Single-particle characterization of “Asian Dust” certified reference materials using low-Z particle electron probe X-ray microanalysis

In order to clearly elucidate whether Asian Dust particles experience chemical modification during long-range transport, it is necessary to characterize soil particles where Asian Dust particles originate. If chemical compositions of source soil particles are well characterized, then chemical compositions of Asian Dust particles collected outside source regions can be compared with those of source soil particles in order to find out the occurrence of chemical modification. Asian Dust particles are chemically and morphologically heterogeneous, and thus the average composition and the average aerodynamic diameter (obtainable by bulk analysis) are not much relevant if the chemical modifications of the particles must be followed. The major elemental composition and abundance of the particle types that are potential subjects of chemical modification can only be obtained using single-particle analysis. A single particle analytical technique, named low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA), was applied to characterize two certified reference materials (CRMs) for Asian Dust particles, which were collected from a loess plateau area and a desert of China. The CRMs were defined by bulk analyses to provide certified concentrations for 13 chemical elements. Using the low-Z particle EPMA technique, the concentrations of major chemical species such as aluminosilicates, SiO₂, CaCO₃, and carbonaceous species were obtained. Elemental concentrations obtained by the low-Z particle EPMA are close to the certified values, with considering that the single particle and bulk analyses employ very different approaches. There are still some discrepancies between those concentration values, resulting from analyses of particles with different sizes, different sample amounts analyzed, and uncertainties involved in the single particle analysis.     

X-Ray analysis of riverbank sediment of the Tisza (Hungary): identification of particles from a mine pollution event

A serious heavy metal pollution of the Tisza River occurred on March 10, 2000, arising from a mine-dumping site in Romania. Sediment samples were taken from the main riverbed at six sites in Hungary, on March 16, 2000. The objective of this work was to distinguish the anthropogenic and crustal erosion particles in the river sediment. The samples were investigated using both bulk X-ray fluorescence (XRF) and thin-window electron probe microanalysis (EPMA). For EPMA, a reverse Monte Carlo method calculated the quantitative elemental composition of each single sediment particle. A high abundance of pyrite type particles was observed in some of the samples, indicating the influence of the mine dumps. Backscattered electron images proved that the size of particles with a high atomic number matrix was in the range of 2 μm. In other words the pyrites and the heavy elements form either small particles or are fragments of larger agglomerates. The latter are formed during the flotation process of the mines or get trapped to the natural crustal erosion particles. The XRF analysis of pyrite-rich samples always showed much higher Cu, Zn and Pb concentrations than the rest of the samples, supporting the conclusions of the single-particle EPMA results. In the polluted samples, the concentration of Cu, Zn and Pb reached 0.1, 0.3 and 0.2 wt.%, respectively. As a new approach, the abundance of particle classes obtained from single-particle EPMA and the elemental concentration obtained by XRF were merged into one data set. The dimension of the common data set was reduced by principal component analysis. The first component was determined by the abundance of pyrite and zinc sulfide particles and the concentration of Cu, Zn and Pb. The polluted samples formed a distinct group in the principal component space. The same result was supported by powder diffraction data. These analytical data combined with Earth Observation Techniques can be further used to estimate the quantity of particles originating from mine tailings on a defined river section.     

Characterisation of Sugar Cane Combustion Particles in the Araraquara Region, Southeast Brazil

Biomass burning is an important primary and secondary source of aerosol particles. The presence of carbonaceous particles in the respirable size range makes the study of this fraction important in view of possible health and climatic effects. The annual burning of sugar cane plantations causes emission of huge amounts of pyrogenic particles. Aerosol samples were collected in Araraquara city, São Paulo state, Brazil, during the harvest season for fine and coarse particles and bulk; they were analysed by electron-probe microanalysis, including facilities for low-Z element determination (low-Z EPMA) and by energy-dispersive X-ray fluorescence (EDXRF), in order to investigate the elemental composition of individual particles and bulk samples, respectively. Numerical analysis of the EPMA results by hierarchical clustering shows high contributions of carbonaceous particles that can be distinguished mainly in two different types: biogenic and carbon-rich. Additionally, two significant contributions of aluminosilicate particles were identified: as rather pure aluminosilicates or mixed with carbonaceous species. The EDXRF results are compatible with those of aerosol particles in Amazon, which is nowadays one of the main sources of biogenic particles in the world.     

