Source Apportionment for the Zinc—Containing Component of Air Particulate Matter using Automated Electron Probe Micro Analysis of Individual Particles

Abstract

A methodology is described for the apportionment of zinc-containing particulate matter sampled in the vicinity of a zinc smelter to their corresponding sources in the factory. Bulk samples of particulate matter from six potential emission sources were analysed by automated electron probe microanalysis (EPMA) in order to characterize the individual particles. Based on a data set of relative peak intensities and with the aid of a binary clustering method, the most important particle classes were identified. They were used as a basis for the development of a set of disjunct identification rules (decision rules), which were able to describe the classes in a unique manner. Applying these rules upon ambient particulate data enabled the estimation of relative contributions of different types of zinc-containing particles. Evidence was found that a large number of particles was modified by a soil component or by gas phase reactions.     

Poly(methyl methacrylate) encapsulation of calcium carbonate particles

Dispersed calcium carbonate particles are encapsulated with poly(methyl methacrylate). The optimum condition for the polymerization is investigated; and the encapsulated particles are characterized by spectrophotometric analysis, acid decomposition, thermal analysis, and microscopic observation. From the conversion comparison of the MMA monomer it is found that the optimum concentration of polymerization initiator is 1.58 × 10^?3 mol/L. The highest yield of encapsulation is obtained at 250 rpm with a concentration of 0.5 wt % surfactant (sodium dodecyl benzene sulfonate). A comparison of the Fourier transform IR spectra distinctly indicates the formation of PMMA on the surface of the calcium carbonate particles. The outcome of an acid decomposition test proves that the PMMA coating protects the particles. In addition, thermal analyses and microscopic observation characterize the PMMA on the surface of encapsulated particles. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4063–4073, 2004     

Rapid preparation and characterization of uniform, large, spherical Ag particles through a simple wet-chemical route

In this article we report the rapid preparation of uniform, large, spherical Ag particles through a simple wet-chemical route. The formation of Ag particles with about 750 nm in diameter occurs in a single process, carried out by direct mix of AgNO3 aqueous solution and ortho-phenylenediamine N-methyl-2-pyrrolidone solution at room temperature, producing a relatively low-polydispersity product. It is also found that raising the temperature results in larger particles. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectra have been used to characterize the resulting product.     

Characterization of anthropogenic sediment particles after a transboundary water pollution of river Tisza using synchrotron radiation

At the beginning of 2000, a major mining accident occurred in the Romanian part of the Tisza catchment area due to tailings dam failure releasing huge amounts of heavy metals to the river. Sediment samples were taken from the main riverbed at six sites in Hungary, on March 16, 2000. The objective of this work was to characterize the anthropogenic particles in river sediment previously selected by single-particle electron probe X-ray microanalysis (EPMA). The trace element composition, heterogeneity and heavy metal speciation of individual particles was studied using synchrotron radiation-based microbeam X-ray emission and absorption methods. Particles were selected only from samples regarded as polluted sediment. White-beam micro X-ray fluorescence (μ-XRF) allowed the quantitative determination of heavy metals such as cadmium in individual particles. The maximum observed concentration of cadmium (>700 μg/g) indicates that this highly toxic heavy metal is concentrated in individual anthropogenic particles. Using the combination of micro X-ray absorption near-edge structure and target-transformation principle component analysis, quantitative chemical speciation of copper and zinc was feasible on individual sediment particles. Heavy metals in most of the particles released from the pollution site remained in the sulfide form resulting in a limited mobility of these metals. Based on the information obtained using microanalytical methods, the estimation of the environmental mobility of heavy metals connected to microparticles becomes possible.     

Extraction of environmental information from large aerosol data sets through combined application of cluster and factor analyses

To reveal useful environmental information which is contained in large analytical data sets, an approach, based on the successive application of hierarchical cluster analysis and factor analysis, is proposed. Estimation criteria to determine the most suitable number of clusters and/or factors, are discussed and the interpretation of the cluster and factor analyses results is performed using visual techniques. The data sets were obtained by scanning electron microscope-energy-dispersive X-ray analysis of individual North Sea aerosol particles.     

Tuning Optical Properties of Encapsulated Clusters of Gold Nanoparticles through Stimuli‐Triggered Controlled Aggregation

Gold nanoparticles entrapped in the hollow polymer nanocapsules undergo pH‐mediated controlled aggregation. Encapsulated clusters of nanoparticles show absorbance at higher wavelengths compared with individual nanoparticles. The size of the aggregates is controlled by the number of nanoparticles entrapped in individual nanocapsules. Such controlled aggregation may permit small biocompatible nanoparticles exhibit desirable properties for biomedical applications that are typically characteristic of large nanoparticles.     

