ToF-SIMS Analysis of Adsorbed Proteins: Principal Component Analysis of the Primary Ion Species Effect on the Protein Fragmentation Patterns

In time-of-flight secondary ion mass spectrometry (ToF-SIMS), the choice of primary ion used for analysis can influence the resulting mass spectrum. This is because different primary ion types can produce different fragmentation pathways. In this study, analysis of single-component protein monolayers were performed using monatomic, tri-atomic, and polyatomic primary ion sources. Eight primary ions (Cs(+), Au(+), Au(3) (+), Bi(+), Bi(3) (+), Bi(3) (++), C(60) (+)) were used to examine to the low mass (m/z < 200) fragmentation patterns from five different proteins (bovine serum albumin, bovine serum fibrinogen, bovine immunoglobulin G and chicken egg white lysozyme) adsorbed onto mica surfaces. Principal component analysis (PCA) processing of the ToF-SIMS data showed that variation in peak intensity caused by the primary ions was greater than differences in protein composition. The spectra generated by Cs(+), Au(+) and Bi(+) primary ions were similar, but the spectra generated by monatomic, tri-atomic and polyatomic primary ion ions varied significantly. C(60) primary ions increased fragmentation of the adsorbed proteins in the m/z < 200 region, resulting in more intense low m/z peaks. Thus, comparison of data obtained by one primary ion species with that obtained by another primary ion species should be done with caution. However, for the spectra generated using a given primary ion beam, discrimination between the spectra of different proteins followed similar trends. Therefore, a PCA model of proteins created with a given ion source should only be applied to datasets obtained using the same ion source. The type of information obtained from PCA depended on the peak set used. When only amino acid peaks were used, PCA was able to identify the relationship between proteins by their amino acid composition. When all peaks from m/z 12-200 were used, PCA separated proteins based on a ratio of C(4)H(8)N(+) to K(+) peak intensities. This ratio correlated with the thickness of the protein films and Bi(1) (+) primary ions produced the most surface sensitive spectra.     

应用渐进因子分析法研究SiO_2/Si样品俄歇深度剖析

首次利用渐进因子分析法对ＳｉＯ２／Ｓｉ样品俄歇深度剖析过程进行研究，发现ＳｉＯ２／Ｓｉ界面处有ＳｉＯｘ成分存在，ｘ值在１０～１５之间，厚度约为３０ｎｍ，含量接近５０％。Ａｒ＋离子束的轰击使得ＳｉＯ２薄膜内分解产生亚稳态ＳｉＯ２，含量在１７％左右。研究结果表明，渐进因子分析法非常适合于俄歇深度剖析的化学态分析。     

Detection of Copper Deposition on Anodes of Over-Discharged Lithium Ion Cells by GD-OES Depth Profiling

A method based on glow discharge optical emission spectroscopy (GD-OES) depth profiling is developed to detect copper deposition on graphite electrodes for the first time. Commercial 18650 cells with graphite anodes were subject to Cu dissolution by over-discharge to 0 V. On a first approach, the depth profiles for Cu show significant differences for over-discharged cells compared to a baseline graphite electrode from cells discharged to the end-of-discharge voltage. An accumulation of Cu is found on the anode surface by GD-OES, which is consistent with SEM and EDX. The trend of the total Cu amount is compared with ICP-OES measurements.     

Formation and Depth Profiling Analysis of Multilayers Derived from Sol-Gel Processing Using Dynamic SIMS, RBS, and TEM

Silica sol-gel single layer AR coatings are used in high peak power pulsed lasers due to their high laser induced damage threshold (LIDT) and their low refractive index (1.22). We have used sol-gel processing to spin and dip coat multilayers of alternating high index (zirconia/hafnia) and low index (base catalysed silica) sol-gels on to fused silica substrates. When tailored at the correct thickness these stacks have shown >95% reflectivity at 355 nm and normal incidence whilst retaining a high LIDT. Depth profiling using Dynamic Secondary Ion Mass Spectrometry (DSIMS) and Rutherford back scattering (RBS) through these multilayer coatings has revealed the effect of increasing the number of layers in the stack. Results are presented for both spin and dip coated multilayers and a significant difference in the interfacial boundary is seen between the two coating processes. These differences are related to changes in the LIDT of the coatings. Individual layer thicknesses were estimated using this technique and compared to values gained from UV-Visible spectroscopy. TEM analysis of an ion-milled cross-section of the multilayers was performed showing the colloidal silica coatings and the depth of interpenetration of the interfaces.     