Application of Thin-Window EPMA to Environmental Problems in Hungary

 The combination of single-particle analysis using thin-window EPMA and a reverse Monte Carlo quantification procedure has been proven to provide semi-quantitative elemental concentrations, including light elements. The capabilities of the method are demonstrated through three different environmental applications in Hungary. Lake Balaton is the largest lake in central Europe. It is suspected that the atmosphere is an important source of environmental deterioration of the Lake, relative to the pollutant supply by rivers and direct discharges. Thin-window EPMA results of around 25,000 individual particles indicated that the composition of the aerosol did not show characteristic seasonal variation, it was more correlated to the daily meteorological circumstances. A serious heavy metal pollution of the river Tisza occurred on 10 March 2000, from a mine-dumping site in Romania. Sediment samples were taken from the main riverbed at six sites, on 16 March 2000. In some of the samples, pyrite type particles were observed in high abundance, revealing their dumping-site origin. Biomass burning for energy production has been increased recently, mostly in households and for space heating. Fly-ash and bottom-ash samples were collected at a 600 kW heating plant at Sződliget during standard winter operation. Most particles contained over 65% of unburned organic substance. The concentrations of major elements were obtained for each individual particle using thin-window EPMA, providing accurate matrix composition for further μ-XRF investigations of the trace element composition.     

Substrate selection for optimum qualitative and quantitative single atmospheric particles analysis using nano-manipulation,sequential thin-window electron probe X-ray microanalysis and micro-Raman spectrometry

Sequential electron probe X-ray microanalysis using thin-window energy dispersive X-ray detection (TW-EDX-EPMA) and micro-Raman spectrometry (MRS) on the same atmospheric particle using nano-manipulation, is demonstrated. The advantageous combination of these two techniques allows information on the morphology, size, elemental and molecular composition, as well as the molecular structure of the same individual particle with a diameter as small as 500 nm. The use of an ultra-thin atmospheric window and a cold stage in EPMA enables qualitative and quantitative analysis of low-Z elements like C, N, and O as well as higher-Z elements. The work illustrates substrate optimisation and subsequent application in the analysis of atmospheric particles. Particle relocation was achieved by manipulative transfer onto transmission electron microscope grids, in an environmental scanning electron microscope, using 100 nm glass tips. A moderate correlation between the elemental composition obtained by TW-EDX-EPMA and the molecular fingerprint obtained by MRS is illustrated and its useful application in the interpretation of indoor air quality is discussed.     

Particulate matter analysis at elementary schools in Curitiba,Brazil

The particulate matter indoors and outdoors of the classrooms at two schools in Curitiba, Brazil, was characterised in order to assess the indoor air quality. Information concerning the bulk composition was provided by energy-dispersive x-ray fluorescence (EDXRF). From the calculated indoor/outdoor ratios and the enrichment factors it was observed that S-, Cl- and Zn-rich particles are of concern in the indoor environment. In the present research, the chemical compositions of individual particles were quantitatively elucidated, including low-Z components like C, N and O, as well as higher-Z elements, using automated electron probe microanalysis low Z EPMA. Samples were further analysed for chemical and morphological aspects, determining the particle size distribution and classifying them according to elemental composition associations. Five classes were identified based on major elemental concentrations: aluminosilicate, soot, organic, calcium carbonate and iron-rich particles. The majority of the respirable particulate matter found inside of the classroom was composed of soot, biogenic and aluminosilicate particles. In view of the chemical composition and size distribution of the aerosol particles, local deposition efficiencies in the human respiratory system were calculated revealing the deposition of soot at alveolar level. The results showed that on average 42% of coarse particles are deposited at the extrathoracic level, whereas 24% are deposited at the pulmonary region. The fine fraction showed a deposition rate of approximately 18% for both deposition levels.     

Molecular mass concentrations for a powdered SRM sample using a quantitative single particle analysis

In a quantitative single particle analysis, named the low-Z particle EPMA, number concentration data for chemical species encountered in aerosol sample are provided. However, it will be more useful if mass concentration data can be obtained from single particle analysis; i.e., the single particle analysis data for weight fractions of chemical species can be complementarily used in combination with the bulk analysis data, for more clearly understanding the behavior of airborne aerosols. In order to investigate how reliably mass concentration data can be obtained from the low-Z particle EPMA technique, a potassium feldspar powdered standard reference material (SRM), of which elemental weight fractions are well defined by various bulk analytical techniques, was analyzed using the low-Z particle EPMA technique. In this work, it is demonstrated that weight fractions of major elements in the powdered SRM sample obtained by the low-Z particle EPMA are within 8% to the certified values obtained by bulk analytical techniques, although the single particle and bulk analyses employ different approaches. Further, it is shown that the quantitative single particle analysis, i.e., low-Z particle EPMA, can provide molecular mass concentration data for chemical species, which is not easy to obtain using bulk analysis.     

