Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (33)
- Vortrag (12)
- Beitrag zu einem Sammelband (5)
- Forschungsbericht (2)
- Monografie (1)
- Buchkapitel (1)
- Beitrag zu einem Tagungsband (1)
- Sonstiges (1)
- Posterpräsentation (1)
- Forschungsdatensatz (1)
Schlagworte
- Gold (58) (entfernen)
Organisationseinheit der BAM
- 6 Materialchemie (14)
- 6.3 Strukturanalytik (7)
- 6.1 Oberflächen- und Dünnschichtanalyse (3)
- 1 Analytische Chemie; Referenzmaterialien (2)
- 1.2 Biophotonik (2)
- 5 Werkstofftechnik (2)
- 5.1 Mikrostruktur Design und Degradation (2)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (2)
- 6.6 Physik und chemische Analytik der Polymere (2)
- 4 Material und Umwelt (1)
Eingeladener Vortrag
- nein (12)
Trace element concentrations in gold grains from various geological units in South Africa were measured in situ by field emission-electron probe microanalysis (FE-EPMA), laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and synchrotron micro X-ray fluorescence spectroscopy (SR-µ-XRF). This study assesses the accuracy, precision and detection limits of these mostly non-destructive analytical methods using certified reference materials and discusses their application in natural sample measurement. FE-EPMA point analyses yielded reproducible and discernible concentrations for Au and trace concentrations of S, Cu, Ti, Hg, Fe and Ni, with detection limits well below the actual concentrations in the gold. LA-ICP-MS analyses required larger gold particles (> 60 µm) to avoid contamination during measurement. Elements that measured above detection limits included Ag, Cu, Ti, Fe, Pt, Pd, Mn, Cr, Ni, Sn, Hg, Pb, As and Te, which can be used for geochemical characterisation and gold fingerprinting. Although LA-ICP-MS measurements had lower detection limits, precision was lower than FE-EPMA and SR-µ-XRF. The higher variability in absolute values measured by LA-ICP-MS, possibly due to micro-inclusions, had to be critically assessed. Non-destructive point analyses of gold alloys by SR-µ-XRF revealed Ag, Fe, Cu, Ni, Pb, Ti, Sb, U, Cr, Co, As, Y and Zr in the various gold samples. Detection limits were mostly lower than those for elements measured by FE-EPMA, but higher than those for elements measured by LA-ICP-MS.
Recent results from a three-year multi-disciplinary project on Ancient Egyptian gold jewellery revealed that items of jewellery from the Middle Kingdom to the New Kingdom were manufactured using a variety of alluvial gold alloys. These alloys cover a wide range of colours and the majority contain Platinum Group Elements inclusions. However, in all the gold foils analysed, these inclusions were found to be absent. In this work a selection of gilded wood and leather items and gold foil fragments, all from the excavations by John Garstang at Abydos (primarily from Middle Kingdom graves), were examined using Scanning Electron Microscopy-Energy Disperse Spectroscopy (SEM-EDS), X-Ray Fluorescence (µXRF), Particle Induced X-Ray Emission (µPIXE) and Double Dispersive X-Ray Fluorescence (D²XRF). The work allowed us to characterise the composition of the base-alloys and also to reveal the presence of Pt at trace levels, confirming the use of alluvial gold deposits. Corrosion products were also investigated in the foils where surface tarnish was visually observed. Results showed that the differences in the colour of corrosion observed for the foils are related not only to the thickness of the corrosion layer but also to a multi-layer structure containing the various corrosion products.
This study intends to clarify the metal provenance of gold archaeological items using the variation of the Au–Ag ratio and the presence of trace elements as Sn, Sb, Te, and Pb, concentrating on gold Dacian Koson coins, recovered recently. It also extends the area of our investigations to the copper provenance of Bronze Age artifacts—axes, sickles, and celts—found on Romanian territory. The experiments were performed by micro-SR XRF at BESSY Berlin, at the BAM-line facility. Two types of coins (Koson, with and without monogram) were analysed. The conclusions we reached were that most of the monogram coins are made from refined gold (3–5% Ag, less than 0.5% Cu), while the without monogram coins are made from native Transylvanian gold (9–20% Ag, 0.5–2% Cu), of alluvial origin, proved by the presence of Sn, Sb and Te embedded in the gold. The problem of provenance for prehistoric Romanian copper and bronze objects consists in linking their elemental compositional patterns to the ones of the Bronze Age regional mines from Bulgaria, Serbia or Transylvania, most likely used as ore sources for their manufacture. The studied samples present relevant traces of As, Ag, Sb, and Co, suggesting the most probable use of copper from Serbia or northern Bulgaria for their manufacture.
