In situ semi-quantitative analysis of zinc dissolution within nanoporous silicon by X-ray absorption fine-structure spectroscopy employing an X-ray compatible cell.

The in situ study of the discharge process in a zinc-based half-cell employing a porous electrode as a structural scaffold is reported. The in situ characterization has been performed by synchrotron X-ray absorption fine-structure spectroscopy and, for this purpose, an inexpensive, simple and versatile electrochemical cell compatible with X-ray experiments has been designed and described. The experimental results reported here have been employed to semi-quantify the dissolved and undissolved zinc species during the discharge, allowing the cell feasibility to be tested and to better understand the functioning of the zinc half-cell based on porous electrodes.

Electrosynthesis of Layered Organo-Manganese Dioxide Framework-Doped with Cobalt for Iodide Sensing.

Aqueous Mn2+ ions were anodized at 70 °C with Co2+ in the presence of cationic surfactant, cetyltrimethylammonium (CTA). X-ray diffraction (XRD) analysis revealed that the deposited film possesses a layered structure of MnO2, the interlayer of which is occupied with the assembled CTA molecules. Inclusion of Co ions in the MnO2 film was evidenced by X-ray photoelectron spectroscopy (XPS). They were located in the MnO2 framework, not in the interlayer. The thus-obtained film, CTA-intercalated Co-framework-doped layered MnO2 (CTA/Co-MnO2), was applied as an electrochemical sensor toward iodide (I-), a hydrophobic anion. The organic phase between MnO2 layers could extract I- ions from solution, providing a better sensitivity than a film consisting of layered MnO2 with hydrated alkali metals. On the other hand, the Co-doped layers of MnO2 achieved faster electron transfer kinetics for the oxidation of I-, which resulted in a drastic reduction in response time compared to the nondoped CTA/MnO2.

Structure and complexation mechanism of aqueous Zn(II)-acetate complex studied by XAFS and Raman spectroscopies.

In this work, the structure of Zn acetate has been determined by a combination of X-ray absorption fine structure and Raman spectroscopy. We have analyzed the local atomic environment and the main vibrational bands of the acetate and Zn acetate at different pH. The results suggest that Zn acetate complex acquires a bidentate structure that modifies its first coordination shell. Meanwhile, the coordination shell of the hydrated Zn cation is formed by 6 hydroxides at a mean distance of 2.06 Å, the coordination shell of the Zn cation in the complex is formed by 2 hydroxides and 2 oxygens from the carboxyl group of the acetate, at a mean Zn-O distance of 1.96 Å. The structure of the Zn acetate complex is compared to those of Zn malonate and Zn citrate, none of which present a reduction in the coordination shell neither a shrinkage of the Zn-O shell distance.

DNA aggregation and cleavage in CGE induced by high electric field in aqueous solution accompanying electrokinetic sample injection.

The phenomenon of peak area decrease due to high injection voltage (Vinj , e.g. 10-30 kV, 200-600 V/cm in the 50 cm capillary) was found in the analysis of very dilute DNA fragments (<0.2 mg/L) by using high-sensitive electrokinetic supercharging-CGE. The possibility of DNA cleavage in aqueous solution was suggested, in addition to the aggregation phenomenon that is already known. The analysis of intentionally voltage-affected fragments (at 200 V/cm) also showed decreased peak areas depending on the time of the voltage being applied. Computer simulation suggested that a high electric field (a few kV/cm or more) could be generated partly between the electrode and the capillary end during electrokinetic injection (EKI) process. After thorough experimental verification, it was found that the factors affecting the damage during EKI were the magnitude of electric field, the distance between tips of electrode and capillary (De/c ), sample concentration and traveling time during EKI in sample vials. Furthermore, these factors are correlating with each other. A low conductivity of diluted sample would cause a high electric field (over a few hundred volts per centimeter), while the longer De/c results in a longer traveling time during EKI, which may cause a larger degree of damage (aggregation and cleavage) on the DNA fragments. As an important practical implication of this study, when the dilute DNA fragments (sub mg/L) are to be analyzed by CGE using EKI, injection voltage should be kept as low as possible.

Density estimations and comparisons of a fragmented single fiber using X-ray computed tomography.

