Lead determination in glasses by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been used to determine the lead content of different types of lead silicate glasses commercially designed as sonorous glass (which contain ∼ 10 wt.% PbO); crystal glass (with at least 24 wt.% PbO) and superior crystal glass (with at least 30 wt.% PbO). Seven different types of glass samples were selected, including historic-original, model and commercially available. The selected samples were artificially weathered under neutral, acid and alkaline attack. Analysis by LIBS was carried out in vacuum under excitation at 266 nm and results were compared with those obtained by conventional techniques used for glass characterization. Composition of the bulk glasses was analyzed by XRF (X-ray fluorescence) and the corroded surfaces were characterized by SEM/EDX (scanning electron microscopy/energy dispersive X-ray microanalysis). A linear correlation was obtained between the intensity of selected Pb lines in the LIB spectra and the PbO content. The effect of corrosion could be characterized by comparing successive LIB spectra recorded on the same area; acid attack resulted in a decrease of PbO, CaO and Na₂O content in the surface with respect to the bulk of the sample, while minor changes in the composition were noticed under alkaline attack. These results show LIBS as a useful technique to classify the different types of lead glasses by their lead content and to determine and asses the degree and type of corrosion.     

Characterization of nanomaterials in food by electron microscopy

Engineered nanomaterials (ENMs) are increasingly being used in the food industry. In order to assess the efficacy and the risks of these materials, it is essential to have access to methods that not only detect the nanomaterials, but also provide information on the characteristics of the materials (e.g., size and shape).This review presents an overview of electron microscopy (EM)-based methods that have been, or have the potential to be, applied to imaging ENMs in foodstuffs. We provide an overview of approaches to sample preparation, including drying, chemical treatment, fixation and cryogenic methods. We then describe standard and non-standard EM-based approaches that are available for imaging prepared samples. Finally, we present a strategy for selecting the most appropriate method for a particular foodstuff.     

The infrared microspectroscopic and energy dispersive X-ray analysis of paints removed from a painted, medieval sculpture of Saint Wolfgang

A spectroscopic study of paints removed from a 15th century sculpture depicting Saint Wolfgang, which is housed in the Ball State Museum of Art, was performed. Infrared spectra on the minute paint samples were obtained using a microscope accessory in the transmission mode, and the spectra were compared to reference spectra of known art pigments and materials. In addition, energy dispersive X-ray spectra were obtained using a scanning electron microscope source. Although many of the pigments found are relatively modern pigments, the first application of paint is composed of materials consistent with the sculpture's medieval date. Pigments identified include brass gilding, calcium carbonate, China clay, lac dye, orpiment, Prussian blue, satin ochre, ultramarine blue and red, and zinc chromate. A zinc tungate finish was also identified.     

Identification and Classification of Iridescent Glass Artifacts with XRF and SEM/EDX

 Art Nouveau (Tiffany, Loetz) and modern (Jack Ink, Strini Art Glass) iridescent glass fragments were characterized using energy dispersive X-ray fluorescence analysis (EDXRF) and energy dispersive X-ray microanalysis in a scanning electron microscope (SEM/EDX) in combination with factor analysis in order to obtain clustring. A character istic of Tiffany glass fragments is leaded bulk glass, whereas in the case of Loetz K-Ca-Si bulk glass could be determined. Modern glass fragments show a high amount of Na (7 wt% in the bulk of Jack Ink) and 0.6–1.5 wt% Sr in the bulk of Strini Art Glass. The contents of Si and Ca are similar to Loetz glass. Furthermore, the differences in the structure of the glass artifacts could be determined. The cross-sections of Tiffany show a layered structure of the bulk without a specific surface layer whereas the cross-sections of Loetz glass reveal a homogeneous bulk material with one or two homogeneous surface layers in the BE-image. In the case of the Jack Ink a homogeneous bulk glass and an inhomogeneous multilayered surface could be determined. Strini Art Glass show a homogeneous bulk glass and a homogeneous surface layer in the backscattered electron image.     

