Mixed ligand complexes in vinyl polymerization-II: [NN-ethylenebis(salicylideneiminato)] (benzoylacetonato)cobalt(III) as an initiator

The polymerization of methyl methacrylate initiated by a mixed ligand complex. [NN-ethylenebis(salicylideneiminato)](benzoylacetonato)cobalt(III) has been studied in bulk and in benzene at 70° and 80°. The rate of polymerization is proportional to (concentration of the chelate)Image and the monomer exponent is close to 1.5. The activation energy and the kinetic and transfer constants are evaluated. A free radical mechanism has been proposed.

Structure-thermal behaviour studies on the salicylato complex of cobalt

The salicylato complex of cobalt was synthesized and its structure established to be [Co(sal)2] · 4 H2O, where, sal =, from elemental analysis, IR spectroscopy, magnetic susceptibility, cryoscopy and conductivity. The X-ray diffractogram of the complex has been given. Thermal decomposition has been studied in air by thermogravimetry (TG), differential thermal analysis and differential scanning calorimetry. TG shows three main steps of decomposition. The intermediates formed at various stages were collected and analysed. From the TG results and chemical analysis of the intermediates, a mechanism has been proposed for the thermal decomposition of the complex, leading to the oxide formation in the final stage.

Effect of iodine doping on surface and optical properties of polyterpenol thin films

This study presents the effect of iodine doping on optical and surface properties of polyterpenol thin films deposited from non-synthetic precursor by means of plasma polymerisation. Spectroscopic ellipsometry studies showed iodine doping reduced the optical band gap from 2.82 eV to 1.50 eV for pristine and doped samples respectively. Higher levels of doping notably reduced the transparency of films, an issue if material is considered for applications that require high transparency. Contact angle studies demonstrated higher hydrophilicity for films deposited at increased doping levels, results confirmed by XPS Spectroscopy and FTIR. Doping had no significant effect on the surface profile or roughness of the film.

Interaction of Metal Ions with 2'-Deoxyribonucleotides. Crystal and Molecular Structure of a Cobalt(l1) Complex with 2'-Deoxyinosine 5'-Monophosphate

The crystal structure of the cobalt( 11) complex with 2'-deoxyinosine 5'-monophosphate (5'- dlMP), [Co(5'-dlMP) (H,0),]-2H20, has been analysed by X-ray diffraction. The complex crystallizes in the space group P2,2,2, with a = 6.877(3), b = 10.904(2), c = 25.421 (6) A, and Z = 4. The structure was solved by the heavy-atom method and refined to an R value of 0.043 using 1 776 unique reflections. The cobalt ion binds only to the 6-oxopurine base of the nucleotide at the N(7) position, the octahedral co-ordination of the metal being completed by five water oxygens. The phosphate oxygens are involved in hydrogen bonding with the co-ordinated water molecules. The structure is closely similar to that of the corresponding ribonucleotide complex. The nucleotide has the energetically preferred conformation: an anti base, a C(3') -endo sugar pucker, and a gauche-gauche conformation about the C(4')-C( 5') bond. The significance of sugar puckering in the monomeric complexes of general formula [ M (5'-nucleotide) (H20),] is explained in terms of the structural requirements for metal-water-phosphate bridging interactions.

Influence of Sm2O3 doping on formation and structure of SrBi2Nb2O9 nanocrystals in lithium borate glasses

New glasses of 16.66SrO–16.66[(1 − x)Bi2O3–xSm2O3]–16.66Nb2O5–50Li2B4O7 (0 ≤ x ≤ 0.5, in molar ratio), i.e., the pseudo-binary Sm2O3-doped SrBi2Nb2O9–Li2B4O7 glass system, giving the crystallization of Sm3+-doped SrBi2Nb2O9 nanocrystals are developed. It is found that the thermal stability of the glasses against the crystallization and the optical band gap energy increases with increasing Sm2O3 content. The formation of fluorite-type Sm3+-doped SrBi2Nb2O9 nanocrystals (diameters: 13–37 nm) with a cubic structure is confirmed in the crystallized (530 °C, 3 h) samples from X-ray powder diffraction analyses, Raman scattering spectrum measurements, and transmission electron microscope observations. The effect of Sm3+-doping on the microstructure, Raman scattering peak positions, and dielectric properties of composites comprising of fluorite-type SrBi2Nb2O9 nanocrystals and the Li2B4O7 glassy phase is clarified. It is found that fluorite-type SrBi2Nb2O9 nanocrystals transform to stable perovskite-type SrBi2Nb2O9 crystals with an orthorhombic structure by heat treatments at around 630 °C.

