Removal of aflatoxin B1 from contaminated milk and water by nitrogen/carbon-enriched cobalt ferrite -chitosan nanosphere: RSM optimization, kinetic, and thermodynamic perspectives

In view of the feed/foods inevitably contaminated by toxic and carcinogenic aflatoxin B1 (AFB1), efficient mesoporous metformin-chitosan/silica‑cobalt ferrite nanospheres (Mt-CS/CFS NSs) was prepared to remove AFB1 from aqueous/non-aqueous media. The morphological, functional, and structural characteristics and adsorption properties of C/N-enriched CS/CFS were investigated systematically. The interactive operating variables (temperature (5.0-35 °C); time (10-100 min); AFB1 dose (50-100 μg/mL); and Mt-CS/CFS dosage (0.5-3.5 mg) were optimized via the Box-Behnken design (BBD), which demonstrated good agreement between the experimental data and proposed model. The adsorption efficiency in artificially contaminated cow's milk as well as aqueous environment reached over 91.0 % in a wide pH range (3.0-9.0), without significant change in the nutritional value of milk. Freundlich isotherm and second-order adsorption kinetics were regarded as the most suitable models to fit the adsorption results, and the adsorption rate is dominated by the intra-particle diffusion and boundary layer diffusion. Thermodynamic analyses proved that the process was spontaneous and exothermic. The adsorption mechanism could be explained as physisorption via hydrogen bonding, n-π interaction, and hydrophobic/hydrophilic interactions. The porous Mt-CS/CFS NS derived from chitosan nanoparticles is therefore outstanding adsorbent, offering great adsorptive performance and recycabilities, which impedes economic losses in the food industry.

Efficient One-Pot Synthesis of 1,4-Dihydropyridines Catalyzed by Magnetic MnFe2O4 Nanoparticles

The efficient one-pot synthesis of some 1,4-dihydropyridines is described by a condensation reaction of some aldehyde derivatives, ethyl acetoacetate and ammonium acetate in the presence of superparamagnetic manganese ferrite nanoparticles at 80 °C. The advantages of this protocol include selectivity, high purity of the products, excellent yields, short reaction times, ease of processing, and environmentally friendly conditions for the synthesis of 1,4-dihydropyridines. In addition, the catalyst can be recovered and reused in multiple runs without significantly reducing the product yield.

Ultrasmall Monodisperse NiO Nanocrystals as a Heterogeneous Catalyst for the A3-Coupling Reaction Toward Propargylamines

Ultrasmall monodisperse NiO nanoparticles (7–9 nm) were synthesized through thermal decomposition of Ni-oleylamine complexes. Various measurement techniques involving Fourier-transform infrared spectroscopy (FT-IR), diffuse reflectance UV-Vis spectroscopy (DRS), X-ray diffractometer (XRD), energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), dynamic light scattering technique (DLS), and vibrating sample magnetometer (VSM) were employed to characterize the synthesized catalyst. Propargylamine derivatives were synthesized with aldehydes, terminal alkynes and primary amines through a one-pot A3-coupling reaction by using a 3 mol% amount of the NiO nanocrystals at 80 °C under solvent-free conditions with good to excellent yields. The structures of the products were confirmed by 1H and 13C NMR spectroscopy. The catalyst presents many advantages including being environmentally friendly, easy to recover, reusable, stable, and applicable to a wide variety of substrates, as well as having cost-effective preparation.

Ultrasmall Monodisperse NiO Nanocrystals as a Heterogeneous Catalyst for the A3-Coupling Reaction Toward Propargylamines

Ultrasmall monodisperse NiO nanoparticles (7-9 nm) were synthesized through thermal decomposition of Ni-oleylamine complexes. Various measurement techniques involving Fourier-transform infrared spectroscopy (FT-IR), diffuse reflectance UV-Vis spectroscopy (DRS), X-ray diffractometer (XRD), energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), dynamic light scattering technique (DLS), and vibrating sample magnetometer (VSM) were employed to characterize the synthesized catalyst. Propargylamine derivatives were synthesized with aldehydes, terminal alkynes and primary amines through a one-pot A3-coupling reaction by using a 3 mol% amount of the NiO nanocrystals at 80 °C under solvent-free conditions with good to excellent yields. The structures of the products were confirmed by 1H and 13C NMR spectroscopy. The catalyst presents many advantages including being environmentally friendly, easy to recover, reusable, stable, and applicable to a wide variety of substrates, as well as having cost-effective preparation.

A Brønsted acidic ionic liquid anchored to magnetite nanoparticles as a novel recoverable heterogeneous catalyst for the Biginelli reaction

In this study, simple and effective methods were used for the preparation of an ionic liquid that immobilized magnetite nanoparticles. Fe₃O₄ nanoparticles were prepared via a chemical co-precipitation method. Then, a SiO₂ shell was coated on the magnetic core via the Stober method. Finally, CPTES (chloropropyltriethoxysilane) and morpholine were coated on the SiO₂ shell. Morpholine sulfate, an acidic ionic liquid, was successfully bound to magnetite nanoparticles (Mag@Morph-AIL) and this was used as an efficient catalyst for the preparation of 3,4-dihydropyrimidinones. Compared to previous works, the easy separation of the nanocatalyst using an external magnet and the recyclability, non-toxicity, versatility, and high stability of the catalyst, combined with low reaction times and excellent yields, make the present protocol very useful for the synthesis of the title products. The synthesized products and catalyst were confirmed via ¹H-NMR, ¹³C-NMR, FT-IR, scanning electron microscope, X-ray diffraction, and elemental analysis.

Kinetic Investigation of the Reactions between Triphenylphosphine, Dialkyl Acetylenedicarboxylates and Sh-Acid Such as 2-Thiazoline-2-Thiol or 2-Mercaptobenzoxazole by Uv Spectrophotometry

Kinetic studies were made of the reactions between triphenylphosphine, dialkyl acetylenedicarboxylates in the presence of SH-acids, such as 2-thiazoline-2-thiol or 2-mercaptobenzoxazole. To determine the kinetic parameters of the reactions, they were monitored by UV spectrophotometery. The second order fits were drawn by the software associated with a Cary UV spectrophotometer model Bio-300 at appropriate wavelength. The values of the second order rate constant (k2) were calculated using standard equations within the program. Within the temperature range studied, the dependence of the second order rate constant (ln k2) on reciprocal temperature was in agreement with the Arrhenius equation, enabling calculation of the activation energies of all reactions. Furthermore, useful information was obtained from studies of the effect of solvent, structure of reactants (different alkyl groups within the dialkyl acetylenedicarboxylates and SH-acids) and also concentration of reactants on the rate of reactions.

Regioselective direct ortho C-acylation of phenol and naphthol derivatives catalyzed by modified ZnCl2on Al2O3as catalyst under solvent-free and microwave conditions

In this study, we present a new and practical method for the synthesis of someorthoC-acylated mono- and di-hydroxyaromatic moieties.

Metal(II) Schiff base complexes as catalysts for the high-regioselective conversion of epoxides to β-hydroxy nitriles in glycol solvents

A facile preparation of 3-hydroxy propanenitrile derivatives is described involving ring opening of epoxides with potassium cyanide in glycol solvents in the presence of Schiff base complexes as catalysts. This method occurs under neutral and mild conditions with high yields and high regioselectivity. Thus, several β-Hydroxy nitriles, useful intermediates toward biologically-active molecules, are easily obtained at room temperature.Key words: β-hydroxy nitrile, Schiff base, epoxide, glycol, catalyst.