Search results for " Spectroscopy"
showing 10 items of 6851 documents
MoO (x≤2) ultrathin film growth from reactions between metallic molybdenum and TiO2 surfaces
2001
Abstract Exposures to oxygen at room temperature and annealings under vacuum were carried out on deposits obtained from molybdenum interacting with (1 1 0) TiO 2 surfaces in order to obtain molybdenum oxide ultra thin films. Exposures to oxygen at room temperature show that the interfacial molybdenum oxide layers resulting from the TiO 2 /Mo interactions are inactive towards oxygen whereas the metallic molybdenum clusters, which grew on top of the interfacial layers, oxidise into MoO 3 . Besides, during annealings under vacuum, substrate oxygen anions can diffuse into the deposit. Thus, between 400 and 500°C, molybdenum oxide layers are progressively oxidised into MoO 2 . Moreover, from the…
Di-n-octyltin(IV) complexes with 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acid: Syntheses and assessment of solid state structures by 119Sn Mössb…
2007
Abstract Reactions of 5-[( E )-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids (LHH′, where the aryl group is an R-substituted phenyl ring such that for L 1 HH′: X = H; L 2 HH′: X=2′-OCH 3 ; L 3 HH′: X = 3′-CH 3 ; L 4 HH′: X = 4′-CH 3 ; L 5 HH′:X = 4′-Cl) with n Oct 2 SnO in 2:1 and 1:1 molar ratios have been investigated. Two types of complexes, n Oct 2 Sn(LH) 2 and {[ n Oct 2 Sn(LH)] 2 O} 2 , were isolated and they have been characterized by 1 H, 13 C, 119 Sn NMR, ESI-MS, IR and 119m Sn Mossbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of n Oct 2 Sn(L 1 H) 2 ( 1 ), {[ n Oct 2 Sn(L 2 H)] 2 O} 2 ( 3 ) and {[ n Oct 2 Sn(L 3 H)] 2 O} 2 ( 4 ) were de…
Synthesis and characterization of the first diorganotin(IV) complexes containing mixed arylazobenzoic acids and having skew trapezoidal bipyramidal g…
2005
Abstract Three diorganotin(IV) complexes of the type, [R 2 Sn(L a H)(L b H)] (R = n Bu or Me and, L a H and L b H are two different 5-[( E )-2-(aryl)-1-diazenyl]-2-hydroxybenzoate residues; a: aryl = 4′-Cl-(held constant) and b: aryl = 4′-Me or 4′-Br) have been prepared either by reacting n Bu 2 SnO, L a HH′ and L b HH′ (1:1:1) in anhydrous toluene or by reacting Me 2 SnCl 2 , L a HNa and L b HNa (1:1:1) in anhydrous methanol. The products were characterized by microanalysis, IR, NMR ( 1 H, 13 C, 119 Sn) and 119m Sn Mossbauer spectroscopy. A full characterization of the structures of the complexes [ n Bu 2 Sn(L a H)(L b H)] ( 1 and 2 ) and [Me 2 Sn(L a H)(L b H)] ( 3 ) in the solid state w…
Analytical Study of a Resinous Material Used as Sealing in Ancient Pottery Found in an Archaeological Site by Thermally Assisted Hydrolysis Methylati…
2009
Abstract A resin sample was found in the archaeological site of Lixus (Morocco), belonging to the second century BC. The resinous material was found inside an amphora containing iron remains used in the plug as sealing material to hermetically close the pottery. The resinous sample was studied by several analytical techniques, as thermally assisted hydrolysis and methylation–gas chromatography–mass spectrometry (THM–GC–MS), Fourier transformed infrared spectroscopy (FTIR), and light microscopy. The material was identified as a Pinaceae resin. Therefore, a modern pine resin was also analyzed to consider the influence of aging in the archaeological sample. The ancient material was found not t…
The Reduction Pathway of End-on Coordinated Dinitrogen. I. Vibrational Spectra of Mo/W−N2, −NNH, and −NNH2 Complexes and Quantum Chemistry Assisted N…
1999
Infrared and Raman spectra of [M(N(2))(2)(dppe)(2)] (M = W, Mo) and the two protonated derivatives [WF(NNH)(dppe)(2)] and [WF(NNH(2))(dppe)(2)](+) (dppe = 1,2-bis(diphenylphosphino)ethane) are presented. Using isotope substituted compounds ((15)N and D) the vibrations of the Y-M-N(2)H(x)() (x = 0, 1, 2; Y = N(2), F) central unit are identified, in particular the M-N and N-N stretching modes. In case of the monoprotonated systems, an equilibrium between metal- and nitrogen-protonated species exists that is clearly detectable in the IR spectra. Making use of theoretical force fields, a quantum chemistry assisted normal coordinate analysis (QCA-NCA) is performed for all three tungsten systems …