Structural Study of Micro and Nanotubes Synthesized by Rapid Thermal Chemical Vapor Deposition

The structures of micro and nanotubes obtained by pyrolysis of hydrocarbons, hold onto silicon (Si) substrates, are reported in this work. The tubes fabrication experiments were carried out by Rapid Thermal Chemical Vapor Deposition (RTCVD) using propane (C₃H₈) as carbon (C) precursor. Selection of parameters such as temperature of deposition, vacuum conditions or surface cleaning leads to the creation of tubular structures. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), selected area electron diffraction (SAED) and energy dispersive X-ray measurements (EDX) are the microbeam techniques that allow to characterize the tubes found in the studied specimens. Different tube configurations such as isolated nanorods, Y-type junctions or fiber-like layers are evidenced. Metallic catalysis seems to be the mechanism involved in the wires formation since Fe particles are present inside the CNT tubes. Other poly-crystalline inclusions are also evidenced by SAED. The composition of the nanotubes changes from tip to tail in an amorphous matrix. The growth mechanisms leading to tube formation are described.     

Energy Dispersive X-Ray Fluorescence Analysis and X-Ray Microanalysis of Medieval Silver Coins

 Austrian medieval silver/copper coins were investigated at their surfaces by energy dispersive X-ray fluorescence analysis (EDXRF) and at the cross-sections by X-ray microanalysis in the scanning electron microscope (SEM/EDX) in order to estimate the error occurring when corroded objects of art and archaeology are analyzed on the surface by non-destructive methods. Additionally, Ag/Cu-standards were treated in diluted sulphuric acid and the depletion of copper on the surface was measured by EDXRF. By calculating the ratio of the Ag-K/Ag-L intensity the process of blanching could be studied.     

Statistical evaluation of potash-lime-silica glass weathering

Two potash-lime-silica model glasses with compositions similar to those of medieval stained glass were exposed at 26 test sites all over Europe and in North America for 3–6 years. The objectives of this large-scale field exposure programme were: (a) a qualitative analysis of the weathering products formed on the surface of the samples in the (environmental) scanning electron microscope in combination with energy dispersive X-ray microanalysis (ESEM/EDX or SEM/EDX, respectively); (b) a statistical evaluation of the weathering phenomena by applying a multiple linear regression (MLR) analysis to find correlations between the degree of weathering, which was measured in terms of surface coverage with reaction products, and environmental parameters such as the concentration (c) of the acidifying gases SO₂, NO₂ and O₃, the temperature (T) and the relative humidity (RH); and (c) the calculation of a time-dependence function of the weathering process of these glasses. Mainly sulfates of calcium and potassium such as gypsum (CaSO₄·2 H₂O), arcanite (K₂SO₄) and syngenite (CaSO₄·K₂SO₄·H₂O) could be identified in the SEM and ESEM. Carbonates, nitrates and many particles deposited on the glass surface were found as well. MLR calculations exhibit significant dependencies of the degree of weathering on T, RH, c(NO_x), c(SO₂) and c(O₃). Applying a time-dependence function of the general form y=a·t^b (t=time) results in a value of approximately 0.42 for the exponent b, which comes close to values expected from various studies in the literature.     

A comparison of scanning electron microscopy energy dispersive X-ray (SEM/EDX) and inductively coupled plasma optical emission spectrometry (ICP-OES) for provenance inferences of grog-tempered Bronze Age pottery

Pottery tempered with former pottery fragments (named grogs) is very common during the Bronze Age in the Cantabrian Cornice (North Spain). Grog tempered pottery from two coeval archaeological sites Santa Maria de Estarrona and Peracho are studied in order to establishes pottery provenance. Chemical analyses of pottery are used to discriminate locally from imported pottery under the assumption that different geological regions exhibit a distinctive chemical fingerprint. However, the pottery-maker usually transforms the original clay by tempering and prepares the material suitable for firing modifying the raw material chemical fingerprint. The problem increases when grogs are used as tempering agent. In these cases the chemical input is clearly contaminated with foreign materials making impossible to assign a source area. SEM-EDX has been applied to both the matrix and the different types of grog tempers and the results have been compared to the whole potsherd analysis performed by ICP-OES. Chemometric analysis of matrices enable to discriminate different raw materials that can be attributed to locally produced pottery. This chemical characterization of the matrices by SEM-EDX is more effective than the chemical composition determined for the whole potsherd by ICP-OES. The occurrence of grogs within grog tempers and various types of grogs indicates modes of production based on intensive recycling. The presence of some pottery vessels at the Estarrona site with chemical features similar to those of Peracho is indicative of the transport of pieces during the migrations of semi-sedentary groups and/or the exchange of pieces between different groups of humans.     

