kb(1), 5.920 × 104 M−1 and Kb(2), 4.445 × 104 M−1. The in silico test is used to predict the most favoured binding mode of 1 and 2 with the active site residues of DHPS (dihydropteroate synthetase) of E. coli and of DNA. The Cu(II) complex (2) binds more efficiently (CDOCKER energy, 2, −61.35 a.u.) in the DHPS cavity than ligand 1 (CDOCKER energy, 1, −43.90 a.u.). The electronic structures and spectral properties of 1 and 2 have been investigated by DFT and TD-DFT computation of optimized geometries of the compounds.

Electroactive and High Dielectric Folic Acid/PVDF Composite Film Rooted Simplistic Organic Photovoltaic Self-Charging Energy Storage Cell with Superior Energy Density and Storage Capability

Herein we report a simplistic prototype approach to develop an organic photovoltaic self-charging energy storage cell (OPSESC) rooted with biopolymer folic acid (FA) modified high dielectric and electroactive β crystal enriched poly(vinylidene fluoride) (PVDF) composite (PFA) thin film. Comprehensive and exhaustive characterizations of the synthesized PFA composite films validate the proper formation of β-polymorphs in PVDF. Significant improvements of both β-phase crystallization (F(β) ≈ 71.4%) and dielectric constant (ε ≈ 218 at 20 Hz for PFA of 7.5 mass %) are the twosome realizations of our current study. Enhancement of β-phase nucleation in the composites can be thought as a contribution of the strong interaction of the FA particles with the PVDF chains. Maxwell-Wagner-Sillars (MWS) interfacial polarization approves the establishment of thermally stable high dielectric values measured over a wide temperature spectrum. The optimized high dielectric and electroactive films are further employed as an active energy storage material in designing our device named as OPSESC. Self-charging under visible light irradiation without an external biasing electrical field and simultaneous remarkable self-storage of photogenerated electrical energy are the two foremost aptitudes and the spotlight of our present investigation. Our as fabricated device delivers an impressively high energy density of 7.84 mWh/g and an excellent specific capacitance of 61 F/g which is superior relative to the other photon induced two electrode organic self-charging energy storage devices reported so far. Our device also proves the realistic utility with good recycling capability by facilitating commercially available light emitting diode.

Structure-activity relationship on DNA binding and anticancer activities of a family of mixed-ligand oxidovanadium(V) hydrazone complexes

The title family of mixed-ligand oxidovanadium(V) hydrazone complexes are [VVO(HL1)(hq)] (1) and [VVO(HL2)(hq)] (2), where (HL1)2− and (HL2)2− are the dinegative form of 2-hydroxybenzoylhydrazone of acetylacetone (H3L1) and benzoylacetone (H3L2), respectively, and hq− is the mononegative form of 8-hydroxyquinoline (Hhq). Complexes were used to determine their binding constant with CT DNA using various spectroscopic techniques namely, electronic absorption, fluorescence and circular dichroism spectroscopy. The binding constant values suggest the intercalative mode of binding with the CT DNA and follow the order: 2 > 1. The bulky size as well as electron withdrawing property of the phenyl group (which is present in the β-diketone part of the hydrazone moiety in complex 2 in place of a CH3 group in complex 1) is responsible for the higher activity of 2 than 1. Complexes were screened for cytotoxic activity on cervical cancer cells and were found to be potentially active (IC50 value for 1 and 2 is 33 and 29 μM, respectively), even better than the widely used cis-platin (IC50 = 63.5 μM) and carboplatin (IC50 = > 200 μM) which is evident from the respective IC50 value. Nuclear staining experiment suggests that these complexes kill the SiHa cancer cells through apoptotic mode. The molecular docking study also suggested the intercalative mode of binding of these complexes with CT DNA and HPV 18 DNA.

An efficient synthesis of 1,3-dimethyl-5-(2-phenyl-4H-chromen-4-ylidene) pyrimidine-2,4,6(1H,3H,5H)-triones and investigation of their interactions with β-lactoglobiulin

An efficient method for synthesis of 1,3-dimethyl-5-(2-phenyl-4H-chromen-4-ylidene)pyrimidine-2,4,6(1H,3H,5H)-triones has been developed by treatment of 2-hydroxychalcones and 1,3-dimethylbarbituric acid in refluxing toluene in the presence of amberlyst-15 as catalyst in air. The process involves the occurrence of a domino sequence of Michael addition, cyclization and aerial oxidation. The compounds synthesized showed an interesting property of free rotation around the bond linking the two heterocyclic moieties and three of them were found to show binding property with the milk protein β-lactoglobulin (β-lg). DFT and docking (with β-lg) studies of one of the compounds have been done.

A facile synthesis of 2-aryl-4-(indol-3-yl)-4H-chromenes using amberlyst-15 as an efficient recyclable heterogeneous catalyst

Starting from 2-hydroxychalcones and indoles, a facile synthesis of 2-aryl-4-(indol-3-yl)-4H-chromenes has been achieved by use of amberlyst-15, a sulfonated polystyrene resin, as a recyclable heterogeneous catalyst. The methodology involves a domino sequence of Michael addition, cyclization, and dehydration.Graphical abstract

Development of oxidovanadium and oxido-peroxido vanadium-based artificial DNA nucleases via multi spectroscopic investigations and theoretical simulation of DNA binding

Benzimidazole is a neutral ligand which is often used to synthesize bioactive compounds. Two transition metal benzimidazole-based complexes, namely, vanadium (IV) dioxido complex (complex 1) and vanadium (V) oxido-peroxido complex (complex 2) with tridentate benzimidazole ligand, 2,6-di (1H-benzo[d]imidazol-2-yl) pyridine (Byim) have been designed with the intention of developing potential DNA nuclease. Different studies involving biochemical and biophysical techniques along with molecular docking suggest that both the complexes interact with DNA, while the mode of binding is intercalation. The complexes were further used for DNA cleavage activity. Both of them were found to have substantial DNA nuclease activity, but complex 2 was more potent than complex 1 in exhibiting such activity.

Synthesis of several types of 2,8-dioxabicyclo[3.3.1]nonanes using amberlyst-15 as an efficient recyclable heterogeneous catalyst

ABSTRACT A facile synthesis of 2,8-dioxabicyclo[3.3.1]nonane derivatives starting from simple molecules, such as 2-hydroxychalcones as one component and dimedone, 4-hydroxycoumarin, 2-hydroxynaphthoquinone, 2-naphthol or 1-naphthol, as the other has been achieved by use of amberlyst-15, a sulfonated polystyrene resin, as a recyclable heterogeneous catalyst. The methodology involves a domino sequence of Michael addition and two-stage cyclisation. GRAPHICAL ABSTRACT

An efficient three-component synthesis of coumarin-3-carbamides by use of Ni–NiO nanoparticles as magnetically separable catalyst

An efficient and ecofriendly synthesis of coumarin-3-carbamides, a class of compounds known for their remarkable biological activities and fluorescent properties, has been developed by a three-component reaction of 2-hydroxybenzaldehydes, aliphatic primary/secondary amines and diethyl malonate using Ni–NiO nanoparticles as catalyst in the green solvent ethanol. The method is compatible with various functional groups and moieties.