Analytische Chemie
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Rigid rod-type metallo-supramolecular coordination polyelectrolytes with Fe(II) centres (Fe-MEPEs) are produced via the self-assembly of the ditopic ligand 1,4-bis(2,2':6',2''-terpyridine-4'-yl)benzene (tpy-ph-tpy) and Fe(II) acetate. Fe-MEPEs exhibit remarkable electrochromic properties; they change colour from blue to transparent when an electric potential is applied. This electrochemical process is generally reversible. The blue colour in the ground state is a result of a metal-to-ligand charge transfer at the Fe(II) centre ion in a quasi-octahedral geometry. When annealed at temperatures above 100 °C, the blue colour turns into green and the formerly reversible electrochromic properties are lost, even after cooling down to room temperature. The thermally induced changes in the Fe(II) coordination sphere are investigated in situ during annealing of a solid Fe-MEPE using X-ray absorption fine structure (XAFS) spectroscopy. The study reveals that the thermally induced transition is not accompanied by a redox process at the Fe(II) centre. From the detailed analysis of the XAFS spectra, the changes are attributed to structural changes in the coordination sphere of the Fe(II) site. In the low temperature state, the Fe(II) ion rests in a quasi-octahedral coordination environment surrounded by six nitrogen atoms of the pyridine rings. The axial Fe–N bond length is 1.94 Å, while the equatorial bond length amounts to 1.98 Å. In the high temperature state, the FeN6-site exhibits a distortion with the axial Fe–N bonds being shortened to 1.88 Å and the equatorial Fe–N bonds being elongated to 2.01 Å.
The adsorption behavior of Platinum nanoparticles was studied for the as-received catalyst (under inert gas), under hydrogen and CO atmosphere using our newly designed in-situ cell. X-ray Absorption Spectroscopy (XAS) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) experiments were performed simultaneously with high data quality. Structural information and the type of adsorbate could be revealed via Extended X-ray Absorption Fine Structure (EXAFS) analysis, Δμ X-ray Absorption Near Edge Structure analysis (Δμ XANES) and in-situ DRIFTS. The as-received catalyst showed sub-surface oxygen and O(n-fold). Under CO atmosphere only CO(atop) was found. Reversible adsorbate induced changes of the Pt nanoparticle structure were derived from changes in the Pt-Pt coordination number and the corresponding bond distance. Under reducing conditions (H2, CO) a significant increase in both values occurred. Temperature dependent desorption of CO revealed a gradual shift from Pt-CO to Pt-O. Reoxidation was clearly assigned to strong metal support interaction from the SiO2 support.
Wilson´s disease (WD) is a rare genetic disorder of the copper metabolism, causing the accumulation of copper in different organs, including the liver, the central nervous system and cornea. This way, WD initiates manifold hepatic, neurological or psychiatric symptoms. To learn about the elemental distribution and present species in WD, liver samples were analyzed by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), micro X-ray fluorescence (μXRF) and X-ray absorption near edge structure spectroscopy (XANES).
Within this work, LA-ICP-MS was applied to study the distribution of copper and iron in human liver samples, which were collected by a liver biopsy of WD and control patients within a medical investigation. The analysis by LA-ICP-MS was performed with a 213 nm Nd:YAG laser using a spatial resolution of 10 μm and a scan rate of 20 μm/s. In a next step, copper and iron were quantified by LA-ICP-MS using homemade matrix-matched standards made of gelatin. Results showed an inhomogeneous copper and iron distribution in human liver with hotspots up to several thousand micrograms per gram liver within the hepatocytes.
Additionally, results for the elemental distribution in WD were validated by means of synchrotron radiation-based μXRF with a beam size of 4 μm at the BAMline at BESSYII (Helmholtz-Zentrum Berlin). Furthermore, XANES was performed to identify the present oxidation states of copper in WD, indicating a mixture of copper(I) and copper(II) within the liver tissue.
In the contemporary medicine, rhodanine staining is routinely used to determine the copper distribution in liver tissues. Nevertheless, this method does not provide results with a high sensitivity in comparison to LA-ICP-MS. Therefore, the presented LA-ICP-MS method offers a new possible diagnostic tool. These results may also contribute to a better understanding of Wilson´s disease and its development.
Airborne particulate matter is an issue of growing concern in industrialized countries.
