Synthesis of Oxazolo[5,4‐d][1,2,4]triazolo[4,3‐a]pyrimidines as a New Class of Heterocyclic Compounds

Several new derivatives of oxazolo[5,4‐d]pyrimidine ( 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h ) have been synthesized through the reaction of 2,4‐dichloro‐6‐methyl‐5‐nitropyrimidine ( 2 ) with aryl carboxylic acids in refluxing POCl₃. Further treatment of compounds ( 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h ) with hydrazine hydrate gave the hydrazine derivatives ( 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h ) that were subsequently cyclized into a novel heterocyclic system, oxazolo[5,4‐d][1,2,4]triazolo[4,3‐a]pyrimidine ( 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l , 5m , 5n , 5o , 5p ) and ( 7a , 7b , 7c , 7d ) on treatment with triethylorthoesters or carbondisulfide and alkylhalides, respectively.     

Bioinspired synthesis,characterization and antifungal activity of enzyme-mediated gold nanoparticles using a fungal oxidoreductase

The development of efficient cell-free systems of nanoparticle synthesis using microbial enzymes is a growing field of biological and green chemistry for the supportable improvement in nano-biotechnology. In the present study, we established a cell-free system for producing gold nanoparticles (AuNPs) using a fungal oxidoreductase named sulfite oxidoreductase purified to homogeneity from Fusarium oxysporum. The enzyme was purified by ultrafiltration followed by anion exchange chromatography on DEAE Sephadex A-50 gel, and its molecular weight was determined by gel filtration chromatography on Sephacryl S-300 gel. The purified enzyme had a molecular weight of 346 kDa. It was composed of three subunits of 176, 94 and 76 kDa. Purified enzyme was successfully used for production of gold nanoparticles in a cell-free system. Synthesized gold nanoparticles showed the highest absorbance at 520 nm wavelength as shown by UV–visible spectroscopy. They were spherical in shape with an average size of 20 nm as determined by scanning and transmission electron microscopy and dynamic light scattering. Assessment of the antifungal properties of synthesized nanoparticles by disk diffusion method indicated a potent growth inhibitory activity against all tested human pathogenic yeasts and molds by inhibition zones ranged from 10 to 18 mm. Taken together, our enzymatically established method of nanoparticle synthesis using a purified sulfite oxidoreductase of F. oxysporum can be considered as an efficient tool for generating harmless bioactive gold nanoparticles with potential applications in biology, medicine and industry.     

Pt–NiO–Al2O3/G derived from graphene-supported layered double hydroxide as efficient catalyst for p-nitrophenol reduction

Research on Chemical Intermediates - The present work reports the synthesis of a Pt-modified NiO–Al2O3 nanocomposite derived from graphene-supported layered double hydroxide (Pt–NiO/G)...     

H2 adsorption on Ag‐nanocluster/single‐walled carbon nanotube composites: A molecular dynamics study on the effects of nanocluster size,diameter, and chirality of nanotube

The H₂ physisorption on Ag_N (with N = 32, 108, 256, 500, and 864)/carbon nanotube (CNT; in armchair and zigzag structures with diameters between 0.54 and 2.98 nm) composites were studied by molecular dynamic simulation to investigate the effect of nanocluster size, diameter, and chirality of nanotube on the adsorption phenomena. The calculations indicate that the effects of nanocluster properties are more important than those of the nanotube, in such a way that increase of nanocluster size, decreases the H₂ adsorption. Also, the diameter and chirality of CNTs have considerable influence on the adsorption phenomena. As the diameter of nanotube is increased, the amount of adsorption is decreased. Moreover, H₂ molecules have more tendencies to those nanoclusters located on the armchair nanotubes than the zigzag ones. Another important result is the reversibility of H₂ adsorption on these materials in which the structure of composite in vacuum and after reduction of H₂ pressure to zero, is not changed, considerably. © 2015 Wiley Periodicals, Inc.     

Isocyanide-based four-component synthesis of 1,3-indandionylamidinium betaines

An efficient approach for the synthesis of novel 1,3-indandionylamidinium betaines via four-component reaction of 1,3-indandione, aldehydes, amines, and isocyanides, without assistance of any catalyst and under mild reaction conditions has been reported. The structures of these compounds were confirmed by IR, mass spectroscopic, ¹H NMR, ¹³C NMR, and single-crystal X-ray diffraction studies.     