Multiple-instrument analyses of single micron-size particles.

Physical, chemical, and isotopic analyses of individual radioactive and other particles in the micron-size range, key tools in environmental research and in nuclear forensics, require the ability to precisely relocate particles of interest (POIs) in the secondary ion mass spectrometer (SIMS) or in another instrument, after having been located, identified, and characterized in the scanning electron microscope (SEM). This article describes the implementation, testing, and evaluation of the triangulation POIs re-location method, based on microscopic reference marks imprinted on or attached to the sample holder, serving as an inherent coordinate system. In SEM-to-SEM and SEM-to-SIMS experiments re-location precision better than 10 microm and 20 microm, respectively, is readily attainable for instruments using standard specimen stages. The method is fast, easy to apply, and facilitates repeated analyses of individual particles in different instruments and laboratories.     

Sintering of passivated gold nanoparticles under the electron beam

Time-lapse studies of a film of passivated gold nanoparticles under electron beam irradiation have been performed using a transmission electron microscope, revealing the microscopic dynamics of the sintering process at the single nanoparticle level. It is found that the sintering of individual passivated gold nanoparticles under electron irradiation is local and mainly depends on the sensitivity of the passivating ligands to the electron beam. A multilayer film is less stable than monolayer film, consistent with the enhanced generation of secondary electrons. The observations also reveal a significant difference between the sintering of passivated nanoparticles and bare metal particles, especially regarding the size effect on the sintering rate. The formation of a neck between adjacent nanoparticles further indicates a mechanism driven by surface diffusion rather than Ostwald ripening at the initial sintering stage.     

Synthesis of highly crystalline and monodisperse maghemite nanocrystallites without a size-selection process.

The synthesis of highly crystalline and monodisperse gamma-Fe(2)O(3) nanocrystallites is reported. High-temperature (300 degrees C) aging of iron-oleic acid metal complex, which was prepared by the thermal decomposition of iron pentacarbonyl in the presence of oleic acid at 100 degrees C, was found to generate monodisperse iron nanoparticles. The resulting iron nanoparticles were transformed to monodisperse gamma-Fe(2)O(3) nanocrystallites by controlled oxidation by using trimethylamine oxide as a mild oxidant. Particle size can be varied from 4 to 16 nm by controlling the experimental parameters. Transmission electron microscopic images of the particles showed 2-dimensional and 3-dimensional assembly of particles, demonstrating the uniformity of these nanoparticles. Electron diffraction, X-ray diffraction, and high-resolution transmission electron microscopic (TEM) images of the nanoparticles showed the highly crystalline nature of the gamma-Fe(2)O(3) structures. Monodisperse gamma-Fe(2)O(3) nanocrystallites with a particle size of 13 nm also can be generated from the direct oxidation of iron pentacarbonyl in the presence of oleic acid with trimethylamine oxide as an oxidant.     

Keratin Coatings for Wool: Shrinkproofing and Nanoparticle Delivery

Summary: Wool fabrics were treated with keratin hydrolysate in isolated systems, in systems incorporating a cross-linking enzyme, and in systems with nanoparticle silver. The dimensions of wool fabric were controlled after keratin applications and the strength of bleached wool fabric was improved. Keratin applications imparted these improved properties when applied alone and when applied with the enzyme. The enzyme was effective for in-situ, solid-state cross-linking of wool fabric, cross-linking keratin-to-keratin, and cross-linking keratin-to-fabric. To further improve the properties of wool, nanoparticle silver was produced in various shapes. Transmission electron microscopy (TEM) micrographs of these particles showed discrete and isolated particles of size 8-100 nm, dependent on the preparation. A combination of TEM and UV-VIS spectroscopy was used to characterize these particles and scanning electron microscopy running in backscattered electron mode confirmed their placement on wool fibers. The application of nanoparticle silver to wool when co-added with keratin may both improve dimensional stability and impart antimicrobial efficacy.     

