有机显微组分的二次离子质谱研究

采用二次离子质谱技术（ＳＩＭＳ）对煤及源岩中不同成熟度的镜质体、丝质体、沥青和笔石进行了详细研究。结果表明不同显微组分具有不同的ＳＩＭＳ谱图，反映出其化学组成和结构的差异性，且ＣＨ２＾＋／ＣＨ３＾＋参数变化趋势可以用来评价有机组分的热演化规律。同时说明ＳＩＭＳ技术是有机显微组分化学成分和结构研究的有效手段。     

二次离子质谱生物成像

二次离子质谱作为目前空间分辨率最高的质谱成像技术,以其免标记、高灵敏、多组分检测优势和亚微米级高空间分辨成像优势为诸多生命科学问题的研究提供了全新的分析手段,在基础细胞生物学、组织生理病理学、生物医药与临床医学等领域的研究中得到了广泛应用.本文综述了二次离子质谱在生物组织、细胞、仿生生物膜等体系中的质谱成像研究进展.     

一种新型二次离子质谱的一次离子源及其离子光学系统

本研究设计了一种新型用于二次离子质谱的一次离子源及其离子光学系统.通过此一次离子源,大气压下产生的一次离子可以被加速、聚焦并传输到位于真空条件下的样品表面并电离样品得到可供质谱仪分析的二次离子.通过理论模拟结合实验系统研究了此一次离子源的主要组成部分——离子光学系统的原理、结构和性能.以电喷雾电离源为例,成功地将大气压...     

磷脂液相二次离子质谱分析中的分子离子簇

对3种极性头不同的磷脂DMPG、DMPC、DMPE的液相二次离子质谱分析中出现 的分子离子簇现象进行了系统的研究。结果表明，虽然分子离子簇的形成与许多因素有关， 如PH值、离子强度等，但起决定作用的是样品在底物中的浓度，浓度增大有利于分子离子簇 的形成。研究还发现，由不同种类磷脂分子形成的分子离子簇峰明显高于由同种磷脂分子所 形成的分子离子簇峰，指出异种磷脂分子间的簇离子形成能力高于同种磷脂分子。此外还讨 论了磷脂分子在离子源条件下的稳定性、裂解规律及相互作用等。结果表明，本实验所选用 的磷脂分子在LSIMS条件下是稳定的，均能得到较强的分子离子峰，其主要碎片峰是磷酰键断裂而产生的碎片离子峰。     

飞行时间二次离子质谱在指纹分析中的研究进展

指纹作为接触类犯罪案件现场最常见的痕迹之一,基于其形态学价值及承载的物质进行分析是个体识别、侦查破案的重要手段。飞行时间二次离子质谱技术（TOF-SIMS）是一种兼具高质量分辨率和高空间分辨能力的表面分析技术,能够同时获得待测物质的质谱信息和成像分布。相较于其他理化分析技术,TOF-SIMS所具备的快速检验、无需前处理、原位近无损分析等优势使其逐渐成为指纹分析领域的前沿课题。该文基于TOF-SIMS在成像增强、物质分析、犯罪信息挖掘等指纹分析领域的研究现状展开综述,分析其在公安实战中的应用前景,以期为该技术在指纹检验领域的推广奠定基础。     

用液相二次离子质谱技术探测Melittin与磷脂膜的相互作用

利用液相二次离子质谱技术(LSIMS)结合特异性蛋白酶降解研究了膜结合Melittin的“抛锚”状态.结果显示,Melittin(蜂毒素)分子在磷脂膜上为平躺α-螺旋结构,其螺旋中含Lys_7,Lys_(21),Arg_(22)的一侧朝向磷脂膜的外部.这一发现对蜂毒素插膜机制的研究具有十分重要的意义.结果还表明,质谱技术与专一性蛋白水解酶的结合为膜插入机制的研究提供了一个崭新的、行之有效的方法.     

