INTERACTION BETWEEN ADSORPTION LAYERS OF MACROMOLECULES

Stability and rheological properties of concentrated emulsions (including those for manufacture of vitamin microcapsules) can be related to elementary coalescence acts and adhesion of emulsion drops interacting through thin layers (microscopic emulsion films) of a dispersion medium

A new procedure was used for measuring the adhesion force f_a between two drops of n-heptane in polymer solutions and lifetime τ of the drops in the contacts depending on the volume concentration C of the polymer, time of formation t_f of adsorption layers, temperature T, capillary pressure P_c in the film, surface area S of the film, and on addition of acetone and tannin. The molecular mechanism of the interaction between adsorption layers of polymers and of the process of film destruction is discussed on the basis of the relationships obtained for interaction free energy Δ F_a, activation energy E, destruction activation volume δ and physico-chemical parameters.     

7-β- and 10-β-Hydroxylated congeners of CAF-603; elucidation of absolute configuration of CAF-603 family,and their SAR studies in the anti-fungal activity

Novel 7-β- and 10-β-hydroxylated congeners of CAF-603 (4 and 5, respectively) were isolated from Trichoderma crassum. Relative configuration of 4 was determined by NOE experiments. Stereochemistry of 7-β-hydroxy group in 5 was established by a combination of vicinal ³J_H–H analyses and quantum chemical calculations. Absolute configurations of 4 and 5 were established by observing the Cotton effects of their bis(2-naphthoate) esters. T. crassum also produce known CAF-603 (1), 14-hydroxy and 8,9-β-epoxy derivatives (2 and 3, respectively). Present study first established the absolute configuration of CAF-603 family by taking their biosyntheses into account. Preliminary biological experiments revealed that the molecular target strictly recognizes the β-side of the cycloheptane ring.     

New N-heterocyclic carbene palladium complex/ionic liquid matrix immobilized on silica: application as recoverable catalyst for the Heck reaction

[reaction: see text] A new concept of simultaneous covalent anchoring of a N-heterocyclic carbene palladium/ionic liquid matrix on the silica surface and the application of the resulting catalyst in the Heck reaction of a variety of different haloarenes is described. The catalyst shows high thermal stability (up to 280 degrees C) and could be recovered and reused for four reaction cycles, giving a total TON congruent with 36 600. Furthermore, TEM coupled with EDX analysis indicate the formation of Pd nanoparticles within the immobilized IL layer.     

Application of ZnO‐Al2O3 Nanocomposite as Nanocatalyst for Photodegradation of Acid Violet 5B

ZnO‐Al₂O₃ nanocomposite (ZANC) is used as nanocatalyst for photodegradation of acid violet 5B (AV5B) as an industrial dye. The experimental data shows that the degradation of AV5B is accelerated by ZANC and UV light. The effects of various parameters such as pH, hydrogen peroxide and ethanol are investigated on the photodegradation efficiency. Photocatalytic degradation rate of AV5B is increased by ethanol and hydrogen peroxide. Based on the kinetic studies, the rate constant of the photodegradation reaction is estimated 2.829 × 10^‐1 min^‐1.     

An Efficient Selective Oxidation of Alcohols with Zinc Zirconium Phosphate under Solvent‐free Conditions

Zinc zirconium phosphate (ZPZn) nanoparticles have been used as an efficient catalyst for the selective oxidation of a wide range of alcohols to their corresponding ketones or aldehydes using H₂O₂ as an oxidizing agent without any organic solvent, phase transfer catalyst, or additive. The steric factors associated with the substrates had a significant influence on the reaction conditions. The results showed that this method can be applied for chemoselective oxidation of benzyl alcohols in the presence of aliphatic alcohols. The catalyst used in the current study was characterized by ICP‐OES, XRD, N₂ adsorption‐desorption, NH₃‐TPD, Py‐FTIR, SEM, and TEM. These analyses revealed that the interlayer distance in the catalyst increased from 7.5 to 8.7 Å when Zn²⁺ was intercalated between the layers, whereas the crystallinity of the material was reduced. This nanocatalyst could also be recovered and reused at least seven times without any discernible decrease in its catalytic activity. This new method for the oxidation of alcohols has several key advantages, including mild and environmentally friendly reaction conditions, excellent yields and a facile work‐up.     

