飞行时间二次离子质谱结合X—射线光电子能谱分析化学清洗后残留的…

用飞行时间二次离子质谱结合Ｘ射线光电子能谱，分析了用化学方法清洗后银片上残留的未知有机物。ＴＯＦ－ＳＩＭＳ与ＸＰＳ提供的互补的表面信息显示，中分子量以上的有机物主要是几种链长２２－２７碳原子、碳链饱和度很高的多酮类化合物，可能还有一些多酯类化合物。这些有机物中的Ｃ＝Ｏ基团易于采取氧原子指向金属基体表面的取向，通过带部分负电荷的氧原子与金属基体镜像力的作用而增强粘附。     

表面残留有机沾污物的TOF－SIMS及XPS研究

飞行时间次级离子质谱（ＴＯＦ－ＳＩＭＳ）结合Ｘ射线光电子能谱（ＸＰＳ）分析了用化学方法清洗后、银片上残留的未知的有机物。结果显示，有机沾污物主要是一些含１８～３０碳原子、碳链饱和度很高的酮类和酯类化合物；个别有机物可能是硬脂酰胺。这种结构特点使有机物中的Ｃ＝Ｏ基团易于采取氧原子指向基体表面的取向，通过带部分负电荷的氧原子与金属基体镜像力的作用而增强粘附。ＴＯＦ－ＳＩＭＳ二维离子像显示有机沾污物在银片表面上呈极稀薄的均匀分布。     

表面残留有机沾污物的TOF—SIMS及XPS研究

飞行时间次级离子质谱（ＴＯＦ－ＳＩＭＳ）结合Ｘ射线光电子能谱（ＸＰＳ）分析了用化学方法清洗后，银片上残留的未知的有机物，结果显示，有机沾污物主要是一些合１８～３０碳原子，碳链饱和度很高的酮类和酯类化合物；个别有机物可能是硬脂酰胺。这种结构特点使有机物中的Ｃ＝Ｏ基团易于采取氧原子指向基本表面的取向。通过带部分负电荷的氧原子与金属基体镜像力的作用而增强粘附，ＴＯＦ－ＳＩＭＳ－二维离子像显示有机沾污物在     

极性有机物在零价态过渡金属表面的配位化学反应

咪唑、腈、酯类等极性有机物吸附在铜、铂、银、汞等过渡金属表面时,氮原子或氧原子上的孤对电子插入金属原子的外层价轨道,在表面生成零价态金属原子的配合物。由于电子的迁移,使金属原子及有机物中相应的化学键同时被活化。这一现象被作者称为"表面吸附层的配位双活化效应"。在有氧存在时,零价态金属原子极易与上述有机物发生化学反应,导致了N-H键、C≡N键或C-O键的破裂,生成超薄化学吸附层覆盖在金属表面。     

Pt/Cu（001）-p（2×2）-O表面吸附结构的总能计算

采用密度泛函理论（DFT）研究了氧吸附后Pt/Cu（001）表面合金的原子结构和表面性质.计算结果表明,在Pt/Cu（001）-p（2×2）-O表面最稳定结构中,衬底表面原子层不发生再构,氧原子吸附于4重对称的Pt原子谷位,每个氧原子吸附能约为2.303 eV.吸附结构的Cu—O和Pt—O键键长分别为0.202和0.298 nm,氧原子的吸附高度ZCu—O约为0.092 nm.吸附前后Pt/Cu（001）-1ML（monolayer）表面合金的表面功函数分别为4.678和5.355 eV.吸附表面氧原子和衬底的结合主要来自氧原子2p轨道和衬底金属原子d轨道的杂化作用,氧原子吸附形成的表面电子态主要位于费米能级以下约-2.7 eV处.     

Pt/Cu(001)-p(2×2)-O表面吸附结构的总能计算

采用密度泛函理论(DFT)研究了氧吸附后Pt/Cu(001)表面合金的原子结构和表面性质.计算结果表明,在Pt/Cu(001)-p(2×2)-O表面最稳定结构中,衬底表面原子层不发生再构,氧原子吸附于4重对称的Pt原子谷位,每个氧原子吸附能约为2.303 eV.吸附结构的Cu-O和Pt-O键键长分别为0.202和0.298 nm,氧原子的吸附高度Zcu-O约为0.092 nm.吸附前后Pt/Cu(001)-1ML(monolayer)表面合金的表面功函数分别为4.678和5.355 ev.吸附表面氧原子和衬底的结合主要来自氧原子2p轨道和衬底金属原子d轨道的杂化作用,氧原子吸附形成的表面电子态主要位于费米能级以下约-2.7 eV处.     