基于飞行时间二次离子质谱的指纹遗留人个体识别的研究

指纹作为法庭科学领域中用于人身认定的重要物证,蕴含了丰富的个体信息。但是,在实际案件现场中,提取到的多为模糊和残缺的指纹,无法利用传统的形态比对方法进行鉴定;而且指纹中物质成分复杂,也很难通过检测其中的具体物质实现遗留人的溯源分析。飞行时间二次离子质谱（TOF-SIMS）能够在不破坏检材的情况下获得指纹物质的离子信号,同时获得对应的离子分布图像,为利用指纹物质信息进行个体识别提供了可能。本研究利用TOF-SIMS采集了5名志愿者十指指纹的质谱信息,初步探究了基于指纹物质离子信号进行遗留人个体识别的可行性。首先筛选出98种代表指纹物质的离子信号,利用主成分分析法对筛选出的离子信号强度进行降维,再将降维后的主成分新变量输入到不同的分类器中对比。结果表明,使用无监督的层次聚类法的结果与实际的分类相差较大,难以进行个体区分;使用有监督的Fisher判别法对个体进行判别,正确率可以达到94%,交叉验证的正确率也达到了90%;将数据输入到多层感知机神经网络中,经过多次训练可以得到更加理想的结果。本研究借助多种统计分析方法建立了个体分类和预测模型,为指纹证据价值的提升提供了新渠道,也为后期利用指纹物...     

基于飞行时间二次离子质谱成像技术的人民币上指纹化学成像研究

长期流通过的人民币上潜在指纹的显现一直是法庭科学领域研究的难点之一。飞行时间二次离子质谱(TOF-SIMS)技术具有原位、准无损、高通量、可多组分平行分析和空间分辨率高等优势。本研究利用TOF-SIMS技术对人民币表面的潜在指纹进行化学成像,比较了TOF-SIMS与几种传统方法的显现效果,研究并分析此技术具有的独特优势,从普适性、灵敏度和指纹三级特征获取的角度进一步探讨了方法的适用性。利用此技术对指纹中的外源性物质进行了分析,检测出保湿乳成分中丙三醇的分子离子峰(m/z 92.06)和碎片离子峰(m/z 43.02),并显示清晰的指纹图像。研究结果表明,TOF-SIMS技术为长期流通过的人民币上潜在指纹的显现提供了一种有效的方法,并有望用于其表面上指纹中物质的检测。     

Quantitative analysis of films by ion microbeam methods. II: SIMS

The performance indicators for a quantitative analysis (random and systematic uncertainties) are defined, and their origin in SIMS (secondary ion mass spectrometry) is discussed. The different methods for quantitative SIMS analysis: calibration curve approach, implanted standard method, relative sensitivity factor (RSF) method, are discussed. Examples are given for successful quantitative SIMS analyses of epilayers, implanted depth profiles and interface (IF) impurity distribution. In conclusion, a comparison is made between SIMS and other advanced techniques for thin film analysis.     

SIMS imaging: Apparatus and applications

Apparatus, software and methods were developed for a microbeam analysis of semiconductor structures or devices based on Si and GaAs with secondary ion mass spectrometry. Semiquantitative analysis methods were based on measuring the relative elemental sensitivity factors. As examples of apparatus and methods applications investigations of various semiconductor materials and devices are described.     

A New Experimental Method for Investigations on Microstructure of Liquid-Vapor Interface?

Many physical, chemical, and biological processes happen in liquid-vapor interface and are profoundly influenced with the local microstructures. In contrast to the liquid bulk, molecular orientation is the remarkable one of asymmetric structural features of the interface. Here we report an experimental method, namely, electron-impact time-delayed mass spectrometry and give a brief review about our recent progresses. This brand-new method not only enables us to have more insights into the interfacial structures, as done with small-angle X-ray and neutron scatterings and vibrational sum frequency generation spectroscopy, but also provides opportunity to explore the electron-driven chemical reactions therein.      

