NaP4及其正负离子的结构和光谱性质

用密度泛函理论(DFT)分析了NaP4及其正负离子的低级电子态的平衡结构、振动频率、能量、原子化能、绝热电子亲合能、绝热离子势等, 并与实验所得的阴离子光电子能谱进行比较. 根据计算结果与实验所得的激发能进行比较, 对NaP-4的阴离子光电子能谱中的峰进行了合理的归属.     

气态肼的三种电子能谱和量子化学研究

本文应用X射线光电子能谱技术测得了气态肼的内层电子能谱、Auger电子能谱和价带电子能谱,对其电子结构进行了系统研究。又采用了不同能量的X射线为激发源,对比了Mg Ka 和 Zr M:价带能谱,定性地获得了肼的分子轨道的组成。本文对肼电子能谱进行了量子化学研究,用从头计算法给出了分子轨道波函数的成分,并指认了能谱,实验结果和计算值之间的一致性很好。     

氧分子1s电子的定域和离域性研究

由于电子能谱的发展,使得对原子和分子中电子的结合能能精确测定。氧分子的电子能谱已经比较详细地研究过,这样就能借助较精确的计算来解释氧分子的能谱,这对于研究分子的电子状态是很有帮助的。如其中一个重要问题就是分子中内层电子是离域的还是定域的,用电子能谱这个手段就可能解决这个问题。Basus等用接近精确的 Hartree-Fock方法计算了氧分子,结论是氧分子的1s电子是定域的。本文的目的是用另一种计算方法,即 SCF-Xα-SW法,来研究氧分子1s电子的定域和离域问题。     

二元合金团簇CoGe-n(n=1~12)的结构和稳定性

用密度泛函(DFT)方法与反射式飞行时间质谱及光电子能谱的实验结果相结合, 研究了二元合金团簇负离子CoGe-n(n=1~12)的结合能、几何结构与电子结构. 理论计算得到的电子亲和势(EA)光电子能谱测量的结果符合得较好. 通过分态密度(PDOS)分析了s, p和d轨道电子的相互作用规律. 讨论了团簇的稳定性, 认为CoGe-10具有幻数团簇的性质.     

ESCA法的进展

自从六十年代末电子能谱法进入实用阶段以来,无论在理论、实验技术和应用等方面都得到了迅速的发展。电子能谱的奠基人——瑞典Uppsala大学的Siegbahn教授于1981年获得了诺贝尔奖金。电子能谱法的基本测量过程是用一种激发源(光子或电子)照射样品后测量从样品发射出来的电子的能量分布,从中得到有关的信息。根据激发源的不同,电子能谱法可分为紫外光电子能谱(UPS),X射线光电子能谱(XPS)和俄歇电子能谱(AES)等分支。由于XPS法对化学分析最有用,又称为化学分析用电子能谱(Electron Spectroscopy for ChemicalAnalysis),缩写为ESCA。有关电子能谱法的基本原理、实验技术和各种应用,国内已有     

用HAM/3法研究胞嘧啶及其甲基衍生物的光电子能谱与紫外光谱

本文用半经验SCF-MO-HAM/3方法计算了胞嘧啶和它的某些甲基衍生物的电离能、激发能和振子强度.指认了这些分子的紫外光电子能谱和紫外电子光谱.讨论了在紫外光电子能谱指认上与CNDO/S的不同之处.分析了胞嘧啶在磷酸三甲酯中可能存在的主要异构体形式.     

固相表面修饰对聚丙烯结晶性能的影响

采用固相表面修饰方法对聚丙烯进行网络修饰,讨论了反应条件对体系凝胶分数的影响,用IR、WAXD、DSC、DMA和电子能谱等方法研究了固相表面修饰对聚丙烯结晶性能的影响,阐明了固相表面修饰过程的特点.     

