Photoelectron Spectroscopy (photoelectron + spectroscopy)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Photoelectron Spectroscopy

  • ultraviolet photoelectron spectroscopy
  • x-ray photoelectron spectroscopy

  • Terms modified by Photoelectron Spectroscopy

  • photoelectron spectroscopy analysis

  • Selected Abstracts

    The entrapment of corrosion products from CoCr implant alloys in the deposits of calcium phosphate: A comparison of serum, synovial fluid, albumin, EDTA, and water

    A. C. Lewis
    Abstract Physical wear of orthopedic implants is inevitable. CoCr alloy samples, typically used in joint reconstruction, corrode rapidly after removal of the protective oxide layer. The behavior of CoCr pellets immersed in human serum, foetal bovine serum (FBS), synovial fluid, albumin in phosphate-buffered saline (PBS), EDTA in PBS, and water were studied using X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). The difference in the corrosive nature of human serum, water, albumin in PBS and synovial fluid after 5 days of immersion was highlighted by the oxide layer, which was respectively 15, 3.5, 1.5, and 1.5 nm thick. The thickness of an additional calcium phosphate deposit from human serum and synovial fluid was 40 and 2 nm, respectively. Co and Cr ions migrated from the bulk metal surface and were trapped in this deposit by the phosphate anion. This may account for the composition of wear debris from CoCr orthopedic implants, which is known to consist predominantly of hydroxy-phosphate compounds. Known components of synovial fluid including proteoglycans, pyrophosphates, phospholipids, lubricin, and superficial zone protein (SZP), have been identified as possible causes for the lack of significant calcium phosphate deposition in this environment. Circulation of these compounds around the whole implant may inhibit calcium phosphate deposition. 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1587,1596, 2006 [source]

    Photoemission study of Eu valency in EuF3 ultrathin buried layers and single crystals

    W. Burian
    Abstract X-ray Photoelectron Spectroscopy was used to investigate Eu valence in the following EuF3 samples: single crystal, buried MBE layers (Au/EuF3/Fe/GaAs and Au/EuF3/Fe/Ag/GaAs) and amorphous thin films. Evidence was found for a surface divalent Eu state present on single crystal and amorphous films, while the MBE ultra thin buried layers only exhibited a trivalent Eu state. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Sulphur passivation of GaSb, InGaAsSb and AlGaAsSb surfaces

    E. Papis
    Abstract The effects of electrochemical treatment in either 21%(NH4)2S-H2O or 16%Na2S-C3H7OH solutions on the surface properties of GaSb, In0.23Ga77As0.18Sb0.82 and Al0.34Ga0.66As0.025Sb0.975 have been investigated by complementary use of Variable Angle Spectroscopic Ellipsometry (VASE) and X-ray Photoelectron Spectroscopy (XPS). We have shown that electrochemical sulphuration enables to produce 94,350 nm thick insulating overcoats with good surface morphology. The main components of the passivating layers are Ga2S3 and Sb2S5when formed on GaSb, while additional components of In2S3, admixture of Al2O3 and appearance of Al-As bond were observed on InGaAsSb and AlGaAsSb, respectively. The main feature distinguishing the effect of electrochemical treatment in Na2S,C3H7OH when comparing to those in (NH4)2S-H2O is that passivating layers contain additional components of Na2SO3 and/or Na2SO4. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Deposition of Plasma-Polymerized 1-Cyanoisoquinoline Thin Films and Their Dielectric Properties

    Xiong-Yan Zhao
    Abstract A novel plasma-polymerized 1-cyanoisoquinoline (PPCIQ) thin film of desired thickness was prepared by plasma polymerization under different glow discharge conditions. The effect of the discharge power on the chemical structure, surface composition and morphology of the PPCIQ thin films were investigated by Fourier Transform Infrared (FTIR) Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and deposition rate measurements. A high retention of the aromatic ring structure of the starting monomer in the deposited plasma films is obtained at a low discharge power of 15 W. The plasma-synthesized films are homogeneous and quite suitable for the measurement of dielectric properties. The dielectric measurements show that a low dielectric constant of 2.62 has been obtained for the PPCIQ thin films for the first time. [source]