Mechanism of vapour phase oxidation of anthracene over cobalt molybdate catalyst

Vapour phase oxidation of anthracene over cobalt molybdate catalyst was investigated in an isothermal flow reactor in the temperature range of 280—340°C. Fifteen different models based on redox, Langmuir—Hinshelwood and Rideal mechanisms were tested in order to elucidate the mechanism of the above reaction. These models were compared on the basis of three criteria and were finally discriminated employing the non-intrinsic parameter method. Two-stage redox mechanism was found to explain the data satisfactorily.

Mixed ligand complexes in vinyl polymerization-II: [NN′-ethylenebis(salicylideneiminato)] (benzoylacetonato)cobalt(III) as an initiator

The polymerization of methyl methacrylate initiated by a mixed ligand complex. [NN′-ethylenebis(salicylideneiminato)](benzoylacetonato)cobalt(III) has been studied in bulk and in benzene at 70° and 80°. The rate of polymerization is proportional to (concentration of the chelate)1/2 and the monomer exponent is close to 1.5. The activation energy and the kinetic and transfer constants are evaluated. A free radical mechanism has been proposed.

Mixed ligand complexes in vinyl polymerization. I. [N,N-ethylenebis (salicylideneiminato)](acetylacetonato)cobalt(III) as an initiator

Polymerization of methyl methacrylate in the presence of a mixed ligand complex, [N,N-ethylenebis(salicylideneiminato)](acetylacetonato)cobalt(III) in benzene was studied. The rate of polymerization was proportional to the square root of the concentration of the chelate and the monomer exponent was 1.67 and 1.69 at 60 and 70°C, respectively. The activation energy and the kinetic and transfer constants were evaluated. A free-radical mechanism has been proposed.

Mechanism of vapour phase oxidation of anthracene over cobalt molybdate catalyst

Vapour phase oxidation of anthracene over cobalt molybdate catalyst was investigated in an isothermal flow reactor in the temperature range of 280—340°C. Fifteen different models based on redox, Langmuir—Hinshelwood and Rideal mechanisms were tested in order to elucidate the mechanism of the above reaction. These models were compared on the basis of three criteria and were finally discriminated employing the non-intrinsic parameter method. Two-stage redox mechanism was found to explain the data satisfactorily.

Combined effect of double antireflection coating and reversible molecular doping on performance of few-layer graphene/n-silicon Schottky barrier solar cells

Few-layer graphene films were grown by chemical vapor deposition and transferred onto n-type crystalline silicon wafers to fabricate graphene/n-silicon Schottky barrier solar cells. In order to increase the power conversion efficiency of such cells the graphene films were doped with nitric acid vapor and an antireflection treatment was implemented to reduce the sunlight reflection on the top of the device. The doping process increased the work function of the graphene film and had a beneficial effect on its conductivity. The deposition of a double antireflection coating led to an external quantum efficiency up to 90% across the visible and near infrared region, the highest ever reported for this type of devices. The combined effect of graphene doping and antireflection treatment allowed to reach a power conversion efficiency of 8.5% exceeding the pristine (undoped and uncoated) device performance by a factor of 4. The optical properties of the antireflection coating were found to be not affected by the exposure to nitric acid vapor and to remain stable over time.

Simple synthesis and spectroscopic studies on cobalt added ZnO nanocrystals

Cobalt doped zinc oxide nanoparticles were prepared through simple wet chemical method. X-ray diffraction studies confirm the prepared particles are in wurtzite structure. Scanning Electron Microscopy studies show the shape and morphology of the particles. To identify the presence of cobalt in ZnO, Energy Dispersive X-ray analysis was done. Optical absorption measurements show the presence of exciton peak at 375 nm. Photoluminescence studies were done with the excitation wavelength of 330 nm, which shows the emission because of exciton recombination and oxygen vacancy.

