Energy Dispersive X-ray Elemental Analysis Research Articles

Synthesis, characterization and evaluation of ionic-imprinted polymers for solid-phase extraction of nickel from seawater

Several nickel ion imprinted polymers were prepared via precipitation polymerization using 4-vinylpyridine or 2-(diethylamino) ethyl methacrylate as monomers (vinylated reagents) and a cross-linking agent divinylbenzene in the presence of nickel(II) alone or nickel(II) and 8-hydroxyquinoline (non-vinylated reagent). For all cases, 2,2′-azobisisobutyronitrile (AIBN) was used as an initiator and an acetonitrile/toluene (3:1) mixture was chosen as a porogen. After packing the polymer particles into empty SPE cartridges, nickel(II) ions were removed by washing with 50 mL of 2.0 M nitric acid. Characterization of the polymer particles has been carried out by scanning electron microscopy, energy dispersive X-ray fluorescence and elemental analysis. The best nickel imprinting properties were given by polymers synthesized in the presence of 8-hydroxyquinoline and 2-(diethylamino) ethyl methacrylate as a monomer. The optimum pH for quantitative nickel retention was 8.5 ± 0.5, while elution was completed with 2.5 mL of 2.0 M nitric acid. When using polymer masses of 300 mg, sample volumes until 250 mL can be passed through the cartridges without reaching the breakthrough volume. Therefore, a pre-concentration factor of 100 has been reached when eluting with 2.5 mL of the elution solution. Electrothermal atomic absorption spectrometry has been used as a detector for nickel determination. The limit of detection of the method was 0.050 μg L −1 (pre-concentration factor of 100), while the relative standard deviation for eleven replicates was 6%. Accuracy of the method was assessed by analyzing different certified reference materials: SLEW-3 (estuarine water) and TM-23.3 and TM-24 (lake water).

Arterial Calcification in Race Horses

Calcification of large arteries has been sporadically reported in horses. The pathogenesis is still unknown, but recent studies in humans suggest that this is a regulated biomineralizing process. This study surveyed the prevalence, distribution, and severity of vascular calcification in Thoroughbred and Standardbred racehorses. Histopathologic, ultrastructural imaging, and energy dispersive X-ray elemental analyses were used to examine the lesions. Calcification of the tunica media, predominantly the pulmonary artery, was found in 82% of horses (83/101). Young adult horses (mean [SD] age in years, 4.44 +/- 2.17) of both breeds and sexes were similarly affected. Lesions appeared as white-to-yellowish, hard, and gritty plaques of variable size. On microscopic examination, elastic fibers within the tunica media were thinned, fragmented, and calcified, and surrounded by dense collagen matrix. Elemental analysis showed distinct peaks for calcium and phosphorus, consistent with hydroxyapatite mineral. The frequent occurrence of calcification in the tunica media of large pulmonary arteries of young racing horses indicates the need to investigate its pathogenesis and potential clinical implications.

Composition-Tunable Properties of CdSxTe1−x Alloy Nanocrystals

Ternary CdSxTe1−x semiconductor quantum dots with both homogeneous and gradient composition have been fabricated via pyrolysis of organometallic precursors. The nanocrystal structure, size, and composition were characterized by UV−visible absorption and fluorescence spectroscopy, transmission electron microscopy, energy-dispersive X-ray elemental analysis, and X-ray diffractrometry. It was found that the band gap of homogeneously alloyed CdSxTe1−x is highly nonlinear with the crystalline composition, which was evidenced by a significant red-shift in the fluorescence of these nanocrystals with respect to the emission wavelength of their CdS and CdTe binary compounds. This effect, also known as optical bowing, seems to be enhanced in CdSxTe1−x nanocrystals because of large differences in atomic radii and electronegativities of S and Te chalcogens. Properties of gradient ternary alloys were found to be markedly different from those of homogeneous CdSxTe1−x. Their absorption and emission profiles, for instanc...

Structural and Functional Characterization of Enzyme-Quantum Dot Conjugates: Covalent Attachment of CdS Nanocrystal to α-Chymotrypsin

In this contribution, we report the synthesis of CdS nanoparticles directly conjugated to an enzyme, R-chymotrypsin (CHT) by chemical reduction in aqueous solution. Matrix-assisted laser desorption ionization (MALDI) mass spectrometry confirms the strong conjugation of CdS nanoparticles to CHT through covalent bonding in the CdS-CHT conjugates. High-resolution transmission electron microscopy (HRTEM) reveals that the CdS nanoparticles are well dispersed with an average diameter of 3 nm, and energy dispersive X-ray elemental analysis (EDAX) verifies the composition of the CdS-protein conjugates. The structural integrity of CHT before and after the conjugation of CdS nanoparticles is confirmed through circular dichroism (CD) studies. The functional integrity of CHT conjugated to CdS nanoparticles is investigated by monitoring the enzymatic activities of CHT and CHT-conjugated CdS nanoparticles by using absorption spectroscopy. The attachment of CdS nanoparticles to an enzyme with its structural and functional integrity may have impact in the future research on nanobio interface.