    Recycling of silicone rubber waste: Effect of ground silicone rubber vulcanizate powder on the properties of silicone rubber

    Arun Ghosh
    The silicone rubber vulcanizate powder (SVP) obtained from silicone rubber by mechanical grinding exists in a highly aggregated state. The particle size distribution of SVP is broad, ranging from 2 m to 110 m with an average particle size of 33 m. X-ray Photoelectron Spectroscopy (XPS) and Infrared (IR) Spectroscopy studies show that there is no chemical change on the rubber surface following mechanical grinding of the heat-aged (200C/10 days) silicone rubber vulcanizate. Addition of SVP in silicone rubber increases the Mooney viscosity, Mooney scorch time, shear viscosity and activation energy for viscous flow. Measurement of curing characteristics reveals that incorporation of SVP into the virgin silicone rubber causes an increase in minimum torque, but marginal decrease in maximum torque and rate constant of curing. However, the activation energy of curing shows an increasing trend with increasing loading of SVP. Expectedly, incorporation of SVP does not alter the glass-rubber transition and cold crystallization temperatures of silicone rubber, as observed in the dynamic mechanical spectra. It is further observed that on incorporation of even a high loading of SVP (i.e., 60 phr), the tensile and tear strength of the silicone rubber are decreased by only about 20%, and modulus dropped by 15%, while the hardness, tension set and hysteresis loss undergo marginal changes and compression stress-relaxation is not significantly changed. Atomic Force Microscopy studies reveal that incorporation of SVP into silicone rubber does not cause significant changes in the surface morphology. [source]

    X-Ray Photoelectron Spectroscopy and Reactivity Studies of a Series of Ruthenium Catalysts

    CHEMCATCHEM, Issue 1 2009
    Katarzyna Jarzembska
    Abstract X-Ray photoelectron spectroscopy (XPS) was applied to six selected ruthenium precatalysts. The XPS data obtained were compared against reactivity and structural results. The XPS data confirmed some dependencies such as the electron-donor properties of the substituents at the ruthenium center. Additionally, the data combined with structural and reactivity results explain the differences between the character of Grubbs and Hoveyda catalysts. It was found that changing the PCy3 ligand to OiPr (PCy3=tricyclohexylphosphane, OiPr=isopropoxy) has a major influence on relative electron-donating properties of the N-heterocyclic carbene ligand (NHC) and PCy3 groups, which was supported by the relative charges on the Ru center for the examined compounds. Moreover, the turnover frequency (TOF) of a selected example reaction decreased when introducing a NHC group in the case of Grubbs catalysts, but increased in the case of Hoveyda-type catalysts. The XPS data also explained the relative activity values of some catalysts (higher reactivity of nitro-Hoveyda than Hoveyda second-generation catalysts). However, the binding energies do not predict TOFs. Sole examination of the XPS data does not provide a base for reaching unambiguous and binding conclusions as to the relative reactivity of all the investigated systems. [source]

    ChemInform Abstract: Photoelectron Spectroscopy of Lanthanide,Silicon Cluster Anions LnSin - (3 , n , 13; Ln: Ho, Gd, Pr, Sm, Eu, Yb): Prospect for Magnetic Silicon-Based Clusters.

    CHEMINFORM, Issue 44 2009
    Andrej Grubisic
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    ChemInform Abstract: Electronic Structure of Cadmium Selenogallate CdGa2Se4 as Studied Using ab initio Calculations and X-Ray Photoelectron Spectroscopy.

    CHEMINFORM, Issue 38 2009
    A. A. Lavrentyev
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    ChemInform Abstract: Photoelectron Spectroscopy and ab initio Study of the Structure and Bonding of Al7N - and Al7N.

    CHEMINFORM, Issue 21 2008
    Boris B. Averkiev
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    Photoelectron Spectroscopy of Doubly and Singly Charged Group VIB Dimetalate Anions: M2O72- , MM,O72- , and M2O7 - (M, M,: Cr, Mo, W).

    CHEMINFORM, Issue 7 2006
    Hua-Jin Zhai
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access the actual ChemInform Abstract, please click on HTML or PDF. [source]

    Photoelectron Spectroscopy of Free Polyoxoanions Mo6O2- 19 and W6O2- 19 in the Gas Phase.

