Investigation on the stability of water-soluble ZnO quantum dots in KB cells by X-ray fluorescence and absorption methods

The structural stability of water-soluble ZnO quantum dots (QDs) in oral epidermoid carcinoma (KB) cells was studied by the External Micro Proton Induced X-ray Emission (External Micro-PIXE) technique and the X-ray absorption fine structure (XAFS) measurement. The External Micro-PIXE and XAFS experiments were respectively performed at the JAEA and the Shanghai Synchrotron Radiation Facility. The elements’ distributions were detected by the External Micro-PIXE technique. The XAFS method was applied to obtain information about zinc (Zn) K-edge spectra. The fits of the XAFS data showed that the Zn-O bond structure of water-soluble ZnO QDs was stable after being absorbed by KB cells. Its local structural parameters were almost identical with those of the standard wurtzite structure. Water-soluble ZnO QDs had good structural stability in KB cells.     

LAMQS analysis applied to ancient Egyptian bronze coins

Some Egyptian bronze coins, dated VI-VII sec A.D. are analyzed through different physical techniques in order to compare their composition and morphology and to identify their origin and the type of manufacture. The investigations have been performed by using micro-invasive analysis, such as Laser Ablation and Mass Quadrupole Spectrometry (LAMQS), X-ray Fluorescence (XRF), Laser Induced Breakdown Spectroscopy (LIBS), Electronic (SEM) and Optical Microscopy, Surface Profile Analysis (SPA) and density measurements. Results indicate that the coins have a similar bulk composition but significant differences have been evidenced due to different constituents of the patina, bulk alloy composition, isotopic ratios, density and surface morphology. The results are in agreement with the archaeological expectations, indicating that the coins have been produced in two different Egypt sites: Alexandria and Antinoupolis. A group of fake coins produced in Alexandria in the same historical period is also identified.     

Micro-PIXE analyses of trace elements in black shales from the Lower Zechstein copper deposits, Poland

Micro-PIXE analyses made, using the Heidelberg proton microprobe, of thucholite-like organic matter and noble metals bearing shale matrices from the Lower Zechstein copper deposits of the Fore-Sudetic Monocline (Poland) are reported. The experimental conditions included a proton microbeam with a beam spot of ˜ 3 × 3 μm, 3 MeV proton energy and a 195 μm thick external Al absorber. Quantitative results and the detection limits for various elements are reported.     

Determination of sulphur and copper depth distribution in patina layers using nuclear reaction techniques

A method for Cu and S profiling in patina layers was developed by applying a combination of nuclear reaction analysis (NRA) and Rutherford backscattering spectroscopy (RBS). The copper profiling was performed by using the 1327 keV γ-ray deexciting the third excited state to the ground state of ⁶³Cu produced by the reaction ⁶³Cu(p,p^′γ)⁶³Cu. For the determination of sulphur the 2230 keV γ-ray was used deexciting the first excited state to the ground state of ³²S formed through the reaction ³²S(p,p^′γ)³²S, which exhibits three sharp resonances at projectile energies 3.094, 3.195 and 3.379 MeV. The relevant cross-sections were measured in the energy range between 3.0 and 3.7 MeV in steps of 20 keV at 125° to the incident proton beam direction. The technique was tested using artificially produced and natural copper patina layers. Supporting information on the depth distribution of the constituent elements of the patina samples was obtained by p-RBS (E_p: 1.5 MeV, θ: 160°).     

Application of micro-PIXE,MRI and light microscopy for research in wood science and dendroecology

Beech (Fagus sylvatica L.) branches were topped and after five months the wound response was analyzed by PIXE, 3D-MRI and light microscopy. From freshly cut and deeply frozen sample 30 μm thick longitudinal-radial tissue sections were prepared for anatomical investigations and micro-PIXE analysis. Light microscopy revealed the structural response to wounding, i.e. occurrence of the reaction zone between the exposed and dehydrated dead tissue and healthy sound wood. The reaction zone was characterized by tylosis in vessels and accumulation of colored deposits in parenchyma cells, fibres and vessels. 3D MRI of a parallel sample showed that the moisture content in the reaction zone was three times higher than in normal healthy wood. Micro-PIXE mapping at margins of compromised wood in beech revealed an increased concentration of potassium in the reaction zone. The increase in the calcium concentration was associated with the dehydrated tissue adjacent to reaction zones.In addition, micro-PIXE was used to determine the elemental distribution in annual tree rings. This may be relevant for retrospective assessment of environmental pollution in wood by measuring yearly increments as a biomonitoring tool. The analysis of European larch (Larix decidua Mill.) wood revealed a high similarity between optical characteristics (i.e. late versus earlywood) and elemental (e.g. Cl, K, Ca, Mn, Zn) distribution.     