Pt/Cu(001)-p(2×2)-O表面吸附结构的总能计算

采用密度泛函理论(DFT)研究了氧吸附后Pt/Cu(001)表面合金的原子结构和表面性质. 计算结果表明, 在Pt/Cu(001)-p(2×2)-O表面最稳定结构中, 衬底表面原子层不发生再构, 氧原子吸附于4重对称的Pt原子谷位, 每个氧原子吸附能约为2.303 eV. 吸附结构的Cu—O和Pt—O键键长分别为0.202和0.298 nm, 氧原子的吸附高度ZCu—O约为0.092 nm. 吸附前后Pt/Cu(001)-1ML(monolayer)表面合金的表面功函数分别为4.678和5.355 eV. 吸附表面氧原子和衬底的结合主要来自氧原子2p轨道和衬底金属原子d轨道的杂化作用, 氧原子吸附形成的表面电子态主要位于费米能级以下约-2.7 eV 处.     

室温下空气与金属铌和钽表面的相互作用

用XPS角分布法研究了铌和钽在室温下与干燥空气的相互作用.结果表明铌和钽表面生成了化学组成分别为Nb_2O_5和Ta_2O_5的氧化物,氧化膜内金属原子和氧原子呈混合状态,从而排除了这种相互作用仅仅是化学吸附的可能性.     

覆氧或氧离子轰击下固体表面二交正离子发射的研究

通过对离子轰击下固体表面电离过程重新考虑认为，在固体表面覆氧或氧离子轰击下除表面原子的直接电离外，激发态双原子间电子交换和断键亦起重要作用，在此基础上修正了局部热力学平衡模型，得到了一个包含各类离子内配分函数、电离能、金属－氧原子键断键能以及表面金属原子与氧原子结合份数等参数决定的新电离几率分析表达式。应用该分析表达式解释了金属表面覆氧、氧离子轰击金属、化合物半导体表面二次离子发射中氧增强效应、充     

醇氧化为醛的银合金催化剂的量子化学研究

本文用EHMO方法计算了氧原子在晶体银及其合金Ag-X(X=Cu,Mg,Cd,Ga,Ge,In,Sn,Se,Te,Al,Bi,Sb)表面上的吸附态;试图通过计算找出这些金属的电子性质与其对甲醇氧化制甲醛反应中催化活性的关系.计算结果表明:银及其合金的的催化活性与体系的电子最高占有轨道HOMO和最低空轨道LUMO的能量差有关,如果HOMO和LUMO的能量差比纯银体系的能量差小,该合金对反应有较好的催化活性,同时吸附在该合金表面上的氧原子有较大的电荷密度分布.     

Properties and structure of manganese oxide-coated clay

In the environment, heavy metals are important contaminants that sorb to and accumulate in soils and sediments. Dominant minerals in the subsurface are oxides and clay, which occur as discrete particles and heterogeneous systems; these surfaces can significantly impact the mobility and bioavailability of metals through sorption. To better understand heterogeneous systems, amorphous (hydrous manganese oxide (HMO)) and crystalline manganese oxides (birnessite and pyrolusite) were coated on montmorillonite. However, the montmorillonite substrate potentially inhibited crystallization of the pyrolusite coating, and also resulted in a poorly crystalline birnessite. Mineralogy and morphology of the coated systems suggest an amorphous structure for HMO and uniform coverage for HMO and birnessite coatings; the presence of Si and Al indicates uncoated areas along intraplanar surfaces. The coating surface charge behaved similarly to that of discrete oxides and clay where the pH(znpc) of HMO- and birnessite-coated clay were 2.8 and 3.1, respectively. Surface area of the coated systems increased while the pore size distribution decreased as compared to the external surface area and pores of montmorillonite. X-ray absorption spectroscopy (XAS) revealed the local structural environment of Mn in the HMO- and birnessite-coated clay was consistent with the pure phase oxides: for HMO-coated clay 3.1 atoms of oxygen at 1.89 +/- 0.02 A in the first shell and 2.7 atoms of manganese at 2.85 +/- 0.02 in the second shell; and, for birnessite-coated clay 6 atoms of oxygen at 1.91 +/- 0.02 A in the first shell and 6 atoms of manganese at distance 2.99 +/- 0.02 A in the second shell. Overall, the surface properties suggest that the coating behaves like that of discrete oxides, an important sink for metal contaminants.     

