利用角分辨XPS评价硬脂酸铜LB膜

一般根据膜衬底XPS峰强的衰减与膜厚的关系即可判断硬脂酸类LB膜的成膜质量,本文利用角分辨XPS技术,根据硬脂酸铜LB膜持征的羧基碳与样品中的总体碳C_(ls),蜂强度的比值(r)在不同电子出射角时的变化(△r),与无序粉末样品比较得出了成膜质量与△r间的对应关系,提出了一种利用XPS监测成膜质量的方法。     

硝基芴酮与N-乙基咔唑电荷转移复合物的研究——-用X射线光电子能谱确定复合物的电荷转移量

Mulliken等从理论上指出电荷转移式复合物必伴有电子从给体原子或分子向受体原子或分子间的电荷转移.而用X射线光电子能谱(XPS)测定的某给定原子内壳电子结合能位移(即XPS化学位移)正是该原子周围环境电荷分布变化的反映.因此XPS技术是确定形成电荷转移复合物和提供电荷转移量信息的有效手段之一.为此,我们用XPS技术研究了2-硝基芴酮(2-MNF);2,7-二硝基芴酮(2,7-DNF);2,4,7-三硝基芴酮(2,4,7-TNF);     

铭酸溶液中金属铬电沉积的机理

从铬酸溶液中电沉积金属铬的机理曾经有过不少探索.许多研究者认为,阴极表面形成难溶的膜层金属铬的电沉积起着关键性的作用.本文应用交流阻抗谱研究金属铬电沉积过程中阴极表面膜的形成,利用X光电子能谱(XPS)和俄歇电子能谱(AES)分析了表面膜的组成,并且对SO_4~(2-)的作用进行了初步的探讨。     

沙林酸印迹聚邻苯二胺纳米膜制备及结构表征

采用电化学聚合法合成了对有机磷毒剂沙林具有特异识别的聚邻苯二胺(PPD)分子印迹纳米膜(iPPD).利用石英晶体微天平(QCM)证实了印迹效应的存在，并用循环伏安法(CV)、AFM、XPS进行了系统的结构表征.结果表明，分子印迹膜的膜厚约20 nm，膜的表面呈“石林”状，疏松多孔，具有良好的吸附性能.分子印迹主要影响聚合物的三维排列，而聚合物的化学组成没有发生改变.该种分子印迹纳米膜在选择性检测军用毒剂沙林中具有良好的应用前景.     

液相沉积法制备TiO2颗粒表面包覆SiO2纳米膜

研究了用液相沉积法在TiO2颗粒表面包覆SiO2纳米膜的过程.通过透射电镜(TEM)和酸溶实验分析,证实本实验在TiO2颗粒表面包覆了一层连续、致密的SiO2纳米膜.ζ-电位分析表明,颗粒表面只需少量包覆就可以显著改变颗粒表面的电动力学行为.采用 X射线荧光光谱分析仪（XRF）测定SiO2包覆量随包覆过程的变化.通过X射线光电子能谱（XPS）分析,获得Ti 2p、Si 2p及 O 1s电子结合能及其相对强度随包覆过程的变化规律,揭示硅酸分子在TiO2颗粒表面的包覆过程.分析表明,初期形成的活性硅酸分子与TiO2颗粒表面的羟基反应形成Ti－O－Si键,后期形成的硅酸分子与已键合在表面的硅酸发生缩合反应,形成连续致密的硅膜,膜层在陈化过程中继续缓慢生长.     

硫醇在Au(111)上SA单分子层膜研究

采用自组装(SA)技术制备了正丁硫醇、正十二硫醇及两种硫醇等摩尔混合物的SA单分子层膜。用椭圆偏振仪、接触角测量仪、扫描电子显微镜(SEM)、X-射线光电子能谱仪(XPS)和原子力显微镜(AFM)对3种SA膜进行了分析表征。结果表明SA膜是取向有序的纳米级超薄膜,分子链长、基片表面的晶格取向和表面的洁净度等对膜有一定的影响,长链分子膜表面是疏水性的。用椭圆偏光、XPS和AFM3种方法测定3种单分子层膜的厚度分别为0.59～0.67nm,1.60～1.69nm,1.23～1.32nm。AFM图象进一步证实了混合单分子层膜是由两种不同厚度的微畴组成。     

N2O多层膜局域结构的多重散射簇理论研究

利用多重散射簇(multiple scattering cluster, MSC)方法计算了N2O多层膜中氮原子的1s芯态近边X射线吸收精细结构(near edge X-ray absorption fine structure, NEXAFS)谱,首次给出N2O多层膜局域结构的模型. MSC研究显示多层膜中N2O分子以短程有序的分层错位链结构排列,并求得链中相邻分子间距为0.233 nm和相邻分子层之间距离为0.240～0.245 nm.用自洽场离散变分(discrete variation, DV)Xα方法计算的N2O多层膜电子结构支持了MSC的计算结果;阐明了NEXAFS谱中弱结构的物理起源.对N2O多层膜中分子之间相互作用的分析显示N2O多层膜的结构具有分子自组装的特性.     

