New Functional Detergents Based on Imidazole Derivatives – Effective Reagents for Cleavage of the Esters of Organic Acids

A detailed kinetic and thermodynamic analysis showed that the new functional detergents in which the head part contains an imidazole ring with oximate, amidoximate, and hydroxamate -nucleophilic fragments linked to it are very powerful supernucleophilic systems in the cleavage of organophosphorus compounds.     

Characterization of Formation Kinetics of Self-Assembled Thiol Monolayers on Gold by Electrochemical Impedance Spectroscopy

Interest in the properties of organized monolayers has grown enormously in recent years because these monolayers can provide a means to control the interface at a molecular level1. The self-assemblies of alkanethiols and their derivatives were probably the most intensively studied due to their stability, well-packed structure, ease in preparation, and flexibility in designing the tail group2. The adsorption kinetics of thiol monolayer has been studied by using several techniques, including con…     

A Novel Electrochemical Sensor Based on Reduced Graphene Oxide–TiO2 Nanocomposites with High Selectivity for the Determination of Hydroxychloroquine

Russian Journal of Electrochemistry - A simply sensitive sensor based on a reduced graphene oxide–TiO2 nanocomposite modified glassy carbon electrode (RGO–TiO2/GCE) was developed for...     

Self-Assembled Anion-Binding Cryptand for the Selective Liquid–Liquid Extraction of Phosphate Anions

The ligands L¹ and L² form trinuclear self-assembled complexes with Cu²⁺ (i.e. [( L¹ )₂Cu₃]⁶⁺ or [( L² )₂Cu₃]⁶⁺) both of which act as a host to a variety of anions. Inclusion of long aliphatic chains on these ligands allows the assemblies to extract anions from aqueous media into organic solvents. Phosphate can be removed from water efficiently and highly selectively, even in the presence of other anions.     

The Influence of Molecular Dipole Moment on the Redox-Induced Reorganization of α-Helical Peptide Self-Assembled Monolayers: An Electrochemical SPR Investigation

Self-assembled monolayers (SAMs) of ferrocene-labeled α-helical peptides were prepared on gold surfaces and studied using electrochemical surface plasmon resonance (EC-SPR). The leucine-rich peptides were synthesized with a cysteine sulfhydryl group either at the C- or N-terminus, enabling their immobilization onto gold surfaces with control of the direction of the molecular dipole moment. Two electroactive SAMs were studied, one in which all of the peptide dipole moments are oriented in the same direction (SAM1), and the other in which the peptide dipole moment of one peptide is aligned in the opposite direction to that of its surrounding peptide molecules (SAM2). Cyclic voltammetry combined with SPR measurements revealed that SAM reorientations concomitant with the oxidation of the ferrocene label were more significant in SAM2 than in SAM1. The substantially greater change in the peptide film thickness in the case of SAM2 is attributed to the electrostatic repulsion between the electrogenerated ferrocinium moiety and the positively charged gold surface. The greater permeability of SAM1 to electrolyte anions, on the other hand, appears to effectively neutralize this electrostatic repulsion. The film thickness change in SAM2 was estimated to be 0.25 ± 0.05 nm using numerical simulation. The timescale of the redox-induced SPR changes was established by chronoamperometry and time-resolved SPR measurements, followed by fitting of the SPR response to a stretched exponential function. The time constants measured for the anodic process were 16 and 6 ms for SAM1 and SAM2 respectively, indicating that the SAM thickness changes are notably fast.     

Study of Catalysts Based on High Surface Area MnO_2 for Catalytic Combustion of CH_4

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Intense Red-Blue Luminescence Based on Superfine Control of Metal–Metal Interactions for Self-Assembled Platinum(II) Complexes

A series of assembled Pt^II complexes comprising N-heterocyclic carbene and cyanide ligands was constructed using different substituent groups, [Pt(CN)₂(R-impy)] (R-impyH⁺=1-alkyl-3-(2-pyridyl)-1H-imidazolium, R=Me ( Pt-Me ), Et ( Pt-Et ), ⁱPr ( Pt- ⁱ Pr ), and ^tBu ( Pt- ^t Bu )). All the complexes exhibited highly efficient photoluminescence with an emission quantum yield of 0.51–0.81 in the solid state at room temperature, originating from the triplet metal-metal-to-ligand charge transfer (³MMLCT) state. Their emission colors cover the entire visible region from red for Pt-Me to blue for Pt- ^t Bu . Importantly, Pt- ^t Bu is the first example that exhibits blue ³MMLCT emission. The ³MMLCT emission was proved and characterized based on the temperature dependences of the crystal structures and emission properties. The wide-range color tuning of luminescence using the ³MMLCT emission presents a new strategy of superfine control of the emission color.     