In the 15th century, Persian manuscripts underwent significant and lasting changes. Possibly as a response to the import of tinted and gold-decorated paper from China, which was used for manuscript production in Greater Iran, Persian papers were also tinted and embellished with gold-decorated and marbled margins or frames. In a joint project between CSMC and the University of St Andrews, and in co-operation with the Golestan Palace Museum, we aim to analyse papers and their decorations in manuscripts in the holdings of the Golestan Palace Library. The analyses aim to determine the consistencies of papers, pigments and metals and the techniques used for their production and application. The support will be first described in its codicological characteristics such as dimensions, thickness, colour (expressed in colour coordinates), pattern left from the sieve (observed in transmitted light). The plant used as raw material in paper production will be studied by fibres analysis, while the sizing agents, the pigments, dyes and metals will be analysed by the application of several methods: in particular Reflectography, X-Ray Fluorescence and InfraRed, Raman and Visible Reflectance Spectroscopy. The results of the analyses will be published in an online database that will form an important resource for the material aspects of Persian manuscripts and be a starting point for establishing a first chronology of the materials and techniques used in Persian manuscript production.
The present study addresses the capability of measurement of relative particle number concentration by scanning electron microscopy for model bimodal silica and gold samples prepared in the frame of the European research project “nPSize - Improved traceability chain of nanoparticle size measurements” as candidate reference nanoparticles.
Measuring in a non-destructive way the characteristic trace elements of the metal allows following the circulation of gold in the past. The aim of this work is to probe the possibilities of X-ray fluorescence with high energy synchrotron radiation (SR-XRF) at the BAMline at BESSY II to determine the concentration of Pt in ancient gold alloys. A HP-Ge detector was used to measure the Pt K-lines excited with an incident energy of 79.5 keV. Data processing was done by subtraction of a Pt free gold standard spectrum from the spectrum of the sample. Depending on the sample composition, the MDL ranges between 40 and 90 ppm. The first results obtained for a small set of gold alloys of different thickness, size and composition showed that high energy SR-XRF is a significant method for the non-destructive determination of Pt in gold.
The structure and composition of ancient gold objects retain information about their long history of manufacture, from the exploitation of the ore to the finishing touches, as well as evidence of their use, deposition, and degradation. By developing an efficient analytical strategy, it is possible to retrieve that information. This chapter sets the necessary foundation 131to explore fully the analytical results presented in the following chapters of this volume. The techniques employed in the analyses of the Egyptian jewellery are described and the analytical parameters provided. For more established techniques, only brief introductions are presented, while more recent developments are presented in greater detail.
Ein Konvolut einzelner Schmuckstücke und die Goldbeigaben eines angeblichen Grabfundes wurden technologisch und analytisch untersucht. Die meisten Objekte sind Blecharbeiten, die aus einer Vielzahl von Einzelteilen mit metallischem Goldlot zusammengefügt und mit Granulation oder granulations-imitierendem Perl- oder Kerbdraht verziert wurden. Nur vier kleine Ohrringe sind massiv gegossen.
Zwei Zierbleche dürften über Patrizen (Positivmodeln), die Deckel der Astragale in Matrizen (Negativmodeln) geformt worden sein. Alle Objekte wurden mit Synchrotron- und atmosphärischer Röntgenfluoreszenz analysiert. Die Daten zeigen das breite Spektrum an Goldlegierungen, die im 7./6. Jahrhundert v. Chr. in Kleinasien verarbeitet wurden: vom natürlichen Seifengold (Elektrum) bis zu geläutertem, fast reinem Gold. Eine Korrelation zwischen Goldqualität und Verarbeitungsmethode konnte nicht festgestellt werden. Sowohl hochreines als auch mit viel Silber und Kupfer legiertes Gold wurde zum Schmieden von Blecharbeiten, aber auch zum Massivguss verwendet. Aus der Goldfarbe kann wegen des Phänomens der oberflächlichen Goldanreicherung nicht auf eine Legierungszusammensetzung geschlossen werden. Der 1963 angekaufte Fundkomplex aus lydischen Metallarbeiten und ostionischen Salbgefäßen aus Ton dürfte einen Grabfund des frühen 6. Jahrhunderts v. Chr. darstellen, dessen Herkunft aus Ephesos jedoch nicht zu sichern ist.
