X-ray photoelectron spectroscopic analysis of halloysites with different composition and particle morphology

Clay Minerals ◽  
1992 ◽  
Vol 27 (4) ◽  
pp. 413-421 ◽  
Author(s):  
M. Soma ◽  
G. J. Churchman ◽  
B. K. G. Theng
Keyword(s):  
Photoelectron Spectroscopy ◽  
Cation Exchange Capacity ◽  
Spectroscopic Analysis ◽  
Surface Composition ◽  
Particle Morphology ◽  
Exchange Capacity ◽  
Surface Layers ◽  
X Ray ◽  
Fe Content ◽  
Before And After

AbstractThe surface composition of some halloysites with different particle morphology has been investigated by X-ray photoelectron spectroscopy (XPS) before and after removal of external Fe. The Fe(III) 2p3/2 binding energy of external Fe is appreciably smaller than that of structural Fe. Particle morphology is influenced by structural Fe content. The long-tubular halloysite has very little surface Fe, and its concentration tends to increase with the proportion of non-tubular particles in the samples. The spheroidal sample contains the most structural Fe which, however, does not appear to influence particle shape directly. Study by XPS indicates that Fe substitutes for Al in octahedral positions in approximately 1 : 2 proportion. As a result, an increase in octahedral vacancies and cation exchange capacity would be predicted. Further, halloysite layers within a crystal are generally inhomogeneous in composition. Built up like “onion skins”, the surface layers would either be enriched or depleted in Fe depending on the chemical environment in which crystal growth occurs.

Article

1999 ◽  
Vol 77 (10) ◽  
pp. 1678-1689 ◽  
Author(s):  
Mark E McGovern ◽  
Michael Thompson
Keyword(s):  
Surface Analysis ◽  
Photoelectron Spectroscopy ◽  
Spectroscopic Analysis ◽  
Thiol Group ◽  
High Coverage ◽  
X Ray ◽  
Functionalized Surfaces ◽  
Before And After ◽  
Substrate Surfaces ◽  
Thiol Functionalization

The immobilization of biomolecules on substrate surfaces for biosensor development requires linking molecules that must meet a specific set of criteria. Two such agents based on bifunctional alkyltrichlorosilane structures, 1-bromo-11-(trichlorosilyl)-undecane and 1-(thiotrifluoroacetato)-11-(trichlorosilyl)-undecane, are employed to generate thiol-functionalized surfaces either by nucleophilic substitution followed by reduction (bromine-containing derivative) or deprotection (fluorine-containing compound). Both molecules have been attached to the surfaces of silicon wafers in conjunction with the diluent silane, octyltrichlorosilane. X-ray photoelectron spectroscopic analysis in the conventional and angle-resolved modes confirms that both silanization reactions were successful. The alkyl-bromine surfaces were subjected to treatment with a set of nucleophilic reactants followed by reduction and derivatization with trifluoroacetic anhydride. The latter in conjunction with surface analysis was used to estimate the level of thiol functionalization achieved. The fluorine-containing undecane surface has been studied by surface analysis both before and after deprotection of the thiol group by hydroxylamine solution. The results indicate that a high coverage of the surface was found for the protected moiety, with approximately 10% of the trifluoro acetate groups remaining after the deprotection procedure.Key words: bifunctional silanes, thiol surface functionalization, biomolecule immobilization, X-ray photoelectron spectroscopy.

An ESCA and SEM Study of Changes in the Surface Composition and Morphology of Low-Calcium Coal Fly Ash as a Function of Aqueous Leaching

1986 ◽  
Vol 86 ◽  
Author(s):  
Myra M. Soroczak ◽  
H. C. Eaton ◽  
M. E. Tittlebaum
Keyword(s):  
Fly Ash ◽  
Photoelectron Spectroscopy ◽  
Surface Composition ◽  
Coal Fly Ash ◽  
Near Surface ◽  
X Ray ◽  
Sem Study ◽  
Before And After ◽  
New Material ◽  
Surface Chemistries

ABSTRACTThe reactivity of coal fly ash is dependent on the chemical composition of the surface. As reactions occur the ash particle size decreases and new material is available for reaction. This means that the near-surface chemistry can also be important. In the present study the surface chemistries of three ashes are determined by x-ray photoelectron spectroscopy both before and after exposure to a hydrating/leaching environment. Scanning electron microscopy is used to reveal ash morphology. The concentration of sulfur, found at the ash surfaces as a sulfate, and sodium decreased after leaching while the amount of iron and aluminum increased. Other elements, including calcium, increased and decreased with leaching depending on which ash was analyzed. Changes which occurred in the ash morphology after the removal of leachable elements are discussed.