    CHEMINFORM, Issue 3 2005
    Xin Yang
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]

    Gas-Phase Structure, Conformation, and Sulfur 2p Photoelectron Spectroscopy of Pentafluorosulfur Fluorosulfonate, SF5OSO2F

    CHEMINFORM, Issue 34 2004
    Christiane Leibold
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]

    ChemInform Abstract: Probing the Electronic Structure and Aromaticity of Pentapnictogen Cluster Anions Pn5 - (Pn: P, As, Sb, and Bi) Using Photoelectron Spectroscopy and ab initio Calculations.

    CHEMINFORM, Issue 33 2002
    Hua-Jin Zhai
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    Towards a Molecular Understanding of Cation,Anion Interactions,Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X-ray Photoelectron Spectroscopy and Theoretical Calculations

    Till Cremer
    Abstract Ten [C8C1Im]+ (1-methyl-3-octylimidazolium)-based ionic liquids with anions Cl,, Br,, I,, [NO3],, [BF4],, [TfO],, [PF6],, [Tf2N],, [Pf2N],, and [FAP], (TfO=trifluoromethylsulfonate, Tf2N=bis(trifluoromethylsulfonyl)imide, Pf2N=bis(pentafluoroethylsulfonyl)imide, FAP=tris(pentafluoroethyl)trifluorophosphate) and two [C8C1C1Im]+ (1,2-dimethyl-3-octylimidazolium)-based ionic liquids with anions Br, and [Tf2N], were investigated by using X-ray photoelectron spectroscopy (XPS), NMR spectroscopy and theoretical calculations. While 1H,NMR spectroscopy is found to probe very specifically the strongest hydrogen-bond interaction between the hydrogen attached to the C2 position and the anion, a comparative XPS study provides first direct experimental evidence for cation,anion charge-transfer phenomena in ionic liquids as a function of the ionic liquid's anion. These charge-transfer effects are found to be surprisingly similar for [C8C1Im]+ and [C8C1C1Im]+ salts of the same anion, which in combination with theoretical calculations leads to the conclusion that hydrogen bonding and charge transfer occur independently from each other, but are both more pronounced for small and more strongly coordinating anions, and are greatly reduced in the case of large and weakly coordinating anions. [source]

    A Study on the Metal Organic CVD of Pure Copper Films from Low Cost Copper(II) Dialkylamino-2-propoxides: Tuning the Thermal Properties of the Precursor by Small Variations of the Ligand,

    R. Becker
    Abstract Pure copper metal thin films were grown on SiO2/Si(100) substrates by metal,organic (MO) CVD in a horizontal cold-wall reactor employing the two metal,organic compounds, Cu(OCHMeCH2NR2)2, where R,=,Et (1) and R,=,Me (2) as precursors. Thermogravimetric analyses proved them to be convenient compounds for the deposition of copper without a reducing agent. Depositions were carried out at various substrate temperatures in the range 230,350,C. X-ray diffraction (XRD) indicated that the resulting films were highly crystalline and showed a strong (111) preferred orientation, which increased with increasing deposition temperature. Photoelectron spectroscopy (XPS) revealed that copper films deposited at 230,C and 260,C consisted solely of metallic copper with no detectable carbon, nitrogen, or oxygen contamination. Copper films obtained from 1 at 260,C had a resistivity of 2.16,,,,cm. [source]

    Synthesis and morphology of nanosized zeolite L

    S. Sadegh Hassani
    Abstract AFM is a powerful tool for imaging nanoscale surface features; it provides two and three dimensional crystal structure images and other information about actual surface of zeolite crystallites. In this paper, nanosized zeolite L is synthesized in different crystallization times and a study of crystal growth of zeolite L is reported using atomic force microscopy (AFM). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques are used for characterization of the as synthesized samples. TEM and two-dimensional AFM images indicate that the zeolite particles are in a nano-range and they have hexagonal structure. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Role of oxygen vacancies in the coloration of 0.65Pb(Mg1/3Nb2/3)O3 -0.35PbTiO3 single crystals

