Papers by Keyword: X-Ray Photoelectron Spectroscopy (XPS)

Abstract: The synthesis of alkylpolyglucosides involves condensation of decanol with dextrose in the presence of mesoporous silica sol-gel as a catalyst. In this study, mesoporous silica was produced using sol-gel technique by converting tetraethyl orthosilicate (TEOS) into silica. The mesoporous silica was characterized using BET surface area measurement and X-ray Photoelectron Spectroscopy surface analysis. The specific BET surface area was 794m²/g. From the XPS analysis, the Si2p binding energy is 103.7 eV while the O1s binding energy is 532.8eV indicating the formation of Si-O-Si bond which attributed to SiO₂. Mesoporous silica has been found efficient to be solid catalyst for synthesis alkylpolyglucosides and easy to be separated. The reaction was carried out 8 hours at 110°C-120°C under vacuum condition. The mass determination of alkylpoluglucosides has been achieved by ESI LC-MS/MS (ToF) positive-mode giving a mass peak at m/z = 343.21 corresponding to [M+⁺ of alkylmonoglucoside peak at retention time 11.0 min.

Abstract: Recyclability effect on catalytic performance of Ru supported on the mixture of bentonite-TiO₂ for the hydrogenolysis of glycerol was investigated under reaction condition of 150°C, 2.0 MPa hydrogen pressure and 7 h reaction time. Interestingly, the recovered Ru/bentonite-TiO₂ catalyst was found to be active in the repeated runs. The conversion of glycerol increased in the four successive reactions as follows: 61.3%, 65.6%, 68.1% and 75.3%. This suggested that a sort of metal activation affect such as in situ reduction occurred during the repeated reaction. In order to confirm in situ reduction had occurred during the repeated reaction, XPS analysis of used catalyst after each reaction were carried out to study the chemical state of Ru 3d species. Narrow scan of peak Ru 3d revealed that intensity of Ru 3d_5/2 peak at BE 280.0 eV which is corresponding to Ru⁰ species increased until three cycle reaction. This result confirmed that in situ reduction had occurred during the repeated reaction and this made the activities of the catalyst increased upon recycling due to the availability of more metallic Ru on the surface of the catalyst. This study also shows that conversion of glycerol increased linearly with the percentage atomic ratio of Ru metal active site available on the surface of catalyst.

Abstract: Al oxide (Al-O) films used as catalyst-support layer for vertical growth of carbon nanotubes (CNTs) were characterized by means of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission, and scanning electron microscopies (TEM and SEM). EB-deposited Al films (20 nm) were thermally-oxidized at 400 ^o C (10 min, static air) to produce the surface structure of Al-O. The Al-O was found amorphous and after the incorporation with Co catalyst, the grown CNTs were twisted together before vertically grown. The prepared Al-O surface is an electron-acceptor-dominated (oxygen-rich) surface where the formation of active catalyst could be enhanced to promote the vertically aligned CNT growth.

Abstract: The Cu thin films were deposited on P type Si (111) substrates by ionized cluster beam (ICB) technique. The surface properties and atomic binding energy of Cu thin films were studied by X-ray Photoelectron Spectroscopy (XPS). The results show that for all XPS spectra of Cu/SiO₂/Si (111) samples deposited by neutral cluster and ionized cluster beam (V_a=5 kV), the atomic binding energy of the films was no differences with bulk materials. The reason may be that the local energy deposition and atomic restructuring caused by surface treatment process resulting in the XPS spectra of the copper films was similar with bulk standard copper.

Abstract: The paper presents the research results of the airborne bacteria collected at the wastewater treatment plants working with activated sludge system. Samples were taken by a six-stage Andersen Impactor placed near the aeration chambers. Bacteria cought at Petri plates were incubated at room temperature for 4 days, then analyzed in a macroscopic and microscopic way. This initial investigation was aimed at morphological characteristics of colonies and breeding characteristics of particular strains to giver general overwiev. Bacteria were identified on the basis of their metabolic properties using API biochemical tests. The essential studies were carried out using JOEL scanning electron microscope (FE-SEM model with field gun 7600[F]), equipped with "Cryo-SEM”, which gives the possibility of testing delicate biological samples in a frozen state. Its high resolving power and large depth of field allows to obtain images of surface structure of microorganisms in a magnification range from 1 000x to 70 000x. Bacteria samples were analyzed also in a fructured state what revealed internal structes and the thickness of cell walls which was in the range of 0,080-0,180 [μm]. Moreover, elemental composition of the surface layer of bacterial was also examined using photoelectron spectroscopy (XPS). Dominant elements were carbon, oxygen and nitrogen. Analysis of main line (C1s, O1s, N1s) allowed the identification of chemical composition of studied bioaerosols. Investigation found that the main compounds were polymers such as peptides and polysaccharides, as well hydrocarbon like compounds.