A Method of Determining Selectivity Coefficients Based on the Practical Slope of Ion Selective Electrodes

It is a problem to be solved that the experimental selectivity coefficients of ion selective electrodes( ISEs) depend on the activity. This paper studied the new method of determining selectivity coefficients. A mixed ion response equation, which was similar to Nicolsky-Eisenman (N-E) equation recommended by IUPAC, was proposed. The equation includes the practical response slope of ISEs to the primary ion and the interfering ion. The selectivity coefficient was defined by the equation instead of the N-E equation. The experimental part of the method is similar to that based on the N-E equation. The values of selectivity coefficients obtained with this method do not depend on the activity whether the electrodes exhibit the Nernst response or non-Nernst response. The feasibility of the new method is illustrated experimentally.     

Mechanistic Investigation of Alkali-Treated Photocatalytic CO2 Reduction: The Role of OH− and Metal Cations for Almost 100 % Selectivity of CO

In this work, the modulation of activity and selectivity via photoreduction of carbon dioxide under simulated sunlight was achieved by treating P25 and P25/Pt NPs with KOH. It found that KOH treatment could significantly improve the overall conversion efficiency and switch the selectivity for CO. Photoelectric characterizations and CO₂-TPD demonstrated that the synergistic effect of K⁺ and OH^- accelerated the separation and migration of photogenerated charges, and also improved CO₂ adsorption level. Significantly, the K ions could act as active sites for CO₂ adsorption and further activation. In situ FTIR measurements and DFT calculations confirmed that K⁺ enhanced the charge density of adjacent atoms and stabilize CO* groups, reducing the reaction energy barrier and inducing the switching of original CH₄ to CO, which played a selective regulatory role. This study provides insights into the photocatalytic activity and selectivity of alkali-treated photocatalysts and facilitates the design of efficient and product-specific photocatalysis.     

High Activity and Selectivity of Cu／SiO2 Catalyst for the Direct Synthesis of Indole

Copper supported over silica exhibited very high activity and selectivity for the direct synthesis of indole at atmospheric pressure. Under the reaction temperature of 325℃,the yield of indole could obtain 88%.     

Amperometric Sensors for Determination of Hydrogen Peroxide Based on Electron Transfer Between Horseradish Peroxidase and 1，1＇－Dimethylferrocene

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Acetylcholinesterase Biosensor Based on Reduced Graphene Oxide – Carbon Black Composite for Determination of Reversible Inhibitors

For the first time, acetylcholinesterase (AChE) biosensors based on mixed carbon nanomaterials (electrochemically reduced graphene oxide (ERGO) and carbon black (CB) particles) were described for the determination of antidementia drugs. Changes in the content of underlying layer allowed varying selectivity and sensitivity of the inhibitor determination. Appropriate limits of detection (LOD) varied in the range from 1 pM to 0.1 nM for donepezil, 5 nM–0.1 μM for berberine, 0.1–50 nM for huperzine A and 0.1–300 nM for galantamine. Variation in the inhibition measurement parameters can be used for increasing selectivity of the measurements.     

Being Positive is Not Everything – Experimental and Computational Studies on the Selectivity of a Self-Assembled,Multiple Redox-State Receptor that Binds Anions with up to Picomolar Affinities

The interaction of the self-assembled trinuclear ruthenium bowl 1 ³⁺, that displays three other accessible oxidation states, with oxo-anions is investigated. Using a combination of NMR and electrochemical experimental data, estimates of the binding affinities of 1 ⁴⁺, 1 ⁵⁺, and 1 ⁶⁺ for both halide and oxo-anions were derived. This analysis revealed that, across the range of oxidation states of the host, both high anion binding affinities (>10⁹ M⁻¹ for specific guests bound to 1 ⁶⁺) and high selectivities (a range of >10⁷ M⁻¹) were observed. As the crystal structure of binding of the hexafluorophosphate anion revealed that the host has two potential binding sites (named the α and β pockets), the host-guest properties of both putative binding sites of the bowl, in all of its four oxidation states, were investigated through detailed quantum-based computational studies. These studies revealed that, due to the interplay of ion-ion interactions, charge-assisted hydrogen-bonding and anion-π interactions, binding to the α pocket is generally preferred, except for the case of the relatively large and lipophilic hexafluorophosphate anionic guest and the host in the highest oxidation states, where the β pocket becomes relatively favourable. This analysis confirms that host-guest interactions involving structurally complex supramolecular architectures are driven by a combination of non-covalent interactions and, even in the case of charged binding pairs, simple ion-ion interactions alone cannot accurately define these recognition processes.     

Effect of an α-Methyl Substituent on the Dienophile on Diels-Alder endo:exo Selectivity

A detailed computational study of the Diels-Alder reaction of cyclopentadiene with acrylonitrile, methylacrylate and their α-methylated counterparts methacrylonitrile and methyl methacrylate at the M06-2X(PCM)/TZVP level of theory has been performed. We want to understand the excellent exo-selectivities observed experimentally due the presence of this substituent. To this end, analysis of the reaction coordinate by means of activation strain model of chemical reactivity (ASM-distortion interaction model) including solvation effects and NBO second order perturbation energy have been carried out.     