    Zhiguo Xia
    Abstract The coloration and oxygen vacancies in 0.65Pb(Mg1/3Nb2/3)O3 -0.35PbTiO3 (PMN-PT(65/35)) (starting composition) single crystals grown by a so-called modified Bridgman technique were investigated in this paper. Light yellow and dark brown colored crystals were generally observed for the typical as-grown PMN-PT(65/35) single crystals. X-ray diffraction results demonstrated that they were both of pure perovskite structure, but good electric properties were only obtained for the light yellow crystal. X-ray photoelectron spectroscopy (XPS) was used to investigate the electronic structure of its components. The O 1s photoelectron spectra of the dark brown colored crystals located at the higher binding energy side, which meant the existence of the more oxygen vacancies. It accordingly led to the formation of the low valence cations associated with the coloration of the crystals, which is also testified by the obtained X-ray photoelectron spectra of Ti and Nb. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    The impact of SiC substrate treatment on the heteroepitaxial growth of GaN by plasma assisted MBE

    A. S. Brown
    Abstract We report on the impact of the preparation of the Si-face 4H-SiC(0001)Si substrate using a Ga flash-off process on the epitaxial growth of GaN by plasma-assisted molecular beam epitaxy. The nucleation, as well as the resultant structural and morphological properties of GaN grown directly on 4H-SiC(0001)Si are strongly influenced by the chemical and morphological modifications of the SiC surface induced by the Ga flash-off process. Herein we describe the impact of the specific concentration of Ga incident on the surface (quantified in terms of monolayer (ML) coverage): of 0.5 ML, 1ML and 2ML. The residual oxygen at the SiC surface, unintentional SiC nitridation and the formation of cubic GaN grains during the initial nucleation stage, are all reduced when a 2 ML Ga flash is used. All of the above factors result in structural improvement of the GaN epitaxial layers. The correlation between the SiC surface modification, the initial nucleation stage, and the GaN epitaxial layer structural quality has been articulated using x-ray photoelectron spectroscopy, x-ray diffraction, atomic force microscopy and spectroscopic ellipsometry data. ( 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Preparation of Novel Arrays Silver Nanoparticles Modified Polyrutin Coat-Paraffin-Impregnated Graphite Electrode for Tyrosine and Tryptophan's Oxidation

    ELECTROANALYSIS, Issue 8 2008
    Guan-Ping Jin
    Abstract A novel array silver nanoparticles and Rutin complex film modified paraffin-impregnated graphite electrode was proposed in this work (denoted as Ag/Rutin/WGE). The characteristics were investigated by the field emission scanning electron microscopy (FE-SEM), infrared spectra (IR), UV-visible (UV), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques. Silver ions were gradually chelated by polyrutin film at 4,-oxo-5,-OH and 5-OH-4-oxo sites accompanying adsorption, then. Silver nanoparticles were highly-dispersed electrodeposited on polyrutin film. The electrochemical behaviors of tyrosine (Tyr) and tryptophan (Trp) were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The Ag/Rutin/WGE electrode shows overlapping catalysis for the oxidation of Tyr and Trp. The linear response of Tyr and Trp were 0.3,10.0 and 0.7,70.0,,M with detection limit of 0.07 and 0.1,,M in a signal-to-noise ratio of 3. [source]

    Evaluation of Thin Film Titanium Nitride Electrodes for Electroanalytical Applications

    ELECTROANALYSIS, Issue 10 2007
    Carolina Nunes, Kirchner
    Abstract Titanium nitride is a hard and inert conducting material that has yet not been widely used as electrode material for electroanalytical applications although there are highly developed protocols available to produce well adherent micro and nanostructured electrodes. In this paper the possibilities of using titanium nitride thin films for electroanalytical applications is investigated. Scanning electrochemical microscope (SECM) was used for analysis of the redox kinetics of a selected fast redox couple at thin films of titanium nitride (TiN) in different thicknesses. The investigation was carried out by approaching an amperometric ultramicroelectrode (UME) to the TiN film while the soluble redox couple (ferrocenemethanol/ferrociniummethanol) served as mediator in a SECM configuration. The substrate was biased at a potential so that it rereduces the species being produced at the UME, thus controlling the feedback effect. Normalized current,distance curves were fitted to the theoretical model in order to find the apparent heterogeneous standard rate constant (k) at the sample. The data are further supported by structural investigation of the TiN films using scanning force microscopy and X-ray photoelectron spectroscopy. It was found that the kinetics are little influenced by prolonged storage in air. The heterogeneous standard rate constants in 2,mM ferrocenemethanol were (0.730.05)10,3,cm s,1 for 20,nm TiN thin layer, (1.50.2)10,3,cm s,1 for 100,nm TiN thin layer and (1.30.2)10,3,cm s,1 for 300,nm TiN thin layer after prolonged storage in air. Oxidative surface treatment (in order to remove organic adsorbates) decreased the kinetics in agreement with a thicker oxide layer on the material. The results suggest that their direct use for amperometric detection of reversible redox systems in particular at miniaturized configurations may be advantageous. [source]

