Graphene and graphene oxide as effective adsorbents toward anionic and cationic dyes

In the present study, exfoliated graphene oxide (EGO) and reduced graphene oxide (rGO) have been used for the adsorption of various charged dyes such as methylene blue, methyl violet, rhodamine B, and orange G from aqueous solutions. EGO consists of single layer of graphite decorated with oxygen containing functional groups such as carboxyl, epoxy, ketone, and hydroxyl groups in its basal and edge planes. Consequently, the large negative charge density available in aqueous solutions helps in the effective adsorption of cationic dyes on EGO while the adsorption is negligible for anionic dyes. On the other hand, rGO that has high surface area does not possess as high a negative charge and is found to be very good adsorbent for anionic dyes. The adsorption process is followed using UV-Visible spectroscopy, while the material before and after adsorption has been characterized using physicochemical and spectroscopic techniques. Various isotherms have been used to fit the data, and kinetic parameters were evaluated. Raman and FT-IR spectroscopic data yield information on the interactions of dyes with the adsorbent. (C) 2011 Elsevier Inc. All rights reserved.

Synthesis and Properties of a Novel (Main-Chain)– (Side-Chain) Polymeric Peroxide

A novel (main-chain)-(side-chain) vinyl polyperoxide, poly(dipentene peroxide)(PDP), an alternating copolymer of dipentene (DP) and oxygen, has been synthesized by thermal oxidative polymerization of DP. The PDP was characterized by 1H NMR, 13C NMR, FTIR, DSC, TGA, and EI-MS studies. The overall activation energies of the degradation from Kissinger’s method were 28 and 33 kcal/mol, respectively, for the endocyclic and acyclic peroxide units. The side-chain peroxy groups were found to be thermally more stable than the main chain. Above 45°C the rate of polymerization increases sharply at a particular instant showing an “autoacceleration” with the formation of knee point. The kinetics of autoacceleration has been studied at various temperatures (45–70°C) and pressures (50–250 psi). © 2000 John Wiley&Sons, Inc. J Appl Polym Sci 79: 1549–1555, 2001

Temperature and density dependent solute vibrational relaxation in supercritical fluoroform

Temperature- and density-dependent vibrational relaxation data for the v6 asymmetric stretch of W(CO)6 in supercritical fluoroform (trifluoromethane, CHF3) are presented and compared to a recent theory of solute vibrational relaxation. The theory, which uses thermodynamic and hydrodynamic conditions of the solvent as input parameters, shows very good agreement in reproducing the temperature- and density-dependent trends of the experimental data with a minimum of adjustable parameters. Once a small number of parameters are fixed by fitting the functional form of the density dependence, there are no adjustable parameters in the calculations of the temperature dependence. © 2001 American Institute of Physics.

Structure and Bonding in Stannadiphospholes and their Dianions SnC(2)P(2)R(2)(m) (R=H, tBu m=0,-2): A Comparative Study with C(5)H(5)(+) and C(5)H(5)(-) Analogues

The potential energy surfaces of both neutral and dianionic SnC(2)P(2)R(2) (R=H, tBu) ring systems have been explored at the B3PW91/LANL2DZ (Sn) and 6-311 + G* (other atoms) level. In the neutral isomers the global minimum is a nido structure in which a 1,2-diphosphocyclobutadiene ring (1,2-DPCB) is capped by the Sn. Interestingly, the structure established by Xray diffraction analysis, for R=tBu, is a 1,3-DPCB ring capped by Sn and it is 2.4 kcal mol(-1) higher in energy than the 1,2-DPCB ring isomer. This is possibly related to the kinetic stability of the 1,3-DPCB ring, which might originate from the synthetic precursor ZrCp(2)tBu(2)C(2)P(2). In the case of the dianionic isomers we observe only a 6 pi-electron aromatic structure as the global minimum, similarly to the cases of our previously reported results with other types of heterodiphospholes.([1,4,19]) The existence of large numbers of cluster-type isomers in neutral and 6 pi-planar structures in the dianions SnC(2)P(2)R(2)(2-) (R=H, tBu) is due to 3D aromaticity in neutral clusters and to 2D pi aromaticity of the dianionic rings. Relative energies of positional isomers mainly depend on: 1) the valency and coordination number of the Sn centre, 2) individual bond strengths, and 3) the steric effect of tBu groups. A comparison of neutral stannadiphospholes with other structurally related C(5)H(5)(+) analogues indicates that Sn might be a better isolobal analogue to P(+) than to BH or CH(+). The variation in global minima in these C(5)H(5)(+) analogues is due to characteristic features such as 1) the different valencies of C, B, P and Sn, 2) the electron deficiency of B, 3) weaker p pi-p pi bonding by P and Sn atoms, and 4) the tendency of electropositive elements to donate electrons to nido clusters. Unlike the C5H5+ systems, all C(5)H(5)(-) analogues have 6 pi-planar aromatic structures as global minima. The differences in the relative ordering of the positional isomers and ligating properties are significant and depend on 1) the nature of the pi orbitals involved, and 2) effective overlap of orbitals.