A commercial X-ray computed tomography (CT) apparatus using a quasi-monochromatic beam was utilized for density estimations and comparisons of a fragmented single fiber. The validation of quasi-monochromaticity of the X-ray source was investigated by radiograph measurements. For the case of a transmittance higher than 50%, the contribution of Cu Kα characteristic X-rays was dominant. To realize a sufficient statistical quality, an attempt to increase the number of averaged voxels was demonstrated using the neighboring slices of the 3D-CT image. A minimum value of the coefficient of variation (CV) was achieved using multiple images rather than using a single image. The observed values of the inverse of the transmitted X-ray intensity (CT value) of the polymers showed a fairly good relationship with their density. An analytical curve derived from measurements of reference samples of known densities could provide the relative density of an unknown fragmented fiber down to the size of 30 µm in diameter and 35 µm in length. The CV of the estimated density was from 1.5 to 2%, which was estimated from the CV of CT values. Moreover, the correlation of CT values was improved with the linear absorption coefficient than the density. A better performance of discrimination of polymers including fibers might be realized with the difference of linear absorption coefficients for X-rays.

Mechanisms of hydrogen sulfide removal with steel making slag.

In the present study, we experimentally investigated the removal of hydrogen sulfide using steel-making slag (SMS) and clarified the mechanism of hydrogen sulfide removal with the SMS. The results proved that SMS is able to remove hydrogen sulfide dissolved in water, and the maximum removal amount of hydrogen sulfide per unit weight of the SMS for 8 days was estimated to be 37.5 mg S/g. The removal processes of hydrogen sulfide were not only adsorption onto the SMS, but oxidation and precipitation as sulfur. The chemical forms of sulfide adsorbed onto the SMS were estimated to be sulfur and manganese sulfide in the ratio of 81% and 19%, respectively. It is demonstrated here that the SMS is a promising material to remediate organically enriched coastal sediments in terms of removal of hydrogen sulfide. Furthermore, using SMS is expected to contribute to development of a recycling-oriented society.

Non-destructive analysis of hollow-shaped single fibers using X-ray computed tomography.

A commercial high-resolution X-ray computed tomography (CT) was utilized for non-destructive analysis of single fibers. The micro-CT apparatus was employed because it is applicable to both colored and colorless fibers. A sample preparation using adhesive sheets was demonstrated, and the method is similar to typical tape-lift sample collection method in crime cases. Different cross-sectional shapes of nylon and polyester single fibers were non-destructively distinguished, and the method is applicable to all types of fibers. Cross-sectional areas, aperture ratios, and volumes of individual fibers were directly and automatically measured using the open-source software. The observed parameters were within a coefficient of variation of 3%. In addition, a mass of a single fragment of a fiber can be estimated when the local density is given.

Feasibility Studies of X-Ray Computed Tomography for Forensic Examination of Single Fibers.

Non-destructive observations of cross-sectional shapes of acrylic single fibers using X-ray computed tomography (CT) were performed. A commercial X-ray CT apparatus (Rigaku nano3DX) was employed because of its micrometer-scale spatial resolution and remarkable image contrast for soft matter. We assessed two types of sample support, a paraffin strip and a nylon string, for single fiber samples in terms of easy handling and sample recovery. Fixed individual single fibers were loaded into a narrow polyimide tube in both cases, and the tube ensured that the sample remained in the field of view during the CT measurements. In both cases, the cross-sectional shapes of individual single fibers could be distinguished, with a circular shape for one sample and a triangular shape for the other. However, the support using a nylon string was found to be more suitable for further analysis. The cross-sectional profile of the obtained tomographic image showed a clear difference between polyimide and nylon. The intensity ratio or the image contrast corresponded to that of the local densities. It was also found that the effect of the artifact appeared at around the boundaries of the objects, but the local density could still be utilized for examining individual single fibers.

Thermal Stability Change of Insoluble Sulfur by a Heat Treatment and Its Mechanism Study.

Insoluble sulfur (IS), used as a vulcanizing reagent of rubber, is prepared by the thermal ring-opening polymerization of sulfur (S8). Enhancing its thermal stability and content ratio (yield) is important for the industrial production of IS. The post-heating process at a high temperature of 70 or 90°C of the mixture of IS and S8 enhanced the thermal stability of IS and reduced the yield of IS. Further, the process at 30°C enhanced its thermal stability and maintained its yield. Since the thermal stability of IS is considered to be closely related to the chain length of polymer sulfur, a method for determining the chain length of IS was investigated by quantifying the amount of electron spin of radicals from sulfur, estimated from electron spin resonance (ESR) measurements. We confirmed that the long-period post-heating process at 30°C induced high thermal stability without reducing the yield of IS due to growth of the sulfur polymer chains.