Micro-PIXE elemental imaging of pyrites from the Bulawayan-Bubi Greenstone Belt, Zimbabwe

Micro-PIXE at the NAC nuclear microprobe was used for studies of a sequence of unusual pyrite-bearing carbonate sediments from the east of Turk Mine, Bubi Greenstone Belt, Zimbabwe. This pyrite mineralization shows a variety of textures, and its petrographic interpretation needed more solid geochemical evidence. Elemental maps were obtained using Dynamic Analysis (DA) (a rapid matrix transform method) which forms part of the GeoPIXE software package, and were complemented by point analyses in selected areas. The implemented on-demand beam deflection system allowed for count rates of the order of 3000 counts/s with negligible dead time. The distribution of As and other elements confirmed the petrographic interpretation of three different pyrite generations. In addition, point analyses showed that Sb and Pb were significantly elevated in the zones of As enrichment.     

Plating of archaeological metallic objects - studies by differential PIXE

The differential PIXE method using an external proton beam up to 3 MeV energy was applied to examine plated layers of tin, silver and gold on bronze, brass, iron and silver objects from Roman and Early Medieval period. The concentration profiles were deduced from the measurements by the method of virtual slicing the target into layers, and minimizing the differences between the measured and calculated X-ray yields. The tinned layers were usually thin (about 1 μm), but the thickness of silver and gold layers was in several cases thicker and exceeded the proton range. The plating techniques were identified as application of the molten metal for tinning, and as fire gilding for the gilded objects.     

Characterization and applications of a new tabletop confocal micro X-ray fluorescence setup

A tabletop confocal three-dimensional micro X-ray fluorescence (3D micro-XRF) setup was designed, based on polycapillary X-ray optics and a micro-focus X-ray source. This confocal setup consists of a polycapillary full lens to focus the incident beam and a polycapillary half lens to collect the X-ray fluorescence. The confocal volume was proved to be ellipsoidal. The full-width at half maximum (FWHM) of the confocal volume in three directions were measured with a “knife edge” scan method to obtain the spatial resolution of the confocal setup. The structure of multilayer samples was studied using the depth scan technique.     

Three-dimensional measurement of elemental distribution in minute samples by combination of in-air micro-PIXE and STIM

A technique of measuring three-dimensional (3D) distribution of trace elements in a minute sample was studied using the in-air micro-PIXE (Particle Induced X-ray Emission) system. A 3D distribution was acquired by means of reconstructing numbers of projection images of the sample obtained by micro-PIXE analyses from different directions. This is basically the same technique as X-ray CT (Computed Tomography). However, when this technique was applied to the in-air micro-PIXE analysis, the X-ray yields should be corrected in taking account of such parameters as the X-ray production cross section, the X-ray attenuation coefficient, the energy of an incident particle, and the 3D densities of major elements in the analysis sample. In this study, STIM (Scanning Transmission Ion Microscopy)-CT was used to obtain the 3D density map of the sample. Corrected 3D distributions of sulfur and iron in a minute test sample were successfully measured with this technique in combination of STIM-CT and in-air micro-PIXE.     