俄歇电子能谱简介

最近十年中,固体表面分析方法获得了迅速的发展,它是目前分析化学领域中最活跃的分支之一。它的发展与催化研究、材料科学和微型电子器件研制等有关领域内迫切需要了解各种固体表面现象密切相关。各种表面分析方法的建立又为这些领域的研究创造了很有利的条件。在表面组分分析方法中,除化学分析用电子能谱(ESCA)以外,俄欧电子能谱是最重要的一种。目前它已广泛地应用于化学、物理、半导体、电子、冶金等有关研究领域中。本文简单介绍俄歇电子能谱(以下简称 AES)的原理、仪器和化学应用。     

甲烷分子价电子的能谱和动量谱

利用电子动量谱仪对甲烷分子价电子测量了电子动量谱和束缚能谱。实验中的入射电子能量为１０００ｅＶ加电子束缚。实验结果与Ｈａｒｔｒｅｅ－Ｆｏｃｋ理论及组态相互作用理论进行比较表明，两者相当一致。     

负离子光电子能谱技术发展及应用

负离子光电子能谱已经成为探索光谱和化学动力学基础问题的最为重要的技术之一。本文简要介绍了负离子光电子能谱的发展历史,回顾了负离子光电子能谱发展过程中的几种主要技术,包括为了提高分辨率而开发出的零动能能谱和慢电子速度成像技术以及为在气相条件下研究多电荷负离子及其对应中性分子电子特性而开发的电喷雾源与负离子光电子能谱结合的技术。随后介绍其在锕系元素及化合物、含铍化合物的电子结构及成键特征研究中的应用及进展。     

Organization-induced charge redistribution in self-assembled organic monolayers on gold

The charge redistribution that occurs within dipolar molecules as they self-assemble into organized organic monolayer films has been studied. The extent of charge transfer is probed by work function measurements, using low-energy photoelectron spectroscopy (LEPS), contact potential difference (CPD), and X-ray photoelectron spectroscopy (XPS), with the latter providing fine details about the internal charge distribution along the molecule. In addition, two-photon photoelectron spectroscopy is applied to investigate the electronic structure of the adsorbed layers. We show that charge transfer acts to reduce the dipole-dipole interaction between the molecules but may either decrease or increase the molecule-to-surface dipole moment.     

Recent advances in dual mode charge compensation for XPS analysis

Dual mode charge compensation has been used successfully for many years to enable X-ray photoelectron spectroscopy (XPS) analysis of a variety of insulating samples. This approach uses a combination of low energy electrons and argon to compensate for positive charge build-up during irradiation by X-rays. Whilst this method works with no detectable side effects in most cases, it was recently reported that the chemical bonding states of some Cr(VI) oxides may be modified by prolonged exposure to the flood source. In this work, we demonstrate successful dual mode charge compensation of CrO₃ with no discernible sample modification from the flood source. Under the same flood source conditions, we extend the analysis to other systems known to undergo reduction and present charge compensated XPS data for V₂O₅ and a copper-based metal-organic framework (MOF) showing little or no modification from the flood source, even with prolonged exposure.     

Interactions of iodoperfluorobenzene compounds with gold nanoparticles

Understanding the interactions of small molecules with gold nanoparticles is important for controlling their surface chemistry and, hence, how they can be used in specific applications. The interaction of iodoperfluorobenzene compounds with gold nanoparticles was investigated by UV-Vis difference spectroscopy, surface enhanced Raman spectroscopy (SERS) and Synchrotron X-ray photoelectron spectroscopy (XPS). Results from UV-Vis difference spectroscopy demonstrated that iodoperfluorobenzene compounds undergo charge transfer complexation with gold nanoparticles. SERS of the small molecule-gold nanoparticle adducts provided further evidence for formation of charge transfer complexes, while Synchrotron X-ray photoelectron spectroscopy provided evidence of the binding mechanism. Demonstration of interactions of iodoperfluorobenzene compounds with gold nanoparticles further expands the molecular toolbox that is available for functionalising gold nanoparticles and has significant potential for expanding the scope for generation of hybrid halogen bonded materials.     