Determination of Water Diffusion Coefficients and Dynamics in Adhesive/Carbon Fiber Reinforced Epoxy Resin Composite Joints

To determinate the water diffusion coefficients and dynamics in adhesive/carbon fiber reinforced epoxy resin composite joints, energy dispersive X-ray spectroscopy analysis(EDX) is used to establish the content change of oxygen in the adhesive in adhesive/carbon fiber reinforced epoxy resin composite joints. As water is made up of oxygen and hydrogen, the water diffusion coefficients and dynamics in adhesive/carbon fiber reinforced epoxy resin composite joints can be obtained from the change in the content of oxygen in the adhesive during humidity aging, via EDX analysis. The authors have calculated the water diffusion coefficients and dynamics in the adhesive/carbon fiber reinforced epoxy resin composite joints with the aid of both energy dispersive X-ray spectroscopy and elemental analysis. The determined results with EDX analysis are almost the same as those determined with elemental analysis and the results also show that the durability of the adhesive/carbon fiber reinforced epoxy resin composite joints subjected to silane coupling agent treatment is better than those subjected to sand paper burnishing treatment and chemical oxidation treatment.

Degree of functionalization of carbon nanofibers with benzenesulfonic groups in an acid medium

Benzene sulfonic groups have been successfully attached to a carbon nanofiber surface by reaction of diazonium benzenesulfonic salt in sulfuric acid. The extent of the functionalization reaction was determined by X-ray photoelectron spectroscopy, energy dispersive X-ray analysis, elemental analysis, and thermogravimetric analysis complemented with temperature-programmed desorption experiments. Good agreement between the degrees of functionalization provided by these techniques was observed. The results pointed to a higher extent of anchorage of –SO 3H groups when the nanofibers were treated in fuming sulfuric acid, for which a surface S/C (%) atomic ratio of 2.4 was obtained. Raman spectroscopy revealed that the D-band does not fully disappear after CNF treatment, indicating that a certain degree of structural disorder is maintained. However, a decrease in the D-band was observed after the diazotization reaction and this was attributed to the chemical change occurring at the edges. No significant changes to the morphological and textural characteristics of the CNFs by surface treatment were observed. This study may offer an important guideline in the application of CNFs modified with benzenesulfonic groups in polymeric membranes for fuel cells.

In vitro bioactivity and degradation of polycaprolactone composites containing silicate fillers

In spite of numerous publications on the potential use of combinations of polycaprolactone (PCL)/bioactive fillers for bone regeneration, little information exists on the assessment of solid, nonporous composites prepared via solventless routes and consisting of unmodified, slowly degrading homopolymer with relatively low amounts of reactive fillers such as bioglass or calcium silicate (CS). Thus, composites of PCL with commercial CS and a bioactive glass (BG45S5) at 30 wt.% were produced by melt mixing in a twin screw extruder. Neat fillers, PCL and their composites were immersed in simulated body fluid (SBF) and phosphate buffer saline and tested for in vitro bioactivity and degradation, respectively, over a 4 month period. Testing methods included scanning electron microscopy with energy dispersive X-ray analysis, X-ray diffraction (XRD), elemental analysis and weight and pH changes before and after immersion. Experiments with neat fillers indicated fast growth of calcium phosphate minerals having different textures; they included clusters and globules of mineral precipitates as well as needle-shaped nanosized crystallites and possibly other calcium phosphate structures with varying Ca/P ratio. The bioactive glass composite initially showed fast growth of the precipitated minerals and partial surface coverage after 1 week, whereas in the CS composite, growth and surface coverage increased as a function of immersion time (over a period of 4 weeks) in the SBF solution. XRD results showed early appearance (1 week) of hydroxyapatite for both types of composites with differences attributed to different dissolution rates and different surface reactions of the fillers. Both fillers appeared to enhance the hydrolytic degradation of the matrix. Overall, the limited observed bioactivity of both composites within the test period may be related to the hydrophobicity of the matrix, insufficient ionic activity since SBF was not replenished and the relatively low content of the low surface areas fillers. Optimization of filler properties, such as surface/volume ratio, surface chemistry and size range, appears as a most important factor that would provide, at the required high filler volume fractions, a balance of melt processability and bioactivity.

