Diffuse reflectance FTIR study of the interaction of alumina surfaces with ozone and water vapor

The interaction of ozone with alumina has been examined at ambient temperature as a function of ozone concentration and relative humidity. The experiments used diffuse reflectance FTIR spectroscopy in a small flow reactor, which provided control of the temperature, pressure, and composition of the gas mixture to which the sample was continuously exposed. Treatment of alumina with ozone produced a new spectroscopic feature at 1380 cm(-1), which we attribute to an aluminum oxide species formed by interaction of O3 with Lewis acid sites on the alumina surface. After exposure of the alumina sample to O3 was stopped, subsequent exposure of the sample to humidified nitrogen resulted in the slow removal of the peak at 1380 cm(-1). Simultaneously, the uptake of water by the alumina increased as indicated by the growth of the adsorbed water features which extend from approximately 3700 to 2500 cm(-1). Treatment of dry alumina with humidified ozone strongly inhibited both the rate of formation of the spectral feature at 1380 cm(-1) and its limiting extent of formation. These observations are analyzed in terms of the adsorption and surface reaction properties of ozone on alumina. The observation that the new oxide feature on alumina, produced by reaction with ozone, can be removed by water is important for assessing the ability of mineral dust aerosols to process atmospheric trace gases over a significant time scale. We believe the work reported here to be the first direct and quantitative kinetic study of the competition between O3 and water for adsorption sites on alumina.     

竹木质素的红外光谱与X射线光电子能谱分析

应用傅里叶转换红外光谱(FTIR)和X射线光电子能谱(XPS), 研究了3种提纯方法得到的竹木质素及其化学反应产物的化学结构特性. 确定竹木质素C_1s的电子结合能分别为283.52 (C—H或C—C), 284.58～285.72 (C—OR或C—OH), 286.10～286.44 (C＝O或HO—C—OR), 287.65～287.72 (O—C＝O) eV. O_1s的电子结合能分别为530.31(羟基氧原子), 531.45～531.72(醛或酮的羰基氧原子), 532.73～533.74(酯键或羧酸中的羰基氧原子) eV. 竹木质素中的结构单元之间主要是通过醚键和碳碳单键连接, 慈竹磨木木质素结构单元中醚键、碳碳单键、酯键、羰基和烯双键的比例为100∶63∶32∶40∶32 (49.3∶31.0∶16.0∶19.9∶16.0)     

Characterization of oxygen and argon ion flux interaction with PET surfaces by in-situ XPS and ex-situ FTIR

The effects of low (2.5, 0.2 keV) energy reactive oxygen ion bombardment and argon ion bombardment on poly(ethylene terephthalate) thin film (PET) surface chemical composition were studied. PET films have a high potential as a material for biomedical and electrical industries. The source of ions was an ECR Ion Gun with settable acceleration voltages. PET films were sputtered by ion bombardment for variable process time and the modified films were investigated by in-situ X-ray Photoelectron Spectroscopy (XPS) and ex-situ Fourier transform infrared spectroscopy (FTIR). The significant changes in the chemical composition of surface layers were quantitatively studied by XPS. The ion bombardment scissions the chains in PET film surface layers. Selective sputtering of oxygen atoms from PET surface was observed when argon ion flux used. The 0.2 keV and 2.5 keV argon ion decreased O/C ratio from 0.37 to 0.25, 0.04 respectively. This phenomenon is responsible for the creation of carbon-rich up 96 at.% surface layer and the oxygen in ester bonds is detached first. The oxygen 2.5 keV ion bombardment had similar effect as argon ion bombardment; the ratio O/C was decreased. The ester bond was broken first. But oxygen 0.2 keV ion flux irradiation created an oxygen rich surface; the O/C ratio was in increased from 0.37 to 0.46. The changes in surface conductivity were investigated by shifts in C1s binding energy. Good agreement with atomic concentration of carbon in C-C bonds on the films surface was found. The FTIR analyses identified changes in chemical composition but with no obvious correlation to surface changes. Photons from the ion source irradiating the PET film during ion bombardment probably caused the observed changes in FTIR spectra.     