A facile method for the preparation of monodisperse hollow silica spheres with controlled shell thickness

This article presents a facile, effective, mild synthesis process for well‐defined hollow spheres by using cationic polystyrene (PS) submicro‐particles as templates. In this approach, the cationic PS templates can be first prepared via emulsifier‐free polymerization by using the cationic monomer 2‐(methacryloyloxy) ethyltrimethylammonium chloride as comonomer, then, the silica shells from the sol‐gel process of tetraethoxysilane were coated on the surfaces of template particles via electrostatic interaction, finally the PS was dissolved in situ by modification of the reaction conditions in the same medium to form monodisperse hollow silica spheres with controlled shell thickness. Fourier transform‐infrared spectroscopy, thermogravimetric analysis, Brunauer‐Emmett‐Teller, transmission electron microscopy, and scanning electron microscope measurements were used to characterize these hollow silica spheres. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1332–1338, 2010     

Surlyn®/silicate nanocomposite materials via a polymer in situ sol–gel process: Morphology

Surlyn®/silicate hybrid materials were produced via diffusion‐controlled polymer in situ sol–gel reactions for tetraethylorthosilicate. The heterogeneous morphologies of these materials were inspected with transmission electron (TEM), atomic force (AFM), and environmental scanning electron microscopic methods. The silicate uptake was highly dependent on the water affinity of the particular Surlyn® form (acid or ionic) rather than on the affinity of the solvent. The morphology consisted of silicate particles with diameters that were on the order of tens of nanometers. Hence, these materials can be classified as nanocomposites. The particle size distributions in both the TEM and AFM images for all composites appeared to be narrow, with un‐neutralized Surlyn® exhibiting a broader distribution. Larger particles were found near the film surfaces, and the silicon elemental distribution across the film thickness indicated higher concentrations near the surfaces, which is most likely due to the fact that the sol–gel reaction is diffusion controlled in these polymeric media. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1563–1571, 2003     

Magnetic–fluorescent Langmuir–Blodgett films of fluorophore-labeled ferritin nanoparticles

We have covalently coupled fluorophore 4-(2-hydroxyethoxy)-7-nitro-2,1,3-benzoxadiazole (NBD) to the external ferritin shell through lysine residues. An increase in the luminescence quantum yield of the fluorescent ferritin particles and a blue shift in its emission peak compared to individual fluorophore were observed. The study of the particles by transmission electron microscopy showed that the native iron core ferritin is intact and that no degradation occurs during chemical functionalization of the protein shell. The NBD-labeled ferritin particles are water soluble, which allowed their controlled deposition by the Langmuir–Blodgett (LB) technique. Superparamagnetic and fluorescent properties of the particles are preserved within the LB film.     

Simultaneous purification and spectrophotometric determination of nickel present in as-prepared single-walled carbon nanotubes (SWCNT)

The quality of single-walled nanotubes (SWCNT) is usually assessed by means of electron microscopic techniques or Raman spectroscopy. However, these sophisticated techniques are not widely available and do not reliably estimate the impurities in highly heterogeneous samples containing metal particles, fullerenes and other carbonaceous materials. We have developed a simple, inexpensive and convenient spectrophotometric method to assess the purity of arc-discharge grown as-prepared SWCNT. Purification process consists of initial gas phase oxidation and refluxing with nitric acid at the optimal conditions including short time period during acid refluxing. We have shown that this method could remove the metal particles effectively with a good yield of high quality SWCNTs, as shown by the spectrophotometric and scanning tunneling microscope studies described here. The extent of removal of the nickel present in as-prepared carbon nanotube sample is followed by spectrophotometeric analysis of the dissolved nickel analyte. The composition of nickel in the SWCNT sample is found to be 17.56%. The method is based on the chelating of Ni²⁺ with dimethylglyoxime in ammoniacal citrate medium to form nickel dimethylglyoxime complex. A second stage purification of SWCNT eliminates the residual metal particles. The purified SWCNT has been studied using scanning tunneling microscopy which shows clearly resolved individual carbon nanotubes.     

Uniform chitosan hollow microspheres prepared with the sulfonated polystyrene particles templates

Biodegradable chitosan hollow microspheres have been fabricated by employing uniform sulfonated polystyrene (PS) particles as templates. The chitosan was adsorbed onto the surface of the sulfonated polystyrene templates through the electrostatic interaction between the sulfonic acid groups on the templates and the amino groups on the chitosan. Subsequently, the adsorbed chitosan was crosslinked by adding glutaraldehyde. After the removal of the sulfonated polystyrene core, chitosan hollow microspheres were obtained. The longer the sulfonation time used, the smaller the size of the hollow particles and the thicker the chitosan wall obtained. Fourier transform infrared spectrometry was used to characterize the component of the microspheres. The morphologies of the PS templates and the chitosan microspheres were observed by transmission electron microscopy and scanning electron microscopy. The controlled release behavior of the chitosan hollow microspheres was also primarily investigated.     