Dithiocarbamate ligand stabilised gold nanoparticles

Dithiocarbamates are used as adsorbates for the preparation of gold nanoparticles. A range of mono- and tetrakis-functionalised dithiocarbamate ligands containing alkyl, benzyl and resorcinarene cavitand substituents are synthesised. Nanoparticles are prepared by a two-phase synthesis and are characterised by 1H NMR spectroscopy, UV-Visible spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and elemental analysis. The colloids are found to be stable over a number of months storage in air. The synthetic versatility of the dithiocarbamate ligand is further demonstrated by the synthesis of ruthenium(II) bipyridyl dithiocarbamate capped gold nanoparticles.

Association between phosphorus and suspended solids in an Everglades treatment wetland dominated by submersed aquatic vegetation

Restoration of the Everglades requires reduction of total phosphorus (TP) in the influent run-off from the Everglades agricultural area (EAA). The Everglades nutrient removal project tested phosphorus (P) - removal efficiencies of several treatment wetland cells. The best TP reduction has occurred within the submersed aquatic vegetation (SAV) - dominated treatment Cell 4. A significant proportion of the P reduction in Cell 4 over several years has been in the form of particulate P (PP). This study was conducted to (i) determine and compare the components of suspended solids in the Cell 4 influent and effluent waters, and (ii) investigate associations between PP and individual particulate components. Identification and quantification of components were accomplished using X-ray diffraction, thermogravimetry, scanning electron microscopy, and energy dispersive X-ray elemental analysis. The dominant particulate components in the Cell 4 water column are organic matter (OM), biogenic Si (predominantly diatom frustules), and calcite. Concentrations of PP, suspended solids, and particulate OM were greater at the Cell 4 inflow than at the outflow; consistent differences between particulate calcite in the influent vs. the effluent were not found. PP was positively correlated with particulate OM, but was not correlated with calcite. Data suggest that particulate OM, including microbial cells, plays an important role in P transport from the EAA. Possibly, a shift from planktonic to periphytic microbial distribution contributes to PP reduction. The importance of planktonic organisms as vectors of P in Everglades water warrants further study.

Morphological analysis and chemical content of natural dentin carious lesion zones

Dentin is one of the earliest bio-mineralization products to appear in the evolution of vertebrates. Dentin reactions to infection mimic earlier phylogenetic patterns, and carious lesions are divided into different zones which reflect the natural patho-morphological reaction of dentin to the carious attack. It was the aim of this study to investigate deep dentin carious lesions of human molars with combined polarization light microscopy, scanning electron microscopy and energy dispersive X-ray element analysis (EDX) for the determination of different zones of the carious lesions, their extent and the chemical content. Sixteen extracted teeth with deep dentin carious lesions were embedded in Technovit 9100 (Kulzer) and serial sections of 80 microm thickness were made. These sections were then examined with polarized light microscopy to identify the different zones of the lesions. The outlines of the zones were traced consecutively and 3D-reconstructions were made for the determination of the extent and calculation of the volumes of the different zones. From the volumes of the demineralizing dentin and the translucent zone a Dentin Demineralization Index (DDI) was calculated. Three sections of each lesion were then coated with carbon and studied with a scanning electron microscope. 3D-reconstruction of the teeth showed the rather stable translucent zone, interrupted by remnants of dead tracts, and very different volumes of demineralizing dentin. Therefore, with increasing size of the demineralizing dentin, the DDI increased. The chemical content was measured using energy dispersive X-ray analysis (EDX) in areas of intertubular dentin. The content of Ca, P, and C was significantly different in all zones. The Ca/P ratio was significantly different between sound dentin and demineralizing dentin. From the results we conclude that the mineral content of intertubular dentin of the translucent zone and demineralizing dentin is different from that of sound dentin, and the unique mineralization pattern of the translucent zone is a biological reaction to the carious attack. Because active dentin lesions exhibit many non-occluded open dentin tubules, further bacterial invasion or, in case of dentin treatment, the penetration of bonding agents towards the pulp is morphologically not prevented and therefore of clinical importance.