原位FTIR及探针反应法研究Pt与L沸石的相互作用

本文报道了一种适合催化研究的金属原位IR池,Pt分散在NH~4L沸石上呈缺电子性,在异丙醇分解反应中不显示脱氢活性,但通过加氢抗结炭作用保护着沸石上的酸位,从而增强了NH~4L沸石的酸性催化作用,负载在碱性KL沸石上的Pt呈富电子性,在反应中极易被噻吩中毒(Pt/KL+NH~4L)混合样品在预处理和反应的过程中Pt从KL 向NH~4L沸石上迁移,导致其催化性能相似于Pt/NH~4L,实验证明:Pt与L 沸石载体之间存在着明显的相互作用,由于Pt易给出电子而不易接受电子,因此与酸位的相互作用强于与碱位的相互作用.     

H2S gas interaction with Pt(II)-containing polymetallaynes of selected chain length: an XPS and EXAFS study

The interaction between gaseous H2S and the surface of several metal-containing oligomers, investigated by emission and absorption spectroscopies, is presented and discussed. The polymetallayne trans-{Cl-[Pt(PBu3)2(CC-C6H4-C6H4-CC)]9Pt(PBu3)2Cl} and related model molecules, i.e. the binuclear transition metal dialkynyl bridged Pt(II) square planar complex trans, trans-[ClPt(PBu3)2(CC-C6H4-C6H4-CC)Pt(PBu3)2Cl], the tetranuclear linear oligomer trans-{Cl-[Pt(PBu3)2(CC-C6H4-C6H4-CC)]3Pt(PBu3)2Cl}, the tetranuclear cyclic oligomer cis-[Pt(PBu3)2(CC-C6H4-C6H4-CC)]4, were exposed to hydrogen sulfide and then investigated by X-ray photoelectron (XPS) and X-ray absorption (XAS) spectroscopies, in order to shed light on the gas/polymer interaction associated to the sensing properties of these materials. XPS measurements evidenced the presence of S in the polymetallayne samples exposed to H2S, and the measured S2p binding energy values correlate with H2S adsorbed by means of sulfur atoms chemically bonded to metal atoms, owing to the formation of sulfur-containing adducts. XAS data analysis suggested a square-pyramidal geometry around the transition metal with H2S in the apical position for the pentacoordinated platinum units.     

XPS,AES, and AFM as tools for study of optimized plasma functionalization

The plasma-based surface modification of polymer materials with desirable bulk properties is a useful way to obtain polymers with tailor-made surface properties. This is necessary because the surface properties of most engineering polymers in use today are less then optimum for many applications. New functionalities such as biocompatibility, adhesion, special functional groups as well as lubricative, friction and wear-and-tear properties are demanded. By optimization of the process parameters during a low pressure plasma treatment, most of these requirements can be fulfilled. A specific functionalization with, e.g., carboxyl, amino, epoxy or hydroxyl groups as well as the generation of ultra thin layers with those functionalities is possible. The most challenging problem is not only to find parameters which do not lead to a fragmentation of the monomeric structure, but moreover the adhesion of the thin films to the substrates must overcome a stability test without delamination. To optimize plasma processes, with their great variety of parameters influencing the obtained surface properties, several surface analytical techniques are indispensable. XPS, AES as well as AFM are helpful tools to characterize the modified sample surfaces and consequently optimize the set of parameters for the glow discharge treatment. With XPS the retention of the monomer structure can be controlled. AES depth profiling clarifies the elemental composition of gradient layers, necessary for a good adhesion of scratch-resistant coatings. AFM visualizes the surface morphology which is important for, e.g., the friction properties of plasma-coated substrates.     

XPS study of pharmacological substances mechanochemically immobilized on the surface of alumina

Piroxicam and meloxicam nanocomposites with alumina were synthesized by mechanochemical treatment of medicinal substances mixed with the oxide. X-ray photoelectron spectroscopy demonstrated that interaction of the components during mechanical activation proceeds via binding the amide and sulfate groups in the molecules of medicinal substances with the active sites of alumina surface. XPS studies confirmed the formation of “core-shell” composites with the shell represented by medicinal substances distributed over the support surface.     

