Chalcogenides nanostructures

The different classes of Ru-based catalysts, including crystalline Chevrel-phase chalcogenides, nanostructured Ru, and Ru-Se clusters, and also Ru-N chelate compounds (RuNj), have been reviewed recently by Lee and Popov [29] in terms of the activity and selectivity toward the four-electron oxygen reduction to water. The conclusion was drawn that selenium is a critical element controlling the catalytic properties of Ru clusters as it directly modifies the electronic structure of the catalytic reaction center and increases the resistance to electrochemical oxidation of interfacial Ru atoms in acidic environments. 

Laboratory of Electrocatatalysis, University of Poitiers, France Keywords Cluster, photocatalysis, Chalcogenide, nanostructure, Oxygen reduction... 

Semiconducting chalcogenide nanostructures have received a great deal of attention for application in optoelectronic devices, such as blue laser diodes, light-emitting diodes, solar cells, IR optical windows, optical limiting, and so on [12-17]. To synthesize them as a pure phase is a... 

One-dimensional nanostructures of chalcogens and chalcogenides. An overview of solution-phase methods for generating one-dimensional nanostructures of chalcogens and chalcogenides has been presented by Mayers et al. (2004). Attention was especially focused on Se and Te because of their characteristic crystal structures and their catenation tendency. Basically, reactions were considered such as ... 

Porous chalcogenide aerogels is another broad class of non-oxidic framework that prepared by template-free routes [71-73]. These materials possess a continuous nanostructured chalcogenide framework that is penetrated by a random network of nanopore channels. Because these high surface area structures are random and not exhibit long-range pore periodicity, such systems are outside of the scope of this review and will not be covered further. 

Photo)Electrocatalysis on Nanostructured TiO2 Surface Modified via Chalcogenide Materials... 

The methods of preparation discussed above do not involve any template and the nanoparticles of the oxide or the trisulfide act as nucleation centers for tube growth. Recently, CNTs have been used as templates to grow MoS2, WS2 and NbS2 coated carbon nanotubes, some of which contain 1-2 layers of the chalcogenide at the exterior. " The CNTs were coated with the metal oxide or its precursor and treated in a H2S/H2/N2 atmosphere at elevated temperatures to convert the oxide to the sulfide However, the CNT core was not removed in the nanostructures (Fig. IS). 

The most likely application of the chalcogenide nanotubes is as solid lubricants. Mo and W chalcogenides are widely used as solid lubricants. It has been observed that the hollow nanoparticles of WS2 show better tribological properties and act as a better lubricant compared to the bulk phase in every respect (friction, wear and life-time of the lubricant).142 Tribological properties of 2H-MoS2 and WS2 powder can be attributed to the weak van der Waals forces between the layers which allow easy shear of the films with respect to each other. The mechanism in the WS2 nanostructures is somewhat different and the better tribological properties may arise from the rolling friction allowed by the round shape of the nanostructures. 

Highly Ordered Semiconductor Nanostructures Based on Ti02 and TiOa/Metal Chalcogenides... 

Typically, electroplating metals and metal alloys is less sophisticated than the corresponding metal oxide or chalcogenide electrodeposition. Further, dense and highly stable deposits are usually obtained. The two-step synthesis approach is more versatile, in a sense that after identifying a synthesis route to a nanostructured metal, various ceramics can be produced by thermal oxidation under an appropriate atmosphere. In fact more porous and sophisticated structures, such as hollow nano-spheres, nanotubes, and nano-peapods, can be synthesized based on the nanoscale Kirkendall effect (NKE) occurring during thermal oxidation [2-5]. 

While the thermal oxidation of a compact metal surface is usually limited to the growth of an oxide layer with a thickness of a few of nanometers, bulk metal nanostmctures can be fully converted into the corresponding oxide or chalcogenide. Again the relative diffusion rate of metal atoms and the oxidation agent in the oxide determine the oxidation kinetics and structure formation. A topographic transformation to a metal oxide nanostructure is observed when the mobility of the oxidation agent exceeds the one of the metal atoms. When this is not the case, the so-called nanoscale Kirkendall effect (NKE) responsible for the formation of sophisticated hollow nanostructures, such as nanospheres, nanotubes, and nanopeapods, proceeds [2-5]. 

A variety of solution methods such as seed-assisted growth, template-based synthesis, polyol method, solvothermal method and oriented attachment have also been developed for the synthesis of one-dimensional nanostructures. Here we will present various examples of the nanowires including metals, oxides, chalcogenides and pnictides with different synthetic methods. 

G.A. Seisenbaeva and V.G. Kessler, Precursor directed synthesis - molecular mechanisms in the Soft Chemistry approaches and their use for template-free synthesis of metal, metaloxide and metal chalcogenide nanoparticles and nanostructures, Nanoscale, Vol. 4, pp. 6229-6244,2004. 

Alonso-Vante N (2003) Physico-chemical properties of novel nanocrystalline ruthenium based chalcogenide materials. In Kokorin AI, Bahnemann DW (eds) Chemical physics of nanostructured semiconductors. VSP Brill Academic, Zeist, pp 135-152... 

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