Investigation of gettering effects in CZ-type silicon with SIMS

Ion implantation is a well-known standard procedure in electronic device technology for precise and controlled introduction of dopants into silicon. However, damage caused by implantation acts as effective gettering zones, collecting unwanted metal impurities. This effect can be applied for proximity gettering reducing the concentration of impurities in the active device region. In this study the consequences of high-energy ion implantation into silicon and of subsequent annealing were analysed by means of secondary ion mass spectrometry (SIMS). Depth profiles were recorded of such impurities as copper, oxygen and carbon to obtain information about their gettering behaviour. The differences in impurities gettering behaviour were studied as a function of the implanted ions, P and Si, of the implantation dose and annealing time at T=900°C. Besides impurities gettering at the mean projected range (Rp) of implanted ions, Rp-effect, defects at around half of the projected ion range, Rp/2-effect, and even in some cases beyond Rp, trans-Rp-effect, have also been found to be effective in gettering of material impurities.     

Characterization of bidentate phosphoryl compounds on soil particulates using SIMS

The presence of organic compounds as surface contaminants on particles can provide valuable data about the particles environment, but identification can be analytically challenging. This is true particularly for compounds that have the potential for strong surface binding, such as compounds capable of multidentate attachment. Direct analysis using time‐of‐flight secondary ion mass spectrometry was evaluated for characterization of soil particles contaminated with low concentrations of two bidentate organophosphoryl compounds, diphenyl‐N,N‐di‐n‐butylcarbamoylmethylphosphine oxide and tetraphenylmethylene diphosphine dioxide. Molecular ions were formed by cationization with H⁺ and alkali elements Na⁺ and K⁺ that are indigenous to the particle surface chemistry. Spectra generated from a contaminated calcareous soil were dominated by K⁺‐containing ions, whereas spectra from a sandy loam had more abundant Na⁺‐species. Cation‐bound dimers were also formed which favored incorporation of K⁺, and a unique aluminosilicate‐phosphoryl conjugate cation was also formed when the diphosphoryl ligand was present on the surface. The phosphoryl ligands also underwent fragmentation reactions, the course of which varied depending on the cation that was bound. Minimum detectable surface concentrations were evaluated and were in the 0.04–0.2 monolayer range, depending on the compound and soil particle matrix they was bound to. The ion signature was detected on soil particle surfaces for time periods exceeding six months, suggesting that the characterization approach could be used for environmental exposure history at times well beyond initial exposure. Copyright © 2009 John Wiley & Sons, Ltd.     

Organic surface analysis with time-of-flight SIMS

In the last few years static secondary ion mass spectrometry (SSIMS) has proved to be a versatile and indispensable method for determining the composition and the structure of the outermost molecular layers of a surface. In particular when using a high-resolution time-of-flight (TOF) mass analyser a high sensitivity can be obtained with SSIMS. In this review it will be shown that the analysis of surfaces with a well-defined chemical structure by means of SSIMS has given detailed insight into the relation between the structure of the fragment ions formed by ion bombardment of the surface and the original surface structure. These studies have also improved the possibilities for quantifying the SSIMS results. In addition, the better knowledge about the ionformation process can be used for the analysis of surfaces of unknown composition and structure. Finally, some recent applications of SSIMS will be presented.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Surface characteristics of glass fibres covered with an aluminum layer after a chemical modification process using secondary ion mass spectrometry (SIMS) and atomic force microscopy (AFM)

Results show investigations of surface of modified glass fibres (before and after chemical modification of their surface), which are candidates for future original matrix-less reference material for volatile ethene analytes (C₂H₄). Used analytical methods are secondary ion mass spectrometry and atomic force microscopy. The investigations were aimed at observation of changes and processes which occurred on the surface of glass fibres covered with an aluminum layer and constituting an ethane carrier.The paper describes the procedure of chemical modification of the surface of 3 cm segments of glass fibres covered with an aluminum layer (660/680 μm, external diameter of quartz/external Al diameter), a surfactant constituting a source of ethene. Ethene (a measured constituent) in a standard gas mixture is obtained during the process of controlled thermal decomposition of a surface compound in a stream of rarefied gas (such kind of mixture is called matrix-less reference material).     

