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Author: Scheu, Christina × DDC: 540 ×

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    Structural and chemical characterization of MoO2/ MoS2 triple-hybrid materials using electron microscopy in up to three dimensions
    (Cambridge : Royal Society of Chemistry, 2021) Frank, Anna; Gänsler, Thomas; Hieke, Stefan; Fleischmann, Simon; Husmann, Samantha; Presser, Volker; Scheu, Christina
    This work presents the synthesis of MoO2/MoS2core/shell nanoparticles within a carbon nanotube networkand their detailed electron microscopy investigation in up to three dimensions. The triple-hybrid core/shellmaterial was prepared by atomic layer deposition of molybdenum oxide onto carbon nanotube networks,followed by annealing in a sulfur-containing gas atmosphere. High-resolution transmission electronmicroscopy together with electron diffraction, supported by chemical analysisviaenergy dispersive X-ray and electron energy loss spectroscopy, gave proof of a MoO2core covered by few layers of a MoS2shell within an entangled network of carbon nanotubes. To gain further insights into this complexmaterial, the analysis was completed with 3D electron tomography. By usingZ-contrast imaging, distinctreconstruction of core and shell material was possible, enabling the analysis of the 3D structure of thematerial. These investigations showed imperfections in the nanoparticles which can impact materialperformance,i.e.for faradaic charge storage or electrocatalysis.
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    Morphology, Optical Properties and Photocatalytic Activity of Photo- and Plasma-Deposited Au and Au/Ag Core/Shell Nanoparticles on Titania Layers
    (Basel : MDPI, 2018-7-6) Müller, Alexander; Peglow, Sandra; Karnahl, Michael; Kruth, Angela; Junge, Henrik; Brüser, Volker; Scheu, Christina
    Titania is a promising material for numerous photocatalytic reactions such as water splitting and the degradation of organic compounds (e.g., methanol, phenol). Its catalytic performance can be significantly increased by the addition of co-catalysts. In this study, Au and Au/Ag nanoparticles were deposited onto mesoporous titania thin films using photo-deposition (Au) and magnetron-sputtering (Au and Au/Ag). All samples underwent comprehensive structural characterization by grazing incidence X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Nanoparticle distributions and nanoparticle size distributions were correlated to the deposition methods. Light absorption measurements showed features related to diffuse scattering, the band gap of titania and the local surface plasmon resonance of the noble metal nanoparticles. Further, the photocatalytic activities were measured using methanol as a hole scavenger. All nanoparticle-decorated thin films showed significant performance increases in hydrogen evolution under UV illumination compared to pure titania, with an evolution rate of up to 372 μL H2 h−1 cm−2 representing a promising approximately 12-fold increase compared to pure titania.