    Xanthine Sensors Based on Anodic and Cathodic Detection of Enzymatically Generated Hydrogen Peroxide

    ELECTROANALYSIS, Issue 6 2007
    Aminur Rahman
    Abstract A xanthine biosensor was fabricated by the covalent immobilization of xanthine oxidase (XO) onto a functionalized conducting polymer (Poly-5, 2,: 5,, 2,-terthiophine-3-carboxylic acid), poly-TTCA through the formation of amide bond between carboxylic acid groups of poly-TTCA and amine groups of enzyme. The immobilization of XO onto the conducting polymer (XO/poly-TTCA) was characterized using cyclic voltammetry, quartz crystal microbalance (QCM), and X-ray photoelectron spectroscopy (XPS) techniques. The direct electron transfer of the immobilized XO at poly-TTCA was found to be quasireversible and the electron transfer rate constant was determined to be 0.73,s,1. The biosensor efficiently detected xanthine through oxidation at +0.35,V and reduction at ,0.25,V (versus Ag/AgCl) of enzymatically generated hydrogen peroxide. Various experimental parameters, such as pH, temperature, and applied potential were optimized. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 5.010,6,1.010,4 M and 5.010,7 to 1.010,4,M, respectively. The detection limits were determined to be of 1.010,6,M and 9.010,8,M with anodic and cathodic processes, respectively. The applicability of the biosensor was tested by detecting xanthine in blood serum and urine real samples. [source]

    Study of Factors Affecting the Performance of Voltammetric Copper Sensors Based on Gly-Gly-His Modified Glassy Carbon and Gold Electrodes

    ELECTROANALYSIS, Issue 12 2006
    Guozhen Liu
    Abstract This paper reports a study of the factors affecting the analytical performance of gold and glassy carbon electrodes modified with the tripeptide Gly-Gly-His for the detection of copper ions. Gly-Gly-His is attached to a glassy carbon (GC) surface modified with 4-carboxyphenyl moieties or a gold surface modified with 3-mercaptopropionic acid by the reaction of the N-terminal amine group of the peptide with the carboxylic acid groups of the monolayer via carbodiimide activation. X-ray photoelectron spectroscopy was used to characterize the steps in the biosensor fabrication. It was found that the analytical performance of a sensor prepared with Gly-Gly-His on a GC electrode was similar to that on a gold electrode under the same conditions. The performance was greatly enhanced at higher temperature, no added salt during copper accumulation and longer accumulation time within a pH range of 7,9. Interference studies and investigations of stability of the Gly-Gly-His sensor are reported. Analysis of natural water samples show that the sensors measure only copper ions that can complex at the sensor surface. Strongly complexed copper in natural water is not measured. Despite greater stability of diazonium salt derived monolayers on carbon surfaces compared with alkanethiols self-assembled monolayers on gold, the stability of the sensors was essentially the same regardless of the modification procedure. [source]

    The Solid State Electrochemistry of Dysprosium(III) Hexacyanoferrate(II)

    ELECTROANALYSIS, Issue 17 2005
    Ping Wu
    Abstract A new electroactive polynuclear inorganic compound of rare earth metal hexacyanoferrate, dysprosium hexacyanoferrate (DyHCF), was prepared chemically and characterized using techniques of FTIR spectroscopy, thermogravimetric analysis (TGA), UV-vis spectrometry and X-ray photoelectron spectroscopy (XPS) etc. The cyclic voltammetric behavior of DyHCF mechanically attached to the surface of graphite electrode was well defined and exhibited a pair of redox peaks with the formal potential of 217,mV (vs. SCE) at a scan rate of 100,mV/s in 0.2,M NaCl solution and the redox peak currents increased linearly with the square root of the scan rates. [source]

