Improvement of the adhesion between polyaniline and commercial carbon paper by acid treatment and its application in supercapacitor electrodes

Commercial carbon paper was coated with polyaniline (PANI) using in situ polymerization of aniline. Prior to the PANI coating, acid treatment was performed to carboxylate the surface of the carbon paper for enhancing PANI adhesion by sonication of the carbon paper in a mixture of concentrated sulfuric and nitric acids. The loading mass density of PANI on the acid-treated carbon paper increased more than three times compared to that on the carbon paper without acid treatment. The specific capacitance also increased from 112 to 174 F/g in a two-electrode system (calculated using a total mass of carbon paper and PANI) due to better PANI coating on the acid-treated carbon paper. The simple acid treatment provides good adhesion of PANI to the commercial carbon paper and can be applied to prepare supercapacitor electrodes.     

Imaging the Bonds of Dehalogenated Benzene Radicals on Cu(111) and Au(111)

Dissociative adsorption of doubly substituted benzene molecules leads to formation of benzyne radicals. In this study, co‐adsorbed hydrogen molecules are used in scanning tunneling hydrogen microscopy to enhance the contrast of the meta‐ and the para‐isomers of these radicals on Cu(111) and Au(111). Up to three hydrogen molecules are attached to one radical. One hydrogen molecule reveals the orientation of the carbon ring and its adsorption site, allowing discrimination between the two radicals. Two hydrogen molecules reflect the bond picture of the carbon skeleton and reveals that adsorption on Cu(111) distorts the meta‐ isomer differently from its gas‐phase distortion. Three hydrogen molecules allow us to determine the bond picture of a minor species.     

Synthesis,properties, and fungal degradation of castor-oil-based polyurethane composites with different cellulose contents

Different contents of bonded cellulose were dispersed in a matrix of castor-oil-based polyurethane to produce composites with high susceptibility to fungal attack. We chose to bond the cellulose filler with free diisocyanate, to increase the crosslinking density. Measurements indicated physical and chemical interactions between the polyurethane matrix and cellulose filler. The cellulose network significantly enhanced the interfacial adhesion and thus improved the thermal stability and Young’s modulus of the composites. The influences of the amount of cellulose on the surface chemical structure, surface morphology, and mechanical properties after fungal attack were also investigated. The tensile strength and elongation at break of these composites substantially decreased after exposure to fungus. These composites with high content of renewable raw materials present an optimal balance of physical properties and biodegradability, with potential applications as ecofriendly biomaterials.     

Clustering and classifying diverse HIV entry inhibitors using a novel consensus shape-based virtual screening approach: further evidence for multiple binding sites within the CCR5 extracellular pocket

HIV entry inhibitors have emerged as a new generation of antiretroviral drugs that block viral fusion with the CXCR4 and CCR5 membrane coreceptors. Several small molecule antagonists for these coreceptors have been developed, some of which are currently in clinical trials. However, because no crystal structures for the coreceptor proteins are available, the binding modes of the known inhibitors within the coreceptor extracellular pockets need to be analyzed by means of site-directed mutagenesis and computational experiments. Previous studies have indicated that there is more than one binding site within the CCR5 extracellular pocket. This article investigates and develops this hypothesis using a novel spherical harmonic-based consensus shape clustering approach. The consensus shape approach is evaluated using retrospective virtual screening of CXCR4 and CCR5 inhibitors. Multiple combinations of CCR5 ligands in multiple trial superpositions are constructed to find consensus queries that give high virtual screening enrichments. Receiver-operator-characteristic performance analyses for both CXCR4 and CCR5 inhibitors show that the new consensus shape matching approach gives better virtual screening enrichments than existing shape matching and docking virtual screening techniques. The results obtained also provide strong evidence to support the notion that there are three main binding sites within the CCR5 extracellular cavity.     

Comparison of ligand-based and receptor-based virtual screening of HIV entry inhibitors for the CXCR4 and CCR5 receptors using 3D ligand shape matching and ligand-receptor docking