Particles with diameters of less than 10 μm, in particular those with less 2.5 μm, are of special
concern, as they can enter the human lungs and contribute to various cardiovascular and
respiratory diseases. As the composition and health effects of airborne particles in urban, rural
and industrial outdoor air has been studied abundantly, our focus lies on the analysis of
airborne particle samples collected indoors, which may also have a significant effect on
human health, depending on the chemical composition of the particles and the chemical
bonding state, in which elements are present. This chemical speciation can be obtained using
X-ray absorption near edge structure (XANES) analysis, which requires a tunable excitation
source and therefore has to be carried out at synchrotron facilities. For this work, samples
were collected in office rooms of the Atominstitut building.
The BAMline at BESSYII, Berlin, features a double-multilayer monochromator (DMM) and a
double-crystal monochromator (DCM). The DCM offers an energy resolution E/ΔE of around
103, which makes it suitable for X-ray absorption fine structure (XAFS) applications. The
Atominstitut SR-TXRF vacuum chamber, formerly located at HASYLAB, Beamline L, is
now available at the BAMline. The chamber offers a sample changer for up to 8 quartz
carriers suitable for total reflection X-ray fluorescence analysis (TXRF) and was equipped
with a 30 mm² silicon drift detector (SDD). Aerosol samples were produced using a modified
three-stage Dekati™ impactor. For this work, only the coarse (2.5 to 10 μm, Stage 2) and the
fine particle fraction (1 to 2.5 μm, Stage 3), were of interest. XANES analysis was performed
for the elements Cr, Cu and Zn. Oxidation states of these 3 elements will be presented.
The X-ray Fluorescence beamline at ELETTRA operates in partnership with the IAEA an
ultra-high vacuum instrument with a 7-axis manipulator suitable for a variety of X-ray
analytical techniques, such as grazing incidence X-ray fluorescence analysis (GI-XRF),
TXRF, X-ray reflectometry (XRR) and XANES. Samples were produced using a four-stage
Sioutas Personal Cascade Impactor. With this impactor, it is possible to produce sizefractionated
samples down to the sub-μm range (Stages: A > 2.5 μm, B 1 to 2.5 μm, C 0.5 to
1 μm and D 0.25 to 0.5 μm). Direct sampling was performed on siliconized 25 mm Si wafers
suitable for TXRF. Cu-K edge SR-TXRF-XANES analysis was carried out for samples of all
impactor stages. Results of these experiments will be shown.
Airborne particulate matter is an issue of growing concern in industrialized countries. Particles with diameters of less than 10 μm (especially those smaller than 2.5 μm) can enter the human respiratory system and contribute to various diseases depending on their chemical composition and the chemical bonding state, in which elements are present. This chemical speciation can be obtained using X-ray absorption near-edge structure analysis (XANES), which requires a tunable excitation source and therefore has to be carried out at synchrotron facilities. Our special interest lies on the analysis of indoor airborne particulate matter, as particle composition and health effects of outdoor particles have been studied abundantly. For this work, samples were collected in various office rooms in the Atominstitut (ATI) building.
The BAMline at BESSYII features a double-multilayer monochromator (DMM) and a double-crystal monochromator (DCM). The DCM offers an energy resolution E/ΔE of around 103, which makes it suitable for XANES applications. The ATI SR-TXRF vacuum chamber, formerly located at HASYLAB, Beamline L, is now available at the BAMline. The chamber offers a sample changer for up to 8 quartz reflectors and a 30 mm² silicon drift detector (SDD) was used. Aerosol samples were produced using a modified three-stage Dekati™ impactor. For this work, only the coarse (2.5 to 10 μm) and the fine particle fraction (1 to 2.5 μm), were of interest. XANES results of Cr, Cu and Zn will be presented on this poster.
The X-ray Fluorescence beamline at ELETTRA operates in partnership with the IAEA an ultra-high vacuum instrument with a 7-axis manipulator suitable for a variety of X-ray analytical techniques, such as grazing incidence and total reflection X-ray fluorescence analysis (GI-XRF and TXRF), X-ray reflectometry (XRR) and XANES. Samples were produced using a four-stage Sioutas Personal Cascade Impactor. With this impactor, it is possible to produce size-fractionated samples down to the sub-μm range (Stages: A > 2.5 μm, B 1 to 2.5 μm, C 0.5 to 1 μm and D 0.25 to 0.5 μm). Direct sampling was performed on siliconized 25 mm Si wafers suitable for TXRF. Cu-K edge SR-TXRF-XANES analysis was carried out for samples of all impactor stages. Results of these experiments will be shown.
