Refine
Year of publication
Document Type
Way of publication
- Open Access (9)
Keywords
- resonant photoelectron spectroscopy (7)
- Graphene (4)
- scoping review (4)
- water splitting (4)
- HBSC (3)
- HOPG (3)
- Health inequalities (3)
- National Educational Panel Study (3)
- XPS (3)
- health inequalities (3)
Institute
- FG Angewandte Physik und Halbleiterspektroskopie (42)
- FG Gesundheitswissenschaften (22)
- FG Pädagogische Psychologie in Gesundheitsberufen (8)
- FG Kommunikationstechnik (6)
- FG Halbleitermaterialien (2)
- Stiftungsprofessur Hochfrequenz- und Mikrowellentechnik (2)
- FG Statik und Dynamik (1)
- FG Technische Mechanik und Maschinendynamik (1)
Einleitung Zielsetzung des Beitrags ist es, zu untersuchen, inwiefern die sozioökonomische Komposition von Schulen mit dem Wohlbefinden von Schülerinnen und Schülern in Deutschland assoziiert ist. Konkret wurden die Assoziationen der Bildung, des Einkommens und des beruflichen Status der Eltern auf Individualebene und aggregiert auf Schulebene sowie die Interaktionen zwischen diesen Ebenen auf das subjektive Wohlbefinden von Schülern der Sekundarstufe I untersucht.
Methoden Es wurden Daten der Startkohorte „Klasse 5“ des Nationalen Bildungspanels (NEPS) herangezogen. Die Kohorte startete 2010 mit einer repräsentativen Stichprobe von Fünftklässlern in Deutschland, welche jährlich nachverfolgt wurden. Es wurden Erhebungswellen von der fünften bis zur neunten Klasse zusammengefasst. Damit konnten 14.265 Beobachtungen mit vollständigen Angaben von 3.977 Schülerinnen und Schülern in 218 Schulen in den Analysen berücksichtigt werden. Mit Mixed-Models wurde getestet, ob die sozioökonomische Position auf individueller und/oder schulischer Ebene und die ebenenübergreifende Interaktion dieser Indikatoren mit dem Wohlbefinden (adaptierter Personal Well-Being – School Children-Index) der Jugendlichen assoziiert ist. Es wurde für Alter, Geschlecht, Migrationshintergrund, Familienform, Schultyp und Notendurchschnitt kontrolliert.
Ergebnisse Auf individueller Ebene war das elterliche Einkommen mit höherem Wohlbefinden verbunden. Der berufliche Status der Eltern zeigte keine signifikanten Assoziationen. Auf Schulebene fanden wir einen geringen, positiven Zusammenhang zwischen dem durchschnittlichen elterlichen Einkommen und dem individuellen Wohlbefinden, aber auch einen mäßig negativen Einfluss eines hohen Anteils hoch gebildeter Eltern auf das Wohlbefinden. In Sensitivitätsanalysen blieben diese Zusammenhänge auch bei separater Betrachtung dieser Indikatoren bestehen. Die Zusammenhänge auf Individualebene wurden nicht durch die sozioökonomische Komposition von Schulen moderiert, es konnten keine signifikanten ebenenübergreifende Interaktionen festgestellt werden.
Schlussfolgerung Es wurde ein Zusammenhang der sozioökonomischen Zusammensetzung der Schule mit dem subjektiven Wohlbefinden der Jugendlichen gefunden. Internationale Befunde einer Moderation der Zusammenhänge auf individueller Ebene durch sozioökonomische Charakteristika auf Schulebene konnten jedoch nicht repliziert werden. Die Zusammenhänge zwischen individueller SEP und Wohlbefinden variieren somit nicht in Abhängigkeit von der SEP auf Schulebene. Es zeigen sich vielmehr in Teilen additive Effekte für die individuelle und schulische SEP.