金属螯合物印迹聚邻苯二胺膜的电化学合成及表征

以邻苯二胺(o-PD)为功能单体, 乙二胺四乙酸铜离子螯合物(Cu(II)-EDTA)为模板分子, 利用循环伏安法(CV)合成了Cu(II)-EDTA分子印迹聚合物(MIPs). 通过紫外-可见(UV-Vis)光谱、X射线光电子能谱(XPS)、差分脉冲伏安法(DPV)、石英晶体微天平(QCM)等手段对合成的聚合物进行了表征. UV-Vis光谱分析表明当溶液的pH≥5.0时有利于邻苯二胺电聚合形成聚合度较高的聚合物; XPS结果证明Cu(II)-EDTA螯合物被成功地包覆在聚合物膜中, 且推断出模板分子和聚合物之间可能主要靠氢键相互作用; DPV实验结果证明模板分子能够被有效洗脱; QCM的测试结果表明此方法合成的Cu(II)-EDTA印迹聚合物膜对Cu(II)-EDTA具有良好的响应度.     

氟硅烷自组装单分子膜的制备及其摩擦学性能

利用分子自组装技术制备了全氟辛酰胺丙基硅烷单分子膜,用X射线光电子能谱(XPS)对组装膜的表面元素进行了表征;接触角测试表明,该组装膜具有很好的疏水疏油性,其对水的接触角高达105°,对正十六烷的接触角为50°.摩擦磨损实验结果表明,全氟辛酰胺丙基硅烷自组装单分子膜可以大大降低基片的摩擦系数,使载玻片的摩擦系数从0.85左右降低到0.14左右,而且低负荷下具有很好的耐磨性.     

DNA在氨基功能化偶氮苯自组装膜表面的固定

采用简单快速的方法制备出将DNA固定在其表面的单分子层敏感膜.首先采用表面自组装技术将硅氧烷基偶氮苯衍生物H2NAzoCONHC3Si(OCH3)3(APDA-N-TMSPBA)组装在硅表面,在详细考察单分子层薄膜的化学结构、表面浸润性和分子表面形貌之后,又通过紫外吸收光谱(UV)在位考察了硅氧烷基偶氮苯衍生物的光学异构特性.在DNA在自组装薄膜固定后,X光电子能谱仪(XPS)结果显示出现了明显的磷元素信号,表明DNA分子可以成功固定在自组装膜表面.     

Modulated electron emission for structural characterization of buried layers and interfaces

Principles and performances of Primary-beam Diffraction Modulated Electron Emission are briefly reviewed. This approach exploits the spatial modulation of the beam electrons waves intensity in ordered atomic arrays, which in turn results in a marked dependence of the electron emission on the incidence angle. Detection of Auger electrons or inelastically backscattered electrons (ionization losses) provides chemical specificity. Surface sensitivity is related to the inelastic mean free path of the detected electrons. Examples are given of the capability of this technique for structural characterization of buried layer and interfaces. They include: i) epitaxial growth of Co oxide on the (001) surface of Co bct film, ii) subsurface behaviour of Co epitaxial layers during the bct→hcp phase transition.     

Inelastic scattering and energy loss of swift electron beams in biologically relevant materials

The inelastic mean free path and the stopping power of swift electrons in relevant biomaterials, such as liquid water, DNA, protein, lipid, carotene, sugar, and ice are calculated in the framework of the dielectric formalism. The Mermin Energy Loss Function – Generalized Oscillator Strength model is used to determine the energy loss function of these materials for arbitrary energy and momentum transfer using electron energy‐loss spectroscopy data as input. To ensure the consistency of the model, efforts are made so that both the Kramers–Kronig and f‐sum rules are fulfilled to better than 2%. Our findings indicate sizeable differences in the inelastic mean free path and stopping power among these biomaterials for low‐energy electrons. For example, at 100‐eV electron energy, the inelastic mean free path in protein is 25% smaller than for water and around 10% smaller than for the other biomaterials. The stopping power values of protein, DNA, and sugar are rather similar but 20% larger than for water. Taking into account these results, we conclude that electron interactions with living tissues at the nanometric scale cannot be reliably described using only liquid water as the surrogate of the biological target. Copyright © 2016 John Wiley & Sons, Ltd.     

Experimental determination of the effective attenuation length of palladium 3d 5/2 photoelectrons in a magnetron sputtered Pd nanolayer

An electron effective attenuation length (EAL) of 1.68 nm for Al Kα excited Pd 3d 5/2 photoelectrons with a kinetic energy of 1.152 keV has been determined experimentally using a sputtered Pd film deposited on an ultra flat fused quartz substrate. The film thickness was reduced by Ar ion sputtering several times in order to obtain different Pd film thicknesses which are used to determine experimental EAL values. These results are compared to data generated by using a Simulation of Electron Spectra for Surface Analysis (SESSA) simulation using an inelastic mean free path (IMFP) calculated with the Tanuma–Powell–Penn (TPP)‐2M formula and with ‘elastic scattering on and off’. Contributions to the uncertainty budget related to the experimental approach are discussed in detail. Proposals on how to further improve the approach are suggested. Copyright © 2016 John Wiley & Sons, Ltd.     