Image analysis in the electron microscopy of cellulose protofibrils

Electron microscope images of parallel arrays of Ramie cellulose protofibrils, obtained at various levels of defocus, are discussed in terms of phase contrast. The optical diffraction pattern of appropriately defocused images shows discrete maxima in the resolution range of 2–5 nm. The pattern is dominated by strong equatorial reflections arising from the lateral spacing of the protofibrils which is about 5 nm. From the observed reciprocal lattice net, it is concluded that the protofibrils are characterized by some form of axial texture that repeats with a periodicity of about 6 nm. The lattice reflections in the optical diffraction pattern are shown to be essentially invariant over a wide range of defocusing conditions. From this it is inferred that the pattern arises from real object order. It is emphasized that the optical diffraction pattern derives from gross structural features related to the morphology of the protofibrils and not from their internal structure.     

Chemometric classification of gunshot residues based on energy dispersive X-ray microanalysis and inductively coupled plasma analysis with mass-spectrometric detection

A gunshot residue sample that was collected from an object or a suspected person is automatically searched for gunshot residue relevant particles. Particle data (such as size, morphology, position on the sample for manual relocation, etc.) as well as the corresponding X-ray spectra and images are stored. According to these data, particles are classified by the analysis-software into different groups: ‘gunshot residue characteristic’, ‘consistent with gunshot residue’ and environmental particles, respectively. Potential gunshot residue particles are manually checked and – if necessary – confirmed by the operating forensic scientist.     

钯纳米线电极的制备及其应用于乙醇的电化学氧化研究

纳米线作为纳米科学领域中的重要一员,因其优异的光学、电学及磁学等特性引起了凝聚态物理学界、化学界以及材料科学界科学家们的极大关注,并己成为当今纳米科技研究的热点领域[1].纳米线的制备方法有多种,本文提及的模板法制备纳米线结构技术是20世纪90年代初发展起来的一种既经济又简便实用的新工艺[2].     

Microstructural characterisation of five simulated archaeological copper alloys using light microscopy, scanning electron microscopy, energy dispersive X-ray microanalysis and secondary ion mass spectrometry

This paper describes the microstructural characterisation of five simulated archaeological copper alloys, produced by modern powder technology. The chemical composition of the examined bronzes covers the major families of archaeological bronzes from antiquity until the Roman period. Light microscopy (LM), energy dispersive X-ray microanalysis (EDX), scanning electron microscopy (SEM) as well as two- and three-dimensional secondary ion mass spectrometry (SIMS) have been used to describe the main properties of the alloys. The results show a heterogeneous microstructure on a micrometer scale, formed by metallic and non-metallic phases. The latter are conglomerates of oxides or sulphides of major or minor elements.     

A scanning electron microscopy study on hollow silica microspheres: defects and influences of the synthesis composition

Defects on hollow silica spheres synthesized in a tetraethylorthosilicate-octylamine-HCl-H₂O system were recorded by scanning microscope. Based on the results, influences of synthesis composition on the formation of these defects are discussed. It is evidenced that products prepared with different octylamine-to-tetraethylorthosilicate ratios may have surface depressions, cracks and non-hollow microspheres. However, by changing water and acid additions, these defects could be reduced or eliminated. Generally, samples synthesized with a large octylamine addition commonly exhibit surface depressions. A small octylamine or a large water addition benefits the formation of solid silica microspheres among the product. Acid, although is not indispensable for the formation of hollow spheres, helps to eliminate or reduce depressions on the hollow shells. It is explained that the added acid gives rise to a relative localized fast hydrolysis versus condensation, facilitating an easy mobility of hydrolyzed silica species, and consequently the shell surface is smoothened.     

