Darinka Primc

Large‐Area Alignment of Tungsten Oxide Nanowires over Flat and Patterned Substrates for Room‐Temperature Gas Sensing

Alignment of nanowires over a large area of flat and patterned substrates is a prerequisite to use their collective properties in devices such as gas sensors. In this work, uniform single-crystalline ultrathin W18 O49 nanowires with diameters less than 2 nm and aspect ratios larger than 100 have been synthesized, and, despite their flexibility, assembled into thin films with high orientational order over a macroscopic area by the Langmuir-Blodgett technique. Alignment of the tungsten oxide nanowires was also possible on top of sensor substrates equipped with electrodes. Such sensor devices were found to exhibit outstanding sensitivity to H2 at room temperature.

Magnetic Nanoplatelet‐Based Spin Memory Device Operating at Ambient Temperatures

There is an increasing demand for realizing a simple Si based universal memory device working at ambient temperatures. In principle, nonvolatile magnetic memory can operate at low power consumption and high frequencies. However, in order to compete with existing memory technology, size reduction and simplification of the used material systems are essential. In this work, the chiral-induced spin selectivity effect is used along with 30-50 nm ferromagnetic nanoplatelets in order to realize a simple magnetic memory device. The vertical memory is Si compatible, easy to fabricate, and in principle can be scaled down to a single nanoparticle size. Results show clear dual magnetization behavior with threefold enhancement between the one and zero states. The magnetization of the device is accompanied with large avalanche like noise that is ascribed to the redistribution of current densities due to spin accumulation inducing coupling effects between the different nanoplatelets.

Doping of TiO2 as a tool to optimize the water splitting efficiencies of titania–hematite photoanodes

Simple metal oxides such as hematite and titania draw tremendous interest as materials for photoelectrochemical (PEC) water splitting photoelectrodes to produce hydrogen as a clean and sustainable energy carrier. However, the high recombination rates of the photogenerated charges limit their application. Herein, we report on highly efficient and stable composite titania–hematite photoanodes prepared by combining doped TiO2 nanoparticles with amorphous iron oxide and subsequent annealing. Studying the effect of various TiO2 doping strategies, by in-depth structural and chemical characterization, carried out through a multiple technique approach, showed that doping of TiO2 allows subtle tuning of the phase composition, microstructure and surface topography of the photoanodes. When the photoanodes were prepared by combining Ta-doped TiO2 nanoparticles and amorphous iron oxide nanoparticles and subsequently annealed, remarkable photocurrents of up to 2.2 mA cm−2 at 1.23 V in 1 M NaOH under 1.5 AM simulated solar illumination were obtained. The high photocurrents, which were traced back to Ta-doping, were elucidated by rutile-hematite heterojunction energetics and the blocking layer formation. In addition to showing promise for a sustainable and cost-effective generation of an energy carrier, the presented strategies can also be expanded to other material combinations opening doors for new modified semiconductors or heterojunction photoanodes.