Effect of potassium permanganate on morphological,structural and electro-optical properties of graphene oxide thin films

This work investigated the effect of Potassium Permanganate (KMnO₄) on graphene oxide (GO) properties, especially on electrical properties. The GO thin films were deposited on a glass substrate using drop casting technique and were analysed by using various type of spectroscopy (e.g. Scanning Electron Microscopy (SEM), Ultra- Violet Visible (UV–VIS), Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD), optical band gap, Raman Spectroscopy). Furthermore, the electrical experiments were carried out by using current–voltage (I-V) characteristic. The GO thin film with 4.5 g of KMnO₄ resulted in higher conductivity which is 3.11 × 10^?4 S/cm while GO with 2.5 g and 3.5 g of KMnO₄ achieve 2.47 × 10^?9 S/cm and 1.07 × 10^?7 S/cm, respectively. This further affects the morphological (SEM), optical (band gap, UV–Vis, FTIR, and Raman), and crystalline structural (XRD) properties of the GO thin films. The morphological, elemental, optical, and structural data confirmed that the properties of GO is affected by different amount of KMnO₄ oxidizing agent, which revealed that GO can potentially be implemented for electrical and electronic devices.     

Study on carbon-hydrogen activation of ketones by Gold(III) complexes and the synthesis and characterization of two ketonylgold(III) complexes

The acetonylgold(III) compound [Au(ppy)(CH₂COCH₃)Cl] (1) (ppy = 2-phenylpyridine) was unexpectedly obtained during the crystallization process of Au(III) lactate complex [Au(ppy)(CH₃CHOHCOO⁻)Cl]. This new structure prompted us to further study the role of Au(III) complexes on the carbon-hydrogen activation of ketones. Complex [Au(ppy)(CH₂COCH₃)NO₃] (2) was synthesized by reacting [Au(ppy)(NO₃)₂] with acetone while the ketonyl Au(III) complex [Au(apd)Cl₂] (3) (Hapd = 2-acetylpyridine) was obtained through carbon-hydrogen bond activation of the acetyl group. The crystal structures of 1 and 2 have common features: a square-planar Au(III) centre coordinated by one five-membered chelate ring, one acetonyl ligand and one anion (chloride or nitrate). Both structures show that carbon-hydrogen activation of acetone by 2-phenylpyridine-Au(III) complexes leads to the formation of acetonyl-Au(III) complexes. The Au-CH₂ bond lengths (2.067(7) Å, 1 and 2.059(5) Å, 2) are similar to each other but longer than the Au-C (phenyl) bond lengths. The two softest ligands (carbanion) are also cis to each other in the thermodynamically most stable isomer. In complex 3, the σ-bonded acetyl group is confirmed by ¹³C DEPT NMR spectroscopy.     

Synthesis,Characterization and Crystal Structure of the Bis(2,4-dinitrobenzoato)tetrabutyldistannoxane(IV) Dimer

Abstract The title compound, bis(2,4-dinitrobenzoato)tetrabutyldistannoxane(IV), was obtained from the reaction of di-n-butyltin(IV) oxide with 2,4-dinitrobenzoic acid. It crystallizes out as the usual dicarboxylatotetrabutyldistannoxane(IV) dimer. In the monoclinic system P2₁/c, a = 12.391(3) ?, b = 19.937(5) ?, c = 15.026(4) ?, α = γ = 90°, β = 102.857(2)°, V = 3618.95(16) ?³ and Z = 2. A crystal structure determination of the title compound reveals the presence of a centrosymmetric planar Sn₂O₂, with two different environments for tin atoms and two distinct carboxylate groups. Two of the carboxylate groups are bonded to the exocyclic tin atom in a bidentate bridging manner and the remaining two carboxylate groups are bonded to the tin atom in a monodentate manner. As a result, both the tin atoms moieties in the complex are five coordinate and exhibit trigonal bipyramid geometry. Index Abstract Synthesis, Characterization and Crystal Structure of the Bis(2,4-dinitrobenzoato)tetrabutyldistannoxane(IV) Dimer Yip Foo Win, Teoh Siang Guan, Lim Eng Khoon, Shea Lin Ng, Hoong Kun Fun A crystal structure determination of the title compound reveals the presence of a centrosymmetric planar Sn₂O₂, with two different environments for tin atoms and two distinct carboxylate groups.      

