Zinc oxide nanoparticles were synthesized using a simple precipitation method with zinc sulfate and sodium hydroxide as starting materials. The synthesized sample was calcined at different temperatures for 2 h. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and proton-induced X-ray emission (PIXE) analysis. SEM images show various morphological changes of ZnO obtained by the above method. The average crystallite sizes of the samples were calculated from the full width at half maximum of XRD peaks by using Debye-Scherrer's formula and were found to be in the nanorange. EDS shows that the above route produced highly pure ZnO nanostructures. PIXE technique was used for trace elemental analysis of ZnO. The optical band gaps of various ZnO powders were calculated from UV-visible diffuse reflectance spectroscopic studies.

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Synthesis, characterization and optical properties of zinc oxide nanoparticles

A second X-ray production database is introduced into GUPIX to complement the existing theoretical (ECPSSR–DHS) database and to provide some estimate of analytical uncertainty due to this aspect of GUPIX; it is based on published compilations and analyses of large numbers of measured K and L subshell X-ray production cross-sections. The two databases are compared through analysis of single-element standards and standard reference materials. Good agreement is observed for the case of K X-rays. In contrast, neither the theoretical nor the “reference” database appears to be entirely satisfactory in the case of L X-rays. New work is required on L subshell X-ray production cross-sections using protons. The tools in GUPIX for film thickness determination are expanded, and tested using the two alternative databases.

The Guelph PIXE software package III: Alternative proton database

An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA Supersite, during the Mexico City Metropolitan Area field study (MCMA-2003) from 31 March-4 May 2003 to investigate particle concentrations, sources, and processes The AMS provides real time in- formation on mass concentration and composition of the non-refractory species in particulate matter less than 1 µm (NR-PM1) with high time and size-resolution In order to account for the refractory material in the aerosol, we also present estimates of Black Carbon (BC) using an aethalome- ter and an estimate of the aerosol soil component obtained from Proton-Induced X-ray Emission Spectrometry (PIXE) analysis of impactor substrates Comparisons of AMS + BC + soil mass concentration with other collocated particle instruments (a LASAIR Optical Particle Counter, a PM25 Tapered Element Oscillating Microbalance (TEOM), and a PM25 DustTrak Aerosol Monitor) show that the AMS + BC + soil mass concentration is consistent with the total PM25 mass concentration during MCMA-2003 within the combined uncertainties In Mexico City, the organic fraction of the estimated PM25 at CENICA represents, on average, 546% (standard deviation =10%) of the mass, with the rest consisting of inorganic compounds (mainly ammonium ni- trate and sulfate/ammonium salts), BC, and soil Inorganic compounds represent 275% of PM25 ( =10%); BC mass concentration is about 11% ( =4%); while soil represents

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Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry: results from the CENICA Supersite

Observed spectra normally contain spurious features along with those of interest and it is common practice to employ one of several available algorithms to remove the unwanted components. Low frequency spurious components are often referred to as 'baseline', 'background', and/or 'background noise'. Here we examine a cross-section of non-instrumental methods designed to remove background features from spectra; the particular methods considered here represent approaches with different theoretical underpinnings. We compare and evaluate their relative performance based on synthetic data sets designed to exemplify vibrational spectroscopic signals in realistic contexts and thereby assess their suitability for computer automation. Each method is presented in a modular format with a concise review of the underlying theory, along with a comparison and discussion of their strengths, weaknesses, and amenability to automation, in order to facilitate the selection of methods best suited to particular applications.

Investigation of selected baseline removal techniques as candidates for automated implementation.

TiO2 particles are commonly used as dietary supplements and may contain up to 36% of nano-sized particles (TiO2-NPs). Still impact and translocation of NPs through the gut epithelium is poorly documented. We show that, in vivo and ex vivo, agglomerates of TiO2-NPs cross both the regular ileum epithelium and the follicle-associated epithelium (FAE) and alter the paracellular permeability of the ileum and colon epithelia. In vitro, they accumulate in M-cells and mucus-secreting cells, much less in enterocytes. They do not cause overt cytotoxicity or apoptosis. They translocate through a model of FAE only, but induce tight junctions remodeling in the regular ileum epithelium, which is a sign of integrity alteration and suggests paracellular passage of NPs. Finally we prove that TiO2-NPs do not dissolve when sequestered up to 24 h in gut cells. Taken together these data prove that TiO2-NPs would possibly translocate through both the regular epithelium lining the ileum and through Peyer’s patches, would induce epithelium impairment, and would persist in gut cells where they would possibly induce chronic damage.

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Titanium dioxide nanoparticle impact and translocation through ex vivo, in vivo and in vitro gut epithelia.

Following the introduction of GUPIXWIN in 2005, a number of upgrades have been made in the interests of extending the applicability of the program. Extension of the proton upper energy limit to 5 MeV facilitates the simultaneous use of PIXE with other ion beam analysis techniques. Also, the increased penetration depth enables the complete PIXE analysis of paintings. A second database change is effected in which recently recommended values of L-subshell fluorescence and Coster–Kronig yields are adopted. A Monte Carlo code has been incorporated in the GUPIX package to provide detector efficiency values that are more accurate than those of the previous approximate analytical formula. Silicon escape peak modeling is extended to the back face of silicon drift detectors. An improved description of the attenuation in dura-coated beryllium detector windows is devised. Film thickness determination is enhanced. A new batch mode facility is designed to handle two-detector PIXE, with one detector measuring major elements and the other simultaneously measuring trace elements.

N. Grassi

Papers

The Guelph PIXE software package IV