HIV infection is initiated by fusion of the virus with the target cell through binding of the viral gp120 protein with the CD4 cell surface receptor protein and the CXCR4 or CCR5 co-receptors. There is currently considerable interest in developing novel ligands that can modulate the conformations of these co-receptors and, hence, ultimately block virus-cell fusion. This article describes a detailed comparison of the performance of receptor-based and ligand-based virtual screening approaches to find CXCR4 and CCR5 antagonists that could potentially serve as HIV entry inhibitors. Because no crystal structures for these proteins are available, homology models of CXCR4 and CCR5 have been built, using bovine rhodopsin as the template. For ligand-based virtual screening, several shape-based and property-based molecular comparison approaches have been compared, using high-affinity ligands as query molecules. These methods were compared by virtually screening a library assembled by us, consisting of 602 known CXCR4 and CCR5 inhibitors and some 4700 similar presumed inactive molecules. For each receptor, the library was queried using known binders, and the enrichment factors and diversity of the resulting virtual hit lists were analyzed. Overall, ligand-based shape-matching searches yielded higher enrichments than receptor-based docking, especially for CXCR4. The results obtained for CCR5 suggest the possibility that different active scaffolds bind in different ways within the CCR5 pocket.     

Methodologies for laboratory Laser Induced Breakdown Spectroscopy semi-quantitative and quantitative analysis—A review

Since its early applications, Laser Induced Breakdown Spectroscopy has been recognized as a useful tool for solid state chemical analysis. However the quantitative accuracy of the technique depends on the complex processes involved in laser induced plasma formation, ablation, atomization, excitation and ion recombination. Problems arising from laser target coupling, matrix effect, fractionation in target vaporization, local thermodynamic equilibrium assumption and interferences from additional air ionization should be properly addressed in order to obtain reliable quantitative results in laboratory to be used as starting point during field campaigns.     

Influence of Film Structure and Precursor Composition on Rhodamine B Retention in Dye-Dopped Ormosils

The interplay between the chemical structure of the precursors, internal organization in the end materials and dye retention was investigated for composites (ormosils) doped with rhodamine B. Besides formulations with triethoxysilanes (RTES) only, we synthesized as well organic–inorganic hybrids with addition of titanium isopropoxide (TIP) and maleic anhydride (MA). The organic (R) functionality of RTES was changed from methyl (MeTES), to phenyl (PTES) and octyl (OTES). Atomic force microscopy and electron microscopy, coupled with thermogravimetric analysis prove that hydrophobicity increase stimulates the transition of film structure: from well-defined, compact particles (for MeTES), to a mixture of porous particles and non-granular material (for MeTES/PTES), with extreme results observed for octyl-based composites. For this latter, the apparent homogeneity comes from cluster-like organization, where the primary entities are pseudo—granules produced by hydrophobic interactions of oligomeric siloxanes. Controlling the composition and gelation procedure resulted in doped composites with good optical transparency and rhodamine B fluorescence emission bands at around 580 nm. Dye transport inside the inorganic structure is not facilitated when: (a) the particles have a compact (nonporous) inner structure and (b) the recipe does not contain the TIP/MA combination. For silica-based films, the dye is located in the macropores (between the granules) of the material and could be easy removed by washing with acetone. On the contrary, using TIP/MA changes not only the internal composition of the granular-like material (by creating a microporous titania-rich outer-shell of the particles) but also the affinity of the Rh-B to permeate and reside inside these new structures.     

Hydrogen-bond self-assembly of DNA-analogues into hexameric rosettes

The self-assembly of a DNA-analogue hexameric rosette from triaminopyrimidine and cyanuric acid-based nucleosides, and its subsequent aggregation into rod-like morphologies is reported.     

Novel Sorbent and Solvent Combination for QuEChERS Soil Sample Preparation for the Determination of Polycyclic Aromatic Hydrocarbons by Gas Chromatography–Mass Spectrometry

Polycyclic aromatic hydrocarbons (PAHs) represent priority contaminants, and the development of fast, reliable and accurate methods for their determination is of essential importance. The soil is a part of the environment which easily accumulates PAHs, making them available for transport to the air and water over long time periods and by plants through the food chain to humans. The aim of present study was to introduce a novel sorbent to the quick, easy, cheap, effective, rugged, and safe technique for soil sample preparation for the determination of 16 European Union priority PAHs by gas chromatography–mass spectrometry. Two solvent systems, 2:1 (v/v) hexane:acetone and ethyl acetate, were investigated in combination with five clean-up sorbents [Primary secondary amine (PSA), C18, florisil, clinoptilolite, and diatomaceous earth] in this study. The highest overall recovery of the method was achieved by the combination of hexane:acetone with clinoptilolite (recoveries of 70–110%) with limits of detection in the range of 0.60–1.53?µg?kg^?1. The analysis of 20 soil samples from Ni?, Serbia resulted in the identification of 11 samples with concentration greater than the values prescribed by law. The ratios of phenanthrene/anthracene and fluoranthene/pyrene were used to elucidate the origin of the PAHs as pyrolytic.