Functionalized and Postfunctionalizable Porous Polymeric Films through Evaporation-Induced Phase Separation Using Mixed Solvents

Condensation of water droplets during rapid evaporation of a polymer solution, under humid conditions, has been known to generate uniformly porous polymer films. Similar porous films are also formed when a solution of the polymer in THF containing small amounts of water, is allowed to evaporate rapidly under air flow; this suggests that water droplets may be formed during the final stages of film formation. In the presence of added surfactants, the interface of water droplets could become lined with the surfactants and consequently the internal walls of the pores generated, upon removal of the water, could become decorated with the hydrophilic head groups of the surfactant molecules. In a series of carefully designed experiments, we have examined the effect of added surfactants, both anionic and cationic, on the formation of porous PMMA films; the films were prepared by evaporating a solution of the polymer in THF containing controlled amounts of aqueous surfactant solutions. We observed that the average size of the pores decreases with increasing surfactant concentration, while it increases with increasing amounts of added water. The size of the pores and their distribution were examined using AFM and IR imaging methods. Although IR imaging possessed inadequate resolution to confirm the presence of surfactants at the pore surface, exchange of the inorganic counterion, such as the sodium-ion of SDS, with suitable ionic organic dyes permitted the unequivocal demonstration of the presence of the surfactants at the interface by the use of confocal fluorescence microscopy.

Synthesis and characterization of some gold(I)-thiolate complexes having N-methylimidazole moiety

Antithyroid drugs inhibit the thyroid hormone synthesis by inactivating the thyroid peroxidase and/or iodothyronine deiodinase, which are involved in iodination and deiodination reactions. Gold(I) compounds also inhibit the thyroid hormone synthesis by interacting with the selenocysteine residue of iodothyronine deiodinase. However, the chemical reactions between these two different classes of compounds have not been studied. In this paper, we describe the interaction of therapeutic gold(I) compounds with the commonly used thiourea-based antithyroid drug, methimazole. It is observed that the gold(I) phosphine complexes (R(3)PAuCl, where R = Me, Et, Ph) react with methimazole only upon deprotonation to produce the corresponding gold(I)-thiolate complexes. Addition of PPh(3) to the gold(I)-thiolates produces (R(3)PAuPPh(3))(+) (R = Me or Et), indicating the possibility of ligand exchange reactions.

Synthesis and characterization of self-assembled nanofiber-bundles of V(2)O(5): their electrochemical and field emission properties

High-quality self-assembled V(2)O(5) nanofiber-bundles (NBs) are synthesized by a simple and direct hydrothermal method using a vanadium(V) hydroxylamido complex as a vanadium source in the presence of HNO(3). The possible reaction pathway for the formation of V(2)O(5) NBs is discussed and demonstrated that HNO(3) functions both as an oxidizing and as an acidification agent. V(2)O(5) NBs are single-crystals of an orthorhombic phase that have grown along the [010] direction. A bundle is made of indefinite numbers of homogeneous V(2)O(5) nanofibers where nanofibers have lengths up to several micrometres and widths ranging between 20 and 50 nm. As-prepared V(2)O(5) NBs display a high electrochemical performance in a non-aqueous electrolyte as a cathode material for lithium ion batteries. Field emission properties are also investigated which shows that a low turn-on field of similar to 1.84 V mu m(-1) is required to draw the emission current density of 10 mu Lambda cm(-2).