Pyrolysis kinetics and chemical composition of Hazro coal according to the particle size

Summary The relationship between particle size and chemical composition of Hazro coal (origin: SE Anatolia, Turkey) has been examined by elemental analysis and by thermogravimetric pyrolysis. The chemical composition of the coal was determined by grinding sample particles physically and separating according to their size in mm by sieving. Particle size distribution of the coal and chemical composition of these fractions were given. The coal has been non-isothermally pyrolyzed in a thermogravimetric analyzer to determine the kinetic factors. Thermal gravimetric (TG/DTG) experiments were performed from ambient temperature to 800°C under a nitrogen atmosphere at heating rate 10 K min^-1 with five different particle size ranges. Kinetic parameters of the samples were determined using a Coats and Redfern kinetic model, assuming a first-order reaction. Depending on the particle size of the coal samples, the mean activation energy values varied between 49.1 and 84.6 kJ mol^-1. The results discussed indicate that activation energies increase as the particle size decreases.     

Chemical Characterization of Airborne Particles in St. Martinus Cathedral in Weert, The Netherlands

Electron probe X-ray microanalysis (EPMA) of single particles and energy dispersive X-ray fluorescence analysis (EDXRF) were applied to determine the chemical composition, size and probable origin of the suspended particulate matter. The aim of the performed research was to determine the chemical composition, size and abundance of aerosol particles responsible for blackening and soiling of the works of art displayed within the Cathedral of Weert in the Netherlands and to verify the possible sources responsible for these processes.     

Determination of Precious Metals in Geological Samples from Four Gold Ore Deposits of the North-East of Russia

Compositions of rare mineral phases containing precious metals (PMs) in samples from Natalka, Pavlik, Vetrenskoe, and Degdekan gold ore deposits (North-East of Russia) are studied by scintillation atomic emission spectrometry (SAES) and electron probe microanalysis (scanning electron microscopy and electron probe X-ray microanalysis, SEM–EPMA). The SAES method found dozens and hundreds of particles carrying gold, silver, and all platinum-group elements as native metals, intermetallides and solid solutions, arsenides, antimonites, sulfoarsenides, tellurides, selenides, etc. The variety of the elemental compositions of PM species (mineral phases) found by SAES significantly exceeds the list of minerals found previously by SEM–EPMA because of different natures of optical and X-ray spectra. The sizes of PM particles calculated by the SAES method and measured by SEM–EPMA are similar. The SAES data on the total concentrations of PMs satisfactorily agree with the results of inductively coupled plasma mass spectrometry.     

Speciation of copper and zinc in size-fractionated atmospheric particulate matter using total reflection mode X-ray absorption near-edge structure spectrometry

The health effects of aerosol depend on the size distribution and the chemical composition of the particles. Heavy metals of anthropogenic origin are bound to the fine aerosol fraction (PM_2.5). The composition and speciation of aerosol particles can be variable in time, due to the time-dependence of anthropogenic sources as well as meteorological conditions. Synchrotron-radiation total reflection X-ray fluorescence (SR-TXRF) provides very high sensitivity for characterization of atmospheric particulate matter. X-ray absorption near-edge structure (XANES) spectrometry in conjunction with TXRF detection can deliver speciation information on heavy metals in aerosol particles collected directly on the reflector surface. The suitability of TXRF-XANES for copper and zinc speciation in size-fractionated atmospheric particulate matter from a short sampling period is presented. For high size resolution analysis, atmospheric aerosol particles were collected at different urban and rural locations using a 7-stage May cascade impactor having adapted for sampling on Si wafers. The thin stripe geometry formed by the particulate matter deposited on the May-impactor plates is ideally suited to SR-TXRF. Capabilities of the combination of the May-impactor sampling and TXRF-XANES measurements at HASYLAB Beamline L to Cu and Zn speciation in size-fractionated atmospheric particulate matter are demonstrated. Information on Cu and Zn speciation could be performed for elemental concentrations as low as 140 pg/m³. The Cu and Zn speciation in the different size fraction was found to be very distinctive for samples of different origin. Zn and Cu chemical state typical for soils was detected only in the largest particles studied (2–4 μm fraction). The fine particles, however, contained the metals of interest in the sulfate and nitrate forms.     