Abstract: Thin films of zirconium oxide have been deposited using pulsed laser deposition on Zr-base alloy substrates, held at 300 K, 573 K and 873 K, in order to understand the effect of substrate temperature on the deposited film. In this study, a KrF excimer laser having 30 ns pulse width and 600 mJ energy at source has been used for depositing the films from a sintered ZrO₂ target using a laser fluence of 5 J.cm^-2. After visual observation, deposited thin films were examined using Raman Spectroscopy (RS) and X-ray Photo-electron Spectroscopy (XPS). It has been found that the oxide deposited at 300 K temperature does not show good adherence with the substrate. The oxide films deposited at 573 K and 873 K are found to be adherent with the substrate and lustrous black in appearance. Thin films of zirconia, deposited using pulsed laser on the Zr-base metallic substrate are initially in amorphous state and possibly little deficient in oxygen. The substrate temperature and the duration of holding at high temperature are responsible for the evolution of nanocrystals in the deposited thin films. The stoichiometry of the amorphous oxide film supports its crystallization, below 573 K, into monoclinic and tetragonal phases and not into cubic phase.

Abstract: A series of organofunctional long-chain alkylfunctional silanes have been synthesized for the purpose of derivatization of micro- and nanoparticles and generation of molecular monolayers and films on the substrates. 11-bromoundecylsilane and 1, 10-disiladecane are evaluated to interact with a variety of clean hydrogenated metal and metalloid including titanium, silicon and silicon dioxide. The surface of those treated substrates has been analyzed by X-ray photoelectron spectroscopy (XPS) and reflection-absorption infrared spectroscopy (RAIRS). Our preliminary results indicate that self-assembled monolayer has been well formed on titanium metal and silicon wafer, minimally on silicon-dioxide. The discussion of experimental results is also provided.

Abstract: _{Subscript text}Reactive ion etching of barium strontium titanate (BST) thin films using an SF₆/Ar plasma has been studied. BST surfaces before and after etching were analyzed by X-ray photoelectron spectroscopy to investigate the reaction ion etching mechanism, and chemical reactions had occurred between the F plasma and the Ba, Sr and Ti metal species. Fluorides of these metals were formed and some remained on the surface during the etching process. Ti can be removed completely by chemical reaction because the TiF₄ by-product is volatile. Minor quantities of Ti-F could still be detected by narrow scan X-ray photoelectron spectra, which was thought to be present in metal-oxy-fluoride(Metal-O-F). These species were investigated from O_1s spectra, and a fluoride-rich surface was formed during etching because the high boiling point BaF₂ and SrF₂ residues are hard to remove. The etching rate was limited to 14.28nm/min. A 1-minute Ar/10 plasma physical sputtering was carried out for every 4 minutes of surface etching, which effectively removed remaining surface residue. Sequential chemical reaction and sputtered etching is an effective etching method for BST films.

Abstract: The in-depth composition of carbon and oxygen in copper beads formed by arc and fire were studied by XPS, respectively. Corresponding to the sputtering depth, the molten product on an arc bead surface layer is with drastic decrease of carbon content and with gentle change of oxygen content which then rapid decreases. While the molten product on a fire bead surface layer is with carbon content decreasing gradually and with oxygen content increasing. As a result, the distributing of C and O and the quantitative results can be used to identify the molten product on a bead induced directly by arc and the molten product on a bead formed by fire, as complementary technique for judgments of fire cause.

Abstract: Zn₃Ta₂O₈ is a promising host for low voltage cathodoluminescence (CL) applications. Surface chemical stability during low voltage electron beam excitation is a prime concern for phosphors to be used in various new generation information displays. Photoluminescence (PL) and CL characteristics of the Zn₃Ta₂O₈ host doped with Pr³⁺ are presented. The phosphors were synthesized via solid-state reaction route at 1100°C. Red CL or PL with a maximum at 611 nm, attributed to the ¹D₂-³H₄ transition of the Pr³⁺ ion, was observed at room temperature under high energy electron (2 keV, 12 μA) or a monochromatic xenon lamp (257 nm) irradiation. Electron stimulated chemical changes on the surface of the Zn₃Ta₂O₈:Pr³⁺ phosphor during an electron beam exposure from 0-350 C/cm² was monitored using Auger electron spectroscopy. The CL exhibited only a 20% loss in the original intensity during the continuous electron beam exposure. X-ray photoelectron spectroscopy (XPS) was used to estimate the redox states of the chemical constituents and a comparison of binding energies was made with the standard Ta₂O₅ and ZnO compounds. A correlation between the structural configuration of Zn₃Ta₂O₈ and the XPS data is also established.