scholarly journals Surface Analysis of Biodegradable Mg-Alloys after Immersion in Simulated Body Fluid

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1740 ◽  
Author(s):  
Darja Steiner Petrovič ◽  
Djordje Mandrino ◽  
Božidar Šarler ◽  
Jelena Horky ◽  
Andrea Ojdanic ◽  
...  
Keyword(s):  
Simulated Body Fluid ◽  
Photoelectron Spectroscopy ◽  
Body Fluid ◽  
Surface Composition ◽  
Degradation Kinetics ◽  
Mg Alloys ◽  
X Ray ◽  
Before And After ◽  
Immersion Testing ◽  
Homogeneous Composition

Two binary biodegradable Mg-alloys and one ternary biodegradable Mg-alloy (Mg-0.3Ca, Mg-5Zn and Mg-5Zn-0.3Ca, all in wt%) were investigated. Surface-sensitive X-ray photoelectron spectroscopy analyses (XPS) of the alloy surfaces before and after immersion in simulated body fluid (SBF) were performed. The XPS analysis of the samples before the immersion in SBF revealed that the top layer of the alloy might have a non-homogeneous composition relative to the bulk. Degradation during the SBF immersion testing was monitored by measuring the evolution of H2. It was possible to evaluate the thickness of the sample degradation layers after the SBF immersion based on scanning electron microscopy (SEM) of the tilted sample. The thickness was in the order of 10–100 µm. The typical bio-corrosion products of all of the investigated alloys consisted of Mg, Ca, P and O, which suggests the formation of apatite (calcium phosphate hydroxide), magnesium hydrogen phosphate hydrate and magnesium hydroxide. The bioapplicability of the analyzed alloys with regard to surface composition and degradation kinetics is discussed.

scholarly journals STUDY OF THE MICROSTRUCTURE AND COMPOSITION OF TIN DIOXIDE LAYERS MODIFIED BY SILVER NANOPARTICLES

2021 ◽  
pp. 447-456
Author(s):  
Замир Валериевич Шомахов ◽  
Светлана Сергеевна Налимова ◽  
Рустам Мухамедович Калмыков ◽  
Кирилл Аубекеров ◽  
Вячеслав Алексеевич Мошников
Keyword(s):  
Silver Nanoparticles ◽  
Gas Sensors ◽  
Photoelectron Spectroscopy ◽  
Tin Dioxide ◽  
Surface Composition ◽  
Metallic Silver ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Before And After

Слои диоксида олова синтезированы гидротермальным методом из водного раствора SnF. Наночастицы серебра осаждены на поверхность полученных слоев методом фотовосстановления. Проведено исследование морфологии поверхности образцов методом атомно-силовой микроскопии. Размер наночастиц серебра зависит от концентрации раствора AgNO, используемого для проведения реакции фотовосстановления. При синтезе из раствора с концентрацией 0,02 М размер полученных наночастиц составляет варьируется от 10 до 100 нм, при увеличении концентрации раствора в два раза размер наночастиц составляет порядка 100 нм. С помощью рентгеновской фотоэлектронной спектроскопии изучен состав поверхности слоев до и после осаждения наночастиц серебра. При выбранных условиях синтеза формируется слой диоксида олова без посторонних включений, и происходит осаждение металлического серебра. Химический сдвиг пиков олова и кислорода после осаждения наночастиц серебра свидетельствует об обмене электронами между оловом и серебром. Полученные слои представляют интерес для применения в области полупроводниковых адсорбционных газовых сенсоров. Tin dioxide layers were synthesized by hydrothermal method from an aqueous solution of SnF. Silver nanoparticles were deposited on the surface of the obtained layers by the photoreduction method. The surface morphology of the samples was studied by atomic force microscopy. The size of the silver nanoparticles depends on the concentration of the AgNO solution used for the photoreduction reaction. When synthesized from 0,02 M solution with a concentration of, the size of the nanoparticles varies from 10 to 100 nm, when the concentration of the solution is doubled, the size of the nanoparticles is about 100 nm. The surface composition of the layers before and after the deposition of silver nanoparticles was studied using the X-ray photoelectron spectroscopy. It was shown that a layer of the tin dioxide is formed without external inclusions, and metallic silver is deposited. The chemical shift of the peaks of tin and oxygen after the deposition of silver nanoparticles indicates the exchange of electrons between tin and silver. The synthesized layers are of interest for application in the field of semiconductor adsorption gas sensors.