Large-scale synthesis of TiO2 nanorods via nonhydrolytic sol-gel ester elimination reaction and their application to photocatalytic inactivation of E. coli

A simple method of synthesizing a large quantity of TiO(2) nanorods was developed. A nonhydrolytic sol-gel reaction between titanium(IV) isopropoxide and oleic acid at 270 degrees C generated 3.4 nm (diameter) x 38 nm (length) sized TiO(2) nanocrystals. The transmission electron microscopic image showed that the particles have a uniform diameter distribution. X-ray diffraction and selected-area electron diffraction patterns combined with high-resolution transmission electron microscopic image showed that the TiO(2) nanorods are highly crystalline anatase crystal structure grown along the [001] direction. The diameters of the TiO(2) nanorods were controlled by adding 1-hexadecylamine to the reaction mixture as a cosurfactant. TiO(2) nanorods with average sizes of 2.7 nm x 28 nm, 2.2 nm x 32 nm, and 2.0 nm x 39 nm were obtained using 1, 5, and 10 mmol of 1-hexadecylamine, respectively. The optical absorption spectrum of the TiO(2) nanorods exhibited that the band gap of the nanorods was 3.33 eV at room temperature, which is 130 meV larger than that of bulk anatase (3.2 eV), demonstrating the quantum confinement effect. Oleic acid coordinated on the nanorod surface was removed by the reduction of the carboxyl group of oleic acid, and the Brunauer-Emmett-Teller surface area of the resulting naked TiO(2) nanorods was 198 m(2)/g. The naked TiO(2) nanorods exhibited higher photocatalytic activity than the P-25 photocatalyst for the photocatalytic inactivation of E. coli.     

Preparation of uniform silica/polypyrrole core/shell microspheres and polypyrrole hollow microspheres by the template of modified silica particles using different modified agents

Silica/polypyrrole (PPY) core/shell microspheres and PPY hollow microspheres were prepared by the template of silica particles whose surface character was modified with different modified agents. The morphology and structure of the particles were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Elemental analysis and X-ray photoelectron spectroscopy (XPS) were carried out to characterize the structure of PPY hollow microspheres. We investigated the effect of different modified agents on the surface character of silica particles and the effect of surface character of silica particles on the morphology of PPY hollow microspheres. The effect of reaction conditions on the size of core/shell particles and hollow particles was also studied.     

Quantitative Characterization of the Structure of PP/Layered Silicate Nanocomposites at Various Length Scales

The structure and rheological properties of a large number of layered silicate polypropylene nanocomposites were studied with widely varying compositions. Unlike general practice, morphology was characterized at different length scales covering several decades by SEM, TEM, and XRD. Rheological measurements supplied additional information about structure. The results showed that these materials possess a very complex structural architecture. The introduction of a functionalized polymer decreases the size of the original clay particles. However, relatively large silicate particles were found also in composite samples yielding XRD traces without silicate reflection. We found that not only two (individual layers, intercalated stacks), but four morphological entities, i.e. also particles and a silicate network, may be present simultaneously in the composites. An attempt was made to characterize morphology quantitatively, wherever possible. SEM and TEM micrographs were evaluated by image analysis, XRD traces by curve fitting, while a model was developed to determine relaxation time from rheological measurements, but only XRD and SEM results are reported here.     

Characterization of individual atmospheric particles by element mapping in electron probe microanalysis

In this paper procedures for the characterization of individual aerosol particles by element mapping in the electron microprobe are presented. The number, size and qualitative chemical composition of particles is derived from a combination of secondary or backscattered electron images and element distribution maps. Accuracy of the size distribution and reliability of the qualitative analysis procedure were checked with silicate samples. In order to obtain a semi-quantitative estimate of the chemical composition of individual particles the count rates taken from element distribution maps are corrected for matrix and geometric effects using particle ZAF procedures.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Dithiocarbamate-capped silver nanoparticles

Nanometer-sized silver particles were synthesized by using didecylamine dithiocarbamates as the protecting ligands. With control of the initial ligand-metal feed ratios, the core diameter of the resulting particles was found to vary from about 5 to 2.5 nm, as determined by transmission electron microscopic measurements. The core size dispersity was also found to decrease with increasing feed ratio. In UV-visible spectroscopic studies, the particle surface plasmon resonance peak diminished in intensity as the particle core size decreased, whereas in electrochemical measurements, smaller sized particles gave rise to well-defined quantized charging voltammetric features, in contrast to the featureless responses with the larger particles. Such single electron-transfer behaviors were consistent with those observed in STM measurements involving individual nanoparticles. Overall, this study provides an effective approach to the synthesis of stable nanometer-sized silver nanoparticles with interesting electronic and electrochemical properties.