FTIR and circular dichroism spectroscopic study of interaction of 5-fluorouracil with DNA

5-Fluorouracil (5FU) is an anticancer chemotherapeutic drug which exerts cytotoxic effect by inhibiting cellular DNA replication. In the present study, we explore the binding of 5FU with DNA and resulting structural and conformational changes on DNA duplex. UV-visible, Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopic techniques were employed to explore these interactions. A constant concentration of calf thymus DNA was incubated with varying concentrations of 5FU. UV-visible and FTIR spectroscopic results revealed that intercalation is the primary mode of interaction between 5FU and nitrogenous bases of the nucleic acid. The binding constant was found to be 9.7×10(4); which is indicative of moderate type of interaction between 5FU and DNA duplex. It was also observed that 5FU intercalates slightly more between AT base pairs compared to GC pairs. FTIR and circular dichroism spectroscopic results revealed that 5FU disturbs native B-conformation of DNA though, DNA remains in its B conformation even at higher concentrations of 5FU.     

A combined density functional and x-ray diffraction study of Pt nanoparticle structure

The structure of 1.7 nm Pt nanoparticles is investigated using x-ray diffraction (XRD) measurements and density functional theory (DFT) calculations. Two types of particles are compared, those made by solution chemistry which are capped either by thiol or amine ligands, and dendrimer encapsulated particles (DENs) which do not have capping ligands. All particles were dried before analyzing their structure. Pair distribution function (PDF) data from XRD measurements show that the ligand-capped particles are more disordered than the DENs. To determine the structure of the particles and the nature of the ligand-induced disorder, we use a hybrid reverse Monte Carlo approach. A weighted average of the calculated binding energy of the particles and a goodness-of-fit parameter to the PDF data is taken as the object function, which is minimized to determine the optimal structure. A scan over different weights gives the set of pareto optimal structures, which show how well simultaneous agreement can be reached to both experiment and theory. Using an embedded atom potential to sample configuration space and DFT to refine the optimal structures, we show that the DEN structure is most consistent with a face centered cubic lattice of truncated octahedral shape. The disorder induced by the capping ligands is consistent with surface relaxation of the particle rather than disorder of the crystal structure.     

XPS study of the interaction of simple gases with zeolites containing transition elements

It has been found by X-ray photoelectron spectroscopy that, upon interaction of Ni-containing zeolites with CO or with CO+O₂, Ni²⁺ is reduced to Ni⁺ and Ni^o. The ability of Ni to reduction decreases in the following series of polycationic forms: Cr>Co>Ni>Cu. The treatment of CuNiNaY and CoNiNaY zeolites with CO leads to the formation of Cu⁺, Cu^o and Co^o, respectively.

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, Ni- CO CO+O₂ 250÷550°C Ni²⁺ Ni⁺ Ni^o. Ni : Cr>Co>Ni>Cu. CuNiNaY CoNiNaY Cu⁺, Cu^o Co^o, .

     

Electronic properties of Ag nanoparticle arrays. A Kelvin probe and high resolution XPS study

The electronic properties of citrate stabilised Ag nanoparticles with sizes ranging from 4 to 35 nm were investigated by the Kelvin probe method and high resolution XPS. Two and three dimensional assemblies of the particles were prepared by electrostatic adsorption from aqueous solution onto poly-l-lysine modified surfaces. The work function of the Ag particles increased from 5.29 +/- 0.05 to 5.53 +/- 0.05 eV as the particle size decreased. These values are approximately 0.8 eV higher than for clean polycrystalline Ag surfaces. The origin of these remarkable high work functions cannot be explained in terms of either citrate induced changes in the surface dipole or image forces in the confined metallic domains. High resolution XPS spectra of the Ag 3d(5/2) core level were characterised by broad bands and a 0.4 eV shift towards lower binding energies for the smallest particles. Comparisons with reported studies on extended Ag surfaces indicate that as-grown particles exhibit partially oxidised surfaces. The behaviour of the work function further suggests that the strength of the Ag-O bonding increases with decreasing particle sizes. These findings are highly relevant to the interpretation of the catalytic properties of Ag nanoparticles.     