Preparation and thermophysical properties of AgGaTe2 crystals

The preparation and thermophysical properties of AgGaTe2 crystals are reported. The synthesis from pure elements was performed in a rocking oven and scanning electron microscopy and energy dispersive X-ray elemental analysis show the presence of additional phases. From simultaneous differential calorimetry and thermogravimetric analysis (SDT) measurements we have found that AgGaTe2 melts at 725.7°C, with a heat of fusion of 104.8J/g−1. High temperature powder X-ray diffraction data confirmed the chalcopyrite structure and yielded the thermal expansion coefficients along the a- and c-axes to 500°C. Heating above that temperature, under inert gas flow, causes the material to sublime incongruently and produce a film of gallium rich surface. Experimental values of thermal diffusivity and estimates of the thermal conductivity values are also presented.

Methods of multivariate data analysis applied to the investigation of fen soils

Fen soils from two sites of the Rhin-Havel-Luch, a peatland in the north-east of Germany, have been investigated. The samples have been collected in two horizons, representing different degrees of degradation and mineralisation of peat. Gravimetric measurements, energy dispersive X-ray fluorescence (EDXRF), elemental analysis, and 1H low resolution nuclear magnetic resonance (LR-NMR) of the fen soil samples have been performed. By multivariate analysis of all the experimental data, especially by the principal component analysis (PCA) and by the cluster analysis, respectively, it was possible to classify the fen soils, to identify their characteristic properties, to detect temporal and local variations, and to prove representative field sampling. Furthermore, the correlation between variables of the applied analytical methods could be interpreted in context to the composition of fen soils and mutual influences of their properties.

Scanning electron microscopy, X-ray microanalysis, and thermogravimetric assessment of linen fabrics treated with crease-resisting compound

The physical, chemical, and thermal changes in fabrics treated with a commercial crease-resisting compound (CPNS) were investigated. The samples were analyzed by a scanning electron microscope equipped with an energy dispersive X-ray microanalyzer, elemental analysis, and differential thermogravimetry. X-ray microanalysis of the treated fabrics revealed that changes in gross integral counts of O, N, Mg, Al, Si, S, Cl, and Ca as a result of the treatments were related to the application rate of the compound. This result was broadly supported by mineral analysis data determined by standard wet chemistry methods. The effects of over- and undercuring were also investigated. In addition, the increase in nitrogen content as a result of the higher application rate can also be detected by EA. Differential thermogravimetric analyses of the samples showed distinct changes in the profile of the thermally stable fraction. This could be due to the formation of a crosslinked cellulose complex, which pyrolyzed at the significantly higher decomposition temperature of 481°C in comparison with 473°C for untreated material. The advantages of using instrumental techniques for assessing the efficiency of treatments are briefly discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1209–1219, 1999

Behaviour of adult hamsters subjected to hypergravity

We studied vestibular function in 20 adult hamsters (3 months old) subjected to either prolonged hypergravity (n = 10) or normal gravity (n = 10) for 2 months. Locomotion and swimming of the hypergravity hamsters under light conditions were normal. Equilibrium maintenance was severely disturbed; only 6 of 10 hypergravity hamsters managed to walk on the small tube after 2 months, whereas all 10 controls were able to walk on the tube. The air-righting reflex was severely disturbed; the hypergravity hamsters made 30% correct air-righting responses, while the control hamsters made 88% correct responses. Finally, 5 of 8 hypergravity hamsters had to be saved from drowning when swimming in total darkness. Histological examination of the utricular otoconial layers afterwards, using energy dispersive X-ray element (EDAX) analysis and scanning electron microscopy, did not reveal any differences in calcium content, shape and size distribution of the otoconia between hypergravity hamsters and controls. We suggest that adult hamsters adapt to hypergravity, leading to problems in normal functioning when tested in 1 G, especially in tasks in which sensory input of the vestibular system is important for spatial orientation. These disturbances were more severe in adult hamsters than in young ones, tested in previous experiments. Therefore, we assume that age is a factor for adaptation to altered gravity conditions.

Inability of energy dispersive X-ray analysis to identify particulate polyethylene.

There are limitations to all techniques used to identify particulate polyethylene in histological specimens. The goal of our study was to determine if remnant metal elements used during the catalytic production of ultra high molecular weight polyethylene, could be used as markers for particulate polyethylene detection in histological specimens. It was hypothesized that these catalyst elements could be detected in polyethylene using energy dispersive X-ray elemental analysis. Six samples from five different companies were evaluated. These included virgin polymer powder, polyethylene bar stock, and artificial joint components. Five specimens from each of the six samples were analyzed with energy dispersive X-ray elemental analysis. After elemental analysis was completed, only 2 of 30 specimens were positive for the catalyst elements. In the remaining 28 specimens, catalyst elements were not detected. Our investigation demonstrates that energy dispersive X-ray elemental analysis is not currently a feasible method of particulate polyethylene detection. Additional techniques will need to be developed to accurately identify particulate polyethylene in histological specimens.