单色化X射线对薄膜表面高分子降解行为的影响

采用聚甲基丙烯酸甲酯(PMMA)和苯乙烯-丙烯腈无规共聚物(SAN)薄膜体系, 在不同的实验温度下, 研究了单色化的X射线对其中一个组分(PMMA)降解行为的影响.     

ESCA-untersuchungen zur ladungsverteilung in alkylierten thioharnstoffderivaten und verwandten thiocarbonylverbindungen

The S 2p, N 1s and C 1s electron binding energies of some substituted thiourea derivatives, isothiouronium salts, thiazolthiones, 1,3,5-thiadiazin-2-thiones and 1,3,5-thiadiazinium salts have been measured using the X-ray photoelectron spectroscopy (ESCA). From binding energy shifts information concerning the charge distribution on the atoms in the molecules was obtained. The positive charge of the isothiouronium salts was found to concentrate on carbon and nitrogen atoms. The charge of the 1,3,5-thiadiazinium cations was found to be delocalized demonstrating the pseudoaromatic character of the electronic system.     

镧系离子掺杂TiO2的制备及其对咪唑降解反应的光催化活性

 以TiCl4和镧系元素的氯化盐溶液为前驱体,采用溶胶-凝胶法制备了不同含量镧系离子掺杂的TiO2光催化剂,用X射线衍射(XRD)、 光致发光光谱(PLS)、 表面光电压谱(SPS)和X射线光电子能谱(XPS)对催化剂进行了表征. XRD结果表明,样品为锐钛矿和金红石的混晶相,镧系离子未进入到TiO2晶格中. PLS和SPS测定结果表明,随着掺杂离子的不同和掺杂含量的不同,样品的谱强度呈现有规律的变化. 在紫外光照射下,以咪唑为目标降解物比较了催化剂的光催化活性. 结果表明,适当含量的镧系离子掺杂可有效促进TiO2表面光生载流子的分离,从而显著提高其光催化活性.     

Photoresponse of p-type zinc-doped iron(III) oxide thin films

Stable zinc-doped iron(III) oxide thin films that exhibit p-type behavior were synthesized by spray pyrolytic deposition (SPD) on conducting indium-doped tin oxide-coated glass substrate. The highest photocurrent density of 1.1 mA/cm2 was observed at an illumination intensity of 40 mW/cm2 at -0.8 V vs Pt for zinc-doped p-Fe2O3 samples prepared at an optimum substrate temperature of 663 K using an optimum spray time of 70 s. A quantum efficiency of 21.1% at 325 nm was found for SPD samples prepared using a dopant concentration of 0.0088 M zinc nitrate hexahydrate. X-ray diffraction results showed structures of alpha-Fe2O3 and ZnFe2O4. A direct band gap energy of 2.2 eV was found from monochromatic photocurrent density data and agrees closely with the band gap obtained from UV-vis absorption. The X-ray photoelectron spectroscopy results also confirm the presence of zinc dopant (4.0 atomic %) in thin films of zinc-doped p-Fe2O3.     

Chemically resolved photovoltage measurements in CdSe nanoparticle films

Light-induced chemically resolved electrical measurements (CREM) under controlled electrical conditions are used to study photovoltaic effects at selected regions in nanocrystalline CdSe-based films. The method, based on X-ray photoelectron spectroscopy (XPS), possesses unique capabilities for exploring charge trapping and charge transport mechanisms, combining spectrally filtered input signals with photocurrent detection and with a powerful, site-selective, photovoltage probe.     

