Search results for "X-Ray"

The structure of pumice: An XPS and27Al MAS NMR study

1992

In order to investigate the surface structure of pumice, an amorphous aluminosilicate, samples of pumice and of standards of silica and alumina have been studied by x-ray photoelectron spectroscopy (XPS). The effect of a mild acid leaching was also considered. The analysis of the Si 2p, Al 2p and O 1s photoelectron peaks and the Si KLL and O KLL Auger peaks indicated that pumice is formed by tetrahedral silica with some units being replaced by aluminate, AlO2−. The acid treatment decreases the alkali and the aluminate ions. X-ray photoelectron spectra of the valence band of pumices and of standards of Al2O3 and SiO2 agree with the core-level results. To support the conclusions from the XPS …

2017

The adsorption of molecular acceptors is a viable method for tuning the work function of metal electrodes. This, in turn, enables adjusting charge injection barriers between the electrode and organic semiconductors. Here, we demonstrate the potential of pyrene-tetraone (PyT) and its derivatives dibromopyrene-tetraone (Br-PyT) and dinitropyrene-tetraone (NO2-PyT) for modifying the electronic properties of Au(111) and Ag(111) surfaces. The systems are investigated by complementary theoretical and experimental approaches, including photoelectron spectroscopy, the X-ray standing wave technique, and density functional theory simulations. For some of the investigated interfaces the trends expecte…

Self-assembly in surfactant-based liquid mixtures: Bis(2-ethylhexyl)phosphoric acid/bis(2-ethylhexyl)amine systems

2010

Surfactant-based liquid mixtures constitute an interesting class of nanostructured materials with promising potential in specialized applications. Here, structural and conductometric properties of liquid mixtures composed of bis(2-ethylhexyl)amine (BEEA) and bis(2-ethylhexyl)phosphoric acid (HDEHP) have been thoroughly investigated with the aim to correlate structural features with system charge transport capability. The evolution of self-assembled local nanostructures with system composition has been investigated by FT-IR and XRD while the conductometric properties were probed by conventional AC complex impedance. Both pure components exhibit nano-segregation due to their amphiphilic natur…

Phase composition of Fe-containing Langmuir-Blodgett layers after thermal treatment in a reactive atmosphere

1993

By the Langmuir-Blodgett technique, mono- and multilayers of ferric stearate were drawn onto silicon wafers. They were thermodesorbed in air at 250–300°C, and the layers formed in this way were found to consist of γ-FeOOH with defective stoichiometry. By heating in H2, the layers can be reduced to Fe2− and even to α-Fe. The latter is magnetically ordered and highly corrosion resistant. Chloride ions, however, induce fast corrosion. FeCl2, formed by this corrosion, is rather unstable and transforms to an Fe3+ phase. The high corrosion resistance of the metallic Fe layer is assumed to be due to its excellent homogeneity. The experiments were performed using XPS, AES, CEMS, and SEM.

Oxygen on Fe(100) and Fe(110)

1995

Investigations of the electronic and magnetic properties of oxygen adsorbed on magnetized iron films have been carried out by means of angle and spin resolving photoelectron spectroscopy. Iron, epitaxially grown on W(100) and W(110) crystals, served as the ferromagnetic substrate. Exchange splittings of the O 2px derived level have been detected, demonstrating a magnetic coupling between the chemisorbate and the iron layer. Variations of the exchange splitting have occurred as a function of the oxygen coverage, photon energy, and emission angle. High oxygen exposures have lead to a FeO overlayer at the surface.

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…

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…

Corrigendum to “Comparison of epimeric methyl lithocholate and methyl iso-lithocholate molecules: Single crystal X-ray structure of methyl lithochola…

2003

Mechanistic and kinetic insight into spontaneous cocrystallisation of isoniazid and benzoic acid

2015

Solid-state cocrystallisation is of contemporary interest, because it offers an easy and efficient way to produce cocrystals, which are recognized as prospective pharmaceutical materials. Research explaining solid-state cocrystallisation mechanisms is important, but still too scarce to give a broad understanding of factors governing and limiting these reactions. Here we report an investigation of the mechanism and kinetics of isoniazid cocrystallisation with benzoic acid. This reaction is spontaneous; however its rate is greatly influenced by environmental conditions (humidity and temperature) and pre-treatment (milling) of the sample. The acceleration of cocrystallisation in the presence o…