Double Laser LIBS and micro-XRF spectroscopy applied to characterize materials coming from the Greek-Roman theater of Taormina
2009
The laser-induced breakdown spectroscopy (LIBS) is an applied physical technique that has shown, in recent years, its great potential for rapid qualitative analysis of materials. The possibility to implement a portable instrument that perform LIBS analysis makes this technique particularly useful for in situ analysis in the field of cultural heritages. The aim of this work is to compare the results, obtained by LIBS measurements with X-Ray Fluorescence (XRF) ones, on calcareous and refractory materials coming from the Greek-Roman theater of Taormina. Calibration curves for LIBS and XRF were obtained by measuring certified reference materials and using them as standards. LIBS measurements we…
13C-Decoupled J-Coupling Spectroscopy Using Two-Dimensional Nuclear Magnetic Resonance at Zero-Field
2017
We present a two-dimensional method for obtaining 13C-decoupled, 1H-coupled nuclear magnetic resonance (NMR) spectra in zero magnetic field using coherent spin-decoupling. The result is a spectrum determined only by the proton–proton J-coupling network. Detection of NMR signals in zero magnetic field requires at least two different nuclear spin species, but the proton J-spectrum is independent of isotopomer, thus potentially simplifying spectra and thereby improving the analytical capabilities of zero-field NMR. The protocol does not rely on a difference in Larmor frequency between the coupled nuclei, allowing for the direct determination of J-coupling constants between chemically equivalen…
Thermal oxidative process in extra-virgin olive oils studied by FTIR, rheology and time-resolved luminescence
2011
Abstract With the aim to characterise the antioxidant properties of different extra-virgin olive oils and to understand in more detail the mechanisms of oil degradation, we have made an experimental study on thermal induced oxidative processes of extra-virgin olive oils by using different techniques: Fourier Transform Infrared (FTIR) spectroscopy, rheology and time-resolved luminescence. The oxidation process was followed at three different heating temperatures (30, 60 and 90 °C) as a function of time up to 35 days. Thermal treatment induced changes in the FTIR spectra in the wavenumbers region 3100–3600 cm −1 : in particular, the absorption profiles show an initial formation of hydroperoxi…
1H, 13C NMR spectral and single crystal structural studies of toxaphene congeners. Quantum chemical calculations for preferred conformers of 2,5-endo…
2005
Abstract The 1H and 13C NMR chemical shifts for six toxaphene congeners: 2-exo,3-endo,6-exo,8,9,10-hexachloro- (1), 2-exo,3-endo,5-exo,9,9,10,10-heptachloro- (2), 2-exo,3-endo,6-exo,8,9,10,10-heptachloro- (3), 2-exo,3-endo,5-exo,6-endo,8,9,10-heptachloro- (4), 2-exo,3-endo,5-exo,6-endo,8,9,9,10-octachlorobornane (5) and 2,5-endo,6-exo,8,9,9,10,10-octachloro-2-bornene (6) are reported. Their chemical shift assignments have been obtained by means of Pulsed Field Gradient (PFG) Double Quantum Filtered (DQF) 1H,1H correlation spectroscopy (COSY), PFG 1H,13C Heteronuclear Multiple Quantum Coherence (HMQC) and PFG 1H,13C Heteronuclear Multiple Bond Correlation (HMBC) experiments. A single crystal…
Comparative multinuclear magnetic resonance spectroscopic study of transition metal (Cr, W and Mn) mesitylene tricarbonyls and transition metal (Ru a…
1993
Abstract Three mononuclear 1,3,5-trimethylbenzene (mesitylene) carbonyl transition metal complexes, mesitylene tricarbonyl chromium, (CH 3 ) 3 C 6 H 3 Cr(CO) 3 ( 1 ), mesitylene tricarbonyl tungsten, (CH 3 ) 3 C 6 H 3 W(CO) 3 ( 2 ), mesitylene tricarbonyl manganese tetra-fluoroborate, [(CH 3 ) 3 C 6 H 3 Mn(CO) 3 ]BF 4 ( 3 ); and three clusters, mesitylene nonacarbonyl tetracobalt, (CH 3 ) 3 C 6 H 3 Co 4 (CO) 9 ( 4 ), mesitylene carbido tetradecacarbonyl hexaruthenium, (CH 3 ) 3 C 6 H 3 Ru 6 C(CO) 14 ( 5 ) and carbido heptadecacarbonyl hexaruthenium, Ru 6 C(CO) 17 ( 6 ), have been studied by means of 1 H, 13 C and natural abundance 17 O NMR spectroscopy. Generally, the 1 H and 13 C NMR chemi…