Synthesis and biological studies of complexes of 2- amino-<Emphasis Type="Italic">N</Emphasis>(2-aminobenzoyl) benzohydrazide with Co(II), Ni(II), and Cu(II)

The present work is concerned with the synthesis and coordination compounds of 2-amino-N(2-aminobezoyl) benzohydrazide (ABH). The ligand was synthesized by the reaction of methylanthranilate and hydrazine in 2:1 molar ratio. It can be viewed as a modified form of hydrazide. The ligand was characterized by ¹H-NMR, ¹³C-NMR, mass spectrometry, elemental analysis, and infrared studies. The ligand has got -NH₂ moeity, the site for chelation. The complexes of Co(II), Ni(II), and Cu(II) chlorides and bromides were prepared. These complexes were characterized by elemental analysis, infrared, conductance, and magnetic susceptibility studies. Infrared spectra studies confirmed the formation of complexes, while elemental studies suggested the complexation of [M(ABH)X₂] (where X = Cl⁻ or Br⁻) composition.     

Impact of graphene on the enhancement of electrochemical and photocatalytic performance of Gd2O3 - Graphene nanocomposites

Gadolinium oxide - Graphene (Gd₂O₃-G) nanocomposites were prepared with different weight ratio of graphene using low temperature solution process. The structural, morphological, electrochemical and photocatalytic properties of the composites were investigated by X-ray diffraction, Raman, FE-SEM, HRTEM, Cyclic voltammetric and photo-degradation analysis. The chemical composition of the composites was studied by elemental mapping analysis using EPMA. The binding states of various elements present in the composites were analyzed by XPS. Cyclic voltammetric studies revealed that the nanocomposite with 5% graphene exhibits the specific capacitance of 26 F g⁻¹, which is higher than that of pure Gd₂O₃ (18 F g⁻¹). The presence of graphene has greatly enhanced the photocatalytic performance of Gd₂O₃G composites as the rate of degradation of MB dye is relatively higher in the composites compared to pure Gd₂O₃. The significant increase in the specific capacitance and rate of degradation of dye suggest that the Gd₂O₃G is a promising material for energy storage and environmental applications.     

立方亚铁氰化锌钾颗粒的制备和抗菌性能研究

研究了以硝酸锌和亚铁氰化钾为原料制备立方状亚铁氰化锌钾抗菌材料的方法。通过比较不同产物的形貌、产率、化学组成、晶型和抗菌性能,确定了最佳的反应物配比。采用SEM、XRD、ICP等方法表征了样品的颗粒形貌、晶型和元素组成等信息;并检测了添加了立方状亚铁氰化锌钾颗粒的涂层的抗菌性能。研究发现当锌离子和亚铁氰化钾的物质的量比在1.5/1时,所得样品白度好、形貌稳定且对金色葡萄球和大肠杆菌都表现出了良好的抗菌性能。     

Characterization of β‐cyclodextrin modified SiO2

Silica particles containing a layer of β‐cyclodextrins were synthesized using a modified method of Armstrong (1985). The modified silica particles were extensively characterized to both the presence and amount of β‐cyclodextrin introduced onto the surface. Raman confirmed that β‐cyclodextrin was introduced onto the particle. The combination of thermogravmetric analysis (TGA) and direct pyrolysis mass spectroscopy were used to determine the amount and the chemical composition of organic material present on the silica, respectively. The two methods confirmed that β‐cyclodextrin was successfully introduced in amounts comparable to earlier literature values. The values obtained by TGA were compared to amounts found by elemental analysis and XPS. The elemental analysis and TGA found the same amount of β‐cyclodextrin, while the XPS values were in the region of 1.5 times higher. This suggests a heterogeneous distribution of the β‐cyclodextrin on the silica particles. Copyright © 2010 John Wiley & Sons, Ltd.     

Radioanalytical separation and size-dependent ion exchange property of micelle-directed titanium phosphate nanocomposites

Nanocomposite titanium-phosphate (TiP) of different sizes was synthesized using Triton X-100 (polyethylene glycol-p-isooctylphenyl ether) surfactant. The materials were characterized by FTIR and powdered X-ray diffraction (XRD). The structural and morphological details of the material were obtained by scanning electron microscopy (SEM) and transmission electron microscopy. The SEM study was followed by energy dispersive spectroscopic analysis for elemental analysis of the sample. The important peaks of the XRD spectra were analyzed to determine the probable composition of the material. The average size distribution of the particles was determined by dynamic light scattering method. Ion exchange capacity was measured for different metal ions with sizes of the TiP nanocomposite and size-dependent ion exchange property of the material was investigated thoroughly. The nanomaterial of the smallest size of around 43 nm was employed to separate carrier-free ^137mBa from ¹³⁷Cs in column chromatographic technique using 1.0 M HNO₃ as eluting agent at pH 5.     

