Surface characterization of cellulose fibres by XPS and inverse gas chromatography

Inverse gas chromatography (IGC) was used to determine the dispersive component of the free energy as well as the acid-base properties of cellulose fibre surfaces, before and after modification by corona treatment. It was found that the corona treatment increases both the dispersive contribution to surface energy and its acidic character, whereas only a slight increase in its basicity was observed. It was also found that some chemical degradation of the surface occurs at high corona currents. The extent of modification of the surface properties, as revealed by IGC, was correlated to the surface chemical composition deduced from XPS analysis as well as with the electrical conductance and the pH of the water suspensions of the cellulose fibres.     

Analysis of the oxidation of cellulose fibres by titration and XPS

The purpose of this study was to evaluate the effect of selective oxidation on the surface properties of cotton cellulose fibres. Four different methods to evaluate the accessibility, nature and content of ionisable acidic groups (charge) in the fibres were applied: potentiometric and conductometric titrations, polyelectrolyte adsorption and X-ray photoelectron spectroscopy (XPS). The results from this combination of methods show that two processes take place when the oxidation method is applied: elimination of low molecular mass non-cellulosic compounds and formation of new acidic groups in the cellulose chains. Which of these processes is predominating depends on oxidation time, but the first one is initially more important. Polyelectrolyte adsorption and XPS show that the surface concentration of acidic groups is considerably lower than the bulk concentration, i.e. during oxidation the content of carboxyl groups in the surface region decreases, while it increases in amorphous regions. The decrease is due to the dissolution of low molecular weight compounds; the increase is due to the formation of new acidic groups. The use of titration methods in combination with XPS appears to be a very useful tool for identification of the formation and distribution of ionic groups in cotton fibres and their surfaces.     

A combined characterization of zinc hot-dip galvanized wireswith DSC, XRD and SEM

The effect of Pb and Sn on the structure of zinc hot-dip galvanized coatings on steel wires is examined. The coating quality is often low because of the Sandelin effect. An improvement could be expected if 1.0 mass% Pb is added to the Zn bath. In this case the η phase formation is enhanced, while the coating thickness is reduced. The Sn addition at the same concentration promotes the formation of the η phase but it does not affect the thickness.     

Investigation of argon ion bombarded RexSi1-x thin film composites by XPS, SEM and AES

The electronic structure of argon ion bombarded Re_xSi_1-x films (～ 100 nm) were investigated by X-ray photoelectron spectroscopy. Argon ion bombardment leads to preferential sputtering of the silicon atoms and produces an subsurface rhenium enrichment. Changes in the core level binding energies and in the valence band structure have been studied as the rhenium concentration in the composites varies between 0 ≤ x ≤ 1 through the metal-semiconductor transition at x ≈ 0.32. The data of the multiplex spectra were subjected to factor analysis in order to determine the relevant components of the ion bombarded metal-silicon system. Four principal components are extracted and are proposed as the pure elements, a rhenium-rich phase and a component near the ReSi₂ stoichiometry. Complementary investigations by SEM and AES provide further proof of the phase assignment in the rhenium-rich component. The silicon-rich component being in composition close to the metal-semiconductor transition can be correlated to the ReSi₂ compound.     

Reduction of CuO-containing catalysts, CuO: II, XRD and XPS

The pyrolysis of methyl t-butyl sulfide has been studied in a stirred-flow system. Isobutene and methanethiol were the main reaction products. The first order rate coefficients yielded E_a=238±4 kJ mol^–1, log A=14.49±0.28 between 509 and 540°C.

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-- . . 509–540°C E_a=238±4 / log A=14,49±0,28.

     

Silver nanofractals: electrochemical synthesis, XPS characterization and application in LDI-MS

Silver nanofractals (Ag-NFs) have been electrosynthesized and characterized by means of morphological and spectroscopic analytical techniques. In particular, X-ray photoelectron spectroscopy has been used to assess the nanomaterial surface chemical state. Ag-NFs show interesting perspectives in bioanalytical applications, particularly as non-conventional desorption and ionization promoters in laser desorption ionization mass spectrometry.     

Arsenopyrite and pyrite bioleaching: evidence from XPS, XRD and ICP techniques

In this work, a multi-technical bulk and surface analytical approach was used to investigate the bioleaching of a pyrite and arsenopyrite flotation concentrate with a mixed microflora mainly consisting of Acidithiobacillus ferrooxidans. X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and X-ray-induced Auger electron spectroscopy mineral surfaces investigations, along with inductively coupled plasma-atomic emission spectroscopy and carbon, hydrogen, nitrogen and sulphur determination (CHNS) analyses, were carried out prior and after bioleaching. The flotation concentrate was a mixture of pyrite (FeS₂) and arsenopyrite (FeAsS); after bioleaching, 95% of the initial content of pyrite and 85% of arsenopyrite were dissolved. The chemical state of the main elements (Fe, As and S) at the surface of the bioreactor feed particles and of the residue after bioleaching was investigated by X-ray photoelectron and X-ray excited Auger electron spectroscopy. After bioleaching, no signals of iron, arsenic and sulphur originating from pyrite and arsenopyrite were detected, confirming a strong oxidation and the dissolution of the particles. On the surfaces of the mineral residue particles, elemental sulphur as reaction intermediate of the leaching process and precipitated secondary phases (Fe–OOH and jarosite), together with adsorbed arsenates, was detected. Evidence of microbial cells adhesion at mineral surfaces was also produced: carbon and nitrogen were revealed by CHNS, and nitrogen was also detected on the bioleached surfaces by XPS. This was attributed to the deposition, on the mineral surfaces, of the remnants of a bio-film consisting of an extra-cellular polymer layer that had favoured the bacterial action.     

