Planar Iron Hydride Nanoclusters: Combined Spectroscopic and Theoretical Insights into Structures and Building Principles

The controlled assembly of well-defined planar nanoclusters from molecular precursors is synthetically challenging and often plagued by the predominant formation of 3D-structures and nanoparticles. Herein, we report planar iron hydride nanoclusters from reactions of main group element hydrides with iron(II) bis(hexamethyldisilazide). The structures and properties of isolated Fe₄, Fe₆, and Fe₇ nanoplatelets and calculated intermediates enable an unprecedented insight into the underlying building principle and growth mechanism of iron clusters, metal monolayers, and nanoparticles.     

Synthesis of chiral α-amino acids

A novel method for the synthesis of chiral α-amino acids has been developed where the acid functionality was constructed by oxidizing a hydroxymethyl group introduced by Evans’ method in the α-position of an appropriate acid substrate and the amino part came from the amide of the original carboxyl group following a modified Hofmann rearrangement reaction.     

Anaerobic-anoxic-aerobic sequential degradation of synthetic wastewaters

This study was conducted in a continuous three-stage system of anaerobic (R1)-anoxic(R2)-aerobic (R3) reactors with synthetic wastewater containing phenol (1000 mg/L), chemical oxygen demand (COD) (3000 mg/L), CN⁻ (30 mg/L), SCN⁻(400 mg/L), and NH ₄ ⁺ -N (600 mg/L) as principal pollutants and well-acclimated heterogeneous microbial cultures. The final effluent was partially returned to R2 with a recycle ratio of 1. Anaerobic stage served to detoxify the feed by removing up to 80% of cyanide. Complete SCN⁻ removal and denitrification could be achieved in the anoxic stage by utilizing phenol as an internal source of carbon. Nitrification efficiency of 93% was obtained in the aerobic reactor. The results demonstrated that the three-stage system can give the desired final treated effluent quality (0 mg/L of phenol, 0.2 mg/L of CN⁻, 210 mg/L of COD, and 20 mg/L of NH ₄ ⁺ -N) and that the NO ₃ ⁻ -N concentration can be lowered by a higher recycle ratio.     

Divagations about the periodic table: Boolean hypercube and quantum similarity connections

In this study, several simple aspects associated with the periodic table (PT) of the elements are commented. First, the connection of the PT with the structure of a seven-dimensional Boolean hypercube leads afterward to discuss the nature of those PT elements bearing prime atomic numbers. Second, the use of quantum similarity (QS) to obtain an alternative insight on the PT element relations will be also developed. The foundation of the second part starts admitting that any element of the PT can be attached to a schematic electronic density function, constructed with a single Gaussian function: a Gaussian atomic density function, allowing to consider the PT elements as a set of quantum objects, and permits a straightforward construction of a QS matrix. Such QS scheme can be applied to the whole PT or to any subset of it. Manipulation of the QS matrices attached to any quantum object set allows the evaluation of statistical-like values, acting as coordinates to numerically or graphically represent the chosen PT atomic element sets. © 2019 Wiley Periodicals, Inc.     

Effect of dispersion on the diffusion zone in two-phase laminar flows in microchannels

Aim of the present work is to investigate the reaction–diffusion process of a two species system under laminar flow in a T-shaped microchannel. A zone formed at the interface between the aqueous solutions of these two species is affected by advection and diffusion. Through theoretical analyses and experimental results, the effect of dispersion has been shown to influence this diffusion zone. We have defined a parameter called effective diffusivity, to account for the dispersion effects and observed it to be a function of the channel Peclet number. In the limiting case of low Peclet number, this parameter is constant and turns out to be equal to the molecular diffusivity. We have also related effective diffusivity and the dispersion coefficient through scaling estimates.     

Preliminary Study on the Effect of pH on Thermal Transformation of Some Diphasic Al2O3-SiO2 Gels

Diphasic Al₂O₃-SiO₂ gels have been synthesized by hydrolyzing ethyl orthosilicate at three different pH ranges in presence of colloidal boehmite. Result shows that dominant mullitization process are sensitive to pH of the gelation process. At highly acidic pH range, solid state reaction between corundum and cristobalite occurs, and develops liquid phase for mullite nucleation. At moderately acidic pH, nucleation and crystallization are most operative for nucleation in aluminosilicate matrix. In highly basic pH region, Al-Si spinel phase develops by incorporation of Si in aluminous phase as intermediary phase. Polymorphic transformation of it may be the cause of sudden mullitization. The changes in crystallization sequence in three distinct processes may be due to variation in the nature and size of silicic acid particle formed by hydrolysis and condensation of TEOS at different pH.     

Study of the Release Mechanism of Terminalia chebula Extract from Nanoporous Silica Gel

Sol/gel-derived silica gel was prepared at room temperature from tetraethyl orthosilicate precursor. The extracts of Terminalia chebula (Haritoki) were entrapped into the porous silica gel. Fourier transform infrared analysis revealed the proper adsorption of herbal values in the nanopores of the silica gel. Porosity was estimated by transmission electron microscope studies. The release kinetics of the extract in both 0.1 N HCl, pH 1.2, and Phosphate-buffer saline (PBS), pH 7.2, were determined using UV–Vis spectroscopy. Different dissolution models were applied to release data in order to evaluate the release mechanisms and kinetics. Biphasic release patterns were found in every formulation for both the buffer systems. The kinetics followed a zero-order equation for first 4 h and a Higuchi expression in a subsequent timeline in the case of 0.1 N HCl. In the case of PBS, the formulations showed best linearity with a first-order equation followed by Higuchi’s model. The sustained release of the extract predominantly followed diffusion and super case II transport mechanism. The release value was always above the minimum inhibitory concentration.     

AgOTf‐catalyzed transesterification of β‐keto esters

AgOTf proved to be an effective catalyst for the transesterification of β‐keto esters with primary, secondary and tertiary alcohols. The products were obtained in high yield within a reasonable reaction time period. The kinetics of the transesterification reaction were also studied and the reaction was found to follow second‐order kinetics. Copyright © 2012 John Wiley & Sons, Ltd.     

Highly stereoselective synthesis of peracylated α-aldopyranosyl chlorides from aldopyranose peracetates and thionyl chloride catalyzed by BiCl3 generated in situ from the procatalyst BiOCl

Aldopyranose peracetates react with thionyl chloride and BiCl₃, generated in situ from a substoichiometric amount of the procatalyst BiOCl, producing the corresponding peracylated aldopyranosyl chlorides in very good to excellent yields (82–97%) with exclusive α-anomeric selectivity.