Physical Properties of Photo-Aged Graphene/Polypropylene Nanocomposites.

In the present research, graphene nanoplatelets/polypropylene (GNP/PP) nanocomposites were prepared by melt mixing and were subjected to accelerated ageing. The effect of graphene on the morphology and physical properties of aged GNP/PP nanocomposites was investigated. The incorporation of graphene to non-aged PP matrix led to changes in its crystal conformation, decreased the ultraviolet-visible (UV-Vis) transmittance and tensile strain and increased the elastic modulus. The ageing of non-reinforced PP increased the ß-phase of PP and caused the formation of cracks on its surface, while voids were observed in its cross-section. The aged PP was also characterized by significantly lower UV-Vis transmittance, thermal stability and tensile strain, but increased elastic modulus compared to non-aged PP. Graphene retarded the ageing of PP matrix, according to Fourier Transform Infrared spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) results. In the aged GNP/PP nanocomposite, the morphology did not present any changes and the examined properties were maintained to similar values with that of non-aged GNP/PP nanocomposite.

Molybdenum(VI) coordination chemistry of the N,N-disubstituted bis(hydroxylamido)-1,3,5-triazine ligand, H2bihyat. Water-assisted activation of the Mo(VI)═O bond and reversible dimerization of cis-[Mo(VI)O2(bihyat)] to [Mo(VI)2O4(bihyat)2(H2O)2].

Reaction of the N,N-disubstituted bis(hydroxylamino) ligand 2,6-bis[hydroxy(methyl)amino]-4-morpholino-1,3,5-triazine (H(2)bihyat) with cis-[Mo(VI)O(2)(acac)(2)] in tetrahydrofuran resulted in isolation of the mononuclear compound cis-[Mo(VI)O(2)(bihyat)] (1). The treatment of Na(2)Mo(VI)O(4)·2H(2)O with the ligand H(2)bihyat in aqueous solution gave the dinuclear compounds cis-[Mo(VI)(2)O(4)(bihyat)(2)(H(2)O)(2)] (2) and trans-[Mo(VI)(2)O(4)(bihyat)(2)(H(2)O)(2)] (3) at pH values of 3.5 and 5.5, respectively. The structures for the three molybdenum(VI) compounds were determined by X-ray crystallography. Compound 1 has a square-pyramidal arrangement around molybdenum, while in the two dinuclear compounds, each molybdenum atom is in a distorted pentagonal-bipyramidal environment of two bridging and one terminal oxido groups, a tridentate (O,N,O) bihyat(2-) ligand that forms two five-membered chelate rings, and a water molecule trans to the terminal oxido group. The dinuclear compounds constitute rare examples containing the {Mo(2)(VI)O(2)(µ(2)-O(2))}(4+) moiety. The potentiometry revealed that the Mo(VI)bihyat(2-) species exhibit high hydrolytic stability in aqueous solution at a narrow range of pH values, 3-5. A subtle change in the coordination environment of the five-coordinate compound 1 with ligation of a weakly bound water molecule trans to the oxido ligand (1w) renders the equatorial oxido group in 1w more nucleophilic than that in 1, and this oxido group attacks a molybdenum atom and thus the dinuclear compounds 2 and 3 are formed. This process might be considered as the first step of the oxido group nucleophilic attack on organic substrates, resulting in oxidation of the substrate, in the active site of molybdenum enzymes such as xanthine oxidase. Theoretical calculations in the gas phase were performed to examine the influence of water on the dimerization process (1 → 2/3). In addition, the molecular structures, cis/trans geometrical isomerism for the dinuclear molybdenum(VI) species, vibrational spectra, and energetics of the metal-ligand interaction for the three molybdenum(VI) compounds 1-3 have been studied by means of density functional theory calculations.

Study of TiO2 anatase nano and microstructures with dominant {001} facets for NO oxidation.

INTRODUCTION: TiO(2) anatase nanoplates and hollow microspheres were fabricated by a solvothermal-hydrothermal method using titanium isopropoxide as a titanium precursor and hydrofluoric acid as a capping agent in order to enhance the formation of the {001} crystal facets of the anatase nanocrystals. METHODS: These different morphological structures of TiO(2) anatase can be achieved by only changing the solvent, keeping the amount of the precursor and of the capping agent identical during the solvothermal-hydrothermal process. RESULTS AND DISCUSSION: After calcination of the samples, the adsorbed fluoride atoms on the {001} crystal facets of the TiO(2) anatase nanocrystals were completely removed from their surface according to XPS analysis. The calcined TiO(2) anatase structures were higher crystallized and the specific surface area of the catalysts increased, enhancing their photocatalytic activity in comparison to the non-calcined TiO(2) anatase structures. All TiO(2) anatase samples with adsorbed as well as non-adsorbed fluoride atoms on their {001} crystal facets, exhibited a higher photonic efficiency than Degussa P25, which was used as a reference. CONCLUSION: The fluoride free TiO(2) anatase nanoplates exhibited the best photocatalytic activity in oxidizing the NO gas to NO(2) and NO(3) (-).