The use of electrochemistry, X-ray photoelectron spectroscopy, and resonant X-ray spectroscopy has unlocked the paradox of interfacial hole conduction through amorphous TiO2 (a-TiO2) to deposited Ni, Ir, and Au metal catalysts. Although electrocatalysts for the oxygen-evolution reaction derived from metallic Ir and Ni have mutually similar overpotentials in alkaline media, Si/a-TiO2/Ir interfaces exhibit higher overpotentials than Si/a-TiO2/Ni interfaces. The data allow formulation of full band energy diagrams for n-Si/a-TiO2/metal interfaces for M = Ni, Ir, or Au. Although both Ni and Ir produce band bending in a-TiO2 favoring hole conduction, only Ni creates multiple states within the a-TiO2 band gap at the a-TiO2/Ni interface, which produces a quasi-metallic interface at the a-TiO2/Ni junction. Au, however, produces a flat-band interface that limits hole conduction without any new band gap states.
Photoelectrochemical (PEC) cells offer the possibility of carbon-neutral solar fuel production through artificial photosynthesis. The pursued design involves technologically advanced III–V semiconductor absorbers coupled via an interfacial film to an electrocatalyst layer. These systems have been prepared by in situ surface transformations in electrochemical environments. High activity nanostructured electrocatalysts are required for an efficiently operating cell, optimized in their optical and electrical properties. We demonstrate that shadow nanosphere lithography (SNL) is an auspicious tool to systematically create three-dimensional electrocatalyst nanostructures on the semiconductor photoelectrode through controlling their morphology and optical properties. First results are demonstrated by means of the photoelectrochemical production of hydrogen on p-type InP photocathodes where hitherto applied photoelectrodeposition and SNL-deposited Rh electrocatalysts are compared based on their J–V and spectroscopic behavior. We show that smaller polystyrene particle masks achieve higher defect nanostructures of rhodium on the photoelectrode which leads to a higher catalytic activity and larger short circuit currents. Structural analyses including HRSEM and the analysis of the photoelectrode surface composition by using photoelectron spectroscopy support and complement the photoelectrochemical observations. The optical performance is further compared to theoretical models of the nanostructured photoelectrodes on light scattering and propagation.
Long-term space missions require extra-terrestrial production of storable, renewable energy. Hydrogen is ascribed a crucial role for transportation, electrical power and oxygen generation. We demonstrate in a series of drop tower experiments that efficient direct hydrogen production can be realized photoelectrochemically in microgravity environment, providing an alternative route to existing life support technologies for space travel. The photoelectrochemical cell consists of an integrated catalyst-functionalized semiconductor system that generates hydrogen with current densities >15 mA/cm2 in the absence of buoyancy. Conditions are described adverting the resulting formation of ion transport blocking froth layers on the photoelectrodes. The current limiting factors were overcome by controlling the micro- and nanotopography of the Rh electrocatalyst using shadow nanosphere lithography. The behaviour of the applied system in terrestrial and microgravity environment is simulated using a kinetic transport model. Differences observed for varied catalyst topography are elucidated, enabling future photoelectrode designs for use in reduced gravity environments.
Oxide surface coatings are of importance in tailoring interface properties with respect to surface passivation, adjustment of surface potentials, or providing active centers for surface reactions. In this contribution, we report about surface coatings prepared by the atomic layer deposition (ALD) method. ALD is known for its conformal growth of ultrathin, dense films which exhibit a low concentration of pinholes.
The performance of a photoelectrochemical solar cell depends strongly on the electrochemical nature of the semiconductor/electrolyte junction [1]. Operando Ambient Pressure X-ray photoelectron spectroscopy
investigation of semiconductor/liquid junctions provides quantitative understanding of the energy bands in these photoelectrochemical solar cells [2, 3, 4]. We demonstrate how OAP-XPS may be used to determine these relationships for semiconductor/liquid systems. The data can be
analyzed to determine the energy relationship between the electronic energy bands in the semiconductor electrode and the redox levels in the solution. The major conditions for semiconductor-electrolyte contacts including accumulation, depletion, and Fermi-level pinning are observed, and the so-called flat-band energy can be determined. [1]
Science 344 (2014) 1005; [2] Sci Rep 5 (2015) 9788; [3] Ener Sci 8 (2015) 2409; [4] J Electrochem Soc 162 (2016) H1
Photoelectrochemical cells based on semiconductor-liquid interfaces provide a method of converting solar energy to electricity or fuels. Recently, we have demonstrated operational systems that involved stabilized semiconductor-liquid junctions [1]. The electrical and spectroscopic properties of the TiO2/Ni protection layer system have been
investigated in contact with electrolyte solutions [2, 3, 4]. From the response of the photoelectron binding energies to variations in applied potential the energetics of the solid/electrolyte interface are elucidated.
