Interface tension of silica hydroxylated nanoparticle with brine: a combined experimental and molecular dynamics study

We have used molecular dynamics simulations to calculate the interfacial tension of hydroxylated SiO(2) nanoparticles under different temperatures and solutions (helium and brine with monovalent and divalent salts). In order to benchmark the atomistic model, quartz SiO(2) interfacial tension was measured based on inverse gas chromatography under He atmosphere. The experimental interfacial tension values for quartz were found between 0.512 and 0.617 N/m. Our calculated results for the interfacial tension of silica nanoparticles within helium atmosphere was 0.676 N/m, which is higher than the value found for the system containing He∕α-quartz (0.478 N/m), but it is similar to the one found for amorphous silica surface. We have also studied the interfacial tension of the nanoparticles in electrolyte aqueous solution for different types and salts concentrations (NaCl, CaCl(2), and MgCl(2)). Our calculations indicate that adsorption properties and salt solutions greatly influence the interfacial tension in an order of CaCl(2) > MgCl(2) > NaCl. This effect is due to the difference in distribution of ions in solution, which modifies the hydration and electrostatic potential of those ions near the nanoparticle.     

Adsorption of nanoparticles at the solid-liquid interface

The adsorption of differently charged nanoparticles at liquid-solid interfaces was investigated by in situ X-ray reflectivity measurements. The layer formation of positively charged maghemite (γ-Fe(2)O(3)) nanoparticles at the aqueous solution-SiO(2) interface was observed while negatively charged gold nanoparticles show no adsorption at this interface. Thus, the electrostatic interaction between the particles and the charged surface was determined as the driving force for the adsorption process. The data analysis shows that a logarithmic particle size distribution describes the density profile of the thin adsorbed maghemite layer. The size distribution in the nanoparticle solution determined by small angle X-ray scattering shows an average particle size which is similar to that found for the adsorbed film. The formed magehemite film exhibits a rather high stability.     

The influence of the support functions on the quality of enhanced multivariance product representation

This paper presents recently developed Enhanced Multivariance Product Representation (EMPR) method for multivariate functions. EMPR disintegrates a multivariate function to components which are respectively constant, univariate, bivariate and so on in ascending multivariance. Although the EMPR method has the same philosophy with the High Dimensional Model Representation (HDMR) method, it has been proposed to get better quality than HDMR’s with the help of the support functions. For this purpose, we investigate the EMPR truncation qualities with respect to the selection of the support functions. The obtained results and a number of numerical implementations to show the efficiency of the method are also given in this paper.     

Regioselective Synthesis of the 5,6‐Dihydro‐4H‐furo[2,3‐c]pyrrol‐4‐one Skeleton: A New Class of Compounds

We hereby report the first preparation of the 5,6‐dihydro‐4H‐furo[2,3‐c]pyrrol‐4‐one ( 3 ) and its derivatives starting from methyl 3‐(methoxycarbonyl)furan‐2‐acetate ( 8 ). The ester functionality connected to the methylene group was regiospecifically converted to the desired monohydrazide 9 . Conversion of 9 into the acyl azide 10 followed by Curtius rearrangement gave the corresponding isocyanate derivative 11 (Scheme 2). Reaction of 11 with different nucleophiles produced urethane and urea derivatives (Scheme 3). Intramolecular cyclization reactions provided the target compounds (Scheme 5). Removal of the amine‐protecting group formed the title compound 3 .     

Effects of annealing on morphological,structural and electrical properties of thermally evaporated WO3 thin films

Tungsten trioxide (WO₃) thin films were prepared by thermal evaporation method onto quartz substrates at room temperature. Effect of annealing temperature (from 200 to 800 °C) to morphology, crystallographic structure and electrical properties were investigated. In order to investigate the temperature dependant resistivity properties of the films dark current–voltage measurements were done at the temperatures of 30, 60, 90, 120 and 150 °C. From the AFM pictures it is seen that the increasing annealing temperature causes an increase in grain sizes. At elevated temperatures the grains combine to each other and thus form continuous and homogenous surfaces. From the XRD patterns it was seen that the as-prepared and annealed films at 200, 300, 310 and 320 °C were amorphous. On the other hand at 330 °C and higher temperatures the films were found as in crystallized structures (monoclinic phase). From the current–voltage measurements it was seen that the contacts areohmic and the current increased with increasing temperatures. From the calculated values it was seen that the produced films shows good semiconducting nature.     