Synthesis and Crystal Structure Study of Diethyl Aryl(benzo[d]thiazol‐2‐ylamino)methyl Phosphonates

A three‐component synthesis of α‐aminophosphonate is described from a reaction between aldehydes, 2‐aminobenzothiazole, and triethyl phosphite in the presence of InCl₃ as a catalyst under solvent‐free conditions for the generation of the particular α‐aminophosphonates. These products have two potentially biologically active parts, aminophosphonate and benzothiazole. This method offers advantages such as short reaction times, good yields, solvent‐free conditions, and easy workup with the green aspects by avoiding toxic catalysts and solvents. The crystal structure of 4b has been determined by X‐ray crystallography. This compound crystallizes in the monoclinic space group C2/c with cell parameters a = 21.9285(5) Å, b = 10.3221(2) Å, c = 18.5979(5) Å, β = 108.759(3)°, V = 3985.99(18) ų, D_calc = 1.301 mg m⁻³, and Z = 8. The final R value is 0.0501 for 3741 reflections. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 24:58–65, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21063     

Permutation entropy and detrend fluctuation analysis for the natural complexity of cardiac heart interbeat signals

We compute fractal dimension and permutation entropy for healthy and people who have experienced heart failure. Our result shows that permutation entropy is a suitable approach as well as detrend fluctuation analysis (DFA). The result of DFA shows that the fractal dimensions for healthy and heart failure are different as well as the permutation entropy result. The fluctuation value for permutation entropy for an individual who has experienced heart failure is bigger than for a healthy person. There is some specific change in the interbeat signal of a person who has experienced heart failure, but there is not previous trend for a healthy person.     

Theoretical study of CuxAg1−xI alloys

We have performed first-principles calculations using full potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT) to investigate the fundamental properties of Cu_xAg_1−xI alloys. We used both GGA96 [J.P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett. 77 (1996) 3865.] and EVGGA [E. Engel, S.H. Vosko, Phys. Rev. B. 47 (1993) 13164.] generalized gradient approximations of the exchange-correlation energy that are based on the optimization of total energy and corresponding potential. Quantities such as lattice constants, bulk modulus, band gap, density of occupied states and effective mass were calculated as a function of copper molar fraction x. These parameters were found to depend non-linearly on alloy composition x, except the lattice parameter, which follows Vegard's law. The microscopic origins of the gap bowing were explained using the approach of Zunger and co-workers; we have concluded that the band-gap energy bowing was mainly caused by the chemical charge-transfer effect and the volume deformation , while the structural relaxation contribute to the gap bowing parameter at smaller magnitude. The calculated phase diagram shows a broad miscibility gap for this alloy with a high critical temperature.     

Effect of temperature on the intrinsic viscosity of poly(ethylene glycol)/poly(vinyl pyrrolidone) blends in aqueous solutions

In this work the intrinsic viscosity of poly(ethylene glycol)/poly(vinyl pyrrolidone) blends in aqueous solutions were measured at 283.1–313.1 K. The expansion factor of polymer chain was calculated by use of the intrinsic viscosities data. The thermodynamic parameters of polymer solution (the entropy of dilution parameter, the heat of dilution parameter, theta temperature, polymer–solvent interaction parameter and second osmotic virial coefficient) were evaluated by temperature dependence of polymer chain expansion factor. The obtained thermodynamic parameters indicate that quality of water was decreased for solutions of poly(ethylene oxide), poly(vinyl pyrrolidone) and poly(ethylene oxide)/poly(vinyl pyrrolidone) blends by increasing temperature. Compatibility of poly(ethylene oxide)/poly(vinyl pyrrolidone) blends were explained in terms of difference between experimental and ideal intrinsic viscosity and solvent–polymer interaction parameter. The results indicate that the poly(ethylene glycol)/poly(vinyl pyrrolidone) blends were incompatible.     

Improving piezoelectric and pyroelectric properties of electrospun PVDF nanofibers using nanofillers for energy harvesting application

In this study, it was aimed to increase the piezoelectric and pyroelectric properties of electrospun polyvinylidene fluoride (PVDF) nanofibers simultaneously by using specific nanofillers. Graphene oxide (GO), graphene, and halloysite nanotubes with different concentrations (0, 0.05, 0.4, and 1.6% wt/wt) were combined with PVDF solution and were fabricated in the form of nanofibers through electrospinning. Pyroelectric properties of samples were measured by submerging sealed samples in hot water (360°K) and ice (270°K). The piezoelectric properties of the samples were evaluated through bending tests. The microstructural, mechanical, and thermal properties of the electrospun PVDF nanocomposite were investigated using scanning electron microscope, Instron instrument, and thermogravimetric analysis, respectively. To further support the experimental observations for generating electric voltage in the bended nanogenerator, the PVDF nanogenerator (PNG) was also modeled by a finite element analysis based on the theory of linear piezoelectricity using COMSOL Multiphysics simulation software. Experimental results showed that adding nanofillers could improve the piezoelectric and pyroelectric properties of all samples, associated with the increment of β‐phase in the nanofibers. It was concluded that adding nanofillers could increase pyroelectricity about 50% more than piezoelectricity in pristine PVDF nanofiber web. The PNG containing 1.6 wt% GO showed the highest efficiency in terms of piezoelectricity and pyroelectricity. In addition, the results showed that the ratio of piezoelectric to pyroelectric coefficients was constant (~1.5) and it was independent of the nanofiller type and content. The effect of external force and vibration frequency on the output voltage was also investigated. Increasing the compressive force and vibration frequency caused a greater output voltage. Finally, the fabricated nanogenerator was integrated on insole and elbow to investigate its energy harvesting capabilities from body movement.