Simulation Analysis on the Profiles of Droplets Wetting on the Substrates

To study the structural characteristics and physical properties of droplets sitting on the inclined substrates and cylindrical surfaces, wetting experiments are conducted in different cases. The profile curves of the droplets are recorded and extracted by a CCD camera and image processing, respectively. Contact angles are figured out by fitting the profile curves and taking the derivative at the front and rear triple points. Based on the experimental results, a Surface Evolver is employed to simulate the morphological changes by minimizing the total energy of the system. Furthermore, theoretical shapes and feature parameters, including the heights and the spreading distances of the droplets, which are hard to obtain by normal experimental measurements are provided. The contact-angle hysteresis when the heavy droplet sitting on the inclined substrate is discussed. Meanwhile, the evolutions of the contour of the three-phase contact line are predicted when heavy droplets spread on the convex and concave cylindrical surfaces, respectively. This study provides a finite-element analysis method to describe the surface properties of molten droplets on different substrates, and the simulation results agree well with the experimental results.     

Confocal Raman Microspectroscopy: Calculation of Corrected Depth Profiles of Wet‐Chemically Modified Polymer Films

Summary: A mathematical approach developed to correct depth profiles of wet‐chemically modified polymer films obtained by confocal Raman microscopy is presented which takes into account scattered contributions originated from a diffraction‐limited laser focal volume and the refractive index of the sample. The method is demonstrated in both virtual and real samples where it is shown that considerable differences between apparent and corrected depth profiles exist at the surface, especially when profiles with strong concentration gradients are dealt with or an instrument with poor depth resolution is used.

Comparison of depth profiles obtained by simple normalization (solid line) and normalization after correction of the data with respect to diffraction effects.     

Depth Profiling by AFM Nanoindentations and Micro‐FTIR Spectroscopy for the Study of Polymer Ageing

Summary: A method of depth profiling by AFM nanoindentations is developed for the characterisation of the heterogeneity of the mechanical properties of oxidised polymers. An increase or a decrease of the sample stiffness is measured close to the surface. A comparison with micro‐FTIR profiles and a knowledge of the photooxidation mechanism permit an interpretation of the chemical and physical changes and give new insights into the understanding of the ageing behaviour.

Photooxidation profile of a TMPC film measured by AFM (•) and by micro‐FTIR (♦) after irradiation.     

非晶Fe40Ni40P14B6合金阳极钝化膜的电子能谱研究

应用表面分析技术ＸＰＳ和ＡＥＳ（包括深度分布）分析了非晶Ｆｅ４０Ｎｉ４０Ｐ１４Ｂ６合金在Ｈ３ＢＯ３－Ｎａ２Ｂ４Ｏ７（ＰＨ＝９．２０）缓冲溶液中不同钝化时间形成的阳极钝化膜的元素化学状态、结构和化学组成，探讨了加入Ⅲ、Ｖ族Ｂ、Ｐ对非晶ＦｅＮｉ基合金钝化金钝化成膜的影响，并给出了阳极钝性成膜的一种机制。     

Systematic Temperature Effects in the Argon Cluster Ion Sputter Depth Profiling of Organic Materials Using Secondary Ion Mass Spectrometry

A study is presented of the effects of sample temperature on the sputter depth profiling of two organic materials, NPB (N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine) and Irganox 1010, using a 5 keV Ar₂₀₀₀ ⁺ cluster ion beam and analysis by secondary ion mass spectrometry. It is shown that at low temperatures, the yields increase slowly with temperature in accordance with the Universal Sputtering Yield equation where the energy term is now modified by Trouton’s rule. This occurs up to a transition temperature, T _T, which is, in turn, approximately 0.8T _M, where T _M is the sample melting temperature in Kelvin. For NPB and Irganox 1010, these transition temperatures are close to 15 °C and 0 °C, respectively. Above this temperature, the rate of increase of the sputtering yield rises by an order of magnitude. During sputtering, the depth resolution also changes with temperature with a very small change occurring below T _T. At higher temperatures, the depth resolution improves but then rapidly degrades, possibly as a result first of local crater surface diffusion and then of bulk inter-diffusion. The secondary ion spectra also change with temperature with the intensities of the molecular entities increasing least. This agrees with a model in which the molecular entities arise near the crater rim. It is recommended that for consistent results, measurements for organic materials are always made at temperatures significantly below T _T or 0.8 T _M, and this is generally below room temperature.