In situ oxidation study of Pt(110) and its interaction with CO

Many interesting structures have been observed for O(2)-exposed Pt(110). These structures, along with their stability and reactivity toward CO, provide insights into catalytic processes on open Pt surfaces, which have similarities to Pt nanoparticle catalysts. In this study, we present results from ambient-pressure X-ray photoelectron spectroscopy, high-pressure scanning tunneling microscopy, and density functional theory calculations. At low oxygen pressure, only chemisorbed oxygen is observed on the Pt(110) surface. At higher pressure (0.5 Torr of O(2)), nanometer-sized islands of multilayered α-PtO(2)-like surface oxide form along with chemisorbed oxygen. Both chemisorbed oxygen and the surface oxide are removed in the presence of CO, and the rate of disappearance of the surface oxide is close to that of the chemisorbed oxygen at 270 K. The spectroscopic features of the surface oxide are similar to the oxide observed on Pt nanoparticles of a similar size, which provides us an extra incentive to revisit some single-crystal model catalyst surfaces under elevated pressure using in situ tools.     

XPS characterisation of carbon‐coated alumina support

Hybrid carbon–alumina supports, synthesised by pyrolysis of grafted 4,4′‐methylenebis‐(phenylisocyanate) moiety on the alumina surface, were characterised by X‐ray photoelectron spectroscopy. The recorded Al 2p and C 1s envelopes showed asymmetry that decreased with an increase in carbon loading. In all experimental Al 2p envelopes, the high‐energy individual components at 75.3–75.9 eV were present along with the low‐energy component at 74.0 eV typical for Al₂O₃. In the case of the C 1s envelope, the component around 284.3–284.4 eV and three high‐energy individual components at 285.9–286.0, 288.0–288.3 and 290.1–290.6 eV were observed. The presence of the high‐energy Al 2p components can be explained considering the occurrence of a steady‐state charging of the different parts of insulating alumina supports. The component around 284.3–284.4 eV in C 1s envelopes can be attributed to carbon, which constitutes the coating and, hence, ensures surface conductivity. The component around 285.9–286.0 eV is connected with carbon in carbonaceous surface species, which do not form the conducting layer on the alumina support. Carbonaceous surface species associated with C? O, C?O and O?C? O groups in carbon coating can be also identified due to the presence of corresponding components in XPS spectra at 285.9–286.0, 288.0–288.3 and 290.1–290.6 eV. Copyright © 2006 John Wiley & Sons, Ltd.     

Pt电极上乙醛吸附及氧化的现场FTIR反射吸收光谱电化学研究

本文用现场FTIR反射吸收光谱法和循环伏安法研究了Pt电极上HCl, H2SO4水溶液中乙醛的吸附及氧化过程。实验结果表明, 0.3至1.0V(vs. SCE)电势范围内乙醛主要以式I吸附于电极表面上, 并发生了生成乙酸的电化学反应, 产物乙酸可能以式II吸附。对于H2SO4水溶液中, 上述电势范围内电极表面上还检测出硫酸根离子与乙醛和乙酸的竞争吸附。     

Characterization of aerogel prepared high-surface-area alumina: in situ FTIR study of dehydroxylation and pyridine adsorption

Mesoporous high-surface-area alumina was prepared by a modified aerogel procedure. Specific surface areas between 530-685 m(2)g(-1) were obtained after heat treatment at 500 degrees C. Nitrogen adsorption studies have shown that surface areas and pore characteristics change upon decomposition of aluminum hydroxide to oxide as well as upon compaction of oxide powders. The surface area of aluminum hydroxide increased to a maximum, while the pore volume and diameter decreased as the hydroxide was heated to a temperature of 400 degrees C. Heating at higher temperatures resulted in sintering of the particles accompanied by a decline in the surface area. Compaction of activated alumina into pellets was accompanied by a relatively gradual change in the surface area and pore characteristics at pressures below 6.9 x 10(7) Pa, while severe changes took place at a pressure of 1.4 x 10(8) Pa. In situ IR studies of the dehydroxylation of the alumina surface, showed nu(OH) absorptions for isolated surface hydroxy groups centering at 3670, 3714, and 3765 cm(-1), which are shifted to lower frequencies than common literature values. Pyridine was found to adsorb on Al(3+) ions as well as through hydrogen bonding to relatively acidic surface OH groups, and IR spectra indicated the presence of strong Lewis acid sites.     

