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nanotimes News in Brief

Using a technique similar to a naturally occurring optical phenomenon, an international team led by scientists in Germany has developed a synthetic, three-dimensional material that allows visible light to be modified in specific and desired ways.

Anton Kuzyk, Robert Schreiber, Zhiyuan Fan, Guenther Pardatscher, Eva-Maria Roller, Alexander Hoegele, Fried- rich C. Simmel, Alexander O. Govorov und Tim Liedl: DNA-based Self-Assembly of Chiral Plasmonic Nano- structures with Tailored Optical Re-sponse, In: Nature, Volume 482(2012), Number 7389, March 15, 2012, Pages 245-368, DOI:10.1038/nature10889: http://dx.doi.org/10.1038/nature10889

Researchers at Fritz Haber Institute of the Max Planck Society, Berlin, Germany, have investigated the adsorption of propane and propylene on multi- walled cabon nanotube (CNT) catalysts. By using calorimetry, the team was able to classify four types of adsorption site on the CNT surface:

A) Homogeneous high-energy sites that react reversibly with propane and irreversibly with propylene.

B) Heterogeneous, lower energy sites that react reversibly with propane and irreversibly with propylene.

C) Sites containing oxygenated species that interact weakly and reversibly with both propane and propylene.

D) Low-energy sites free of oxygen corresponding to the graphitic carbon base.

These interactions play a key role in the oxidative dehydrogenation of hydrocarbons – a process that

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has yet to be commercialized due to the higher reactivity of the products than the starting materials. Understanding the role of each type of site could aid the development of commercial catalysts.

B. Frank, S. Wrabetz, O. V. Khavryuchenko, R. Blume, A. Trunschke, R. Schlögl: Calorimetric Study of Propane and Propylene Adsorption on the Active Surface of Multi- walled Carbon Nanotube Catalysts, In: ChemPhysChem, Vol. 12(2011), Issue 15, October 24, 2011, Pages 2709- 2713, DOI:10.1002/cphc.201100491: http://dx.doi.org/10.1002/cphc.201100491

Prof. Rüssel and his colleagues of the Otto-Schott- Institute for Glass Chemistry succeeded in produ- cing a new kind of glass-ceramic with a nanocrys- talline structure, which seems to be well suited to be used in dentistry due to their high strength and its optical characteristics.

“We achieve a strength five times higher than with comparable denture ceramics available today,” Prof. Rüssel explains. The Jena glass chemists have been working for a while on high density ceramics, but so far only for utilisation in other fields, for instance as the basis of new efficient computer hard drives. “In combination with new optical characte- ristics an additional field of application is opening up for these materials in dentistry,” Prof. Rüssel is convinced.

To achieve these characteristics, the glass-ceramics are produced according to an exactly specified tem- perature scheme: First of all the basic materials are