Carbon Doping of Defect Sites in Stone–Wales Defective Boron-nitride Nanotubes: A Density Functional Theory Study

We have performed a density functional theory study to investigate the effect of carbon doping on Stone–Wales (SW) defective sites in the armchair (4, 4), (5, 5) and (6, 6) BNNTs, in order to remove structural instability induced by homonuclear N–N and B–B bonds. Two different orientations of SW defect are considered, parallel and diagonal, and then C atoms are doped at different positions of the defect sites. In general, it seems that among the considered arrangements, C atoms prefer to be substituted for the homonuclear B–B bond. The larger HOMO–LUMO band gaps for the most stable configurations indicate that C doping at B–B sites is kinetically more favorable than the other ones. According to calculated nuclear quadrupole resonance (NQR) parameters as a result of C-doping on SW defective sites, the quadrupole coupling constants (C _Q ) of boron nuclei at defective sites decrease by about 0.508–1.406 MHz while ¹⁴N C _Q of the defective sites, except for N₈, increases. Interestingly, C _Q of the N sites directly connected to dopant sites has maximum increment (0.612–2.596 MHz) while C _Q of the N sites belonging to the B₂N₃ pentagon is undergone to some minor changes.     

Approaches to the construction of substituted 4-amino-1H-pyrrol-2(5H)-ones

Fully substituted 4-aminopyrrolones are easily accessed via simple routes starting from imines, ketones, or α-bromophenyl acetonitriles. Imines were reacted with KCN/NH(4)Cl in aqueous ethanol to produce α-arylamino benzyl cyanides. On the other hand, ketones were transformed to the desired α-amino nitriles using a modified Strecker reaction. Then, α-amino nitrile precursors were allowed to react with a suitable acyl halide to produce the corresponding amides. Further treatment of these amides with ethanolic KOH converted them to highly substituted 4-amino-1H-pyrrol-2(5H)-one derivatives in moderate to excellent yields.     

Investigation into the potential ability of Pickering emulsions (food-grade particles) to enhance the oxidative stability of oil-in-water emulsions

In this study the potential ability of food-grade particles (at the droplet interface) to enhance the oxidative stability was investigated. Sunflower oil-in-water emulsions (20%), stabilised solely by food-grade particles (Microcrystalline cellulose (MCC) and modified starch (MS)), were produced under different processing conditions and their physicochemical properties were studied over time. Data on droplet size, surface charge, creaming index and oxidative stability were obtained. Increasing the food-grade particle concentration from 0.1% to 2.5% was found to decrease droplet size, enhance the physical stability of emulsions and reduce the lipid oxidation rate due to the formation of a thicker interfacial layer around the oil droplets. It was further shown that, MCC particles were able to reduce the lipid oxidation rate more effectively than MS particles. This was attributed to their ability to scavenge free radicals, through their negative charge, and form thicker interfacial layers around oil droplets due to the particles size differences. The present study demonstrates that the manipulation of emulsions' interfacial microstructure, based on the formation of a thick interface around the oil droplets by food-grade particles (Pickering emulsions), is an effective approach to slow down lipid oxidation.     

New mononuclear diorganotin(IV) dithiocarboxylates: synthesis,characterization and study of their cytotoxic activities

Since organotin complexes have been reported to show fewer side effects relative to other heavy metal anticancer compounds, in the present study we report for the first time four novel organotin(IV) derivatives with the general formula R₂SnL₂, where R = methyl (1), n‐butyl (2), phenyl (3), benzyl (4) and L = morpholine‐1‐carbodithioate (MCDT). The newly synthesized ligand was monodentate or bidentate, coordinating through a sulfur atom. The complexes were synthesized by directly mixing, refluxing and stirring the ligand, with diorganotin(IV) dichlorides in a suitable solvent. The complexes were found to be pure and their solid and solution phase structural configuration was investigated by FT‐IR, multinuclear NMR (¹ H, ¹³ C, ¹¹⁹Sn) and mass spectrometry. Complex 2 was also studied for its thermal decomposition by thermogravimetry and differential thermal analysis. The results obtained on the basis of these techniques are in full concurrence with the proposed 1:2 (Sn:L) stoichiometry. The cytotoxic activity of the MCDT and diorganotin(IV) complexes (1–4) was tested against tumor cell lines – human cervix carcinoma HeLa and human myelogenous leukemia K562 – and normal immunocompetent cells: peripheral blood mononuclear cells PBMC. Results of bioassay demonstrated that organotin derivatives were in general more active than the anticancer drug cisplatin. Copyright © 2012 John Wiley & Sons, Ltd.     

Comparative study on the antioxidant activities of the different extracts and the composition of the oil extracted by n-hexane from Iranian Vitex pseudo-negundo

Antioxidant activities of different extracts obtained from the aerial parts of Vitex pseudo-negundo from Kashan, central Iran, were evaluated for the first time in this study using β-carotene/linoleic acid and scavenging of free-radical (DPPH) assays. Water extract showed the highest activity in both assays. GC-MS analysis of the oil extracted by n-hexane revealed 46 compounds with trans-β-farnesene being the main component. Several new compounds, not reported in the previous literature, were identified in the essential oil of this chemo-type.     

Electrochemical Properties of Ag@iron Oxide Nanocomposite for Application as Nitrate Sensor

Ag@iron oxide nanocomposite powders were synthesized via a two‐step chemical method. Characterization by UV‐Vis, XRD, SEM‐EDX and TEM revealed they are composed of nanosized crystalline silver particles in strict contact with amorphous iron oxide(s). The electrochemical behavior of the synthesized Ag@iron oxide composite was investigated by cyclic voltammetry. Compared with the single phase‐modified electrodes, the Ag@iron oxide/SPCE electrode exhibits an enhanced cathodic current in response to the target analyte, due to a synergistic effect between Ag crystallites and amorphous iron oxide nanoparticles. An amperometric sensor for detection of nitrate based on Ag@iron oxide modified screen‐printed electrode (Ag@iron oxide/SPCE) has been fabricated, showing a good sensitivity (663 µA mM^?1 cm^?2) and a detection limit of 30 µM.     

Preparation of a pH-sensitive pantoprazole-imprinted polymer and evaluation of its drug-binding and -releasing properties

The aim of this work was to synthesize a pantoprazole-imprinted polymer(MIPs)and study its binding and release properties in an aqueous media.Methacrylic acid(MAA),methacrylamide(MAAM),hydroxyethyl methacrylate(HEMA),and 4-vinyl pyridine(4VP)were tested as functional monomers.Different solvents were also applied as polymerization media under heat or UV radiation.The optimized MIP was prepared in chloroform as a solvent,4-vinyl pyridine as a functional monomer,and ethylene glycole dimethacrylate(EGDMA)as a crosslinker monomer under UV irradiation.Binding and release properties of MIP were studied in comparison with a non-imprinted polymer(NIP)in aqueous media,at different pH values.The protective effect of polymer for drugs against acidic conditions was evaluated at pH 2.Results indicated that the MIP had superior binding properties compared to NIP for pantoprazole.The percentage of drug released from MIP was significantly less than from NIP at all pH values,which was attributed to the presence of imprinted cavities in the MIP matrix.MIP also had a stronger protective effect for pantoprazole in acidic media,in comparison with NIP.