Effects of electron density shift in five-coordinated Pt(II) complexes with olefins: An XPS study

XP spectra of seven five-coordinated Pt(II) complexes of general formula [Pt(olefin)(NN)Cl₂] reveal significant differences from analogous four-coordinated Pt(II) complexes. Pt4f and N1s signals, give evidence for π-back-donation from Pt onto both the olefin and the nitrogen chelating ligands, provided the latter belong to conjugated moieties. As a result, π-back-donation is more intense and Pt atoms more positive in 5- than in 4-coordinated complexes with similar ligands; this is in keeping with the previously reported decrease of nucleophilic reactivity of coordinated olefins in 5-coordinated Pt(II) complexes. The above electronic shifts are strongly reinforced by conjugation within the coordinated olefin such as with 2-butenedinitrile.     

A study of FTIR and XPS analysis of alkaline-based cleaning agent for removing Cu-BTA residue on Cu wafer

This study is to focus on the benzotriazole (BTA) residue problem in the postchemical mechanical planarization (post-CMP) cleaning process. The adsorption of BTA on copper surface was studied by analyzing the FTIR spectra; it indicates that the oxidation of the copper surface could affect the adsorption of BTA on the wafer surface. It used an alkaline-based chelating agent, ethylenediamine tetra acetic acid with four equivalents of 3,4-diaminobutane-1,1,2,2-tetraol, to deal with Cu-BTA film, compared with the tetraethyl ammonium hydroxide at the same pH of 10.3, and used X-ray photoelectron spectroscopy (XPS) analysis to characterize the BTA residue on Cu wafer. The results show that the alkaline-based chelating agent is very effective in removing the Cu-BTA from the Cu surface and leaving the cuprous species to passivate the Cu surface.     

XPS and TDS study of CO interaction with Pd–AlOx systems

The metal–substrate and metal–metal interactions (MSI, MMI) represent important effects determining the properties of supported catalysts, gas sensors and gettering alloys. We investigated the MSI and MMI effects by the X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) in the case of Pd films deposited on Al₂O₃ and Al substrates. The study shows that the particle-size dependent metal–substrate interaction plays an important role in CO–Pd chemisorption, namely, in the case of “aluminium rich” Pd–aluminium oxide interface. CO chemisorption exhibits a low-temperature desorption feature at 360 K characteristic for Pd–Al and very small Pd particles. The MSI is explained by the formation of a Pd–Al intermetallic interface exhibiting a strong bimetallic Pd–Al interaction.     

FTIR spectroscopy study of the interaction between fibre of polyamide 6 and iodine

The IR spectra of several samples of polyamide 6 fibres treated with solutions of different concentrations of iodine and potassium iodide were studied. The IR spectra of their respective iodine desorptions, obtained by means of treatment with sodium thiosulphate, were also studied. The spectral changes observed are related to variations in the polymorphic crystalline α and γ forms of the polyamide, which demonstrate the formation of a complex between the tri-iodide ion and the polymer during the iodine sorption process and a structural change during desorption.     

Chemical functionalization of silica and alumina particles for dispersion in carbon dioxide

The steric stabilization and flocculation of modified silica and alumina particle suspensions in condensed CO(2) were studied. Silica particles (average diameters of 7 and 12 nm) were functionalized using chlorosilanes of the form C(n)F(2n+1)CH(2)CH(2)Si(CH(3))(2)Cl (n = 8, 4, or 1) to give C(n)F(2n+1)-silica. Alumina particles (diameter of 8-14 nm) were grafted with C(8)F(17)CH(2)CH(2)Si(OEt)(3) and chemically modified with perfluorononanoic acid to yield C(8)F(17)-alumina and C(8)F(17)COOH-alumina, respectively. Elemental analysis and thermogravimetric analysis on the derivatized particles were carried out, and surface coverage was calculated. The stabilization of these modified particles in condensed CO(2) was quantified using turbidimetry. Particle stability was found to increase with increasing fluorinated tail length, temperature, and CO(2) density. Unmodified particles and those modified with only -CF(3) tails were unstable in condensed CO(2). Stabilization in supercritical CO(2) is continuous up to 24 h for the C(n)F(2n+1)-silica (n >/= 4) particles and 96 h for the C(8)F(17)-alumina particles. The C(8)F(17)COOH-alumina particles gave a significantly higher graft density than the C(8)F(17)-alumina particles but are not as stable in CO(2). The C(8)F(17)-alumina particles were stable at lower CO(2) densities than the modified silica particles. This stability difference may be attributed to the precursor organosilanes being monofunctional (modified silica) versus trifunctional (modified alumina), producing different structures on the surface.