CO2 Reduction to Propanol by Copper Foams: A Pre- and Post-Catalysis Study

2020 ◽  
Author(s):  
Jennifer A. Rudd ◽  
Ewa Kazimierska ◽  
Louise B. Hamdy ◽  
Odin Bain ◽  
Sunyhik Ahn ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Photoelectron Spectroscopy ◽  
Carbon Capture ◽  
Surface Composition ◽  
Co2 Reduction ◽  
Structural Rearrangement ◽  
Copper Electrode ◽  
Ex Situ ◽  
X Ray ◽  
Copper Electrodes

The utilization of carbon dioxide is a major incentive for the growing field of carbon capture. Carbon dioxide could be an abundant building block to generate higher value products. Herein, we describe the use of porous copper electrodes to catalyze the reduction of carbon dioxide into higher value products such as ethylene, ethanol and, notably, propanol. For <i>n</i>-propanol production, faradaic efficiencies reach 4.93% at -0.83 V <i>vs</i> RHE, with a geometric partial current density of -1.85 mA/cm<sup>2</sup>. We have documented the performance of the catalyst in both pristine and urea-modified foams pre- and post-electrolysis. Before electrolysis, the copper electrode consisted of a mixture of cuboctahedra and dendrites. After 35-minute electrolysis, the cuboctahedra and dendrites have undergone structural rearrangement. Changes in the interaction of urea with the catalyst surface have also been observed. These transformations were characterized <i>ex-situ</i> using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. We found that alterations in the morphology, crystallinity, and surface composition of the catalyst led to the deactivation of the copper foams.

scholarly journals Evaluation of the Antimicrobial Protection of Pharmaceutical Kaolin and Talc Modified with Copper and Zinc

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1173
Author(s):  
Fotini Martsouka ◽  
Konstantinos Papagiannopoulos ◽  
Sophia Hatziantoniou ◽  
Martin Barlog ◽  
Giorgos Lagiopoulos ◽  
...  
Keyword(s):  
Cation Exchange ◽  
Photoelectron Spectroscopy ◽  
Antimicrobial Properties ◽  
Exchange Capacity ◽  
Elevated Concentration ◽  
Chemical Mapping ◽  
Exchange Method ◽  
X Ray ◽  
Copper And Zinc ◽  
Antimicrobial Protection

Six pharmaceutical pastes were prepared using chemically modified kaolin and talc powders. Tests were conducted to determine their structural and chemical characteristics as well as their antimicrobial protection, thus rendering them suitable for cosmetic and pharmaceutical uses. Kaolin and talc were treated chemically via the cation exchange method to load the clay particles with copper and zinc ions, two cations well known for their antimicrobial properties. Mineralogical analyses were conducted by using X-ray diffraction (XRD) before and after the modification, confirming the mineralogical purity of the samples. Scanning electron microscopy was also used in conjunction with energy dispersed spectroscopy (SEM-EDS) to obtain chemical mapping images, revealing the dispersion of the added metals upon the clay minerals surfaces. Moreover, chemical analysis has been performed (XRF) to validate the enrichment of the clays with each metal utilizing the cation exchange capacity. All modified samples showed the expected elevated concentration in copper or zinc in comparison to their unmodified versions. From the X-ray photoelectron spectroscopy (XPS), the chemical state of the samples’ surfaces was investigated, revealing the presence of salt compounds and indicating the oxidation state of adsorbed metals. Finally, the resistance of pastes in microbial growth when challenged with bacteria, molds, and yeasts was assessed. The evaluation is based on the European Pharmacopeia (EP) criteria.

scholarly journals Synthesis of Novel Arginine-Based Flame Retardant and Its Application in Lyocell Fabric

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3588
Author(s):  
Jiayi Chen ◽  
Yansong Liu ◽  
Jiayue Zhang ◽  
Yuanlin Ren ◽  
Xiaohui Liu
Keyword(s):  
Fourier Transform ◽  
Heat Release ◽  
Flame Retardant ◽  
Photoelectron Spectroscopy ◽  
Fourier Transform Infrared ◽  
Ftir Analysis ◽  
Excellent Thermal Stability ◽  
X Ray ◽  
Cone Calorimeter Test ◽  
Before And After