Weathering Phenomena on Naturally Weathered Potash-Lime-Silica-Glass with Medieval Composition Studied by Secondary Electron Microscopy and Energy Dispersive Microanalysis

 Samples of two model glasses with chemical compositions similar to medieval stained glass were exposed to the natural environment at 23 test sites for a period of 6 months, 1 and 2 years within an exposure programme of the “Working Group of Effects on Materials, Including Historic and Cultural Monuments” of the Economic Commission for Europe of the United Nations. During the exposure the environmental data were measured and collected at each test site in order to enable a correlation between the pollutant load in the ambient atmosphere and the weathering phenomena of the glass samples. After the exposure, which was performed in a sheltered as well as in an unsheltered mode for gaining information about the influence of dry and wet deposition of air pollutants, the glass samples were analysed in the scanning electron microscope with energy dispersive microanalysis (SEM/EDX). Model glass M1 – a potassium rich glass – was covered to a high amount with crystalline weathering products (above all syngenite), whereas glass M3 – a glass with a higher Ca and Si content – turned out to be more stable against weathering. This glass was covered with gypsum and arcanite crystals but in total to a less extent than glass M1. Received March 30, 1998. Revision February 8, 2000.     

Image analysis in the electron microscopy of cellulose protofibrils II. Digital correlation methods

Electron micrographs of parallel arrays of negatively stained ramie cellulose protofibrils were analyzed using the two-dimensional digital autocorrelation function (ACF). The method is based upon the statistical analysis of images in real space. The ACF shows strong parallel streaks of high correlation, and the lateral distance between adjacent streaks allows the mean interfibrillar distance to be estimated as 3.7 nm. The intensity profile along the streaks shows a weak modulation with peaks occurring at integral multiples of 3 or 6 nm. These results provide direct evidence that there is a regular axial texture in the protofibrils, and corroborate the conclusions previously drawn from optical diffraction analysis. Using the difference vectors found in the ACF it has been possible to reduce the picture noise level by linear integration, thereby obtaining an enhanced image. A preliminary result obtained in this way suggests that the projected protofibril morphology associated with the observed axial periodicity is a ribbon-like zigzag structure. Possible applications of the method for future work are discussed.     

Energy filtered transmission electron microscopy for the physico-chemical characterization of aquatic submicron colloids

A combination of energy filtered transmission electron microscopic (EF-TEM) procedures is proposed for the non-perturbing physico-chemical characterization of submicron mineral and organic colloids in aquatic systems. Synthetic hematite microparticles and xanthan polysaccharides were used as well-characterized model colloids in order to determine the optimum EF-TEM analysis conditions. In this paper, it is demonstrated that (i) our model colloids are morphologically representative of naturally occurring mineral/organic associations, (ii) EF-TEM allows the detection of fine xanthan ultrastructures without artefacts of conventional staining methods and (iii) submicron hematite particles can be specifically visualized and spectrometrically measured by EF-TEM within a hematite/xanthan mixture. This EF-TEM procedure appears to be appropriate for the characterization of real aquatic samples.     

扫描电化学显微镜在电催化表面反应分析中的现代应用

能源和环境问题成为制约未来可持续发展的关键问题之一,因此,针对不同电催化反应设计电催化剂变得越来越重要.电催化剂因其能量效率高、制备简单和易操作等优点,而应用于可再生能源的相关反应(如水分解和人工光合作用)中.明确不同反应电催化剂的设计原理,深入理解其在相关反应中的催化机理,可进一步优化催化剂性能.本文综述了扫描电化学显微镜(SECM)应用于电催化反应的历程、关键方法以及一些代表性的工作,阐明了电催化剂的工作机理以推进电催化剂的设计.本文还介绍了为提高SECM的空间分辨率而尝试的纳米尺寸电极方面的新进展,分享了纳米电极在以前研究无法涉及的单一催化实体方面的应用.     

扫描电化学显微镜在生物医学领域的应用研究进展

研究病变细胞和组织的异常表现可为理解重大疾病发生发展的病理机理和新型药物筛选提供重要参考.扫描电化学显微镜(Scanning electrochemical microscopy, SECM)是一种基于电化学原理的扫描探针显微镜,通过记录探针在样品表面扫描时的电流或电位等信息,对活细胞的形态和多种化学信息进行原位、实时...