有机波谱分析双语课件 (45).pdf

《有机波谱分析双语课件 (45).pdf》由会员分享，可在线阅读，更多相关《有机波谱分析双语课件 (45).pdf（14页珍藏版）》请在淘文阁 - 分享文档赚钱的网站上搜索。

1、X-射线光电子能谱 II 有机波谱分析 Organic Spectroscopic Analysis X-ray Photoelectron Spectroscopy(XPS)II Where do binding energy shifts come from?Or how can we identify elements and compounds?Electron-electron repulsion Electron-nucleus attraction Electron Nucleus Binding Energy Pure Element Electron-Nucleus Sepa

2、ration Fermi Level Look for changes here by observing electron binding energies Binding Energy Shifts Elemental Shifts Binding Energy(eV)Element2p3/23pFe70753654Co77860718Ni85367786Cu93375858Zn102289933Electron-nucleus attraction helps us identify theelementsCarbon-Oxygen Bond Valence Level C 2p Cor

3、e Level C 1s Carbon Nucleus Oxygen Atom C 1s Binding Energy Electron-oxygen atom attraction(Oxygen Electro-negativity)Electron-nucleus attraction(Loss of Electronic Screening)Shift to higher binding energy Chemical Shifts-Electronegativity Effects The exact binding energy of an electron depends not

4、only upon the level from which photoemission is occurring,but also upon:1.the formal oxidation state of the atom 2.the local chemical and physical environment Changes in either(1)or(2)give rise to small shifts in the peak positions in the spectrum-so-called chemical shifts.Such shifts are readily ob

5、servable and interpretable in XPS spectra.Chemical ShiftsShifts 6 C 1s spectrum of CF3COOCH2CH3 285 XPS-Chemical Shifts In practice,the ability to resolve between atoms exhibiting slightly different chemical shifts is limited by the peak widths which are governed by a combination of factors;especial

6、ly 1.the intrinsic width of the initial level and the lifetime of the final state 2.the line-width of the incident radiation-which for traditional x-ray sources can only be improved by using x-ray monochromators 3.the resolving power of the electron-energy analyzer In most cases,the second factor is

7、 the major contribution to the overall line width.Chemical Shifts 8 XPS-Chemical Shifts S2p spectrum of sodium hyposulfite 6.04ev S-2 S+6 170 165 160 BE（eV）FunctionalGroupBinding Energy(eV)hydrocarbonC-H,C -C 285.0amineC-N 286.0alcohol,etherC-O-H,C -O-C 286.5Cl bound to CC-Cl 286.5F bound to CC-F 28

8、7.8carbonylC=O 288.0Chemical Shifts-Electronegativity Effects Example 1:Oxidation States of Titanium Titanium exhibits very large chemical shifts between different oxidation states of the metal Note:(i)the two spin orbit components exhibit the same chemical shift(4.6 eV)Chemical Shifts Chemical Shif

9、ts of Si Oxide Si 2p3/2 Core Level Applications of X-ray Photoelectron Spectroscopy(XPS)XPS Analysis of Pigment from Mummy Artwork 150 145 140 135 130 Binding Energy(eV)PbO2 Pb3O4 500 400 300 200 100 0 Binding Energy(eV)O Pb Pb Pb N Ca C Na Cl XPS analysis showed that the pigment used on the mummy w

10、rapping was Pb3O4 rather than Fe2O3 Egyptian Mummy 2nd Century AD World Heritage Museum University of Illinois Analysis of Carbon Fiber-Polymer Composite Material by XPS Woven carbon fiber composite XPS analysis identifies the functional groups present on composite surface.Chemical nature of fiber-p

11、olymer interface will influence its properties.-C-C-C-O-C=O-300-295-290-285-280Binding energy(eV)N(E)/EAnalysis of Materials for Solar Energy Collection by XPS Depth Profiling-The amorphous-SiC/SnO2 Interface The profile indicates a reduction of the SnO2 occurred at the interface during deposition.Such a reduction would effect the collectors efficiency.Photo-voltaic Collector Conductive Oxide-SnO2 p-type a-SiC a-Si Solar Energy SnO2 Sn Depth 500 496 492 488 484 480 Binding Energy,eV Data courtesy A.Nurrudin and J.Abelson,University of Illinois