Hydrothermal syntheses, crystal structures and physicochemical properties of 2-D and 3-D inorganic coordination cobalt(II)-sulfite polymers.

The hydrothermal reaction of [Co(III)(NH(3))(6)]Cl(3) with Na(2)SO(3) yields, depending on the concentration of Na(2)SO(3), compounds {Na[Co(II)(2)(SO(3))(2)(mu(3)-OH)(H(2)O)]}(infinity) (1) and {Na(4)[Co(II)(2)(SO(3))(4)]}(infinity) (2). When (NH(4))(2)SO(3) x H(2)O was substituted for Na(2)SO(3), the trinuclear mixed valence cobalt(II/III) complex (NH(4))(4){Co(II)[Co(III)(SO(3))(3)(NH(3))(3)](2)} x 2H(2)O (3 x 2H(2)O) was isolated. The cobalt-sulfites 1-3 x 2H(2)O were structurally characterized. In 1, the 1-D chains along the a-axis of the subunit [Co(II)(2)Co(II)(3)(OH)(2)(SO(3))(2)] are cross-linked with Co(II)(1) atoms via Co-O(sulfite) and Co-O(hydroxide) bonds in 2-D sheets, that are further stacked through interlayer hydrogen bonds. In 2, the [Co(II)(2)(SO(3))(2)](infinity) chains along the b-axis are cross-linked with tetrahedral cobalts via Co(II)-O(sulfite) bonds in 2-D sheets parallel to the ab-plane and the sheets are further bound to sodium atoms via Na(+)-O(sulfite) bonds to form a 3-D structure. The 3-D inorganic coordination polymer, 2, crystallizes in the non-centrosymmetric space group P2(1)2(1)2(1). In addition, in compound 2 octahedral and tetrahedral cobalt atoms coexist, which is rather unusual for cobalt clusters. Compound 3 x 2H(2)O is a 0-D mixed-valence {[(NH(3))(3)Co(III)(mu-SO(3))(3)]Co(II)[(mu-SO(3))(3)Co(III)(NH(3))(3)]}(4-) trinuclear cluster and can be considered as an octahedral {Co(II)O(6)} complex ligated to two tridentate [(NH(3))(3)Co(III)(SO(3))(3)](3-) ligands. The trinuclear clusters are stacked through an extended network of hydrogen bonding into a 3-D structure. Variable temperature magnetic susceptibility studies for 1-3 x 2H(2)O revealed that 1 and 2 are 2-D magnetic systems with strong antiferromagnetic interaction between the Co(II) atoms leading to an S = 0 ground state for 1, while in compound 2 there is an almost zero interaction between the cobalt(II) atoms leading to a non-zero ground state. The trinuclear compound 3 x 2H(2)O has two diamagnetic Co(III) atoms and a high-spin Co(II) atom with D = 84(1) cm(-1), E = 6(1) cm(-1) and g = 2.56(1). The IR, the solid-state UV-vis spectra and the thermogravimetric analyses of compounds 1-3 x 2H(2)O are also reported.

Polynuclear cobalt(II/III) sulfites: synthesis, structure, and magnetic properties of the octanuclear cluster (NH4)11(Li subset[Co4IICo4III(SO3)16(NH3)8]).10H2O encapsulating a lithium cation.

Partial oxidation of an aqueous solution of CoIICl(2).6H2O with (NH4)6[Mo7VIO24].4H2O in the presence of (NH4)2SO3.H2O and LiCl, at pH approximately 5.3, leads to isolation of the octanuclear cluster (NH4)11(Li subset[Co4IICo4III(SO3)16(NH3)8].10H2O), 1. The structure of the anion of 1 consists of a central [Co4II], almost ideal square planar unit, and a pair of symmetry-related CoIII dimers above and below the Co4II plane grafting onto the tetramer by 16 bridging sulfite groups. The [Co8(SO3)16(NH3)8]12- cluster encapsulates a lithium cation which lies at the center of the Co4II square.