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介孔分子筛孔道结构对药物巯甲丙脯酸释放性能的影响

以巯甲丙脯酸为药物模型, 研究了不同孔道结构的介孔分子筛载体的药物释放性能.     

Depth Profile Analysis on the Nanometer Scale by a Combination of Electron Probe Microanalysis (EPMA) and Focused Ion Beam Specimen Preparation (FIB)

Electron probe microanalysis (EPMA) offers high sensitivity and high accuracy in quantitative measurements of chemical compositions and mass coverages. Owing to the low detection limits of the wavelength-dispersive technique, monolayers with mass coverages of about 0.05µgcm^–2 can be detected. Assuming a density of 5gcm^–3 this corresponds to a thickness of 0.1nm. With these advantages in mind, EPMA was extended to depth profile analysis in the sub-micron range using a surface removal technique.The present paper shows how depth profile analysis can be improved by combining EPMA and the focused ion beam (FIB) technique. The focused ion beam system uses a Ga⁺ ion beam. The ion beam allows the milling of defined geometries on the nanometer scale, so that very shallow bevels with exactly defined angles in relation to the surface can be obtained. Low surface damage is expected due to low sputtering effects. Calibrated WDX measurements along the bevel deliver quantitative concentration depth profiles. First results obtained with this new combination of methods will be presented for a multilayered sample used in optical data storage.     

Effects of pretreatment temperature on the analysis of size-fractionated aerosol particles using ToF-SIMS

Size-fractionated aerosol particles were collected with a MOUDI 10-stage cascade impactor from an urban roadside place in a downtown area of Hong Kong. Fine aerosol particulate samples from stage 6 (aerodynamic particle diameter between 0.56 and 1 μm) and stage 9 (aerodynamic particle diameter between 0.10 and 0.18 μm) were pretreated at a chosen temperature, including −100°C, −50°C, 25°C, and 60°C, in a load lock chamber and then analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS) at the same temperature (−100°C). Principal component analysis (PCA) was applied to further analyze ToF-SIMS spectra of aerosol particles with different pretreatment temperatures from two selected stages. ToF-SIMS results showed that the intensities of aliphatic hydrocarbon ions such as C₄H₇⁺ and C₄H₉⁺ and amine ions such as C₂H₈N⁺ and C₄H₁₂N⁺ decreased with an increase of the pretreatment temperature under ultrahigh vacuum conditions. We have shown that analyses of this type of aerosol particles using ToF-SIMS should not be conducted at ambient temperature but at low temperature (eg, −50°C). In addition, we also developed a procedure that can be used to analyze aerosol particle samples under ultrahigh vacuum environment.     

硒素营养对麦芽质量指标的影响

大麦在制麦过程中的溶解对麦芽质量、啤酒的酿造以及成品啤酒的质量有重要的影响。本文利用生物转化技术，以微量元素硒作为制麦添加剂，以提高麦芽质量。本实验中，浸麦采用第一次浸6h以下采用浸二断四的工艺，浸水时每小时换水一次，一直通风，当浸麦度达40％～42％时，用硒溶液处理1h。发芽前两天每天补水两次，后期促进其凋萎。焙燥过程中前期低温大风量排湿，中期合理稳步升温，后期严格控制焙焦温度，使整个过程稳定。测定制得的成品麦芽的糖化力、α-AN、无水浸出率、色度等质量指标。发现硒对麦芽的质量有一定的影响。     

饮用水水质与人体健康

水对人体是极其重要的,本文介绍了水中常量、微量元素、水的卫生、水分子簇团大小等对人体健康的重要影响,并由此谈到了自来水的消毒以及对纯净水的几点探索性认识。     

The application of ToF-SIMS to the analysis of herbicide formulation penetration into and through leaf cuticles

Understanding the movement of the active ingredient in relation to the other formulation components following application is crucial to an overall understanding of herbicide performance. We describe the novel use of time-of-flight secondary ion mass spectrometry (ToF-SIMS) as a tool for following the movement of herbicide formulation components into and across plant cuticles. This technique provides new insights since it provides both high (sub-micron) spatial resolution combined with the chemical specificity associated with organic mass spectrometry. The components studied include the oligomeric ethoxylate surfactants Synperonic A7 and A20 and active ingredient Sulfosate (trimesium glyphosate). The movement of these molecules, both separately and when combined in a simple formulation, into the surface of Prunus laurocerasus leaves and across the isolated plant cuticle was investigated and clear differences in penetration/diffusion behaviour were identified. ToF-SIMS was uniquely able to (simultaneously) spatially resolve all the species involved, including the anion and cation components of the active ingredient. Also, using spectral reconstructions from the imaging raw data streams, the behaviour of individual oligomers within the surfactant distributions, could be assessed. The observations are discussed with reference to the action of surfactants identified in parallel micro-structural studies and the current understanding of herbicide uptake.     

