Binary fluid mixture of hard ellipses: Integral equation and weighted density functional theory

We study a two-dimensional (2D) classical fluid mixture of hard convex shapes. The components of the mixture are two kinds of hard ellipses with different aspect ratios. Two different approaches are used to calculate the direct, pair and total correlation functions of this fluid and results are compared. We first use a formalism based on the weighted density functional theory (WDFT), introduced by Chamoux and Perera [Phys. Rev. E 58 (1998) 1933]. Second, in general the Percus-Yevick (PY) and the hypernetted chain (HNC) integral equations are solved numerically for the 2D fluid mixtures of hard noncircular particles. Explicit results are obtained for the fluid mixtures of hard ellipses and comparisons are made by the two approaches. Also, the results are compared with the recent Monte Carlo simulation for the one-component fluids of hard ellipses. Finally we obtained the equation of state of hard ellipses for the aspect ratio sufficiently close to 1 and compared our results with the simulations of the fluid mixtures of hard disks.     

A convex treatment of numerical radius inequalities

We prove an inner product inequality for Hilbert space operators. This inequality will be utilized to present a general numerical radius inequality using convex functions. Applications of the new results include obtaining new forms that generalize and extend some well known results in the literature, with an application to the newly defined generalized numerical radius. We emphasize that the approach followed in this article is different from the approaches used in the literature to obtain such versions.

     

Synergic effect of Pt-Co nanoparticles and a dopamine derivative in a nanostructured electrochemical sensor for simultaneous determination of <Emphasis Type="Italic">N</Emphasis>-acetylcysteine,paracetamol and folic acid

A carbon paste electrode (CPE) was modified with Pt-Co nanoparticles and 2-(3,4-dihydroxyphenethyl)isoindoline-1,3-dione (3,4-DHPID) and then used for determination of N-acetylcysteine (N-AC) in the presence of paracetamol (PC) and folic acid (FA). The Pt-Co nanoparticles were synthesized by the polyol method and characterized by X-ray diffraction, energy dispersive X-ray analysis and transmission electron microscopy. The modified CPE displays good electrocatalytic activity towards the electrooxidation of N-AC in solution of pH 7.0. It was applied to the determination of N-AC in the presence of PC and FA (with well separated signals peaking at 0.2, 0.55 and 0.86 V vs. Ag/AgCl) by using square wave voltammetry. The peak currents are linearly dependent on the concentrations of N-AC, PC and FA in the respective ranges from 0.07 to 500, 1.0 to 850, and 2.0 to 550 μmol·L^?1, with detection limits of 0.009, 0.6 and 0.8 μmol·L^?1. The modified CPE was applied to the determination of N-AC, PC and FA in (spiked) pharmaceutical and biological samples.

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Graphical abstract Pt-Co nanoparticles and 2-(3,4-dihydroxyphenethyl)isoindoline-1,3-dione were used for modification of a carbon paste electrode which then was used for sensitive determination of N-actylcysteine in the presence of paracetamol and folic acid.

     

On the Stanley–Reisner ideal of an expanded simplicial complex

Let Δ be a simplicial complex. We study the expansions of Δ mainly to see how the algebraic and combinatorial properties of Δ and its expansions are related to each other. It is shown that Δ is Cohen–Macaulay, sequentially Cohen–Macaulay, Buchsbaum or k-decomposable, if and only if an arbitrary expansion of Δ has the same property. Moreover, some homological invariants like the regularity and the projective dimension of the Stanley–Reisner ideals of Δ and those of their expansions are compared.     

Coupled electrochemical-chemical procedure used in construction of molecularly imprinted polymer-based electrode: a highly sensitive impedimetric melamine sensor

A novel molecularly imprinted sensor was fabricated and used for the impedimetric detection of melamine. Considering the identity of polymeric film and the pK _a of a melamine template, an effective procedure was established to construct the MIP-based melamine sensor. The proposed method is based on the electropolymerization of pyrrole (Py) in the presence of melamine on the electrochemically reduced graphene oxide modified glassy carbon electrode (ERGO/GCE), followed by treatment with the solution of 1% H₂O₂ in alkaline water/CH₃CN-mixed solvents. The surface morphology and the electrical feature of molecularly imprinted polymer (MIP) were characterized by scanning electron microscopy (SEM), Fourier transformation infrared spectroscopy (FTIR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The EIS was also utilized to transduce the change of charge transfer resistance (R _ct) at the interface of polymer film-electrolyte, after subsequent incubation of electrode in the solution containing different concentrations of analyte, and consequently, a linear response was obtained over the range of 4.0 to 240 nM with a detection limit of 0.83 nM (S/N = 3). The effect of possible interferences on the response of sensor was studied, and the results confirmed the good selectivity of the proposed device for melamine assay. The MIP sensor was successfully applied to determine melamine in a multiple concentration-spiked milk sample.     