Fingerprinting ancient gold work requires the use of nondestructive techniques with high spatial resolution (down to 25 µm) and good detection limits (micrograms per gram level). In this work experimental setups and protocols for synchrotron radiation induced X-ray fluorescence (SRXRF) at the BAMline of the Berlin electron storage ring company for synchrotron radiation (BESSY) in Berlin for the measurement of characteristic trace elements of gold are compared considering the difficulties, shown in previous works, connected to the quantification of Pt. The best experimental conditions and calculation methods were achieved by using an excitation energy of 11.58 keV, a silicon drift chamber detector (SDD) detector, and pure element reference standards. A detection limit of 3 µg/g has been reached. This newly developed method was successfully applied to provenancing the Xiongnu gold from the Gol Mod necropolis, excavated under the aegis of the United Nations Educational, Scientific and Cultural Organization (UNESCO). The composition of the base alloys and the presence of Pt and Sn showed that, contrary to what is expected, the gold foils from the first powerful empire of the steppes along the Great Wall were produced with alluvial gold from local placer deposits located in Zaamar, Boroo, and in the Selenga River.
(Bio)geochemical cycling of gold (Au) has been demonstrated in present-day (semi)-arid, (sub)-tropical and temperate environment. Hereby biofilms on Au-bearing mineral- and Au-particle surfaces drive Au dispersion and reconcentration, thereby (trans)forming the particles. However, it is unknown if biogeochemical cycling of Au occurs in polar environments, where air temperatures can reach −40 °C and soils remain frozen for much of the year. Therefore, placer Au-particles, soils and waters were collected at two placer mining districts in arctic Finland, i.e., the Ivalojoki and Lemmenjoki goldfields. Sites were chosen based on contrasting settings ((glacio)-fluvial vs. glacial-till deposits) and depths (surface to 5m below current surface). Gold particles were studied using a combination of tagged 16S rRNA gene next generation sequencing and electron microscopic/microanalytical techniques. Across all sites a range of Au-particle morphologies were observed, including morphotypes indicative of Au dissolution and aggregation. Elevated Au concentrations indicative of Au mobility were detected in placer particle bearing soils at both districts. Typically Au-particles were coated by polymorphic biofilm layers composed of living and dead cells embedded in extracellular polymeric substances. Intermixed were biominerals, clays and iron-sulfides/oxides and abundant secondary Au morphotypes, i.e., nano-particles, microcrystals, sheet-like Au, branched Au networks and overgrowths and secondary rims. Biofilms communities were composed of Acidobacteria (18.3%), Bacteroidetes (15.1%) and Proteobacteria (47.1%), with β-Proteobacteria (19.5%) being the most abundant proteobacterial group. Functionally, biofilms were composed of taxa contributing to biofilm establishment, exopolymer production and nutrient cycling, abundant taxa capable of Au mobilization, detoxification and biomineralization, among them Cupriavidus metallidurans, Acinetobacter spp. and Pseudomonas spp., were detected. In conclusion, these results demonstrate that placer Au-particle transformation and Au dispersion occur in cold, arctic environments. This corroborates the existence of biogeochemical Au cycling in present-day cold environments.
The article discusses representative examples published in the field of functional biomimetic chemistry of hybrid materials between 2004 and mid-2007. First, we focus on the modification of morphological aspects of (bio)organicinorganic hybrid materials to create sophisticated gating and switching mechanisms. The architecture of the systems is presented and the elements of control by external stimuli that have been established in recent years, such as optical, electrochemical, chemical, thermal, or magnetic means, are described. Various functions ranging from (site-specific) delivery to indication at the nanometric level are reported. Next we develop the idea of utilizing hybrid frameworks for biomimetic signaling inspired by the way nature has created binding pockets and the concept of induced-fit. Such a merging of inorganic scaffolds with supramolecular concepts results in enhanced molecular recognition and signaling. Finally selected recent advances in the field of hybrid biomimetic motors both of linear and rotary types are presented. The contribution shows how novel biomimetic functions can arise from synergisms between specifically designed hybrid materials and the implementation of supramolecular and/or bioorganic concepts.
The article discusses representative examples published in the field of functional biomimetic chemistry of hybrid materials between 2004 and mid-2007. First, we focus on the modification of morphological aspects of (bio)organicinorganic hybrid materials to create sophisticated gating and switching mechanisms. The architecture of the systems is presented and the elements of control by external stimuli that have been established in recent years, such as optical, electrochemical, chemical, thermal, or magnetic means, are described. Various functions ranging from (site-specific) delivery to indication at the nanometric level are reported. Next we develop the idea of utilizing hybrid frameworks for biomimetic signaling inspired by the way nature has created binding pockets and the concept of induced-fit. Such a merging of inorganic scaffolds with supramolecular concepts results in enhanced molecular recognition and signaling. Finally selected recent advances in the field of hybrid biomimetic motors both of linear and rotary types are presented. The contribution shows how novel biomimetic functions can arise from synergisms between specifically designed hybrid materials and the implementation of supramolecular and/or bioorganic concepts.