Mechanisms of molecular doping of graphene: A first-principles study

Doping graphene with electron donating or accepting molecules is an interesting approach to introduce carriers into it, analogous to electrochemical doping accomplished in graphene when used in a field-effect transistor. Here, we use first-principles density-functional theory to determine changes in the electronic-structure and vibrational properties of graphene that arise from the adsorption of aromatic molecules such as aniline and nitrobenzene. Identifying the roles of various mechanisms of chemical interaction between graphene and a molecule, we bring out the contrast between electrochemical and molecular doping of graphene. Our estimates of various contributions to shifts in the Raman-active modes of graphene with molecular doping are fundamental to the possible use of Raman spectroscopy in (a) characterization of the nature and concentration of carriers in graphene with molecular doping, and (b) graphene-based chemical sensors.

Zr4+ doping in Li4Ti5O12 anode for lithium-ion batteries: Open Li+ diffusion paths through structural imperfection

One-dimensional nanomaterials have short Li+ diffusion paths and promising structural stability, which results in a long cycle life during Li+ insertion and extraction processes in lithium rechargeable batteries. In this study, we fabricated one-dimensional spinel Li 4Ti5O12 (LTO) nanofibers using an electrospinning technique and studied the Zr4+ doping effect on the lattice, electronic structure, and resultant electrochemical properties of Li-ion batteries (LIBs). Accommodating a small fraction of Zr4+ ions in the Ti4+ sites of the LTO structure gave rise to enhanced LIB performance, which was due to structural distortion through an increase in the average lattice constant and thereby enlarged Li+ diffusion paths rather than changes to the electronic structure. Insulating ZrO2 nanoparticles present between the LTO grains due to the low Zr4+ solubility had a negative effect on the Li+ extraction capacity, however. These results could provide key design elements for LTO anodes based on atomic level insights that can pave the way to an optimal protocol to achieve particular functionalities. Distorted lattice: Zr4+ is doped into a 1 D spinel Li4Ti5O12 (LTO) nanostructure and the resulting electrochemical properties are explored through a combined theoretical and experimental investigation. The improved electrochemical performance resulting from incorporation of Zr4+ in the LTO is due to lattice distortion and, thereby, enlarged Li+ diffusion paths rather than to a change in the electronic structure.

Amino Acid Based MOFs: Synthesis, Structure, Single Crystal to Single Crystal Transformation, Magnetic and Related Studies in a Family of Cobalt and Nickel Aminoisophthales

Four new 5-aminoisophthalates of cobalt and nickel have been prepared employing hydro/solvothermal methods: [Co2(C8H5NO4)2(C4H4N2)(H2O)2]·3H2O (I), [Ni2(C8H5NO4)2(C4H4N2)(H2O)2]·3H2O (II), [Co2(H2O)(μ3-OH)2(C8H5NO4)] (III), and [Ni2(H2O)(μ3-OH)2(C8H5NO4)] (IV). Compounds I and II are isostructural, having anion-deficient CdCl2 related layers bridged by a pyrazine ligand, giving rise to a bilayer arrangement. Compounds III and IV have one-dimensional M−O(H)−M chains connected by the 5-aminoisophthalate units forming a three-dimensional structure. The coordinated as well as the lattice water molecules of I and II could be removed and inserted by simple heating−cooling cycles under the atmospheric conditions. The removal of the coordinated water molecule is accompanied by changes in the coordination environment around the M2+ (M = Co, Ni) and color of the samples (purple to blue, Co; green to dark yellow, Ni). This change has been examined by a variety of techniques that include in situ single crystal to single crystal transformation studies and in situ IR and UV−vis spectroscopic studies. Magnetic studies indicate antiferromagnetic behavior in I and II, a field-induced magnetism in III, and a canted antiferromagnetic behavior in IV.