Fe3O4@SiO2@ADMPT/H6P2W18O62: a novel Wells–Dawson heteropolyacid-based magnetic inorganic–organic nanohybrid material as potent Lewis acid catalyst for the efficient synthesis of 1,4-dihydopyridines

A novel Wells–Dawson heteropolyacid-based magnetic Inorganic–organic nanohybrid, Fe₃O₄@SiO₂@ADMPT/H₆P₂W₁₈O₆₂, was fabricated and used as a green, efficient, eco-friendly, and highly recyclable catalyst for the one-pot and multi-component synthesis of 1,4-Dihydopyridine (1,4-DHP) derivatives from the reaction of various aromatic aldehydes with ethyl acetoacetate and ammonium acetate with good to excellent yields and in a short span of time. The nanohybrid catalyst was prepared by the chemical anchoring of Wells–Dawson heteropolyacid H₆P₂W₁₈O₆₂ onto the surface of functionalized Fe₃O₄ nanoparticles with 2,4-bis(3,5-dimethylpyrazol)-triazine (ADMPT) linker. These nanocatalysts were identified by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and vibrating sample magnetometer (VSM). This protocol is developed as a safe, cost-effective and convenient alternate method for the synthesis of 1,4-DHP derivatives utilizing an eco-friendly, and a highly reusable catalyst.     

Palladium-catalyzed alpha-arylation of esters

A new and simple one-pot procedure for the palladium-catalyzed intermolecular alpha-arylation of esters is described. A number of esters can be functionalized with a wide range of aryl bromides using Pd(OAc)(2) or Pd(2)(dba)(3) and bulky electron-rich o-biphenyl phosphines 1-3. Under the reaction conditions, using LiHMDS as base, alpha-arylation proceeds at room temperature or at 80 degrees C with very good yields and high selectivities for monoarylation. Important nonsteroidal antiinflammatory drug derivatives such as (+/-)-naproxen tert-butyl ester and (+/-)-flurbiprofen tert-butyl ester can be prepared in 79% and 86% yield, respectively. The catalyst system based on the di-tert-butylphosphine (2) is also active for the alpha-arylation of esters using aryl chlorides. Furthermore, using (3) the alpha-arylation of trisubstituted ester enolates can be accomplished to provide compounds that have quaternary centers.     

An ab Initio study of conformational properties of (Z,Z)-, (E,Z)- and (E,E)-cycloocta-1,5-diene

Ab initio calculations at HF/6-31G* level of theory for geometry optimization and MP2/6-31G*//HF/6-31G* for a single point total energy calculation are reported for the three geometrical isomers of cycloocta-l,5-diene 1–3.     

Incorporation of Fe in mixed CoCu-alkoxide hollow sphere for enhancing the electrochemical water oxidation performance

The promotion of water electrolysis performance heavily relies on the development of affordable and efficient electrocatalytic materials for the oxygen evolution reaction (OER). In this study, ternary Fe-substituted CoCu-glycerate microspheres (CoCuFe(X)-Gly) with cobalt (Co):copper (Cu):iron (Fe) atomic ratio of 2:1-X:X (X = 0.15, 0.3, 0.5, 0.8) have been prepared through facile template-free solvothermal method to examine their performance as alkaline OER catalyst. The results suggested that Fe incorporation could enhance the OER activity, and all Fe-modified samples showed lower overpotential with faster kinetic, as revealed by their Tafel slope and electrochemical impedance spectroscopy (EIS) analysis. Among the fabricated samples, CoCuFe(0.5)-Gly possessed the smallest overpotential of 317 mV at 10 mA/cm² with 3.58-fold higher current density than that of Fe-free CoCu-Gly at the overpotential of 350 mV. Cyclic voltammetry (CV) disclosed that Fe incorporation imposed strong electronic interactions that facilitate the transformation of metal-glycerate surface into active oxyhydroxide species under anodic condition prevalent before oxygen evolution reaction. Using various characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) method of surface area analysis, and thermogravimetric analysis (TGA), the physiochemical traits of samples have been carefully elucidated to determine the changes applied upon Fe substitution. Also, through Fe introduction, owing to the outward diffusion of ions to replace 2-propanol with glycerol, the solid microspheres partly become hollow which results in higher BET surface area and increase in accessible active sites. However, the evaluation of current density normalized by electrochemical active surface area (ECSA) indicates that the promotional effect of Fe was not solely related to the higher surface area but also because the intrinsic activity of Fe-modified samples has also been enhanced. The durability of optimal CoCuFe(0.5)-Gly catalyst has been examined using chronopotentiometry, chronoamperometry and potential cycling methods the findings of which suggest the good short-term and long-term stability of catalyst.     

Loading of g-C3N4 on Core-Shell Magnetic Mesoporous Silica Nanospheres as a Solid Base Catalyst for the Green Synthesis of some Chromene Derivatives under Different Conditions

Using heterogeneous basic catalysts has a great importance in chemical reactions because of their advantages (such as easy separation and thermal stability at harsh conditions) over homogeneous catalysts. In this study, magnetic mesoporous silica nanoparticles (mSiO₂) containing graphitic carbon nitride layers (mSiO₂/g-C₃N₄(x)) were fabricated through a facile process (x signifies the amount of melamine applied during synthesis). Graphitic carbon nitride layers were decorated on mSiO₂ by calcination of immobilized melamine (as graphitic carbon nitride precursor) on mSiO₂ in the last step of catalyst synthesis. The structure of the prepared catalysts was confirmed using XRD, BET, FESEM, EDX, elemental mapping and TEM methods. The catalytic efficiency of the so-obtained solid base composite was investigated for the synthesis of some dihydropyranochromenes and spiro-dihydropyranochromenes under thermal and microwave conditions. Using mSiO₂/g-C₃N₄(x) led to high yields under green conditions and in short reaction times and without a decrease in catalytic activity after four consecutive cycles.