In situ XPS and SIMS analysis of O2+ beam‐induced silicon oxidation

The chemical composition variation of silicon under 4 keV O₂⁺ ion beam bombardment at different incident angles was studied by in situ small‐area XPS. The changes in secondary ion profile (³⁰Si⁺, ⁴⁴SiO⁺, ⁵⁶Si₂⁺, ⁶⁰SiO₂⁺) during oxygen ion beam bombardment also have been monitored. We present a direct correlation of the changes in secondary ion depth profile with surface composition during sputtering. Evolution of the secondary ion profile obtained from SIMS shows similar trends with variation of oxygen concentration in the crater surface measured by XPS. It is shown that when the oxygen ion beam incidence angle is < 40° silicon dioxide is the dominant species on the crater surface and the matrix ion species ratio (MISR) value for ⁴⁴SiO⁺/⁵⁶Si₂⁺ is higher than for ³⁰Si⁺/⁵⁶Si₂⁺. For incidence angles of >40°, the formation of sub‐oxide is favoured and thus the MISR value for ⁴⁴SiO⁺/⁵⁶Si₂⁺ is lower than for ³⁰Si⁺/⁵⁶Si₂. At 40° bombardment there are similar amounts of SiO₂ and sub‐oxides present on the crater surface and the MISR values for ⁴⁴SiO⁺/⁵⁶Si₂⁺ and ³⁰Si⁺/⁵⁶Si₂⁺ are also similar. Copyright © 2004 John Wiley & Sons, Ltd.     

Parallel detection,quantification, and depth profiling of peptides with dynamic-secondary ion mass spectrometry (D-SIMS) ionized by C60–Ar co-sputtering

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) using pulsed C₆₀⁺ primary ions is a promising technique for analyzing biological specimens with high surface sensitivities. With molecular secondary ions of high masses, multiple molecules can be identified simultaneously without prior separation or isotope labeling. Previous reports using the C₆₀⁺ primary ion have been based on static-SIMS, which makes depth profiling complicated. Therefore, a dynamic-SIMS technique is reported here. Mixed peptides in the cryoprotectant trehalose were used as a model for evaluating the parameters that lead to the parallel detection and quantification of biomaterials. Trehalose was mixed separately with different concentrations of peptides. The peptide secondary ion intensities (normalized with respect to those of trehalose) were directly proportional to their concentration in the matrix (0.01–2.5 mol%). Quantification curves for each peptide were generated by plotting the percentage of peptides in trehalose versus the normalized SIMS intensities. Using these curves, the parallel detection, identification, and quantification of multiple peptides was achieved. Low energy Ar⁺ was used to co-sputter and ionize the peptide-doped trehalose sample to suppress the carbon deposition associated with C₆₀⁺ bombardment, which suppressed the ion intensities during the depth profiling. This co-sputtering technique yielded steadier molecular ion intensities than when using a single C₆₀⁺ beam. In other words, co-sputtering is suitable for the depth profiling of thick specimens. In addition, the smoother surface generated by co-sputtering yielded greater depth resolution than C₆₀⁺ sputtering. Furthermore, because C₆₀⁺ is responsible for generating the molecular ions, the dosage of the auxiliary Ar⁺ does not significantly affect the quantification curves.     

Reduction of matrix effects in TOF‐SIMS analysis by metal‐assisted SIMS (MetA‐SIMS)

We investigated reduction of the matrix effect in time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) analysis by the deposition of a small amount of metal on the sample surfaces (metal‐assisted SIMS or MetA‐SIMS). The metal used was silver, and the substrates used were silicon wafers as electroconductive substrates and polypropylene (PP) plates as nonelectroconductive substrates. Irganox 1010 and silicone oil on these substrates were analyzed by TOF‐SIMS before and after silver deposition. Before silver deposition, the secondary ion yields from the substances on the silicon wafer and PP plate were quite different due to the matrix effect from each substrate. After silver deposition, however, both ion yields were enhanced, particularly the sample on the PP plate, and little difference was seen between the two substrates. It was therefore found that the deposition of a small amount of metal on the sample surface is useful for reduction of the matrix effect. By reducing the matrix effect using this technique, it is possible to evaluate from the ion intensities the order of magnitude of the quantities of organic materials on different substrates. In addition, this reduction technique has clear utility for the imaging of organic materials on nonuniform substrates such as metals and polymers. MetA‐SIMS is thus a useful analysis tool for solving problems with real‐world samples. Copyright © 2005 John Wiley & Sons, Ltd.