Solution processed multi-layered thin films of Ge20Sb5S75 and Ge20Sb5Se75 chalcogenide glasses.

Solution processed non-toxic Ge20Sb5Se75 chalcogenide glass thin films were deposited using spin-coating method from n-propylamine-methanol solvent mixture in specular optical quality. Optical properties, composition, structure, and chemical resistance were studied in dependence on the annealing temperature. Significant increase of refractive index and chemical resistance caused by thermoinduced structural polymerization and release of organic residua were observed. The high chemical resistance of hard-baked thin films allowed repeated direct depositions by spin-coating, increasing total thickness. Multilayered thin films of amorphous Ge20Sb5Se75 and Ge20Sb5S75 were also successfully prepared by direct deposition for the first time. Solution based deposition of non-toxic Ge20Sb5Se75 thin films in specular optical quality significantly widens the applicability of solution processed chalcogenide glass thin films. Moreover, solution based direct deposition of different glasses on hard-baked thin films opens the way to simple and cost-effective preparation of more sophisticated optical elements (e.g. beam splitters, photonic mirrors).

Skin Barrier Fine Tuning through Low-Temperature Lipid Chain Transition.

The lipids in the mammalian stratum corneum (SC) adopt an unusually rigid arrangement to form a vital barrier preventing water loss and harmful environmental impacts. Just above the physiological temperature, a subset of barrier lipids undergoes a phase transition from a very tight orthorhombic to a looser hexagonal arrangement and vice versa. The purpose of this lipid transition in skin physiology is unknown. Permeability experiments on isolated human SC indicated that the transition affects the activation energy for a model compound that prefers lateral movement along lipid layers but not for water or a large polymer that would cross the SC through the pore pathway. The orthorhombic phase content of SC lipids, as determined by infrared spectroscopy, was also modulated by (de)hydration. Spontaneous rearrangement of human SC lipid monolayers into 10 nm higher multilamellar islets at 32-37 °C but not at room temperature was revealed by atomic force microscopy. Our findings add to our knowledge of fundamental skin physiology suggesting a fine temperature- and hydration-controlled switch from fluid lipids (required for lipid barrier assembly) to rigid and tightly packed lipids in the mature SC (necessary for the water and permeability barriers).

2D FeSx Nanosheets by Atomic Layer Deposition: Electrocatalytic Properties for the Hydrogen Evolution Reaction.

2-dimensional FeSx nanosheets of different sizes are synthesized by applying different numbers of atomic layer deposition (ALD) cycles on TiO2 nanotube layers and graphite sheets as supporting materials and used as an electrocatalyst for the hydrogen evolution reaction (HER). The electrochemical results confirm electrocatalytic activity in alkaline media with outstanding long-term stability (>65 h) and enhanced catalytic activity, reflected by a notable drop in the initial HER overpotential value (up to 26 %). By using a range of characterization techniques, the origin of the enhanced catalytic activity was found to be caused by the synergistic interplay between in situ morphological and compositional changes in the 2D FeSx nanosheets during HER. Under the application of a cathodic potential in alkaline media, the as-synthesized 2D FeSx nanosheets transformed into iron oxyhydroxide-iron oxysulfide core-shell nanoparticles, which exhibited a higher active catalytic surface and newly created Fe-based HER catalytic sites.