Synthesis,characterization and properties of novel cellulose derivatives containing phosphorus: cellulose diphenyl phosphate and its mixed esters

Using ionic liquid 1-allyl-3-methylimidazolium chloride as reaction medium, a series of novel cellulose esters containing phosphorus including cellulose diphenyl phosphate (C-Dp) and cellulose acetate (CA)–diphenyl phosphate mixed esters was synthesized homogeneously. The degree of substitution was well controlled by altering reaction conditions, such as the molar ratio of the acylating reagents/anhydroglucose unit and reaction time. The structure and thermal properties of cellulose esters were characterized by FTIR, NMR, wide-angle X-ray powder diffraction and differential scanning calorimetry. All the products possessed excellent solubility in some common organic solvents, and transparent films of cellulose esters were obtained by solution casting. In contrast to C-Dp, CA–diphenyl phosphate mixed esters showed clear glass transitions. More interestingly, these cellulose mixed esters exhibited thermoplastic behavior and could be processed by traditional melt processing methods.     

Surface characterization by XPS, contact angle measurements and ToF-SIMS of cellulose fibers partially esterified with fatty acids

The topochemistry of the controlled heterogeneous esterification of cellulose fibers with fatty acid chlorides of different chain length, both in swelling and non-swelling media, was assessed by X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and contact angle measurements. On the one hand, the results provided by the combined use of these three powerful techniques showed unambiguously the occurrence of the reaction at the fibers' surface and, on the other hand, the XPS results showed that the surface coverage with the fatty acid moieties increased with their chain length, but was only modestly affected by the degree of substitution (DS), suggesting that when the esterification yield was increased (higher DS values), an in-depth reaction also occurred, particularly when DMF was used as a cellulose swelling medium, involving the OH groups buried below the fibers' surface.     

Mesoporous nanotubes of iron phosphate: synthesis, characterization, and catalytic property

Iron phosphate nanotubes with mesoporous walls are solvothermally synthesized using sodium dodecyl sulfate (SDS) as a template. With different template concentrations, various shapes of nanosized iron phosphates can be obtained. When the concentration of SDS is set at the transition regions between the lamellar and the hexagonal mesophases, according to its phase diagram, the coassembly of iron phosphate precursor and SDS forms a flake-type mesoporous iron phosphate. Otherwise, nanoparticles or bulky sheets of iron phosphates are obtained. The followed solvothermal treatments on the mesoporous iron phosphate flakes produce iron phosphate nanotubes with mesoporous walls. The removal of the surfactant by acetate exchange and heat treatment results in the clean mesoporous nanotubes of iron phosphate with diameters of 50-400 nm and lengths of several microns. The nanotubular and mesoporous iron phosphate possesses a specific surface area of 232 m2/g and a bimodal distribution of pore sizes, corresponding to the size of mesopores in the walls and the diameter of the nanotubes, respectively. The novel nanotubular iron phosphate with composite meso-macroporous structure, in favor of the diffusion of reactive molecules, has been tested for direct hydroxylation of benzene with hydrogen peroxide and has shown better catalytic performance compared with the conventional particulate mesoporous iron phosphate.     

XRD and SEM characterization of Cu/Co catalysts supported on Si-Al-zeolite made by a modified sol-gel technique

Cu, Co and Cu/Co catalysts supported on a Si-Al-Zeolite matrix, made by a modified sol-gel method, were characterized by XRD and SEM. The formation of some spinels was identified in some of the samples. Of particular interest were those spinels whose composition included Cu and Co in a mixed oxide. The identification of such structures would explain higher activities in those catalysts. This revised version was published online in June 2006 with corrections to the Cover Date.     

Acid sites characterization of niobium phosphate catalysts and their activity in fructose dehydration to 5-hydroxymethyl-2-furaldehyde

The nature of different acid sites on the surface of various niobium-based catalysts has been spectroscopically investigated by means of FT-IR and UV–VIS techniques. Surface acidity has been further characterized by acetonitrile adsorption and subsequent FT-IR analysis. The catalytic activity of the different examined samples has been preliminarily tested in the fructose dehydration to 5-hydroxymethyl-2-furaldehyde, a reaction of relevant industrial interest.     