Otoconial alterations after embryonic development in hypergravity

The relation between prolonged hypergravity and structural adaptation of otoconia was studied in hamsters ( n = 56). Three groups of hamsters ( n = 27), were conceived and born in a centrifuge: group 1 ( n = 10) 1 month under 2.5 G, group (2 n = 9) 5 months under 2.5 G and 4 months under 1 G, group 3 ( n = 8) 1 month under 2.5 G and 8 moths under 1 G. Control hamsters ( n = 29) were conceived and born under 1 G (1 month old, n = 7; 9 months old, n = 22). Histological study of the otoconial layers (energy dispersive x-ray element analysis and scanning electron microscopy) showed similar calcium content, size, and shape in utricular and saccular otoconia in all groups. Different were the utricular otoconial size classes, large, medium-sized, a and small. The area with small otoconia increased in group 1 ( p = 0.002). In group 2, the large otoconial area decreased ( p < 0.001) and the medium-sized one increased ( p < 0.001). In group 3, the large otoconial area decreased ( p = 0.003) and the medium-sized one increased ( p = 0.007). For age-related effects we found group 1 with an increased area of large otoconia ( p = 0.001) and a decreased medium-sized one compared to groups 2 ( p < 0.001) and 3 ( p = 0.02). Hypergravity during formation of otoconia does not affect calcium content, size, or shape, but changes relative size of the areas with large, medium-sized, or small otoconia and the development of these areas. This resulted in a structural adaptation to hypergravity.

Effects of sustained acceleration on the morphological properties of otoconia in hamsters.

We investigated the effect of prolonged hypergravity on the otoconial layer of the maculae utriculi and the maculae sacculi in hamsters. The animals were placed in a centrifuge under conditions of 2.5 G, and remained there for 6 months. We then determined the calcium contents of the otoconia with energy dispersive X-ray element analysis, and recorded the size, shape and distribution of the otoconia. Scanning electron microscopy was used to make photos to determine the effects of hypergravity on the shape and size of the otoconia, and on the distribution of smaller and larger otoconia. No differences were found in the calcium content, shape, size or distribution of otoconia between centrifuged hamsters and control animals. Our findings indicate that structural adaptation to hypergravity does not take place at the otoconial level, at least not in animals subjected to hypergravity after the vestibular system was fully matured.

High-performance liquid chromatography on polypyrrole-modified silica

Bare silica and C 18-bonded silica were modified with polypyrrole chloride and polypyrrole chloride-dodecyl sulfate. The packing materials were characterised using scanning electron microscopy, energy dispersive X-ray analysis, elemental analysis and surface area analysis. Both reversed-phase and anion-exchange chromatographic behaviour were determined using a selection of test compounds.

Synthesis of bulk superconducting La2CuO4 in an electrochemical cell.

Superconductivity has been observed in originally semiconducting ceramic samples of ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$ following oxidation in an electrochemical cell at room temperature. After processing, the room-temperature resistivity is lowered by over an order of magnitude and, on cooling below 150 K, acquires a metallic temperature dependence. The superconducting transition occurs near 45 K. Magnetic-susceptibility measurements confirm the bulk nature of the superconductivity. Furthermore, by reversing the polarization of the cell, semiconducting ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$ can again be produced. The homogeneity of the processed samples was verified by x-ray powder diffraction and energy-dispersive x-ray elemental analysis.

Complex zoning and resorption in Breunnerite from hall in Tyrol, Austria: Evidence from back-scattered electron microscopy

Back-scattered electron imagery (BSE) coupled with energy-dispersive X-ray elemental analysis was applied to petrographic investigations of recrystallized, anchimetamorphic breunnerites (ferroan magnesites). Analyses of polished thin sections allowed the recognition of a complex zoning pattern, invisible by transmitted or reflected light microscopy. Breunnerite precipitation and replacement started with (Mg0.90Fe0.07Ca0.01Mn0.02) CO3 and proceeded towards (Mg0.73Fe0.22Ca0.00Mn0.05)CO3. This precipitation sequence was interrupted by at least two major events of reverse zoning (i.e. Fe-rich zones followed by Fe-poor ones). Resorption surfaces in Fe-poor zones are common and prove that short-term fluctuations occurred in the paleobrine composition and/or paleotemperature.