Modelling deuterium release during thermal desorption of D-irradiated tungsten

Thermal desorption profiles were modelled based on SIMS measurements of implantation profiles and using the multi-trap diffusion code TMAP7 [G.R. Longhurst, TMAP7: Tritium Migration Analysis Program, User Manual, Idaho National Laboratory, INEEL/EXT-04-02352 (2004)]. The thermal desorption profiles were the result of 500 eV/D⁺ irradiations on single crystal tungsten at 300 and 500 K to fluences of 10²²-10²⁴ D⁺/m². SIMS depth profiling was performed after irradiation to obtain the distribution of trapped D within the top 60 nm of the surface. Thermal desorption spectroscopy (TDS) was performed subsequently to obtain desorption profiles and to extract the total trapped D inventory. The SIMS profiles were calibrated to give D concentrations. To account for the total trapped D inventory measured by TDS, SIMS depth distributions were used in the near-surface (surface to 30 nm), NRA measurements [V.Kh. Alimov, J. Roth, M. Mayer, J. Nucl. Mater. 337-339 (2005) 619] were used in the range 1-7 μm, and a linear drop in the D distribution was assumed in the intermediate sub-surface region (∼30 nm to 1 μm). Traps were assumed to be saturated so that the D distribution also represented the trap distribution. Three trap energies, 1.07 ± 0.03, 1.34 ± 0.03 and 2.1 ± 0.05 eV were required to model the 520, 640 and 900 K desorption peaks, respectively. The 1.34 and 1.07 eV traps correspond to trapping of a first and second D atom at a vacancy, respectively, while the 2.1 eV trap corresponds to atomic D trapping at a void. A fourth trap energy of 0.65 eV was used to fit the 400 K desorption peak observed by Quastel et al. [A.D. Quastel, J.W. Davis, A.A. Haasz, R.G. Macaulay-Newcombe, J. Nucl. Mater. 359 (2006) 8].     

Micro-elemental analysis of some Transylvanian meteorites and lunar samples

Micro-PIXE investigations on some Transylvanian chondritic meteorite fragments and on small Moon soil pieces from the LUNA-16 mission were performed at the Legnaro and Rossendorf proton microprobes. The most exciting finding of the study was the presence of Pt grains in the Moci meteorite. The results are compared to previously published data.     

The concentration and distribution of essential elements in brown rice associated with the polishing rate: Use of ICP-AES and Micro-PIXE

The concentration and distribution of essential elements in brown rice grains (Oryza sativa L. var. japonica) associated with the polishing rate was determined. Rice samples were collected in Japan and polished to 5%, 10%, 15% and 20% loss of the total weight of brown rice. Concentrations of eight essential elements (P, K, Ca, Mg, Cu, Fe, Mn and Zn) were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), and distributions of the elements in a single grain were visualized as elemental distribution maps of a cross section by micro particle induced X-ray emission (Micro-PIXE) analysis. Results of ICP-AES analysis indicated that in rice which polished from 0% to 10% loss of weight, there were three patterns in the P/B ratio, which is the mean concentration of an element in polished rice divided by that of the element in the brown rice: no change (Cu and Zn), a gradual decrease (P, Mg, Mn and Fe), and a decrease after a constant phase (Ca and K). There was no remarkable change of the P/B ratio in rice grains which polished from 10% to 20% loss of weight. Micro-PIXE analysis images showed that P, K, Ca, Mg, Fe and Mn were present in large amounts in the surface layer (approx. <200 μm thickness) of brown rice. Two sub-layers were mainly recognized in the grain surface layer in the elemental distribution maps of a cross section. The first sub-layer was approximately 130-170 μm thick. The second sub-layer was approximately 20-50 μm thick, and the primary part of the grain (endosperm cells and starch granules) was under it. The images showed Cu and Zn were uniformity distributed in brown rice, and their concentrations of polished rice were not affected by the polishing rate. Although ICP-AES measurements could not provide the detail structure of the surface layer of the rice grains, the trend of concentration of the elements generally agreed with the elemental distribution maps obtained Micro-PIXE analysis.     

2D and 3D refraction-based visualization of breast cancer for early clinical check

Duetal carcinoma in-situ （DCIS） has been visualized by 2D XDFI （X-ray dark-field imaging） and further by a 3D X-ray CT, and the data was acquired by the X-ray optics DEI （diffraction-enhanced imaging）. A newly made al- gorithm was used for CT, Data of 900 projections with interval of 0.2 degrees were used. Ductus lactiferi, microcalci- fication in a 3D form have been clearly visible. The spatial resolution available was approximately 30 μm.     

Micro-PIXE studies of char populations in northern Canada

Micro-PIXE analysis of trace elements in otoliths has been used as the basis for several projects on char, a fish that is important for aboriginal subsistence fisheries in Arctic Canada. Life-history patterns were originally inferred from micro-PIXE line scans of Sr distribution. These were confirmed by superposition of Sr distribution patterns on optical images of otoliths of tag-recaptured fish. Char from various populations showed differentiation in otolith primordial Sr concentration; this enables us to differentiate biological stocks and, it is hoped, eventually to assign individuals from mixed-stock fisheries to their stock of origin. Zn oscillations also correlate with annular structure and provide additional temporally constrained information on fish habitat and behaviour.     