基于掺Zn氮化碳和BiVO4构建Z型光催化系统实现完全分解水

随着现代工业的迅猛发展和化石燃料的过量使用, 全球范围内能源和环境问题日益严峻, 因此利用丰富的太阳光能分解水来直接制取清洁的氢气具有诱人的应用前景. 目前, 聚合物半导体石墨相氮化碳(g-C3N4)因其廉价、稳定、不含金属组分和独特的电子能带结构已被广泛应用于光解水产氢研究. 然而, 氮化碳具有结晶度差、光生载流子易复合的缺点.众所周知, Z型体系可以很好地减少电子和空穴的复合问题. 同时, 催化剂只需分别满足光解水过程的一端, 这使得半导体光催化剂的选择非常丰富, 可以大大拓宽材料体系. 因此, 将g-C3N4运用到Z型体系中的研究得到了广泛关注. 然而, 这些研究多集中在如何增强g-C3N4的产氢能力方面, 对实现水的完全分解的研究鲜见报道.本实验设计了这样一种Z型体系: 使用掺Zn的g-C3N4作为产氢端, BiVO4作为产氧端, Fe3+/Fe2+作为氧化还原对. 实验结果表明, 该体系可以在全波段下实现水的完全分解(氢氧比为2:1), 并且保持相当高的稳定性.实验所使用的氮化碳为固相法烧结尿素制得, Zn的掺杂采用浸渍法, 同时通过水热法合成BiVO4, 使用Pt作为助催化剂. 通过搭建含有不同组成成分的Z型体系, 将它们的性能和表征结果进行比较分析.通过XRD, UV-Vis, SEM和XPS等测试手段对催化剂进行表征. XRD分析结果表明成功合成了掺杂Zn的石墨相氮化碳. UV-Vis则显示随着Zn浓度的提高, 吸收边发生变化. 通过改变掺杂Zn的浓度, 得到了能够实现完全分解水的Z型体系,其最佳掺杂比例为: ZnCl2和氮化碳的质量比为1:10. 为了排除单催化剂和Pt颗粒对完全分解水性能的影响, 分别作了单独产氢端、单独产氧端、预负载Pt和光沉积Pt的性能测试. 从SEM中没有发现g-C3N4和BiVO4的异质结结构. 这些结果表明所搭建的是典型的利用氧化还原离子对为中间电子传输载体的Z型体系, 经长达12 h的持续测试证明其具有较高的稳定性.为了研究Zn在构建Z型中所起的作用, 分别采用文献中报道的原位和浸渍法实现Zn的掺杂. 对这两种掺杂方式的性能测试表明, 只有采用浸渍法时, 所构建的Z型体系具有完全分解水的能力. 对这两种方法得到的掺Zn氮化碳进行表面化学组成和价态(XPS)的分析. 结果显示, 两种掺杂方法都可以通过形成Zn=N键的形式实现Zn的掺杂, 但浸渍法使Zn在g-C3N4表面分布更均匀, 同时对氮化碳原本三嗪环的破坏较小, 因此具有更好的还原能力, 可以与BiVO4匹配以构成Z型体系.实验通过采用掺杂Zn的氮化碳作为产氢催化剂, BiVO4作为产氧催化剂, Fe3+/Fe2+作为氧化还原中间体, 构建了典型的Z型体系. 该体系在Zn的掺杂浓度为10%时能够实现长时间稳定的完全分解水.     

Charging of ionic liquid surfaces under X-ray irradiation: the measurement of absolute binding energies by XPS

Ionic liquid surfaces can become electrically charged during X-ray photoelectron spectroscopy experiments, due to the flux of photoelectrons leaving the surface. This causes a shift in the measured binding energies of X-ray photoelectron peaks that depends on the magnitude of the surface charging. Consequently, a charge correction method is required for ionic liquids. Here we demonstrate the nature and extent of surface charging in ionic liquids and model it using chronopotentiometry. We report the X-ray photoelectron spectra for a range of imidazolium based ionic liquids and investigate the use of long alkyl chains (C(n)H(2n+1), n ≥ 8) and the imidazolium nitrogen, both of which are part of the ionic liquid chemical structure, as internal references for charge correction. Accurate and reproducible binding energies are obtained which allow comparisons to be made across ionic liquid-based systems.