Nondestructive Differentiation of Polyester Single White Fibers Using Synchrotron Radiation Microbeam X-ray Fluorescence Spectrometry with Vertical Focusing.

In this study, the nondestructive differentiation of individual white polyester clothing fibers was accomplished via synchrotron radiation microbeam X-ray fluorescence (SR-µ-XRF) analysis. SR-µ-XRF with vertical focusing is a useful nondestructive method for the analysis of a single polyester clothing fiber. Kirkpatrick-Baez (KB) mirror was used to vertically focus 20 keV X-rays for the analysis of 22 individual white polyester fibers taken from clothing commonly sold in Japan. SR-µ-XRF with a vertical focused 2 µm (V) × 300 µm (H) beam was approximately 12.8 times more sensitive than SR-XRF with an unfocused 300 µm (V) × 300 µm (H) beam for the detection of elements in single fibers. The minimum detection limits (MDLs) of the SR-µ-XRF method were 8.15 ppm for Cl and 0.06 ppm for Br. In addition to Ti in TiO2 delustering agents, Zr and Nb impurities in the delustering agents were detected in individual fibers. Sb from a polymerization catalyst and Co from a transesterification catalyst were also detected in individual fibers. Comparing the Ti Kß /Sb Lα,ß and Zr Kα /Nb Kα X-ray intensity ratios was a useful way to distinguish individual clothing fibers, and 98% of the fibers were differentiated when additional trace elements were used as discrimination indicators.

Identifying sulfur species adsorbed on particulate matters in exhaust gas emitted from various vessels.

Ship fuels are highly associated with the emission of particulate matter and sulfur. Sulfur adsorbed on particulate matter in exhaust gases from fuels is generally considered to be sulfate. However, other chemical species of sulfur adsorbed on particulate matter in ship exhaust gases are not well known. The purpose of this study is to identify sulfur species adsorbed on particulate matter in ship exhaust gases using X-ray absorption fine structure. Particulate matter and soot samples were collected from a container carrier, a tugboat, an electric propulsion vessel, training vessels, and a marine engine, and sulfur species of particulate matter and soot were identified by X-ray absorption fine structure analysis. Sulfur emission adsorbed on particulate matter and sulfur species did not change between high and middle loads. In this study, sulfonate derived from fuel or oxidation of sulfide in fuel was identified in addition to sulfate. Total sulfur and sulfate concentrations in soot increased with increasing fuel sulfur content. The concentration of organosulfurorganosulfurs in soot such as thiophen and sulfonate, which originated mainly from fuel and engine oil, tended to increase with increasing fuel sulfur content.

Characterization of calcium carbonate polymorphs with Ca K edge X-ray absorption fine structure spectroscopy.

Ca K edge X-ray absorption fine structure (XAFS) spectroscopy was utilized for the characterization and quantification of calcium carbonate polymorphs and their mixtures. The advantage of the XAFS is the small sample quantity required for measurements, and a flexible sample environment. The near-edge XAFS spectra of calcite, aragonite and vaterite were measured with the conversion electron yield (CEY) method, and the obtained spectra showed characteristic features that can be utilized as fingerprints. The quantification of mixed polymorphs was examined by using a linear combination fitting of reference XAFS spectra. Though the quality of the fits was satisfactory, discrepancies in the evaluated values were observed between those with X-ray diffraction (XRD) and XAFS. The nonuniformity of samples may be enhanced by the surface sensitivity of the CEY method.

Spatial distribution of hydrogen sulfide and sulfur species in coastal marine sediments Hiroshima Bay, Japan.

This study aims to reveal spatial distribution of hydrogen sulfide and sulfur species in marine sediments in Hiroshima Bay, Japan, by direct analyses using a combination of detection tubes and X-ray absorption fine structure spectroscopy. In summer and autumn, the hydrogen sulfide concentration ranged from <0.1 to 4 mg-S L-1. In this study, only hydrogen sulfide was observed in autumn and at two stations in summer. In contrast, some earlier studies reported in all seasons in Hiroshima Bay the presence of acid volatile sulfide, which is used as a proxy of sulfide content. The sulfur species in sediments were mainly identified as sulfate, thiosulfate, elemental sulfur, and pyrite. Thiosulfate was a minor component compared to the other sulfur species. The formation of pyrite and sulfur derived from hydrogen sulfide oxidation played an important role in the scavenging of hydrogen sulfide.