    Multistep Anchoring Route of Luminescent (5-Amino-1,10-phenanthroline)tris(dibenzoylmethane)europium(III) on Si(100)

    Guglielmo G. Condorelli
    Abstract A multistep route for the covalent anchoring of (5-amino-1,10-phenanthroline)tris(dibenzoylmethane)europium(III)molecules on silicon (100) has been developed. The anchoring route consists of Si functionalization with N -hydroxysuccinimide (NHS) activated carboxylic acid, followed by nucleophilic substitution at the carboxylic acid sites. Characterization of the resulting Si based hybrid materials was achieved by using several complementary techniques: X-ray photoelectron spectroscopy (XPS), attenuated total reflection FTIR spectroscopy (ATR-FTIR), AFM and fluorescence spectroscopy. Comparison of results obtained for NHS activated Si surfaces with those of inert alkyl functionalized Si surfaces proved the covalent anchoring of the Eu complex and ruled out the presence of physisorbed Eu species. The 1.8 nm thickness of the grafted layer, estimated by atomic-force lithography, is compatible with the presence of the anchored complex on the surface. Fluorescence measurements proved that luminescence properties are retained in the grafted complex. [source]

    Heteroleptic Guanidinate- and Amidinate-Based Complexes of Hafnium as New Precursors for MOCVD of HfO2

    Ke Xu
    Abstract The synthesis and characterization of four new heteroleptic complexes [Hf{,2 -(iPrN)2CNMe2}2Cl2] (1), [Hf{,2 -(iPrN)2CNMe2}2Me2] (2), [Hf{,2 -(iPrN)2CMe}2Cl2] (3), and [Hf{,2 -(iPrN)2CMe}2Me2] (4) are reported. All the complexes were characterized by spectroscopic methods, while compounds 1,3 were further examined by single-crystal X-ray diffraction, revealing that the complexes are monomers with the hafnium center in a distorted octahedral geometry. The thermal properties of the chlorine-free complexes (2, 4) were examined to determine their suitability for metalorganic chemical vapor deposition (MOCVD) applications, and compound 2 showed good volatility and thermal stability. On the basis of these results, compound 2 was selected for MOCVD of HfO2 with oxygen as oxidant. Depositions were carried out on Si(100) substrates in the temperature range 300,700 C. The as-deposited HfO2 films crystallized in the monoclinic phase at temperatures above 500 C, and the composition analysis determined by Rutherford back-scattering (RBS) and X-ray photoelectron spectroscopy (XPS) revealed that the films were stoichiometric and free of carbon. Thus, alkylguanidinatohafnium complex 2 is a promising precursor for growing HfO2 films in a wide temperature range with the desired stoichiometry, because of its adequate volatility, sufficient temperature window between vaporization and decomposition, as well as its ability to decompose cleanly in the presence of oxygen. [source]

    Tartatric Acid and L -Cysteine Synergistic-Assisted Synthesis of Antimony Trisulfide Hierarchical Structures in Aqueous Solution

    Jun Pan
    Abstract Alveolate amorphous Sb2S3 microspheres about 2 ,m in diameter were hydrothermally synthesized in aqueous solution without the use of a surfactant at 180 C by using SbCl3, L -cysteine, and tartaric acid as starting materials. After annealing at 250 C for 3 h under a nitrogen atmosphere, polycrystalline Sb2S3 hollow spheres were obtained. The morphology, structure, and phase composition of alveolate Sb2S3 microspheres were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy. It was demonstrated that tartaric acid and L -cysteine play a key role in the formation of such hierarchical structures. In addition, the possible aggregation mechanism was proposed to illustrate the formation of Sb2S3 microspheres on the basis of the experimental results and analyses.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Facile and Reproducible Synthesis of Nanostructured Colloidal ZnO Nanoparticles from Zinc Acetylacetonate: Effect of Experimental Parameters and Mechanistic Investigations