The structure of nanoparticles typically differs
from its bulk counterpart. Predominantly, the structures of
gold nanoparticles have been under exceedingly intense
discussion since the discovery of their high catalytic
activity. We found an increasing bond length contraction
with decreasing particle size for citrate-stabilized gold
nanoparticles in aqueous solution as determined by in situ
extended X-ray absorption fine structure (EXAFS) spectroscopy.
Particle sizes and size distributions were determined
by small-angle X-ray scattering. The analysis of the
obtained EXAFS spectra employing ab initio calculations
reveals that the Au–Au bond length undergoes a contraction
of 2 pm for nanoparticles with a radius of 2.9 nm. NIST
reference material RM 8011 gold nanoparticles with a
radius of 4.4 nm exhibit a smaller contraction of approximately
1 pm. Finally, gold atoms in RM 8013 particles
with a radius of 25.7 nm show distances of 288 pm—
identical to the distance in gold foil—and exhibits bulk-like
properties. The observed bond length contraction of gold
nanoparticles in solution is significantly smaller than
previously reported for gold nanoparticle deposited on
surfaces, which is up to 15 pm. This indicates that the
bond length contraction effect of 'free' and 'surfaceimmobilized'
nanoparticles differ fundamentally. Such
difference could be essential for the understanding of
nanoparticle-supported catalysis.
Gold ist eines der sieben bereits in der Antike bekannten Metalle und wurde wegen seines Glanzes und seiner Seltenheit seit jeher als Tauschmittel und zur Herstellung von Schmuck verwendet. Außerdem ist es leicht zu bearbeiten und weitgehend resistent gegen chemische Einflüsse.
Die Analyse von Gold mit der durch Synchrotronstrahlung angeregten Röntgenfluoreszenzanalyse ist zerstörungsfrei und liefert Informationen über die in der untersuchten Probe vorhandenen chemischen Elemente.
Im Mittelpunkt der hier vorgestellten Untersuchungen an der BAMline stehen Fragen nach der Herkunft, dem Herstellungsprozess und der Zugehörigkeit von Goldfunden. Die verschiedenen Fragestellungen werden anhand einer Reihe von Beispielen erläutert, die vom Wikingerschatz von Hiddensee über die Himmelsscheibe von Nebra bis hin zu Funden aus Ägypten reichen. Darüber hinaus werden die heute am Synchrotron verfügbaren modernen Messmethoden vorgestellt.
The mechanism of the recrystallization of nano-scale bacterial surface protein layers (S-layers) on solid substrates is of fundamental interest in the understanding and engineering of biomembranes and e.g. biosensors. In this context, the influence of the charging state of the substrate had to be clarified. Therefore, the electrochemical behaviour of the S-layers on gold electrodes has been investigated by in-situ electrochemical quartz microbalance (EQMB) measurements, scanning force microscopy (SFM) and small-spot X-ray photoelectron spectroscopy (SS-XPS) of potentiostatically emersed substrates. It was shown that the negatively charged bonding sites of the S-layer units (e.g. carboxylates) can bond with positively charged Au surface atoms in the positively charged electrochemical double layer region positive of the point of zero charge (not, vert, similar-0.8 V vs. saturated mercury-mercurous sulphate electrode). Surface conditions in other potential regions decelerated the recrystallization and fixation of S-layers. Time-resolved in-situ and ex-situ measurements demonstrated that two-dimensional S-layer crystal formation on gold electrodes can occur within few minutes in contrast to hours common in self-assembled monolayer (SAM) generation. These results proved that the recrystallization and fixation of 2D-crystalline S-layers on an electronic conductor can be influenced and controlled by direct electrochemical manipulation.
Gold ist eines der sieben schon im Altertum bekannten Metalle und wurde wg. seines Glanzes und seiner Seltenheit von alters her als Tauschmittel und zur Herstellung von Schmuck benutzt. Außerdem ist es einfach bearbeitbar und weitestgehend gegen chemische Einflüsse resistent.
Die Untersuchungen von Gold mit synchrotronstrahlungsangeregter Röntgenfluoreszenzanalyse sind zerstörungsfrei und geben Auskunft über die in der untersuchten Probe vorhandenen chemischen Elemente.
Bei den hier vorgestellten Untersuchungen an der BAMline stehen Fragestellungen wie Herkunft, Herstellungsverfahren und Zusammengehörigkeit von Goldfunden im Vordergrund. Die verschiedenen Fragestellungen werden an einer Reihe von Beispielen erläutert die vom Wikingerschatz aus Hiddensee über die Himmelsscheibe von Nebra bis hin zu Funden aus Ägypten langen. Zusätzlich werden die modernen Messmethoden vorgestellt, die am Synchrotron heutzutage zur Verfügung stehen.