HRTEM-EELS cross-sectional structural analyses of glassy carbon substrate irradiated by platinum ions using a coaxial arc plasma gun

A glassy carbon (GC) substrate was irradiated by Pt ions using a coaxial arc plasma gun in vacuum. The structure of the substrate was studied in the atomic scale using high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) with a thin foil specimen prepared by cross-sectioning using focused ion beam milling. HRTEM combined with the EELS measurements of the cross-sectioned sample indicated a disordering of the GC substrate surface and the detection of phenol-type species, carbon atoms in aliphatic chain molecules, and carboxyl groups, which are considered to have been formed by chemical reaction between the carbon atoms of the GC substrate surface and hydrogen or oxygen atoms. Penetrated Pt atoms were observed inside the GC substrate, and the surface position of the GC substrate was located from the depth profiles of the EELS spectra. STEM-EELS analyses of a pristine GC substrate without Pt ion irradiation were also conducted for reference.     

Non-bonded organo-mineral interactions and sorption of organic compounds on soil surfaces: a model approach

Molecular mechanics and molecular dynamics calculations have been performed on organo-mineral composites that model the sorption of high-molecular-weight humic polymers on mineral surfaces and the sorption of low-molecular-weight organic contaminants on both mineral and organic surfaces in soil. Muscovite mica was chosen as a mineral model; an oxidized topological lignin-carbohydrate complex was chosen as a humic model; benzene, sodium benzoate, atrazine, and DDT represent different classes of contaminants. Sorption energies were estimated based on molecular mechanics calculations. Flexible linear polymers undergo drastic conformational changes when approaching the mineral surface, to ensure a gain in the interaction energy that outweighs a loss in the conformational energy proper. Therefore, the gas-phase conformation composi tion of environmental organic polymers is not directly related to their spatial organization in soil composites. Molecular dynamics simulation suggests high stability of the organic polymer coatings of mineral surfaces in the environment. Low-molecular-weight organic molecules demonstrate much less affinity for the mineral surface, which implies unhindered exchanges between the surface and its near environment. Ionizable compounds, e.g. salts of organic acids, are different, because they can form strong associations with a mineral surface through cation bridges. Sorption energies are compound-specific and depend on the sorbate-sorbent orientation. The calculations suggest some preference for the edges of a model muscovite sheet in comparison with the basal oxygen surface as a sorption site. Coating of mineral surfaces with organic polymers does not hinder the sorption of organic molecules except in the special case of organic ions.     

Current challenges in compound-specific stable isotope analysis of environmental organic contaminants

Compound-specific stable-isotope analysis (CSIA) has greatly facilitated assessment of sources and transformation processes of organic pollutants. Multielement isotope analysis is one of the most promising applications of CSIA because it even enables distinction of different transformation pathways. This review introduces the essential features of continuous-flow isotope-ratio mass spectrometry (IRMS) and highlights current challenges in environmental analysis as exemplified for the isotopes of nitrogen, hydrogen, chlorine, and oxygen. Strategies and recent advances to enable isotopic measurements of polar contaminants, for example pesticides or pharmaceuticals, are discussed with special emphasis on possible solutions for analysis of low concentrations of contaminants in environmental matrices. Finally, we discuss different levels of calibration and referencing and point out the urgent need for compound-specific isotope standards for gas chromatography-isotope-ratio mass spectrometry (GC-IRMS) of organic pollutants.     

Effect of the pore surface modification of an inorganic substrate on the plasma‐grafting behavior of pore‐filling‐type organic/inorganic composite membranes

We have investigated the effect of the surface state and surface treatment of the pores of an inorganic substrate on the plasma‐grafting behavior of pore‐filling‐type organic/inorganic composite membranes. Shirasu porous glass (SPG) was used as the inorganic substrate, and methyl acrylate was used as the grafting monomer. The grafting rate increased as the density of silanol on the SPG substrate increased. This result suggests that radicals are generated mainly at the silanol groups on the pore surface by plasma irradiation. The SPG substrates were treated with silane coupling agents used to control the mass of organic material bonded to the pore surface. The thickness of the grafted layer became thinner as the mass of organic material bonded to the pore surface of SPG increased. This decrease in the thickness of the grafted layer could be explained by the decrease in the penetration depth of vacuum ultraviolet rays contained in plasma having a wavelength of less than 160 nm that generated radicals in the pores of the substrate. The thickness of the grafted layer inside the SPG substrates could be controlled through the control of the mass of organic material bonded to the pore surface of the SPG substrate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 846–856, 2006     

Aversatile β-cyclodextrin functionalized silver nanoparticle monolayer for capture of methyl orange from complex wastewater

