Modeling of electrochemical deionization across length scales: Recent accomplishments and new opportunities

Theoretical models have recently been used to simulate deionization technology by capturing electrochemical processes at atomistic, electrode, and plant length scales in electrodialysis, capacitive deionization using electric double layers, and Faradaic deionization using intercalation materials and redox-active polymers. We review the salient features of such models, identifying their major accomplishments in quantifying energy consumption and ion removal, analyzing the feasibility of large-scale systems, and discovering new electrode materials and understanding their deionization mechanisms. After summarizing strengths and weaknesses of recent modeling strategies, we identify research directions to expand modeling capabilities that can be used to inform electrode material/microstructure design, to assign energy losses to electrode-scale mechanisms, to bridge length scales, and to capture Faradaic kinetic/diffusion processes.     

Determination of thermodynamic pKa values of pharmaceuticals from five different groups using capillary electrophoresis

A determination of the thermodynamic acid dissociation constants (pK_a) of 22 frequently used pharmaceuticals using capillary electrophoresis in aqueous media is presented in this work. The investigated pharmaceuticals belong to different pharmacological groups: macrolides, fluoroquinolones, sulfonamides, β‐lactams, tetracyclines, and other miscellaneous pharmaceuticals. The electrophoretic mobilities of the investigated analytes were monitored in a pH range from 2.00 to 10.82. The data were fitted with an appropriate mathematical model using a nonlinear regression analysis to obtain pK_a values. Experimentally obtained data were well described by the mathematical model chosen for each analyte that was confirmed by r² values higher than 0.99 for most of the investigated analytes. Extrapolations to zero ionic strength were used to determine the thermodynamic pK_a values. Experimentally obtained acid dissociation constants were interpreted using structural formulae of investigated analytes and the moieties corresponding to specific pK_a were identified.     

ChemInform Abstract: Electronic Structure of Germanium Monohydrides GenH,n = 1—3

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Adsorption of As(III) from aqueous solution based on porous magnetic/chitosan/ferric hydroxide microspheres prepared via electrospraying

Porous chitosan(CS)/magnetic(Fe3O4 )/ferric hydroxide(Fe(OH)3 ) microsphere as novel and low-cost adsorbents for the removal of As(Ⅲ) have been synthesized via the electrospraying technology by a simple process of two steps. Characterization of the obtained adsorbents was studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The adsorption kinetics and equilibrium isotherms were investigated in batch experiments. The Langmuir, Freundlich isotherm and pseudo-second order kinetic models agree well with the experimental data. The adsorption of As(Ⅲ) onto CS/Fe3O4 /Fe(OH)3 microspheres occurred rapidly and reached adsorption equilibrium after about 45 min. The maximum adsorption capacity of CS/Fe3O4 /Fe(OH)3 microspheres, calculated by the Langmuir isotherm model, was 8.47 mg g-1 , which is higher than that of CS/Fe3O4 /Fe(OH) 3 prepared by the conventional method (4.72 mg g-1 ). The results showed that the microspheres had a high adsorption capacity for As(Ⅲ) and a high separation efficiency due to their microporous structure and superparamagnetic characteristics. Present research may eventually lead to a simple and low cost method for fabricating microporous materials and application for removal of arsenic from aqueous solution.     

Electrochemical Phenylselenoetherification as a Key Step in the Synthesis of (±)‐Curcumene Ether

Two variants of a new pathway for the synthesis of (±)‐curcumene ether are described. The key steps in these procedures are intramolecular cyclizations of 6‐methyl‐2‐(4‐methylphenyl)hept‐6‐en‐2‐ol and 2‐methyl‐6‐(4‐methylphenyl)hept‐6‐en‐2‐ol by means of an electrochemically generated phenylselenyl cation. This synthetic approach provides significantly better yields than the previously reported protocols.     

Luminescent Copper(I)-Complexes with an Anionic NHC obtained via a Coordination Polymer as Versatile Precursor**

The anionic diamido N-heterocyclic carbene 1 is used to prepare a series of linear as well as trigonal, heteroleptic Cu^I complexes with small molecular ligands such as pyridine derivatives or triphenylphosphine. A key role lies in the versatile precursor for these complexes, a moisture- and air-stable 1D coordination polymer [1 ⋅ Cu] _n composed of only the NHC ligand and Cu^I, such that the copper is linearly coordinated by the carbene carbon atom and one oxygen atom of the backbone of the carbene. This polymer can easily be cleaved into monomeric complexes by addition of the desired ligand to dispersions of the polymer in dichloromethane. In solution, the complexes are in equilibrium with this highly insoluble polymer and free ligand. Thus, analytical and spectroscopical experiments with the compounds are limited to their crystalline state, characterized by single crystal X-ray diffraction experiments. Some of the complexes exhibit visible luminescence in the solid state upon irradiation with ultraviolet light. The spectral features (emission wavelength, Stokes shift, width of the emission band, vibrational fine structure) significantly differ among the complexes. Quantum mechanical computations reveal a subtle interplay of several factors such as coordination number and charge transfer character of the emissive state.     

Bottom-Up Synthesis,Dispersion and Properties of Rectangular-Shaped Graphene Quantum Dots

Carbon nanomaterials have attracted the attention of the scientific community for more than 30 years now; first with fullerene, then with nanotubes and now with graphene and graphene related materials. Graphene quantum dots (GQDs) are nanoparticles of graphene that can be synthesized following two approaches, namely top-down and bottom-up methods. The top-down synthesis used harsh chemical and/or physical treatments of macroscopic graphitic materials to obtain nanoparticles, while the second is based on organic chemistry through the synthesis of polycyclic aromatic hydrocarbons exhibiting various sizes and shapes that are perfectly controlled. The main drawback of this approach is related to the low solubility of carbon materials that prevents the synthesis of nanoparticles containing more than few hundreds of sp² carbon atoms. Here we report on the synthesis of a family of rectangular-shaped graphene quantum dots containing up to 162 sp² carbon atoms. These graphene quantum dots are not functionalized on their periphery in order to keep the maximum similarity with nanoparticles of pure graphene. We chose water with sodium deoxycholate surfactant to study their dispersion and their optical properties (absorption, photoluminescence and photoluminescence excitation). The electronic structure of the particles and of their aggregates are studied using Tight-Binding (TB). We observe that the larger particles ( GQD 3 and GQD 4 ) present a slightly better dispensability than the smaller ones, probably because the larger GQDs can accommodate more surfactant molecules on each side, which helps to stabilize their dispersion in water.     

N‐Linked Glycosyl Auxiliary‐Mediated Native Chemical Ligation on Aspartic Acid: Application towards N‐Glycopeptide Synthesis

A practical approach towards N‐glycopeptide synthesis using an auxiliary‐mediated dual native chemical ligation (NCL) has been developed. The first NCL connects an N‐linked glycosyl auxiliary to the thioester side chain of an N‐terminal aspartate oligopeptide. This intermediate undergoes a second NCL with a C‐terminal thioester oligopeptide. Mild cleavage provides the desired N‐glycopeptide.     

Antimicrobial Secondary Metabolites from the Marine-Derived Actinomycete Nocardiopsis synnemataformans HT06

Chemistry of Natural Compounds - Analysis of an antimicrobial extract prepared from the culture broth of the marine-derived actinomycete Nocardiopsis synnemataformans (HT06 strain) led to the...