The degree of conductivity depended on the chemical state of the Ni on the TiO2 surface. The combinations of these techniques provide a powerful tool for the investigation of hybrid electrode/solution contacts. [1] Science 344 (2014) 1005; [2] Sci Rep 5 (2015) 9788; [3] Ener & Env Sci 8 (2015) 2409; [4] J Electrochem Soc 162 (2016) H1
Probing the TiO2/Liquid Interface of a Photoelectrochemical Cell by X-Ray Photoelectron Spectroscopy
(2016)
Amorphous TiO2 coatings can stabilize semiconductor photoanodes such as Si, GaAs, and GaP that are otherwise unstable in aqueous media [1]. Using tender X-rays with their substantially increased inelastic mean free scattering length of photoelectrons and using the classical three-electrode potentiostatic arrangement allows one to follow of the influence of the applied potentials on the semiconductor electrode energetics such as band bending and band edge shifts directly [2, 3]. The observed shifts in binding energy with respect to the applied potential have directly revealed rectifying junction behavior on semiconducting samples. Accumulation, depletion and Fermi level pinning were observed. Additionally, the non-linear response of the core level binding energies to changes in the applied electrode potential has revealed the influence of defect-derived electronic states on the Galvani potential across the complete cell. [1] Science 344 (2014) 1005; [2] Sci Rep 5 (2015) 9788; [3] Ener & Env Sci 8 (2015) 2409
Spin State and Satellite Structures of ε-Fe₂O₃ as determined by Resonant Photoelectron Spectroscopy
(2015)
We use resonant photoelectron spectroscopy at the Fe2p and the O1s absorption edges to report on spectroscopic investigation of Fe-oxides nanoparticles. We discuss the spectroscopic details like multiple Auger decays, satellite emission in the X-ray absorption process and the core level data. We explain these data by a novel mechanism in which the resonant excitation between Fe3d and Fe4s states are involved.
This mechanism is observed when the photo-excited electron becomes polarized by the electron–hole pairs existing in the conduction and valence bands.
In the framework of this thesis synchrotron radiation spectroscopy is applied to study the electronic structure of organic semiconductors, of Graphene, and of transition metal (TM) oxide water splitting catalysts (Co-PI) with emphasis on excitonic and polaronic effects.
For a correct theoretical description of the electronic structure of these material classes electron-phonon and electron-electron coupling as well as polarization and excitonic effects have to be considered. Excitons and Polarons are localized in-gap states. They are known to affect the optical properties of the material. Their influence can also be revealed in the resonant Auger decay profile.
Even in TM-oxides Polarons and Excitons are observed as a consequence of an oxygen 2p to TM3d charge transfer.
Therefor, the following three material classes are chosen for the fundamental study of Excitons and Polarons in resonant Auger decay processes.
First, the existence of localized polaronic and excitonic states is investigated for regioregular-Poly(3 hexylthiophene-2,5-diyl) (rr-P3HT) and Phenyl-C61-butyric acid methyl ester (PCBM) used as a light absorber in organic solar cells. The existence of 2D-Polarons, singlet Exciton, and triplet Exciton is demonstrated for rr-P3HT whereas for PCBM only singlet Excitons are observed. Singlet Excitons show an influence on the resonant Auger decay by a combined spectator-participator (S+P) Auger decay in the π*-band.
Second, for a more detailed study of the (S+P) decay Highly Ordered Pyrolytic Graphite (HOPG) is chosen. For Graphene as a single layer of HOPG without van der Waals force another combination of Auger decays can be observed: a double spectator Auger (S+S) and a double spectator Auger-Gain (S+S)* decay.
Third, Co-PI (cobalt oxide compound) is investigated. It is a TM-oxide catalyst used for the oxygen evolution reaction in photo-electrochemical cells. Self-trapped Excitons formed by resonant core electron excitation into self-trapped hole states give rise to a combined Auger decay process (S+P).
For all three novel Auger decay processes {(S+P), (S+S), and (S+S)*} a model is proposed.