非晶Fe40Ni40P14B6合金阳极钝化膜的电子能谱研究

应用表面分析技术XPS和AES（包括深度分布）分析了非晶Fe40Ni40P14B6合金在H3BO3－Na2B4O7（pH＝9．20）缓冲溶液中不同钝化势或不同钝化时间形成的阳极钝化膜的元素化学状态、结构和化学组成，探讨了加入Ⅲ、Ⅴ族B、P对非晶FeNi基合金钝化成膜的影响，并给出了阳极钝性成膜的一种机制．     

ToF-SIMS imaging of the nanoscale phase separation in polymeric light emitting diodes: effect of nanostructure on device efficiency

The nanostructure of the light emissive layer (EL) of polymer light emitting diodes (PLEDs) was investigated using force modulation microscopy (FMM) and scanning time-of-flight secondary ion mass spectrometry (ToF-SIMS) excited with focused Bi(3)(2+) primary beam. Three-dimensional nanostructures were reconstructed from high resolution ToF-SIMS images acquired with different C(60)(+) sputtering times. The observed nanostructure is related to the efficiency of the PLED. In poly(9-vinyl-carbazole) (PVK) based EL, a high processing temperature (60 °C) yielded less nanoscale phase separation than a low processing temperature (30 °C). This nanostructure can be further suppressed by replacing the host polymer with poly[oxy(3-(9H-9-carbazol-9-ilmethyl-2-methyltrimethylene)] (SL74) and poly[3-(carbazol-9-ylmethyl)-3-methyloxetane] (RS12), which have similar chemical structures and energy levels as PVK. The device efficiency increases when the phase separation inside the EL is suppressed. While the spontaneous formation of a bicontinuous nanostructure inside the active layer is known to provide a path for charge carrier transportation and to be the key to highly efficient polymeric solar cells, these nanostructures are less efficient for trapping the carrier inside the EL and thus lower the power conversion efficiency of the PLED devices.     

Effect of Culture Conditions on Fatty Acid Profiles of Bacteria and Lipopolysaccharides of the Genus Pseudomonas—GC-MS Analysis on Ionic Liquid-Based Column

The profiling of bacterial fatty acids is a well-established technique in identifying and classifying bacteria. Cultivation conditions may affect the biosynthesis, thereby, changing the fatty acid profile in bacteria. The effect of the culture conditions on the fatty acid components of Pseudomonas aeruginosa PAO1, Pseudomonas aeruginosa ATCC 27853, Pseudomonas aeruginosa polyresistant and Pseudomonas putida all are aligned to the genus Pseudomonas. The fatty acids in the lipopolysaccharides of Pseudomonas aeruginosa PAO1 were also examined. The effects of the cultivation conditions were followed by using agar and blood agar media at the characteristic temperatures, 25 °C, 37 °C and 42 °C, respectively, and an analysis was made during the 1st, 3rd and 5th day following inoculation. In addition to quantitative differences, we also experienced qualitative differences in the fatty acid profiles which detect newly appearing fatty acids, due to changes in environmental factors. The application of ionic liquid-based column unveils new possibilities for the analyses of fatty acids in GC-MS experiments for bacterial fatty acid profiling. The validation results (response linearity, limit of detection, limit of quantification, system suitability, intraday and interday repeatability and accuracy) show the high separation efficiency of the ionic liquid-based column in the analyses.     

BSA adsorption on titanium: ToF-SIMS investigation of the surface coverage as a function of protein concentration and pH-value

The adsorption properties of bovine serum albumin (BSA) on pure titanium (99.99%+) were studied by time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). For this purpose, films consisting of BSA were prepared on cleaned titanium sheets in a phosphate buffered solution under different conditions and analysed by ToF-SIMS. The dependence of the surface coverage on the concentration of the protein solution could be determined from the secondary ion mass spectrometry signals. The results agree satisfactorily with the corresponding results obtained by XPS. The observed adsorption behaviour can be fitted by the well-known formula describing a Langmuir isotherm. The Langmuir constant for pH 7 was found to be K = 174±99lg ^{- 1} K = {174}\pm {99}{\lg^{{ - 1}}} .