Study of new sheep bone and Zn/Ca ratio around TiAlV screw: PIXE-RBS analysis

This study reports on in vivo particle induced X-ray emission (PIXE) measurements combined with Rutherford backscattering spectroscopy (RBS) analyses of new remodeled sheep bone formed around TiAlV screws. The implants (screws) were anodized by a modified TiMax™ process. The interface between the implant and the bone was carefully investigated. [Zn]/[Ca] in-depth composition profiles as well as Ca, Fe elemental maps were recorded. The thickness of new bone formed around the screw reached 300-400 μm. Osteon and Osteoid phases were identified in the new bone. A higher [Zn]/[Ca] ratio was observed in the new bone as compared to the mature bone. Blood vessels were observed in the bone in close contact with the screw.This study shows the potential of ion beam analysis for biological and biomedical characterization.     

Two and/or three dimensional Au nano-clusters on oxide supports analyzed by high-resolution ion scattering

The present study shows that high-resolution medium energy ion scattering (MEIS) can determine the shape and size of two (2D: height below two atomic-layers) and/or three (3D) dimensional nano-clusters of gold, for example, grown on oxide supports. We synthesized a computer program to simulate MEIS spectra from 2D- and/or 3D-clusters approximated by an appropriate analytic function and from underlying substrates. The observed MEIS spectra are well reproduced assuming a partial sphere for 3D-islands. The height, diameter and areal occupation ratios for 2D- and 3D-clusters together with size fluctuation are taken as fitting parameters. The MEIS spectra measured at different scattering geometries allows derivation of a unique solution for the above fitting parameters. The lateral size and its fluctuation determined in such a way agree with those observed by a scanning electron microscope of a field emission type. This paper also presents the initial growth process of gold nano-clusters on reduced TiO₂(1 1 0) substrates.     

Quantitative depth profiling of deuterium up to very large depths

Quantitative depth profiles of deuterium up to very large depths are achieved from the energy spectra of protons created by the D(³He,p)α nuclear reaction at incident energies up to 6 MeV. The advantages of this method compared to the more often applied resonance method are discussed. For light target materials the achievable depth resolution is mainly limited by geometrical spread due to the finite size of the detector aperture, while for heavy materials the resolution is mainly limited by multiple small-angle scattering. A reasonable depth resolution throughout the whole analyzed depth can be obtained by using several different incident energies. Depth profiling up to 38 μm is demonstrated for a-C:D layers deposited on the limiter of Tore Supra, and up to 7.5 μm in tungsten coatings from the divertor of ASDEX Upgrade.     

On the carbon and tungsten sputtering rate in a magnetron discharge

Magnetron discharge as sputtering source can serve as an alternative tool for the study of the plasma-wall interaction, with applications for ITER divertor. The present work reports on the influence of the target power density and the nature of the projectile on the erosion of C and W targets. The experimental results concern the sputtering rate of carbon and tungsten targets of a d.c. magnetron discharge in argon and helium atmosphere, at different gas pressures in the range of 10-100 mTorr and discharge power densities up to 40 W cm⁻² while the discharge current intensity was used as control parameter. In this investigation, carbon and tungsten sputtering rates were measured using two conventional methods based on gravimetric mass loss and profilometry. Target erosion profiles were compared with the profiles of the ion energy flux bombarding the target, calculated from a 2D fluid model.     

基于扫描核探针技术的大气气溶胶单颗粒物源识别与解析方法研究与应用

将高分辨、高灵敏的扫描核探针(SNM)技术与人工神经网络(ANN)模式识别方法相结合,以单个气溶胶颗粒物化学表征为基础,开展大气气溶胶源识别与解析的新方法研究。摸索出单颗粒气溶胶SNM靶样的制备方法。建立了SNM多站多参量分析模式的数据获取系统和分析条件。用SNM测定了单个大气气溶胶粒子的元素谱特征。基于标准的误差反向传输神经网络算法,建立ANN模式识别系统,直接对单个气溶胶粒子的SNM分析能谱模式进行识别,判别其来源,计算源的贡献率。将建立的方法初步应用于上海市大气PM10源识别与解析研究。结果表明该方法解析能力强,解析结果客观,具有查找未知污染源、解析低浓度污染源的特点。