Experimental and Theoretical Studies of Unusual Four-Membered Metallacycles from Reactions of Group 4 Metallocene Bis(trimethylsilyl)-acetylene Complexes with the Sulfurdiimide Me3SiN=S=NSiMe3

The use of the sulfurdiimide RN=S=NR' (R = R' = SiMe3, 3) in reactions with group 4 metallocene bis(trimethylsilyl)-acetylene complexes of the type [Cp2M(L (eta(2)-Me3Si-C2SiMe3)] (1: M = Ti, no L; 2: M = Zr, L = pyridine) has led to the formation of four-membered metallacycles 4M containing the group 4 metal, nitrogen and sulfur. DFT calculations performed on compound 4Ti indicate that this complex is best described as a sigma-complex with cyclic delocalisation of the ring electrons. Moreover, pseudo-Jahn-Teller distortion plays a significant role in stabilising this complex.

Synthesis and Molecular Structures of Carboxylic Acid Group Bearing Two Ketoimines that Exist in Enaminone Form

Condensation reaction involving substituted aminobenzoic acids (2-aminobenzoic acid and 4-aminobenzoic acid) and acetylacetone results in the formation of ketoimines [CH3C(= O)CH2C(CH3)(= NAr)] (Ar = C6H4COOH-4; 1 and C6H4COOH-2 2). Compounds 1 and 2 have been characterized by spectroscopic techniques and by single crystal X-ray diffraction studies. The absorption, emission and lifetime measurement studies have also been performed for the new compounds. While compound 1 forms a linear chain type of aggregation though intermolecular hydrogen bonding, compound 2 forms a discrete dimer in the solid state.

Monodispersity and stability: case of ultrafine aluminium nanoparticles (< 5 nm) synthesized by the solvated metal atom dispersion approach

The synthesis of THF coordinated aluminium nanoparticles by the solvated metal atom dispersion (SMAD) method is described. These colloids are not stable with respect to precipitation of aluminium nanoparticles. The precipitated aluminium nanopowder is highly pyrophoric. Highly monodisperse colloidal aluminium nanoparticles (3.1 +/- 0.6 nm) stabilized by a capping agent, hexadecyl amine (HDA), have also been prepared by the SMAD method. They are stable towards precipitation of particles for more than a week. The Al-HDA nanoparticles are not as pyrophoric as the Al-THF samples. Particles synthesized in this manner were characterized by high-resolution electron microscopy and powder X-ray diffraction. Annealing of the Al-HDA nanoparticles resulted in carbonization of the capping agent on the surface of the particles which imparts air stability to them. Carbonization of the capping agent was established using Raman spectroscopy and TEM. The annealed aluminium nanoparticles were found to be stable even upon their exposure to air for over a month which was evident from the powder XRD, TGA/DSC, and TEM studies. The successful passivation was further confirmed with the determination of high active aluminium content (95 wt%) upon exposure and storage under air.

Synthesis and characterization of cobalt(II), nickel(II), copper(II) and zinc(II) complexes of 2-nitrobenzoic acid with methyl carbazate as ancillary ligand. Crystal structure of the copper(II) complex

Divalent metal complexes of general formula M(2-nb)(2)(mc)(2)].2(2-nbH), where M = Co(II), Ni(II), Cu(II) or Zn(II), 2-nbH = 2-nitrobenzoic acid and mc = methyl carbazate (NH2NHCOOCH3), have been prepared and characterized by physicochemical and spectroscopic methods. Single-crystal X-ray study of the Cu(II) complex revealed that the molecule is centrosymmetric, with two N,O-chelating mc ligands in equatorial positions and a pair of monodentate 2-nb anions in the axial positions. The lattice 2-nbH molecules help to establish the packing of monomers through hydrogen-bonding interactions. Thermal stability and reactivity of the complexes were studied by TG-DTA. Emission studies show that these complexes are fluorescent.