Photoconductive detection of hydrogen in ZnO and rutile TiO2

Hydrogen donors in ZnO and rutile TiO2 are probed by means of photoconductivity and IR absorption. It is shown that the O–H bonds giving rise to the local vibrational modes (LVMs) of interstitial hydrogen at 3611 and 3290 cm−1 in the case of ZnO and TiO2, respectively, also occur in the photoconductivity spectra as Fano resonances. The effects of isotope substitution, concentration, sample thickness, influence of other donors present in both oxides are considered. Based on the shape and frequency of these resonances, it is concluded that the apparent ionization energy of interstitial hydrogen in rutile TiO2 is less than 300 meV. By a direct comparison, we also demonstrate that photoconductive detection of LVMs of defects in thin semiconductor films is superior to the standard IR absorption

On the method of photoconductive detection of defects in semiconductors by vibrational mode-related Fano resonances

The method of photoconductive detection of defect-related vibrational modes in semiconductors by Fano resonances is validated by a combined photoconductivity and infrared absorption study of the interstitial hydrogen donor in ZnO. Depth-resolved isotopic substitution experiments with varying concentrations of H and D show that the effect of vibrational mode-related absorption has to be taken into account in order to allow for an unambiguous interpretation of the experimental data. A quantitative model is presented which describes the influence of sample thickness, defect concentration, and the presence of other donors on the sign, magnitude, and shape of the Fano resonances. Implications for the photoconductive detection of defect-related vibrational modes are discusse

Effect of uniaxial stress on substitutional Ni in ZnO

The influence of uniaxial stress on the electronic T13(F)→T23(F) transitions of Ni2+ (d8) in ZnO at 4216, 4240, and 4247 cm-1 is studied. It is shown that the split pattern and polarized properties of IR absorption lines are consistent with a dynamic Jahn-Teller effect in the T23(F) state of the defect. © 2013 Elsevier Ltd

Biocompatibility assessment of silk nanoparticles : hemocompatibility and internalization by human blood cells

Many nanoparticles are designed for use as potential nanomedicines for parenteral administration. However, emerging evidence suggests that hemocompatibility is important, but is highly particle- and test-bed dependent. Thus, knowledge of bulk material properties does not predict the hemocompatibility of uncharacterized nanoparticles, including silk nanoparticles. This study compares the hemocompatibility of silk versus silica nanoparticles, using whole human blood under quasi-static and flow conditions. Substantial hemocompatibility differences are noted for some nanoparticles in quasi-static versus dynamic studies; i.e., the inflammatory response to silk nanoparticles is significantly lower under flow versus quasi-static conditions. Silk nanoparticles also have very low coagulant properties - an observation that scales from the macro- to the nano-level. These nanoparticle hemocompatibility studies are complemented by preliminary live cell measurements to evaluate the endocytosis and trafficking of nanoparticles in human blood cells. Overall, this study demonstrates that nanoparticle hemocompatibility is affected by several factors, including the test bed design

Binding energy referencing for XPS in Alkali metal-based battery materials research (II): Application to complex composite electrodes

X-ray photoelectron spectroscopy (XPS) is a key method for studying (electro-)chemical changes in metal-ion battery electrode materials. In a recent publication, we pointed out a conflict in binding energy (BE) scale referencing at alkali metal samples, which is manifested in systematic deviations of the BEs up to several eV due to a specific interaction between the highly reactive alkali metal in contact with non-conducting surrounding species. The consequences of this phenomenon for XPS data interpretation are discussed in the present manuscript. Investigations of phenomena at surface-electrolyte interphase regions for a wide range of materials for both lithium and sodium-based applications are explained, ranging from oxide-based cathode materials via alloys and carbon-based anodes including appropriate reference chemicals. Depending on material class and alkaline content, specific solutions are proposed for choosing the correct reference BE to accurately define the BE scale. In conclusion, the different approaches for the use of reference elements, such as aliphatic carbon, implanted noble gas or surface metals, partially lack practicability and can lead to misinterpretation for application in battery materials. Thus, this manuscript provides exemplary alternative solutions

Standardization of Marine Meteorological Data from FINO Offshore Platforms

KlimawandelDer Ausbau der Offshore-Windenergie gehört zu den erklärten Zielen der Bundesregierung. Um bessere Ken ntnisse der Bedingungen auf See zu erlangen, wurden drei Forschungsplattformen in der Nordsee (FINO 1 und 3) und Ostsee (FINO 2) errichtet. An diesen werden meteorologische und ozeanographische Größen in unterschiedlichen Höhen gemessen, um unter anderem Aussagen zu Vertikalprofilen der Windgeschwindigkeit treffen zu können. Da sich die Plattformen und Masten im Design unterscheiden und sich insbesondere bei den Windmessungen deutlich ein richtungsabhängiger Einfluss auf die Messungen zeigt, ist für die Vergleichbarkeit der Standorte eine standardisierte Auswertung der Messergebnisse erforderlich. Ziel des Projektes FINO-Wind ist es, die Vergleichbarkeit der Daten der drei Standorte zu verbessern und den Datennutzern nach standardisierten Methoden qualitätsgeprüfte Daten zur Verfügung zu stellen. Es sollen deshalb Standardisierungsverfahren zur Auswertung der Winddaten entwickelt werden. Insbesondere die verschiedenen Masteffekte werden eingehend untersucht und durch Windkanalmessungen, Vergleich mit LiDAR-Daten, CFD (Computational Fluid Dynamics)-Modellierungen und Anwendung der UAM (Uniform ambient flow mast correction)-Methode abgeschätzt. Daraus werden Korrekturfaktoren für Windmessungen abgeleitet, die später angewendet werden sollen. Die Messdaten, die als 10-Minuten-Werte vorliegen, werden des Weiteren einer umfassenden und automatisierten Qualitätsprüfung unterzogen. Dabei durchlaufen die Daten in aufeinanderfolgenden Schritten formale, klimatologische, zeitliche, Wiederholungs- und Konsistenzprüfungen und werden nach erfolgreichem Abschluss jeder Sequenz mit spezifischen Qualitätsflags gekennzeichnet. Aus der Analyse und dem Vergleich der Instrumentierung in unterschiedlichen Höhen, der Installation und Ausrichtung sowie die Mastkonstruktionen sollen Empfehlungen herausgearbeitet werden, wie zukünftige Anwendungen im Bereich der Offshore-Windmessungen verbessert werden können

Identification of shallow Al donors in ZnO

A combined magnetic resonance, photoluminescence, photoconductivity, and Raman scattering study of ZnO is presented. Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy identify substitutional Al as a binding core of a shallow, effective-mass-like donor in ZnO. Based on the correlation between the EPR and photoluminescence data it is shown that recombination of an exciton bound to Al gives rise to the 3360.7meV photoluminescence line (I 6). A 1s→ 2p donor transition at 316cm -1 is detected in photoconductivity and Raman spectra. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim