Luc Van Vaeck

Static secondary ion mass spectrometry : (S-SIMS). Part 1. Methodology and structural interpretation

Static secondary ion mass spectrometry (S-SIMS) allows the chemical characterization of the constituents in the upper monomolecular layer of a solid sample. Within the range of micro-analytical methods, S-SIMS occupies a rather unique position in that it combines monolayer sensitivity with the capability to generate molecular information. In general, elemental ions, structural fragments, molecular and adduct ions are generated from both inorganic and organic molecules, including polymers. The chemical analysis of the upper monolayer makes S-SIMS especially suited to the study of the interface chemistry in a variety of materials. Polymer applications take an important place because S-SIMS allows a lot of information on these often intractable materials, e.g., identification, detection of surface functionalities, study of segregation of copolymer components and molecular weight (MW) distributions. In addition to the qualitative identification, S-SIMS allows high reproducibility and thereby permits quantitative studies with the aid of standards. Finally, S-SIMS offers imaging capabilities to visualize directly the distribution of given components within the upper surface layer of solids. Mapping with high lateral resolution is feasible for elemental ions and in favorable cases also for organic compounds. This review aims at a comprehensive coverage of the S-SIMS literature of the past decade. It comprises two parts, of which the first part deals with the more general aspects of the technique. It begins with a brief tutorial review of instrumentation, methodology and current concepts of ion formation. Particular attention is given to the link and difference with the matured dynamic SIMS method. Finally, imaging in S-SIMS is discussed. Application of S-SIMS to complex materials makes the interpretation of signals, in terms of the sample composition, intricate but crucial. Therefore, the features of inorganic and organic mass spectra are surveyed to assess the structure specificity and the kind of information obtainable. The second part of this review focuses on a variety of applications, primarily in the field of material sciences. Detailed studies on the surface chemistry of catalysts are discussed. The increasing importance of surface modification and tailoring to improve the interface properties has generated a wide range of applications. Examples from different technologies and industrial processes, such as semiconductors, paint, composite materials and corrosion protection of metals, are highlighted. Attention is devoted to the complementarity between S-SIMS and other micro-analytical surface techniques. The review aims at being of interest on the one hand to the S-SIMS users looking for interesting application areas and on the other hand, to the application chemists searching a method, potentially capable of yielding specific information for their material analysis problem.

Luminal Foam Cell Accumulation Is Associated With Smooth Muscle Cell Death in the Intimal Thickening of Human Saphenous Vein Grafts

BACKGROUND Occlusion of saphenous vein grafts is a major problem after coronary artery bypass graft surgery. Diffuse intimal thickening develops in all implanted aortocoronary saphenous vein grafts within 6 months to 1 year. In some regions of the thickened intima, foam cells accumulate along the luminal margin. This particular morphology resembles the morphology of unstable atherosclerotic plaques as they occur in coronary arteries. In the present study, we focused on the possible topographic relation between luminal foam cell accumulation and cell death of smooth muscle cells (SMCs) within the adjacent thickened intima. METHODS AND RESULTS Segments of occluded and suboccluded implanted human aortocoronary saphenous vein grafts were obtained during reintervention coronary artery bypass graft surgery in 30 patients. In the regions of the vein grafts with luminal foam cell accumulation, the percentage of SMC alpha-actin immunoreactive area of the superficial intimal thickening was 6 +/- 1.4%, which was different from the 17.6 +/- 2.3% of the deep intimal thickening. A strong negative correlation between the number of foam cell nuclei and the percentage of SMC alpha-actin immunoreactive area in the adjacent superficial intimal thickening was present (r = -.77, P < .001). Within the superficial intimal thickening, cytoplasmic and DNA fragmentation could be detected, which points to apoptotic cell death. A fraction of the cytoplasmic fragments fitted the ultrastructural characteristics of matrix vesicles and showed pronounced calcium and phosphorus accumulation as demonstrated with the use of x-ray microanalysis. CONCLUSIONS The close spatial relation among foam cell accumulation, pronounced intimal SMC loss, and cell death suggests the presence of a foam cell-derived factor that can induce cell death in the SMC population of the intimal thickening. The depletion of the intimal SMC population could promote plaque rupture and thrombotic complications in the grafts.

The analysis of volatile siloxanes in waste activated sludge

The increasing presence of siloxanes in waste activated sludge (WAS) considerably hampers the energy use of the biogas obtained during the anaerobic digestion of the sludge when concentrations exceed critical limits. To prevent the occurrence of unacceptable operating conditions, it is hence necessary to have a reliable analysis method for determining the siloxane content of the sludge. This paper describes and validates such a method, consisting of the extraction of the siloxanes using n-hexane and a subsequent analysis of the extract using GC-FID. The validation procedure confirms the excellent recovery and repeatability of the proposed method.

Adhesion Strength of the Epoxy Polymer/Copper Interface for Use in Microelectronics

The adhesion of plated metals on top of chemically treated epoxy layers for build-up purposes was examined. Specifically, the influence of wet chemical pretreatments on the adhesion of plated copper to epoxy polymer is investigated. This adhesion is related to the surface roughness of the polymer and the chemical composition of its surface. The chemical composition of the surface was examined by X-ray photoelectron spectrscopy and placed in the context of the development of the interface during the wet chemical pretreatments and related to the theory developed in previous publications. Various combinations of pretreatments were followed by an identical electrochemical Cu deposition and peel strength measurement sequence. This allowed interpretation of the changes of the peel strength with pretreatments. Using this interpretation, the peel strength of build-up layers was maximized. We propose that the surface of the polymer layer develops into a fractal surface during wet chemical oxidation. Using this proposition, in combination with pore diffusion for the oxidizer, the evolution of peel strengths with chemical pretreatment times can be qualitatively understood. The peel strength of electrochemically deposited copper can be quantitatively related to the atomic force microscopy measurements for limited oxidation treatment times.

