Synthesis and characterization of NiFe2O4 nanoparticles using the hydrothermal method as magnetic catalysts for electrochemical detection of norepinephrine in the presence of folic acid

In this article, we present a simple and efficient method to synthesize a magnetic NiFe₂O₄ nanocatalyst under hydrothermal conditions. Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X‐ray spectroscopy (EDX) analyses confirmed the synthesis of NiFe₂O₄ nanoparticles. These nanoparticles showed satisfactory catalytic activity for determination of norepinephrine (NE) in the presence of folic acid (FA) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. Differential pulse voltammetry peak currents of NE increased linearly with their concentrations in the range of 1.0 × 10^?7–5.0 × 10^?4 M, and the detection limit for NE was 2.3 × 10^?8 M, respectively. The modified electrode displayed strong function for resolving the overlapping voltammetric responses of NE and FA into two well‐defined voltammetric peaks. In the mixture containing NE and FA, the two compounds can well separate from each other with a potential difference of 510 mV between NE and FA, which was large enough to determine NE and FA individually and simultaneously. Additionally, the prepared electrochemical sensor demonstrated a practical feasibility for real sample determination.     

Modeling the cohesive energy and melting point of nanoparticles by their average coordination number

We present a relation between the average coordination number and the cohesive energy for nanoparticles that shows that the ratio of nanoparticles cohesive energy to the bulk value is equal to the ratio of the nanoparticles average coordination number to that of the bulk. We consider the effect of lattice and surface packing factors on the average coordination numbers of the atoms in the nanoparticle. The melting temperature of nanoparticles has been calculated from the obtained relation for cohesive energy, and predictions for the cohesive energy and melting temperature of the nanoparticles have been compared with other theoretical models and available experimental data and the results of molecular dynamics simulations.     

Mixed convection heat transfer of a nanofluid in a closed elbow-shaped cavity (CESC)

Journal of Thermal Analysis and Calorimetry - The current survey’s primary purpose is to conduct the computational modeling of laminar mixed convection heat transfer of nanofluids inside a...     

An Efficient Synthesis of Sulfonylhydrazides and Sulfonylsemicarbazides by Utilizing Alumina as a Catalyst

Sulfonyl hydrazides and sulfonyl semicarbazides are readily prepared by the reacting of hydrazine derivatives with sulfonyl chlorides in the presence of basic alumina under solvent‐free conditions. Reaction of a sulfonyl chloride with t‐butylcarbazate, followed by hydrolysis provides the corresponding sulfonyl hydrazides in higher yield and shorter time than previously reported.     

V‐N‐C catalysts anchored to mesoporous Al‐SBA‐15 with tailorable pore sizes for the synthesis of spirooxindole dihydroquinazolinones derivatives

Heterogeneous nanoscale catalyst was successfully synthesized via anchoring of V‐bis(2‐aminobenzamide) complex on the Al‐SBA‐15. This modified mesoporous was identified by several characterization techniques, such as X‐ray diffraction, field emission‐scanning electron microscopy, Fourier transform‐infrared, Brunauer–Emmett–Teller and transmission electron microscopy. V‐Bis(2‐aminobenzamide)@Al‐SBA‐15 was found to be an efficient heterogeneous catalyst for the rapid and desirable synthesis of various spirooxindole dihydroquinazolinones derivatives. In addition, the heterogeneous nanocatalyst was chemically stabilized in organic and aqueous solutions as well as can be expeditiously reused for at least seven cycles without a significant loss in catalytic activity.     

Thermal analysis and thermo-hydraulic characteristics of zirconia–water nanofluid under a convective boiling regime

Journal of Thermal Analysis and Calorimetry - In this research, flow boiling heat transfer of zirconia–water nanofluid inside a heat exchanger was experimentally investigated. The system was...     

Highly sensitive kinetic spectrophotometric method for tramadol trace level detection and process optimization using response surface methodology

Tramadol is a centrally acting analgesic‐anodyne agent of high oral bioavailability. The tramadol contains a weakly absorbing chromophore in its molecule and it was determined by kinetic spectrophotometric method in pharmaceutical, urine, and blood plasma. Response surface methodology and the central composite design was applied to study the influence of maximum sensitivity, reagents concentration, temperature, and time on the UV–Vis spectrophotometry analysis of tramadol. Analysis of variance showed a high coefficient of determination (R²) value for responses, confirming adjustment of the models with experimental data. The change in absorbance was followed spectrophotometrically at 478 nm. Under optimum experimental conditions, calibration curve was linear over the range 0.45–100.0 μg/L of tramadol. The limit of detection was 0.12 μg/L of tramadol. The developed method was successfully applied for the determination of tramadol in real samples.     

The effect of the averaged structural and energetic features on the cohesive energy of nanocrystals

The size dependency of the cohesive energy of nanocrystals is obtained in terms of their averaged structural and energetic properties, which are in direct proportion with their cohesive energies. The significance of the effect of the geometrical shape of nanoparticles on their thermal stability has been discussed. The model has been found to have good prediction for the case of Cu and Al nanoparticles, with sizes in the ranges of 1–22 nm and 2–22 nm, respectively. Defining a new parameter, named as the surface-to-volume energy-contribution ratio, the relative thermal stabilities of different nanoclusters and their different surface-crystalline faces are discussed and compared to the molecular dynamic (MD) simulation results of copper nanoclusters. Finally, based on the size dependency of the cohesive energy, a formula for the size-dependent diffusion coefficient has been presented which includes the structural and energetic effects. Using this formula, the faster-than-expected interdiffusion/alloying of Au_(core)–Ag_(shell) nanoparticles with the core–shell structure, the Au-core diameter of 20 nm and the Ag-shell thickness of 2.91 nm, has been discussed and the calculated diffusion coefficient has been found to be consistent with its corresponding experimental value.     

Regioselective multi-component synthesis of 1H-pyrazolo[3,4-d]pyrimidine-6(7H)-thiones

A variety of pyrazolo[3,4-d]pyrimidine-6(7H)-thione derivatives were easily synthesized with a novel, simple, efficient, and regioselective method via three-component condensation reaction of 5-methyl-1H-pyrazol-3-amine, arylisothiocyanates, and aldehydes in the presence of catalytic amount of p-toluenesulfonic acid (p-TSA) in 1-butyl-3-methylimidazolium bromide ionic liquid with excellent yields and short reaction times.     

Synthesis and characterization of two binuclear iron(III) complexes of aminoethanol derivatives of aminophenol as models for non-heme iron enzymes active sites

Two aminoethanol derivatives of aminophenol ligands were synthesized and characterized by IR and ¹H NMR spectroscopies. The binuclear iron(III) complexes of these ligands have been prepared and characterized by IR, ¹H NMR and UV-Vis spectroscopic techniques, cyclic voltammetry, single crystal X-ray diffraction and magnetic susceptibility studies. X-ray analysis revealed binuclear complexes, Fe₂(L₂), in which Fe(III) centers are surrounded by two phenolate and hydroxyl oxygen atoms, and amine nitrogens of the ligands. The metal active sites of both complexes are held together by the two above mentioned hydroxyl bridges. Variable temperature magnetic susceptibility indicates antiferromagnetic coupling between the iron centers of both complexes. This exchange coupling is stronger for Fe₂(L^ae)₂, such that it shows a room temperature strong coupling between the two iron centers. The investigated complexes undergo irreversible electrochemical oxidation and reduction.