Optimum reaction ratio of coal fly ash to blast furnace cement for effective removal of hydrogen sulfide.

Reducing hydrogen sulfide concentration in eutrophic marine sediments is crucial to maintaining healthy aquatic ecosystems. Managing fly ash, 750 million tons of which is generated annually throughout the world, is another serious environmental problem. In this study, we develop an approach that addresses both these issues by mixing coal fly ash from coal-fired power plants with blast furnace cement to remediate eutrophic sediments. The purpose of this study is to optimize the mixing ratio of coal fly ash and blast furnace cement to improve the rate of hydrogen sulfide removal based on scientific evidence obtained by removal experiments and XAFS, XRD, BET, and SEM images. In the case of 10 mg-S L-1 of hydrogen sulfide, the highest removal rate of hydrogen sulfide was observed for 87 wt% of coal fly ash due to decreased competition of adsorption between sulfide and hydroxyl ions. Whereas regarding 100 mg-S L-1, the hydrogen sulfide removal rate was the highest for 95 wt% of coal fly ash. However, for both concentrations, the removal rate obtained by 87 wt% and 95 wt% were statistically insignificant. The crushing strength of the mixture was over 1.2 N mm-2 when the coal fly ash mixing ratio was less than 95 wt%. Consequently, the mixing ratio of coal fly ash was optimized at 87 wt% in terms of achieving both high hydrogen sulfide removal rate and sufficient crushing strength.

Elemental distribution in individual rain droplets determined by a combination of the replication method and the synchrotoron radiation X-ray fluorescence microprobe technique.

The main objective of the present study is to specify the chemical properties of individual rain droplets. For this purpose, we have combined the collodion replication method and the SR-XRF microprobe technique. The dry residual materials retained in a single rain droplet, which correspond to the former cloud condensation nuclei and the scavenged particles during droplet falling, were successively reconstructed by the multiple elemental maps using SR-XRF microprobe analytical system. Also the SR-XRF microprobe system allows us to quantify the masses of ultra trace elements in residues of individual rain droplet with fg level. The proposed combination method in the present study is found to be helpful to understand the physicochemical properties of individual rain droplets.

Investigation of individual micrometer-size Kosa particle with on-site combination of electron microscope and synchrotron X-ray microscope.

The Kosa (yellow sand) aerosol affects the global environment as well as human health because it migrates from the interior of China to other areas, absorbing various atmospheric elements. Investigation into individual Kosa aerosol particles, which are submicroscopic to several tens of micrometers in diameter, is required to resolving the issue. We installed a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDX) on a synchrotron radiation (SR) beam line and introduced the SR beam into the SEM chamber for combinatorial application of SEM-EDX and SR X-ray fluorescence (SR-XRF) spectrometry to individual particles. It should be noted that detailed topographic observation by SEM and sensitive elemental analysis by SR-XRF, both crucial for individual particle measurement but which previously had to be carried out separately, were jointly performed inside the SEM chamber in this setup. Here, we show that SR-XRF results, in conjunction with SEM images, contributed toward resolving individual particle dispositions. Atmospheric sulfur primarily adheres to calcium in the aerosol particles and the particle surface roughens as a consequence of the chemical reaction between the two elements.

Field experiments on remediation of coastal sediments using granulated coal ash.

Field experiments were carried out to evaluate the effect of Granulated Coal Ash (GCA) on remediation of coastal sediments in terms of removing phosphates and hydrogen sulfide. Phosphate concentrations in the sediment were kept below 0.2 mg/l after the application of GCA, whereas those in the control sites increased up to 1.0 mg/l. The concentration of hydrogen sulfide in the sediment was maintained at almost zero in the experimental sites (GCA application sites) for over one year, whereas it ranged 0.1-2.4 mg S L(-1) in control sites. Meanwhile, individual number of benthos increased in the experimental sites by several orders of magnitude compared to the control sites. The major process involved in hydrogen sulfide removal by GCA was thought to be the increase in pH, which suppresses hydrogen sulfide formation. From our findings, we concluded that GCA is an effective material for remediating organically enriched coastal sediment.