Preparation of Silica/Poly(tert‐butylmethacrylate) Core/Shell Nanocomposite Latex Particles

Nanocomposite latex particles, with a silica nanoparticle as core and crosslinked poly(tert‐butylmethacrylate) as shell, were prepared in this work. Silica nanoparticles were first synthesized by a sol‐gel process, and then modified by 3‐(trimethoxysilyl)propyl methacrylate (MPS) to graft C?C groups on their surfaces. The MPS‐modified silica nanoparticles were characterized by elemental analysis, FTIR, and ²⁹Si NMR and ¹³C‐NMR spectroscopy; the results showed that the C?C groups were successfully grafted on the surface of the silica nanoparticles and the grafted substance was mostly the oligomer formed by the hydrolysis and condensation reaction of MPS. Silica/poly(tert‐butylmethacrylate) core/shell nanocomposite latex particles were prepared via seed emulsion polymerization using the MPS‐modified silica nanoparticle as seed, tert‐butylmethacrylate as monomer and ethyleneglycol dimethacrylate as crosslinker. Their core/shell nanocomposite structure and chemical composition were characterized by means of TEM and FTIR, respectively, and the results indicated that silica/poly(tert‐butylmethacrylate) core/shell nanocomposite latex particles were obtained.     

Light Element Analysis of Individual Microparticles Using Thin-Window EPMA

 The determination of the concentration of light elements, such as carbon, nitrogen and oxygen, in e.g. atmospheric aerosol particles is important to study the chemical behaviour of atmospheric pollution. The knowledge of low-Z element concentrations gives us information on the speciation of nutrients (species having nutritional value for plants) and toxic heavy metals in the particles. The capability of the conventional energy-dispersive EPMA is strongly limited for the analysis of low-Z elements, mainly because the Be window in the EDX detector hinders the detection of characteristic X-rays of light elements such as C, N, O and Na. WDS is suitable for analysis of light elements, but the measurement of beam sensitive microparticles requires the minimisation of the beam current and the measurement time. A semi-quantitative analytical method based on EPMA using an ultra-thin window EDX detector was developed. It was found that the matrix and geometric effects that are important for low-energy X-rays can be reliably evaluated by Monte Carlo calculations. Therefore, the quantification part of the method contains reverse Monte Carlo calculation done by iterative simulations. The method was standardised and tested by measurements on single particles with known chemical compositions. Beam-sensitive particles such as ammonium-sulphate and ammonium-nitrate were analysed using a liquid nitrogen cooled sample stage. The shape and size of the particles, which are important for the simulations, were determined using a high-magnification secondary electron image. Individual marine aerosol particles collected over the North Sea by a nine-stage Berner cascade impactor were analysed using this new method. Preliminary results on five samples and 4500 particles show that the method can be used to study the modification of sea-salt particles in the troposphere.     

Origin and impact of particle-to-particle variations in composition measurements with the nano-aerosol mass spectrometer

In the nano-aerosol mass spectrometer, individual particles in the 10–30 nm size range are trapped and irradiated with a high pulse energy laser beam. The laser pulse generates a plasma that disintegrates the particle into atomic ions, from which the elemental composition is determined. Particle-to-particle variations among the mass spectra are shown to arise from plasma energetics: Low ionization energy species are enhanced in some spectra while high ionization energy species are enhanced in others. These variations also limit the accuracy and precision of elemental analysis, with higher deviations generally observed when low ionization energy species are dominant in the mass spectrum. For standard datasets generated from nominally identical particles, it is shown that that the error associated with composition measurement is random and that averaging the spectra from a few tens of particles is sufficient for measuring the mole fractions of common elements to within about 10 % of the expected value. Averaging a greater number of particles offers limited improvement of the measurement precision but has the deleterious effect of degrading the measurement time-resolution, which is given by the time needed to obtain the required number of particle spectra for averaging. An internally mixed ambient particle dataset was found to give a similar result to the standard datasets, that is, the measured elemental composition converged to the average value after a few tens of particles were averaged.