The toxic organic dye contaminants in wastewater are extremely harmful to the ecosystem.Surface enhanced Raman scattering(SERS) is a technique with high sensitivity and chemical specificity which fulfills the requirements for monitoring dye contaminants in wastewater.However,as one of the common dye contaminants,methyl orange(MO) has very weak affinity to metallic surfaces and is difficult to be detected by SERS at low concentrations.Therefore,a new type of SERS substrate with Ag nanoparticle monolayer functionalized by mono-6-deoxy-6-thio-β-cyclodextrin(β-CD-SH) was prepared to efficiently capture and detect MO in wastewater with a limit of detection of 5×10^-7 mol/L.The hydrophobic cavity of β-CD is responsible for the efficient trap and enrichment of MO on the Ag NPs surface,achieving a strong SERS signal of MO at low concentrations and at different pH values.This study provides new insight into designing a well-performed adsorbent for the capture and detection of organic contaminants.     

Surface cleaning of germanium nanodot ionization substrate for surface‐assisted laser desorption/ionization mass spectrometry

In surface‐assisted laser desorption/ionization mass spectrometry (SALDI‐MS), a chemical background signal, arising from organic contaminants such as plasticizers, is frequently observed mainly under m/z ca. 600, which impairs the advantages of the matrix‐free approach. Silver salts, which are used for the cationization of aromatic compounds, are also difficult to remove completely after the measurements. In this study, surface cleaning techniques used in semiconductor processing were used to clean our developed silicon‐based SALDI substrate on which self‐assembled germanium nanodots (GeNDs) had been deposited (termed a GeND chip). An immersion cleaning method using acetone with sonication, and a sulfuric‐peroxide mixture (SPM) cleaning method using a mixture of H₂SO₄/H₂O₂/deionized water, were examined for their effectiveness in removing organic compounds and residual silver salts. Removal of both types of contaminants was successfully performed by SPM cleaning. The limit of detection for glutathione was improved from ca. 5 pmol without cleaning to ca. 50 fmol after the SPM cleaning. Since GeND chips can tolerate acidic cleaning and sonication due to their chemical inertness and rigid nanodot structures, they appear to be an ideal reusable SALDI substrate. Copyright © 2009 John Wiley & Sons, Ltd.     

A novel ATR FT-IR microspectroscopy technique for surface contamination analysis without interference of the substrate.

Surface contaminants, such as powder and thin film on various solid surfaces, were analyzed by ATR FT-IR microspectroscopy. An ATR accessory consisting of a miniature-Ge IRE with contact area smaller than 50 microm, in diameter was fabricated and employed for a non-destructive characterization. The IRE was pre-aligned and fixed onto a 15x Schwarzschild-Cassegrain infrared objective. Easy maneuvering of the microscope stage enabled an accumulative collection of the contaminant at the tip of a miniature-Ge IRE, where the contaminants were analyzed under the ATR condition. By making a gentle contact between the Ge tip and selected area on the surface, any removable contaminants were transferred onto the Ge tip where its molecular information was acquired without any interference from the solid substrate. A thin organic film (i.e., mineral oil or fluorolube) was coated at the tip of the IRE in order to enhance the collecting efficiency of the removable contaminants.     

Self-assembled macrocycles with pentavalent silicon linkages

Organic substrates containing two catechol (ortho-dihydroxybenzene) components at opposite ends self-assemble with a silicon substrate containing three nucleofugic groups (methoxy or ethoxy) under basic conditions to produce macrocycles ranging from monomers to pentamers. Silicon in all the macrocycles is pentacoordinate, negatively charged, and possessed of one organic monodentate ligand attached via carbon and two catechol bidentate ligands attached via oxygen. The organic materials with the two catechol structures thus serve as struts between the corners provided by the pentacoordinate silicon atoms.     

Interface diffusion and chemical reaction of PZT layer/Si (111) sample during the annealing treatment in air

The interface diffusion and chemical reaction between a PZT (PbZrxTi1-xO3) layer and a Si(111) substrate during the annealing treatment in air have been studied by using XPS (X-Ray Photoelectron Spectroscopy) and AES (Auger Electron Spectroscopy). The results indicate that the Ti element in the PZT precursor reacted with residual carbon and silicon, diffused from the Si substrate, to form TiCx, TiSix species in the PZT layer during the thermal treatment. A great interface diffusion and chemical reaction took place on the interface of PZT Si also. The silicon atoms diffused from silicon substrate onto the surface of PZT layer. The oxygen atoms, which came from air, diffused into silicon substrate also and reacted with Si atoms to form a SiO2 interlayer between the PZT layer and the Si (111) substrate. The thickness of SiO2 interlayer was proportional to the square root of treatment time. The formation of the SiO2 interlayer was governed by the diffusion of oxygen in the PZT layer at low annealing tempera