Potamogeton densus

The ordering transition of an amorphous carbon layer into graphene was investigated by high-temperature scanning tunneling microscopy. A disordered C layer was prepared on a Ru(0001) surface by chemical vapor deposition of ethylene molecules at ∼660 K. The carbon layer grows in the form of dendritic islands that have almost the same density as graphene. Upon annealing of the fully covered surface, residual hydrogen desorbs and a coherent but still disordered carbon layer forms, with almost the same carbon coverage as in graphene. The ordering of this layer into graphene at 920 to 950 K was monitored as a function of time. A unique mechanism was observed that involves small topographic holes in the carbon layer. The holes are mobile, and on the trajectories of the holes the disordered carbon layer is transformed into graphene. The transport of C atoms across the holes or along the hole edges provides a low-energy pathway for the ordering transition. This mechanism is prohibited in a dense graphene layer, which offers an explanation for the difficulty of removing defects from graphene synthesized by chemical methods

High-Temperature Scanning Tunneling Microscopy Study of the Ordering Transition of an Amorphous Carbon Layer into Graphene on Ruthenium(0001)

The ordering transition of an amorphous carbon layer into graphene was investigated by high-temperature scanning tunneling microscopy. A disordered C layer was prepared on a Ru(0001) surface by chemical vapor deposition of ethylene molecules at ∼660 K. The carbon layer grows in the form of dendritic islands that have almost the same density as graphene. Upon annealing of the fully covered surface, residual hydrogen desorbs and a coherent but still disordered carbon layer forms, with almost the same carbon coverage as in graphene. The ordering of this layer into graphene at 920 to 950 K was monitored as a function of time. A unique mechanism was observed that involves small topographic holes in the carbon layer. The holes are mobile, and on the trajectories of the holes the disordered carbon layer is transformed into graphene. The transport of C atoms across the holes or along the hole edges provides a low-energy pathway for the ordering transition. This mechanism is prohibited in a dense graphene layer, which offers an explanation for the difficulty of removing defects from graphene synthesized by chemical methods

High-Temperature Scanning Tunneling Microscopy Study of the Ordering Transition of an Amorphous Carbon Layer into Graphene on Ruthenium(0001)

The ordering transition of an amorphous carbon layer into graphene was investigated by high-temperature scanning tunneling microscopy. A disordered C layer was prepared on a Ru(0001) surface by chemical vapor deposition of ethylene molecules at ∼660 K. The carbon layer grows in the form of dendritic islands that have almost the same density as graphene. Upon annealing of the fully covered surface, residual hydrogen desorbs and a coherent but still disordered carbon layer forms, with almost the same carbon coverage as in graphene. The ordering of this layer into graphene at 920 to 950 K was monitored as a function of time. A unique mechanism was observed that involves small topographic holes in the carbon layer. The holes are mobile, and on the trajectories of the holes the disordered carbon layer is transformed into graphene. The transport of C atoms across the holes or along the hole edges provides a low-energy pathway for the ordering transition. This mechanism is prohibited in a dense graphene layer, which offers an explanation for the difficulty of removing defects from graphene synthesized by chemical methods

Nanocellulose-Assisted Formation of Porous Hematite Nanostructures

We report the formation of porous iron oxide (hematite) nanostructures via sol–gel transformations of molecular precursors in the confined space of self-organized nanocrystalline cellulose (NCC) used as a shape-persistent template. The obtained structures are highly porous α-Fe₂O₃ (hematite) morphologies with a well-defined anisotropic porosity. The character of the porous nanostructure depends on the iron salt used as the precursor and the heat treatment. Moreover, a postsynthetic hydrothermal treatment of the NCC/iron salt composites strongly affects the crystal growth as well as the porous nanomorphology of the obtained hematite scaffolds. We demonstrate that the hydrothermal treatment alters the crystallization mechanism of the molecular iron precursors, which proceeds via the formation of anisotropic iron oxyhydroxide species. The nanocellulose templating technique established here enables the straightforward fabrication of a variety of mesoporous crystalline iron oxide scaffolds with defined porous structure and is particularly attractive for the processing of porous hematite films on different substrates

Phase Separation within Vanadium Oxide Islands under Reaction Conditions: Methanol Oxidation at Vanadium Oxide Films on Rh(111)

Submonolayer coverages of V-oxide on Rh(111) condense during catalytic methanol oxidation into a pattern of macroscopic stripes or islands. Under reaction conditions, a phase separation occurs within the VOx islands that has been studied in a pressure range of 10–6–10–4 mbar with photoemission electron microscopy (PEEM), low-energy electron microscopy (LEEM), microspot-low-energy electron diffraction (μLEED), and microspot-X-ray photoelectron spectroscopy (μXPS). An oxidized outer ring with a (√7 × √7)R19.1° structure coexists with an inner (12 × 12) Moiré-type boundary layer and a reduced core exhibiting a (√3 × √3)R30° Moiré type pattern. The dependence of the substructure on the reaction conditions, on V coverage, and on island size was investigated. With μXPS, the V coverages of the different phases in the VOx islands were determined