Search results for " Coating."
showing 10 items of 2558 documents
Fe(III)-DOTA/Fe(III)-NOTA Complexes: Attractive Alternative Markers for Future Electrochemical Biosensors
2020
Metallic complexes of macrocycles chelators 1,4,7-triazacyclononane-N,N,N-triacetic acid (NOTA) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) were synthetized with iron (III) giving Fe(III)-DOTA and Fe(III)-NOTA complexes. They were studied in comparison of ferricyanide and ferrocenemethanol on cyclic voltammetry with glassy carbon working electrode (GC) and screen-printed carbon electrode (SPCE). Diffusion coefficients and heterogeneous electron transfer rate constants were determined with Randles-Sevcik and Nicholson-Lavagnini methods. Using SPCE. The average values of diffusion coefficient and transfer rate constant were respectively of 1.34 × 10−6 cm2 s−1 and 1.01 …
Microanalysis of the surfaces of natural iron-based minerals by means of synchrotron radiation based experimental techniques
2001
We investigated the surfaces of natural iron-based minerals that are magnetite, hematite, goethite, pyrite, pyrrhotite, chalcopyrite, bornite and vivianite, using synchrotron radiation based techniques. Most iron chalkogenides are very suitable for photoemission microscopy studies due to their low resistivity, which prevents from surface charging. The local compositions were studied employing photoemission microscopy in combination with X-ray absorption spectroscopy. Imaging of the sample in the near-edge region of the absorption edges was used to visualise the spatial distributions of the chemical phases on the surface. Distributions of trace elements are imaged with high chemical and late…
Electronic and magnetic properties of Mn 12 molecular magnets on sulfonate and carboxylic acid prefunctionalized gold surfaces
2012
Structural, electronic, and magnetic properties of [Mn 12O 12(bet) 16(EtOH) 4](PF 6) 14·4CH 3CN·H 2O (in short Mn 12bet, bet = betaine = +N(CH 3) 3-CH 2-COO -) single-molecule magnets (SMMs) deposited on previously functionalized gold surfaces have been investigated. Self-assembled monolayers (SAMs) either of sodium mercaptoethanesulfonate (MES) or mercaptopropionic acid (MPA) are used as functionalization to avoid the direct interaction between the Mn 12bet molecules and the Au surface with the aim of preserving the main functional properties of the molecules. Scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS) analysis show deposited Mn 12bet SMMs well-isolated …
Localized magnetic moments in the Heusler alloy Rh2MnGe
2009
X-ray magnetic circular dichroism (XMCD) of core-level absorption (x-ray absorption spectroscopy, XAS) spectra in the soft x-ray region has been measured for the ferromagnetic Heusler alloy Rh2MnGe at the Rh M3,2 and Mn L3,2 edges. The ratio of Rh and Mn spin moments amounts to 0.05 which is smaller than the ratio of 0.1 determined by a local density approximation electronic band structure calculation. We have found that the orbital moments of the Rh 4d and Mn 3d states are very small. The observed Rh 2p XAS spectrum can be understood on the basis of the Rh 3d partial density of unoccupied states as is typical for metals. The observed features of the Mn 2p XAS and XMCD spectra are dominated…
Interfacial reaction between deposited molybdenum and TiO2(110) surface: role of the substrate bulk stoichiometry
2004
Abstract The interfacial reaction between deposited molybdenum and three different TiO2(1 1 0) substrates (a bulk and surface stoichiometric TiO2; a bulk stoichiometric and surface reduced crystal; a bulk and surface slightly reduced crystal) was investigated by means of X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge spectroscopy (XANES). While the interfacial reaction is not a function of the substrate at room temperature (in any case, molybdenum layers grow with oxygen dissolved in), this study clearly reveals a strong effect of the substrate bulk stoichiometry on the chemical state of the deposit after annealing up to 750 °C whereas the substrate surface stoichiome…
Redox and Catalytic Properties of Promoted NiO Catalysts for the Oxidative Dehydrogenation of Ethane
2017
[EN] NiO and metal-promoted NiO catalysts (M-NiO, with a M/(M+Ni) atomic ratio of 0.08, with M = Nb, Sn, or La) have been prepared, tested in the oxidative dehydrogenation (ODH) of ethane, and characterized by means of XRD, TPR, HRTEM, Raman, XPS, and in situ XAS (using H-2/He, air or C2H6/He mixtures). The selectivity to ethylene during the ODH of ethane decreases according to the following trend: Nb NiO Sn NiO > La NiO > NiO, whereas the catalyst reducibility (determined by both TPR and XAS using H-2/He mixtures) shows the opposite trend. However, different reducibility and catalytic behavior in the absence of oxygen (ethane/He mixtures) have been observed, especially when comparing Nb- a…
Metal-support interaction and redox behavior of Pt(1 wt %)/Ce0.6Zr0.4O2
2006
The catalyst Pt(1 wt %)/Ce(0.6)Zr(0.4)O(2) is studied by CO-temperature programmed reduction (CO-TPR), isothermal oxygen storage complete capacity (OSCC), X-ray absorption spectroscopy (XAS) at the Pt L(III) edge, and in situ X-ray diffraction (in situ XRD), with the aim of elucidating the role of supported metal in CO oxidation by ceria-based three-way catalysts (TWC). The redox behavior of Pt(1 wt %)/Ce(0.6)Zr(0.4)O(2) is compared to that of bare ceria-zirconia. OSCC of redox-aged Pt/ceria-zirconia is twice that of bare ceria-zirconia, and the maximum of CO consumption occurs at a temperature about 300 K lower than redox-aged ceria-zirconia. XAS analysis allows one to evidence the formati…
Chemical microimaging and microspectroscopy of surfaces with a photoemission microscope
1997
We applied element sensitive photoemission electron microscopy (PEEM) to investigate surfaces of devices built from complex materials. Conventional PEEM suffers from lack of information about the chemical composition of the imaged surface. Such information can be obtained by PEEM via tuning the photon energy to X-ray absorption edges. To apply spectromicroscopy we acquired and subtracted microscopic images using photon energies just below and at the edges. The resulting difference gives a micro-image of the lateral distribution of a specific element. Microspectroscopy is performed by recording the intensity of secondary electrons in selected spots during a sweep of the photon energy. We app…
The lateral variation of solid state reactions at surfaces studied by means of photoemission electron microscopy: formation of titanium silicides
2001
The alloying and oxygen reduction at titanium silicon interfaces were studied by means of photoemission microscopy. The microscopic chemical composition of the sample surface was characterised by means of imaging X-ray absorption. The silicide formation was studied at clean and oxidised silicon substrates both covered with micron-sized titanium patterns.
Astronomical soft x-ray mirrors reflectivity enhancement by multilayer coatings with carbon overcoating
2004
A number of X-ray astronomical missions of near future will make use of hard X-ray optics with broad-band multilayer coatings. However multilayer mirrors can be also useful to enhance the effective area of a given X-ray telescope in the "classical" low energy X-ray band (0.1 – 10 keV), the window where X-ray spectroscopy provides very useful plasma diagnostics) with a consistent gain with respect to usual single-layer reflectors. Multilayers for soft X-rays are based on stacks with constant d-spacing (in order to minimize the loss due to the photoelectric effect). A further gain in reflectivity (however only restricted to the energy range between 0.5 and 4 keV) can be achieved by using a lo…