Lyocell fabrics are widely applied in textiles, however, its high flammability increases the risk of fire. Therefore, to resolve the issue, a novel biomass-based flame retardant with phosphorus and nitrogen elements was designed and synthesized by the reaction of arginine with phosphoric acid and urea. It was then grafted onto the lyocell fabric by a dip-dry-cure technique to prepare durable flame-retardant lyocell fabric (FR-lyocell). X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) analysis demonstrated that the flame retardant was successfully introduced into the lyocell sample. Thermogravimetric (TG) and Raman analyses confirmed that the modified lyocell fabric featured excellent thermal stability and significantly increased char residue. Vertical combustion results indicated that FR-lyocell before and after washing formed a complete and dense char layer. Thermogravimetric Fourier-transform infrared (TG-FTIR) analysis suggested that incombustible substances (such as H2O and CO2) were produced and played a significant fire retarding role in the gas phase. The cone calorimeter test corroborated that the peak of heat release rate (PHRR) and total heat release (THR) declined by 89.4% and 56.4%, respectively. These results indicated that the flame retardancy of the lyocell fabric was observably ameliorated.

Oxidation of Alloy-X in Subcritical, Transition, and Supercritical Water

CORROSION ◽  
10.5006/3881 ◽  
2021 ◽  
Author(s):  
Zachary Karmiol ◽  
Dev Chidambaram
Keyword(s):  
Supercritical Water ◽  
Photoelectron Spectroscopy ◽  
Focused Ion Beam ◽  
Elevated Temperatures ◽  
Subcritical Water ◽  
Ion Beam ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nickel Based Superalloy ◽  
Before And After

This work investigates the oxidation of a nickel based superalloy, namely Alloy X, in water at elevated temperatures: subcritical water at 261°C and 27 MPa, the transition between subcritical and supercritical water at 374°C and 27 MPa, and supercritical water at 380°C and 27 MPa for 100 hours. The morphology of the sample surfaces were studied using scanning electron microscopy coupled with focused ion beam milling, and the surface chemistry was investigated using X-ray diffraction, Raman spectroscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy before and after exposure studies. Surfaces of all samples were identified to comprise of a ferrite spinel containing aluminum.

scholarly journals Dual Light- and pH-Responsive Composite of Polyazo-Derivative Grafted Cellulose Nanocrystals

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1725 ◽  
Author(s):  
Xiaohong Liu ◽  
Ming Li ◽  
Xuemei Zheng ◽  
Elias Retulainen ◽  
Shiyu Fu
Keyword(s):  
Cellulose Nanocrystals ◽  
Photoelectron Spectroscopy ◽  
Surface Composition ◽  
X Ray Diffraction ◽  
Responsive Materials ◽  
X Ray ◽  
Ph Response ◽  
Transmission Electron ◽  
Ft Ir ◽  
Hexyl Methacrylate

As a type of functional group, azo-derivatives are commonly used to synthesize responsive materials. Cellulose nanocrystals (CNCs), prepared by acid hydrolysis of cotton, were dewatered and reacted with 2-bromoisobuturyl bromide to form a macro-initiator, which grafted 6-[4-(4-methoxyphenyl-azo) phenoxy] hexyl methacrylate (MMAZO) via atom transfer radical polymerization. The successful grafting was supported by Fourier transform infrared spectroscopy (FT-IR) and Solid magnetic resonance carbon spectrum (MAS 13C-NMR). The morphology and surface composition of the poly{6-[4-(4-methoxyphenylazo) phenoxy] hexyl methacrylate} (PMMAZO)-grafted CNCs were confirmed with Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The grafting rate on the macro-initiator of CNCs was over 870%, and the polydispersities of branched polymers were narrow. The crystal structure of CNCs did not change after grafting, as determined by X-ray diffraction (XRD). The polymer PMMAZO improved the thermal stability of cellulose nanocrystals, as shown by thermogravimetry analysis (TGA). Then the PMMAZO-grafted CNCs were mixed with polyurethane and casted to form a composite film. The film showed a significant light and pH response, which may be suitable for visual acid-alkali measurement and reversible optical storage.

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