Occurrence of organochlorine pesticides and polychlorinated biphenyls in soils and sediments from Eastern Romania

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), such as DDT and analogues, hexachlorocyclohexane (HCH) isomers and hexachlorobenzene (HCB), were measured in surface soils and sediments from Eastern Romania. Thirty-nine soil samples from the forested zone, eight soil samples from a municipal waste-disposal site, and 10 sediment samples from the Bahlui River along the Iassy city were analysed using accelerated solvent extraction (ASE) and gas chromatography coupled to electron capture detection or mass spectrometry. The low mean concentrations of OCPs (11–31 and 22–84 ng g−1 for HCHs and DDTs, respectively) and PCBs (8–43 ng g−1) in soil samples from the forested zone suggest that contamination at most of these sites occurred predominantly through atmospheric transport from zones where these compounds were used and subsequently through atmospheric deposition. Contrarily, soil samples collected in the vicinity of a waste-disposal site near Iassy contained higher mean levels of PCBs (278 ng g−1, range 34–1132 ng g−1) than OCPs (6 and 101 ng g−1 of soil for HCHs and DDTs, respectively). The sediment samples collected along the Bahlui river throughout the Iassy city revealed higher mean levels of PCBs (59 ng g−1, range 24–158 ng g−1) compared with OCP levels (2 and 37 ng g−1 of soil for HCHs and DDTs, respectively). Furthermore, PCB profiles and concentrations in the sediment samples varied considerably along the river due to a wide variety of sources, such as different industries and waste sites. Although their sources are difficult to evaluate, the presence of POPs at most sites (especially at the waste-disposal site) may constitute a potential health hazard.

Inhibition of inositol monophosphatase by lithium chloride induces selective macrophage apoptosis in atherosclerotic plaques

BACKGROUND AND PURPOSE Lithium chloride (LiCl) inhibits inositol monophosphatase (IMPase) at therapeutic concentrations. Given that LiCl induces death in cultured macrophages and that macrophages play an active role in atherosclerotic plaque destabilization, we investigated whether LiCl would induce selective macrophage death to stabilize the structure of the plaque.

Speciation analysis of oxides with static secondary ion mass spectrometry.

Speciation analysis of inorganic solids, without dissolution of the sample, aims at specific molecular information. Two potentially useful microanalytical techniques emerge, namely, laser microprobe mass spectrometry (LMMS) and static secondary ion mass spectrometry (S-SIMS). This paper focuses on the molecular characterisation of oxides by application of the S-SIMS method. For this purpose, mass spectra of pure oxides were acquired under static conditions. Analytical parameters such as repeatability, accuracy and resolution were assessed. Also, the peak patterns in the mass spectra are discussed in connection with the older Plog model, describing the relative ion yield as a function of the cluster size. Finally, a comparison is made with the mass spectra from a S-SIMS library and with those obtained by Fourier transform LMMS. Copyright 1999 John Wiley & Sons, Ltd.

Fourier Transform Laser Microprobe Mass Spectrometry for the Molecular Identification of Inorganic Compounds

This study attempted to determine the molecular composition of inorganic analytes at the surface of solids by Fourier transform laser microprobe mass spectrometry (FT LMMS) with an external ion source. A database was established from the analysis of pure compounds. FT LMMS uses a similar ionization as the older LMMS instruments with time-of-flight (TOF) mass analyzer. However, apart from the mass resolution, the mass spectral patterns can be significantly different in FT LMMS compared to TOF LMMS. FT LMMS yields detailed information on the analyte by means of structural fragments, enabling us to specify the main building blocks, as well as adduct ions, consisting of the analyte molecule and a stable ion. Hence, deductive reasoning allows tentative characterization of the analogs without reference spectra, except for compounds with the same elements in different stoichiometries. In that case comparative data are needed.

DESORPTION/IONIZATION OF INORGANIC COMPOUNDS IN FOURIER TRANSFORM LASER MICROPROBE MASS SPECTROMETRY WITH EXTERNAL ION SOURCE

Application of FT LMMS to inorganic compounds offers the advantage of direct speciation. This means that signals which refer to intact analyte molecules are detected. Current concepts of desorption and ionization in LMMS are mainly based on time-of-flight data and hence on ions formed during the laser pulse. This paper focuses on indications about the desorption and ionization mechanisms for inorganic compounds that can be deduced from the mass spectra in our FT LMMS database. Specifically, the occurrence of continuing ion formation during several hundreds of microseconds is demonstrated. These data are relevant to the possible role of selvedge ionization versus direct ion emission from the solid state.

Surface Modification of a Photo-Definable Epoxy Resin with Polydopamine to Improve Adhesion with Electroless Deposited Copper

Abstract This paper describes the influence of polydopamine surface modifications on the adhesion strength of electroless deposited copper on roughened epoxy resin substrates. The surfaces are characterized with XPS and ToF-S-SIMS. Next, a thorough investigation of the copper–epoxy interface is performed using SEM. Both the polydopamine modification and the variation of the electroless plating bath temperature lead to new insights into the different contributions of chemical and physical adhesion to the overall adhesion strength.