The adsorption behavior of Platinum nanoparticles was studied for the as-received catalyst (under inert gas), under hydrogen and CO atmosphere using our newly designed in-situ cell. X-ray Absorption Spectroscopy (XAS) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) experiments were performed simultaneously with high data quality. Structural information and the type of adsorbate could be revealed via Extended X-ray Absorption Fine Structure (EXAFS) analysis, Dl X-ray Absorption Near Edge Structure analysis (Dl XANES) and in-situ DRIFTS. The as-received catalyst showed sub-surface oxygen and O(n-fold). Under CO atmosphere only CO(atop) was found. Reversible adsorbate induced changes of the Pt nanoparticle structure were derived from changes in the PtAPt coordination number and the corresponding bond distance. Under reducing conditions (H2, CO) a significant increase in both values occurred. Temperature dependent desorption of CO revealed a gradual shift from PtACO to PtAO. Reoxidation was clearly assigned to strong metal support interaction from the SiO2 support.
The preparation and characterization of a Titanium dioxide (TiO2) by a simple, cost effective, facile and eco-friendly green synthesis method using Peltophorum pterocarpum plant extract is presented. The green synthesized nanoparticles were characterized using X-ray diffraction (XRD), Raman spectroscopy, High-resolution transmission electron microscopy (HR-TEM) and X-ray absorption near edge spectroscopy (XANES). XRD results show that the prepared TiO2 NPs were significantly crystalline with various percentages of anatase and rutile phases. The nanoparticles were found to have different diameters ranging from 20 to 80 nm. No evidence of any intermediate or different TiO2 phases were found in XANES measurements performed at the Ti K- and L-edge. It is shown that the TiO2 NPs with high uniformity, high surface area and minimum aggregation can be prepared with relative ease and the desired anatase: rutile phase ratio can be obtained by controlling the experimental conditions.
The BAMline at the synchrotron BESSY II in Berlin supplies users with up to date analytical x-ray methods for the energy range between 5 and 50 keV. Additional to XRF with micron Resolution it provides amongst other things the possibility to use TXRF and XANES. Especially the use of
the so-called Color X-Ray Camera (CXC) opens the possibility to use new and effective detection schemes, which allow to measure simultaneously distributions of elements or Absorption spectra in a motionless mode.
In this talk the analytical possibilities at the BAMline for samples with biological Background will be introduced. The available methods will be presented and discussed for various examples.
A perspective for the future use for XANES in grazing emission and TXRF geometries for plant materials will be given.
News from the BAMline
(2017)
Airborne particulate matter is a topic of growing interest. Particles with aerodynamic diameters less than 10 μm (PM 10) and especially the fine fraction below 2.5 μm (PM2.5) are of particular importance, as they can enter the human respiratory system and cause acute and
chronic respiratory or cardiovascular diseases. The mass distribution of airborne particles in dependence of their diameters is well-known, but also the abundance and temporal variation of trace elements in air (mass concentrations down to the pg/m³ range) are crucial.
These elements originate from various natural (abrasion, erosion) and anthropogenic sources (combustion, road traffic), which complicate the discrimination between harmless and toxic emissions. Some new methods of investigation are therefore needed and X-ray fluorescence spectroscopy has ascertained ist huge potential in this matter, thanks to the possibility to determine simultaneously, in a time-resolved manner, the mass concentrations of critical elements which can be considered as markers of a potential toxic source. A method for the quantitative Analysis of airborne particles directly collected on sample substrates (30 mm quartz reflectors and 1" Si wafers suited for total-reflection X-ray fluorescence analysis (TXRF) will be presented.
Samplings were performed using a three- stage Dekati™ PM10 impactor (>10 μm, 2.5 to 10 μm and 1 to 2.5 μm) and a four-stage Sioutas Personal Cascade Impactor (>2.5 μm, 1 to 2.5 μm,0.5 to 1 μm and 0.25 to 0.5 μm) at indoor and outdoor sites at the Atominstitut (Vienna, Austria). Quantitative results of two outdoor test sampling campaigns (July 2016 and January 2017) will be presented and discussed. Low detection limits were assessed via TXRF and range from several 10 to several 100 pg/m³ depending on the element and particle size fraction.