RESUMO
A liquid organic hydrogen carrier (LOHC) is an interesting concept for hydrogen storage. We describe herein a new, active catalyst system for dehydrogenation of perhydrogenated dibenzyl toluene (H18-DBT), which is a promising LOHC candidate. Pt supported on a rutile-anatase form of titania was found to be more active than Pt supported on anatase-only titania, or on alumina, and almost equally active as Pt supported on carbon. Robust and durable metal oxide supports are preferred for catalysing reactions at high temperatures.
RESUMO
In this study, slot waveguide ring resonators patterned on a silicon-on-insulator (SOI) wafer and coated with an atomic layer deposited nanolaminate consisting of alternating layers of tantalum pentoxide and polyimide were fabricated and characterized. To the best of our knowledge, this is the first demonstration of atomic layer deposition (ALD) of organic materials in waveguiding applications. In our nanolaminate ring resonators, the optical power is not only confined in the narrow central air slot but also in several parallel sub-10 nm wide vertical polyimide slots. This indicates that the mode profiles in the silicon slot waveguide can be accurately tuned by the ALD method. Our results show that ALD of organic and inorganic materials can be combined with conventional silicon waveguide fabrication techniques to create slot waveguide ring resonators with varying mode profiles. This can potentially open new possibilities for various photonic applications, such as optical sensing and all-optical signal processing.
RESUMO
A biopolymer-based template assembly constructed around the spines of the bristle worm Aphrodita aculeata (sea mouse) was used to fabricate very high aspect ratio nanowires and nanotubes using established methods adopted from nanofabrication in porous membranes. The easily available bio-originated template contains more than 100 000 highly ordered, very high aspect ratio nanochannels, each about 150 to 200 nm in diameter but up to a centimetre in length. Their parallel, hexagonal arrangement in the spine constitutes a photonic crystal, which gives the animal its colourful, iridescent appearance. Around the nanochannels, the spines consist of a chitin/protein composite material, which has been shown to withstand the chemical and thermal conditions needed for established template-assisted nanofabrication strategies. A template preparation procedure was developed and the template was used to fabricate copper and nickel nanowires by electrodeposition and aluminium oxide nanotubes by atomic layer deposition. Due to their high thermal and chemical stability, decomposition of the filled templates proved to be difficult, and different approaches to obtain separated nanostructures are described and discussed. Alongside this, the presented system of parallel nanowires or nanotubes in a biopolymer matrix might be utilized in applications, where such separated structures are not needed. Comparing to porous membranes, the presented template allows us to increase the maximum length of nanotubes and nanowires produced using nanochannel-based templates by at least one order of magnitude.