Effects of the Different Supports on the Activity and Selectivity of Iron-Cobalt Bimetallic Catalyst for Fischer-Tropsch Synthesis

Silica, alumina, and activated carbon supported iron-cobalt catalysts were prepared by incipient wetness impregnation. These catalysts have been characterized by BET, X-ray diffraction (XRD), and temperature-programmed reduction (TPR). Activity and selectivity of iron-cobalt supported on different carriers for CO hydrogenation were studied under the conditions of 1.5 MPa, 493 K, 630 h-1, and H2/CO ratio of 1.6. The results indicate that the activity, C4 olefin/(C4 olefin C4 paraffin) ratio, and C5 olefin/(C5 olefin C5 paraffin) decrease in the order of Fe-Co/SiO2, Fe-Co/AC1, Fe-Co/Al2O3 and Fe-Co/AC2. The activity of Fe-Co/SiO2 reached a maximum. The results of TPR show that the Fe-Co/SiO2 catalyst is to some extent different. XRD patterns show that the Fe-Co/SiO2 catalyst differs significantly from the others; it has two diffraction peaks. The active spinel phase is correlated with the supports.     

Preparation,Characterisation and Properties of Nanocomposites Based on Epoxy Resins – An Overview

An overview about the use of nanoparticles in epoxy resins is given. Deaggregated fumed silica, sol gel materials and other spheroidic nanoparticles improved the abrasion resistance and the mechanical properties of filled epoxides, and several properties can be improved by specific particles. Combustion properties, strength and permeation can be improved by organically modified layered silicates. The proper characterisation of the nanocomposites is still an art. TEM analysis of the cured materials and light scattering with 3D cross-correlation for the liquid samples were sufficient methods for the characterisation of filled epoxides.     

High Performance Affinity Chromatography of Antithrombin III Based on Monodisperse Poly (glycidyl methacrylate) Beads

Antithrombin III, a (2-glycoprotein and one of the major proteinase inhibitors in mammalian plasma, shows specific interaction with heparin. Therefore, immobilized heparin has been widely used as an adsorbent for the separation and purification of plasma components in blood-coagulation systems. Traditionally, affinity chromatography has been carried out at low pressure using soft gels made of polysaccharide1,2. Soft gels, however, is flow rate limited, susceptible to microbial degradation, an…     

Synthesis and Characterization of a Novel 3D Coordination Polymer Based on Cu(Ⅱ) Cations and Mellitic Acid

A new mellitate complex [Cu3(μ2-mellitate)(μ2-H2O)(H2O)2·H2O]n 1 has been synthesi- zed by the reaction of mellitic acid and Cu(CH3COO)2·H2O in the presence of base. Crystallogra- phic data for 1: C12H80O16Cu3, Mr = 598.80, orthorhombic, Pbcn, a = 8.4378(6), b = 10.0396(7), c = 17.6799(12) A, V = 1497.70(18) A3, Z = 4, Dc = 2.656 g/cm3,μ = 4.327 mm-1, F(000) = 1180, R = 0.0431 and wR = 0.0964 for 1075 observed reflections (Ⅰ> 2σ(Ⅰ)). X-ray crystal structural analysis revealed that the mellitate anions behave as the bridging ligands and link eight copper atoms repeatedly to form a novel three-dimensional metal-organic coordination polymer with two different rhombic tunnels in the solid-state structure.     

High Yield Synthesis of α Propargylic Acrylic Ester: A General Access to α Substituted Acrylic Esters

A heterogeneous mediated, high yield, monopropargyla-tion of ethyl benzoylacetate followed by a methyle-nation reaction using a formaldehyde addition-benzoyl elimination mechanism is described. This useful method is extended to the synthesis of a substituted acrylic esters.     

Transport Selectivity of a Diethylene Glycol Dimethacrylate- Based Thymine-imprinted Polymeric Membrane over a Cellulose Support for Nucleic Acid Bases

The binding mechanism between 9-vinyladenine and pyrimidine base thymine in methanol was studied with UV-visible spectrophotometric method. Based on this study, using thymine as a template molecule, 9-vinyladenine as a novel functional monomer and diethylene glycol dimethacrylate as a new cross-linker, a specific diethylene glycol dimethacrylate-based molecularly imprinted polymeric membrane was prepared over a cellulose support. Then, the resultantly polymeric membrane morphologies were visualized with scanning electron microscopy and its permselectivity was examined using thymine, uracil, cytosine, adenine and guanine as substrates. This result showed that the imprinting polymeric membrane prepared with diethylene glycol dimethacrylate exhibited higher transport capacity for the template molecule thymine and its optimal analog uracil than other nucleic acid bases. The membrane also took on higher permselectivity than the imprinted membrane made with ethylene glycol dimethacrylate as a cross-linker. When a mixture including five nucleic acid bases thymine, uracil, cytosine, adenine and guanine passed through the diethylene glycol dimethacrylate-based thymine-imprinted polymeric membrane, recognition of the membrane for the template molecule thymine and its optimal analog uracil was demonstrated. It was predicted that the molecularly imprinted membrane prepared with diethylene glycol dimethacrylate as cross-linker might be applicable to thymine assay of absolute hydrolysates of DNA or uracil assay of absolute hydrolysates of RNA in biological samples because of its high selectivity for the template molecule thymine and its optimal analog uracil.