Analysis of Fe-Si layered structures by reflected electron energy loss spectroscopy and inelastic scattering cross-section

This paper reports on our study of the formation of an interface of layered structures in the Fe-Si system by reflected electron energy loss spectroscopy (REELS). Quantitative element analysis was performed using the product of the mean length of the inelastic free path by the inelastic scattering cross-section of electrons. It is shown that the Fe-Si interface is quite uniform.     

The inelastic mean free paths of auger electrons in thin films of copper and nickel

The inelastic mean free paths of 600–1000 eV Auger electrons have been determined in Cu and Ni films. Thin films of known thickness were produced by the vapor deposition of Cu on Ni substrates and vice versa. The strengths of the characteristic Auger signals of Cu and Ni were monitored as a function of film thickness. Values of the mean free paths are presented and compared to values previously published by other workers. By monitoring the strengths of the Auger signals from the condensate, it is concluded that backscattering factors for a Ni substrate carrying a Cu film are higher than the backscattering factors for a Cu substrate carrying a Ni film.     

Chemical‐Reaction‐Induced Hot Electron Flows on Platinum Colloid Nanoparticles under Hydrogen Oxidation: Impact of Nanoparticle Size

Generation of hot electron flows and the catalytic activity of Pt nanoparticles (NPs) with different sizes were investigated using catalytic nanodiodes. We show that smaller Pt NPs lead to higher chemicurrent yield, which is associated with the shorter travel length for the hot electrons, compared with their inelastic mean free path. We also show the impact of capping on charge carrier transfer between Pt NPs and their support.     

Thermal-transport studies on two-dimensional quantum spin liquids

Quantum spin liquids (QSLs) are fluidlike states of quantum spins in which the long-range ordered state is destroyed by quantum fluctuations. The ground state of QSLs and their exotic phenomena, which have been extensively discussed for decades, have yet to be identified. We employ thermal-transport measurements on newly discovered QSL candidates κ-(BEDT-TTF)(2)Cu(2)(CN)(3) and EtMe(3)Sb[Pd(dmit)(2)](2), and report that the two organic insulators have different QSLs characterized by different elementary excitations. In κ-(BEDT-TTF)(2)Cu(2)(CN)(3), heat transport is thermally activated at low temperatures, and this suggests the presence of a spin gap in this QSL. In stark contrast, in EtMe(3)Sb[Pd(dmit)(2)](2), a sizable linear temperature dependence of thermal conductivity is clearly resolved in the zero-temperature limit, and shows gapless excitation with a long mean free path (ca. 1000 lattice distances). Such a long mean free path demonstrates a novel feature of QSL as a quantum-condensed state with long-distance coherence.     

Molecular Weight Effect on Latex Film Formation from Polystyrene Particles: A Photon Transmission Study

The photon transmission method was used to probe the time evolution of film formation from latex particles. Two different latex films were prepared from high molecular weight (HM) and low molecular weight (LM) polystyrene particles at room temperature and were annealed at various temperatures in 2.5-min time intervals above the glass transition. The increase in the transmitted photon intensity (Itr) is attributed to the increase in "crossing density" at the junction surface. The Prager-Tirrell model was employed to interpret the increase in crossing density at the junction surface. The back and forth activation energies were measured for HM and LM films and found to be around 59 and 87 kcal/mol for a reptating polymer chain across the junction surface. Monte Carlo simulations were performed for photon transmission through a rectangular lattice. The number of transmitted photons (Ntr) was calculated as a function of the mean free path of photons. It was observed that Ntr, similar to Itr, increases as the square of the mean free path of photons is increased. Copyright 1999 Academic Press.     

Contact instability of thin elastic films on patterned substrates

The free surface of a soft elastic film becomes unstable and forms an isotropic labyrinth pattern when a rigid flat plate is brought into adhesive contact with the film. These patterns have a characteristic wavelength, lambda approximately 3H, where H is the film thickness. We show that these random structures can be ordered, modulated, and aligned by depositing the elastic film (cross-linked polydimethylsiloxane) on a patterned substrate and by bringing the free surface of the film in increasing adhesive contact with a flat stamp. Interestingly, the influence of the substrate "bleeds" through the film to its free surface. It becomes possible to generate complex two-dimensional ordered structures such as an array of femtoliter beakers even by using a simple one-dimensional stripe patterned substrate when the instability wavelength, lambda approximately 3H, nearly matches the substrate pattern periodicity. The free surface morphology is modulated in situ by merely varying the stamp-surface separation distance. The free surface structures originating from the elastic contact instability can also be made permanent by the UV-ozone induced oxidation and stiffening.