Characterization of gold-thiol-8-hydroxyquinoline self-assembled monolayers for selective recognition of aluminum ion using voltammetry and electrochemical impedance spectroscopy

Gold electrode surface is modified via covalent attachment of a synthesized thiol functionalized with 8-hydroxyquinoline, p-((8-hydroxyquinoline)azo) benzenethiol (SHQ), for the first time. The behavior of the nanostructured electrode surface (Au–SHQ) is characterized by electrochemical techniques including cyclic and differential pulse voltammetry (CV and DPV), and electrochemical impedance spectroscopy (EIS). The modified surface is stable in a wide range of potentials and pHs. A surface pK_a of 6.0 ± 0.1 is obtained for Au–SHQ electrode using surface acid/base titration curves constructed by CV and EIS measurements as a function of pH. These results helped to determine the charge state of the surface as a function of pH. The gold modified electrode surface showed good affinity for sensing the Al(III) ion at pH 5.5. The sensing process is based on (i) accumulation and complex formation between Al(III) from the solution phase and 8HQ function on the Au electrode surface (recognition step) and (ii) monitoring the impedance of the Au–SHQ–Al(III) complex against redox reaction rate of parabenzoquinone (PBQ) (signal transduction step). The PBQ is found to be a more suitable probe for this purpose, after testing several others. Thus, the sensor was tested for quantitative determination of Al(III) from the solution phase. At the optimized conditions, a linear response, from 1.0 × 10⁻¹¹ to 1.2 × 10⁻⁵ M Al(III) in semi-logarithmic scale, with a detection limit of 8.32 × 10⁻¹² M and mean relative standard deviation of 3.2% for n = 3 at 1.0 × 10⁻⁷ M Al(III) is obtained. Possible interferences from coexisting cations and anions are also studied. The results show that many ions do not interfere significantly with the sensor response for Al(III). Validity of the method and applicability of the sensor are successfully tested by determination of Al(III) in human blood serum samples.     

Impedimetric sensing of uranyl ion based on phosphate functionalized cysteamine self-assembled monolayers

A phosphate functionalized cysteamine self-assembled monolayer based on gold electrode is designed for uranyl ion (UO₂²⁺) detection. The response of the modified electrode is studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The EIS data are approximated using constant phase element (CPE) model from which kinetic and analytical parameters are evaluated. Uranyl ion is recognized based on blocking effect against charge transfer between p-benzoquinone as a probe and the modified electrode. This effect is detected from linear variation of charge transfer resistance (R_ct) as a function of UO₂²⁺ concentration. From the analysis of the EIS data and approximated parameters, a method is developed for UO₂²⁺ determination based on impedimetric measurements.     

Using graphene/TiO2 nanocomposite as a new route for preparation of electroconductive,self-cleaning,antibacterial and antifungal cotton fabric without toxicity

A novel and efficient process is reported for fabrication of electroconductive, self-cleaning, antibacterial and antifungal cellulose textiles using a graphene/titanium dioxide nanocomposite. Cotton fabric was loaded with graphene oxide using a simple dipping coating method. The graphene oxide-coated cotton fabrics were then immersed in TiCl₃ aqueous solution as both a reducing agent and a precursor to yield a fabric coated with graphene/titanium dioxide nanocomposite. The crystal phase, morphology, microstructure and other physicochemical properties of the as-prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and UV-Vis reflectance spectroscopy. Electrical resistance, self-cleaning performance, antimicrobial activity and cytotoxicity of treated fabrics were also assessed. The electrical conductivity of the graphene/titanium dioxide nanocomposite-coated fabrics was improved significantly by the presence of graphene on the surface of cotton fabrics. The self-cleaning efficiency of the treated fabrics was tested by degradation of methylene blue in aqueous solution under UV and sunlight irradiations. The results indicated that the decomposition rates of methylene blue were improved by the addition of graphene to the TiO₂ treatment on fabrics. Moreover, the graphene/titanium dioxide nanocomposite-coated cotton samples had negligible toxicity and possessed excellent antimicrobial activity.     

High-performance supercapacitors based on an ionic liquid-derived nanofibrillated mesoporous carbon

This article reports the superior specific capacitance, energy, and power density of a nanofibrillated mesoporous carbon derived from an ionic liquid source (IFMC). It was concluded that high specific capacitance and good electrical conductivity were originated from contribution of nitrogen content of IFMC, also the interesting nanofibrillated structure. A specific capacitance of 235 F g^?1 at a high discharge current of 5 A g^?1 was estimated for IFMC-based electrode which is higher than the most reported capacitance for carbon materials. An excellent performance of the nanofibrillated mesoporous carbon along with proper concentration of nitrogen constituent in the carbonaceous framework is indicative for important effects of tuning the carbon nanostructure for energy storage applications.