Synthesis and mesomorphic behaviors of a series of heterocyclic pyridine-imine-ester based liquid crystals

ABSTRACT

A series of new calamitic liquid crystals, 4-{[(5-methylpyridin-2-yl)imino]methyl}phenyl 4-alkoxybenzoates were synthesized. This series consists of nine members wherein they are differed by the length of alkoxy chain. Spectral analysis results were in accordance with the expected structure. Their thermotropic behaviors were analyzed with Differential Scanning Calorimetry (DSC), Polarizing Optical Microscopy (POM) and powder X-ray diffraction techniques. First member with the shortest alkoxy chain (n?=?2) is a non-mesogen. As the alkoxy chain increased to n?=?4, the monotropic nematic phase appeared. An enantiotropic mesophase (nematic) was observed for the following three members (n?=?6, 8, 10). As the alkoxy chain increased to n?=?12, enantiotropic nematic phase exhibited together with monotropic smectic A (SmA) phase. As the alkoxy chain continuously increased to n?=?14 and 16, enantiotropic phases were observed for both N and SmA. When moving to n?=?18, the nematic phase disappeared and this compound only exhibited a single mesophase (SmA).     

Role of pH and charge on silk protein assembly in insects and spiders

Silk fibers possess impressive mechanical properties, dependant, in part, on the crystalline β-sheets silk II conformation. The transition to silk II from soluble silk I-like conformation in silk glands, is thought to originate in the spinning ducts immediately before the silk is drawn down into a fiber. However the assembly process of these silk molecules into fibers, whether in silkworms or spiders, is not well understood. Extensional flow, protein concentration, pH and metal ion concentrations are thought to be most important in in vivo silk processing and in affecting structural conformations. We look at how parameters such as pH, [Ca²⁺], [K⁺], and [Cu²⁺], and water content, interact with the domain structure of silk proteins towards the successful storage and processing of these concentrated hydrophobic silk proteins. Our recent domain mapping studies of all known silk proteins, and 2D Raman spectroscopy, NMR, and DLS studies performed on sections of silkworm gland, suggest that low pH and gradual water removal promote intermolecular over intramolecular hydrogen bonding. This discussion helps to provide the necessary ground rules towards the design of silk protein analogues with specific hydrophobicity and charge profiles to optimize expression, solubility and assembly with implications in structural biology and material science. PACS 87.14.Ee; 87.15.Cc; 87.15.Kg     

Alkali metal ion conductors based on sulfonated poly(p-phenylene terephthalamide)

To obtain thermally stable and mechanically strong sodium and lithium conducting polymers, we prepared Na⁺ and Li⁺ poly(phenylene terephthalamide sulfonate salts) (MW ～ 5500). We also synthesized oligo(ethylene oxide) (3, 5, or 7 units of ethylene oxide) substituted ethylene carbonate and poly[oxymethylene-oligo(oxyethylene)]. These are high boiling point liquids with high dielectric constants as well as metal chelating properties. Polyelectrolyte systems were prepared by mixing Na⁺ or Li⁺ poly(phenylene terephthalamide sulfonate) salts with various amounts of modified ethylene carbonate and/or poly[oxymethylene-oligo(oxyethylene)]. Films (0.1–0.5 mm thick) obtained from the blends were found to have considerable mechanical strength; forming free standing films. The ionic conductivities of the Na⁺ and Li⁺ polyelectrolyte systems were 10^?6?10^?5 S/cm at 25°C. Thermal properties of these blend systems were investigated in detail. © 1994 John Wiley & Sons, Inc.