    Alessia Famengo
    Abstract A facile and reproducible route to nanostructured colloidal ZnO nanoparticles was developed by controlled hydrolysis and condensation of zinc acetylacetonate in alkaline conditions. By reaction of an ethanolic solution of Zn(acac)2 with NaOH in a 1:2 molar ratio, after reflux, ZnO spherical nanoparticles were obtained that displayed a homogeneous size distribution; particle diameters ranged from 6 to 10 nm, as evidenced by transmission electron microscopy (TEM) analysis. The same reaction was carried out also in water, glycerol and 1,2-propanediol, to investigate the effect of the solvent viscosity and dielectric constant on the final features of the obtained material. Irrespective of the nature of the solvent, X-ray diffraction (XRD) analysis shows the formation ofhexagonal ZnO, whereas the presence of residual unreacted Zn(acac)2 could be ruled out. Indeed, different particle sizes and very different morphologies were obtained. Also the reflux step was shown to be a key factor in avoiding the fast precipitation of a floc and achieving a pure compound, which was isolated and thoroughly characterised. The composition of the obtained ZnO was determined by elemental analysis, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), showing the formation of pure ZnO. IR spectroscopy evidenced the presence of adsorbed organic ligands on the colloid surfaces. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) revealed the presence of medium- to high-strength acidic sites on the ZnO surface. To gain a deeper insight into the formation mechanisms of these nanostructures, time-resolved UV/Vis and XAS studies were performed on the ethanol solution used for the synthesis of the oxide and also on the solid specimen, obtained after the refluxing step. No remarkable changes could be evidenced in the solution after the addition of an understoichiometric amount of NaOH, but the growth of the ZnO nanoparticles could be followed by UV/Vis spectra. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Ultrasound-Assisted Synthesis of CuO Nanorods in a Neat Room-Temperature Ionic Liquid

    Tarek Alammar
    Abstract CuO nanorods were prepared via ultrasound-assisted synthesis in the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide [C4mim][Tf2N] as a reaction medium. The structure and morphology of CuO nanorods were characterized with X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), vibrational and UV/Vis absorption spectroscopy. The synthesized CuO nanocrystals are of rod like shape with lengths from 30 to 100 nm and diameters of about 10 nm. Quantum size effects were observed as the bandgap of the CuO nanorods was determined to 2.41 eV from UV/Vis absorption measurements, which is significantly larger than the bulk value. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Influence of Surface Chemistry on Dehydrogenation in Carbon Cryogel Ammonia Borane Nanocomposites

    Saghar Sepehri
    Abstract This paper reports the synthesis and characterization of boron- and nitrogen-modified carbon cryogel (CC) ammonia borane (AB) nanocomposites (BNCC-AB) for hydrogen storage. Resorcinol,formaldehyde (RF) derived CCs were modified by homogeneous dispersion of AB in RF hydrogel prior to pyrolysis. Nanocomposites were fabricated by immersing CC in the AB solution. Nitrogen sorption analysis, X-ray photoelectron spectroscopy, and differential scanning calorimetry at multiple heating rates were used to study the structure and dehydrogenation properties of the nanocomposites. The results demonstrated lower dehydrogenation temperatures and reduced activation energies for AB when confined inside pores of B- and N-modified CCs relative to AB when confined in the unmodified CC with the same pore size.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Electronic Structure of Binary Phosphoric and Arsenic Triazides

    Zeng Xiaoqing
    Abstract Two highly explosive binary triazides of the group 15 elements P(N3)3 and As(N3)3 have been obtained in the gas phase through the heterogeneous reaction of PCl3 and AsCl3, respectively with AgN3 at room temperature. The electronic structures of both triazides have been characterized by photoelectron spectroscopy, combined with quantum chemical calculations. This represents the first electronic study of covalent triazides. The first experimental vertical ionization potentials for P(N3)3 and As(N3)3 are 9.74 and 9.98 eV, with the contribution primarily from the lone pairs of the azido moiety and the arsenic atom, respectively. The results indicate the relative "isolation" of azido moieties in triazides and less stability of these highly explosive compounds in comparison to monoazides and diazides. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]