非化学计量比SnO~2~-~x纳米微晶材料的XRD,XPS和ESR研究

采用溶胶凝胶法, 以无水四氯化锡及异丙醇为原料, 制得非化学计量比的SnO~2~-~x纳米微晶材料。透射电镜图片显示700℃焙烧2h得到的粉体的粒度为20nm,由X射线衍射及X射线光电子能谱的分析可知, 300℃焙烧2h得到颗粒边界部分原子无规排布的纳米粉体, 而700℃焙烧2h得到的是晶格趋于完整的纳米微晶,它们都存在氧空位及晶格缺陷, 利用这些结论可以解释SnO~2~-~x纳米微晶材料中出现的顺磁信号。     

New fluoro triazol porphyrin‐cellulose: synthesis,characterization and antibacterial activity

This work describes the modification and the characterization of cellulose that was superficially modified with a cationic fluoro porphyrin. The porphyrin was synthesized and affixed onto the cellulose surface via a copper nanoparticles‐catalyzed Huisgen‐Meldal‐Sharpless. 1,3‐Dipolar cycloaddition has been occurred between azide groups present on the cellulosic surface and porphyrinic alkynes. The modified cellulose fabric was characterized with infrared spectroscopy, and with thermogravimetric analysis by a scanning electron microscopy (SEM). The antibacterial effects of fluoro triazol porphyrin‐cellulose fabric against Escherichia coli O157:H7 (ATCC 43889) and Staphylococcus aureus (ATCC 25923) have been tested, and were excellent. Copyright © 2016 John Wiley & Sons, Ltd.     

Bioinspired choline-like ionic liquids: their penetration ability through cell membranes and application to SEM visualization of hydrous samples

This letter proposes the use of choline-like hydrophilic ionic liquids (ILs) to visualize hydrous samples (e.g., seaweed and other biological or food samples) for scanning electron microscopy (SEM) observation. Some of the water in the samples was successfully replaced with these ILs, which penetrated the cell membranes. The treated samples did not contract much even after drying. The ILs' ionic conductivity decreased the charging of sample surfaces, and good SEM images were obtained.     

New iso-propoxides, tert-butoxides and neo-pentoxides of niobium(V): synthesis, structure, characterization and stabilization by trifluoroheteroarylalkenolates and pyridine ligands

The synthesis and characterization of nine new heteroleptic alkoxides of niobium is described. Metathesis reactions of Nb(2)Cl(10) with (t)BuCH(2)OH and pyridine (py) or 4-dimethylaminopyridine (DMAP) affords monomeric octahedral complexes Nb(OCH(2)(t)Bu)(5)py (1) and Nb(OCH(2)(t)Bu)(5)DMAP (2), respectively, in high yields (>60%). The same reaction with (t)BuOH resulted in a chloro functionalized alkoxide Nb(O(t)Bu)(4)pyCl (3) and could not be pushed to complete removal of remaining Cl(-) ligand. The introduction of a chelating bidental ligand 3,3,3-trifluoro-1-(pyridine-2-yl)propen-2-ol (2-PyCHCOHCF(3)) (4') in the dimeric framework of Nb(2)(O(i)Pr)(10) (4') produced a heteroleptic, monomeric niobium complex Nb(O(i)Pr)(4)(2-PyCHCOCF(3)) (4) with significantly enhanced stability and volatility. As a comparison to (4), five different heteroaryl systems (5-9) with the same side chain have been synthesized and examined in order to understand the influence upon physio-chemical properties. All the new compounds (1-9) have been characterized by microanalysis, variable temperature multinuclear NMR spectroscopy, mass spectrometry, thermal analysis and single crystal X-ray diffraction studies ((3), (4) and (9)). The molecular structure of (3) revealed mononuclear species with Nb atoms present in the distorted octahedral environment of four (t)BuO, one chloride and one pyridine ligand. Compounds (4) and (9) consisting of four (i)PrO and a trifluoroheteroarylenolate exhibited a stronger distortion in the molecular geometry due to the rigidity of chelating β-alkenolate moiety.     

MnO octahedral nanocrystals and MnO@C core-shell composites: synthesis, characterization, and electrocatalytic properties

We present a simple and facile synthesis of MnO octahedral nanocrystals and MnO@C core-shell composite nanoparticles. The synthesis is accomplished by a single-step direct pyrolysis of cetyltrimethylammonium permanganate in specially made Let-lock union cells. The products are characterized by HRSEM, HRTEM, Raman spectroscopy, and cyclic voltammetry (CV). The product consists mainly of octahedral MnO nanocrystals and MnO coated with carbon (MnO@C). The core-shell particles are observed only when the core size is smaller than 150 nm. The shape of the nanocrystals can be controlled by varying parameters such as reaction temperature and duration. As the temperature increases from 600 to 800 degrees C, the octahedral MnO crystals observed are without any carbon shell. The effect of time and temperature on the octahedral MnO nanocrystal formation is described. The electrocatalytic activities of the products are studied for oxygen reduction reaction in aqueous basic medium and are compared with bulk MnO. The MnO nanocrystals and core-shell composites exhibit higher activity than that of bulk MnO.