Directed development of high-performance membranes via high-throughput and combinatorial strategies

Combinatorial strategies are for the first time applied in membrane technology and prove to be a powerful new tool in the search for novel membrane materials. The selected system for this study is a polyimide solvent-resistant nanofiltration membrane prepared via phase inversion. The phase inversion process is a typical membrane synthesis procedure involving a large number of compositional components, which can each be varied in a wide concentration range. The optimization of the membrane dope composition was performed using evolutionary optimization via genetic algorithms. Compared with the best commercially available membranes, a substantially improved membrane performance could be realized, both on the level of membrane selectivity and on that of permeability. The miniaturized high-throughput synthesis procedure could be scaled up successfully when the polymer dope was sufficiently viscous. It can be anticipated that application of combinatorial techniques can potentially lead to major improvements in all fields of membrane technology, for example water treatment, gas separation, and dialysis, not only on the compositional level but also for instance on the level of membrane synthesis posttreatment and operational conditions.     

Molecular mass and dynamics of poly(methyl acrylate) in the glass-transition region

The segmental dynamics of bulk poly(methyl acrylate) (PMA) were studied as a function of molecular mass in the glass-transition region using 2H NMR and modulated differential scanning calorimetry (MDSC). Quadrupole-echo 2H NMR spectra were obtained for four samples of methyl-deuterated PMA-d3 with different molecular masses. The resulting spectra were fit using superpositions of simulated spectra generated from the MXQET simulation program, based on a model incorporating nearest-neighbor jumps from positions on the vertices of a truncated icosahedron (soccer-ball shape). The lower molecular-mass samples, influenced by the presence of more chain ends, showed more heterogeneity (broader distribution) and lower glass transitions than the higher molecular-mass samples. The MDSC experiments on both protonated and deuterated samples showed behavior consistent with the NMR results, but temperature shifted due to the different frequency range of the measurements in terms of both the position and breadth of the glass transition as a function of molecular mass.     

Surface modification of polyacrylonitrile film by anchoring conductive polyaniline and determination of uricase adsorption capacity and activity

Polyacrylonitrile (PAN) films were modified with chemical polymerization of conductive polyaniline (PANI) in the presence of potassium dichromate as an oxidizing agent. The effect of aniline concentration on the grafting efficiency and on the electrical surface resistance of PAN and (PAN/PANI)-1-3 composite film was investigated. The surface resistances of the conductive composite films were found to be between 6.32 and 0.97 kΩ/cm. As the amount of grafted PANI increased on the PAN films, the electrical resistance of composite film decreased. The PAN/PANI composite films were also characterized using SEM and FTIR. The changes in the surface properties of the films were characterized by contact angle measurements. As expected, the PAN, PAN/PANI and PAN/PANI-uricase immobilized films, exhibited different contact angle values and surface free energy due to different interactive functional groups of the films.The conductive films were well characterized and used for immobilization of uricase. The amount of adsorbed enzyme increases with the increase of surface concentration of grafted fibrous polyaniline polymer. The maximum amount of immobilized enzyme onto composite film containing 2.4% PANI was about 216 μg/cm² (i.e., PAN/PANI-3). The immobilized uricase was reused 24 times in batch wise assay in a day. Finally, the immobilized uricase enzyme system was successfully fabricated and applied to determine the uric acid level in human serum samples.     

Propynylferrocene and (phenyl­ethyn­yl)­ferrocene

The title compounds, propynylferrocene, [Fe(C₅H₅)(C₈H₇)], (I), and (phenyl­ethyn­yl)ferrocene, [Fe(C₅H₅)(C₁₃H₉)], (II), are stabilized by weak C—H⋯π inter­actions. The C[triple‐bond]C bond distances in these mol­ecules are in the range 1.182 (3)–1.192 (3) Å. In (II), the ferrocenyl and phenyl groups are perpendicular, making an angle of 89.06 (13)°, which is a rare occurrence.     

The synthesis of unusual isocoumarin derivatives: the chemistry of homophthalic acid

Homophthalic acid was reacted with thionyl chloride/DMF and ethyl chloroformate/NEt₃ in the presence and absence of NaN₃. In all cases completely different isocoumarin derivatives were obtained. These unusual isocoumarin derivatives were characterized and their mechanism of formation is discussed.