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nanotimes News in Brief

The CMOS image sensor will be on show at the Vision trade fair from November 9 to 11, 2010, in Stuttgart (Stand 6 D12). http://www.ims.fraunhofer.de/193.html

National Synchrotron Radiation Laboratory (NSRL), University of Science and Technology of China made a great breakthrough in X-ray phase- contrast computed tomography (CT) recently. The simple, fast and low radiation dose X-ray phase- contrast CT technique was newly put forward by the research team led by Prof. Ziyu Wu, director of NSRL. It is developed based on the principle that the absorption contrast is the same but the refraction contrast opposite between front projec- tion and back projection. Wu and his team present an innovative, highly sensitive X-ray tomographic phase-contrast imaging approach based on grating interferometry, which extracts the phase-contrast signal without the need of phase stepping.

The new technique set the prerequisites for fast and low-dose phase-contrast X-ray imaging techniques in the future. In comparison, the existing X-ray phase-contrast imaging technique is subjected to long exposure time, high radiation dose and com- plicated operation, which impairs its wide appli- cation. Experiments show that the new technique can address all these shortages with lower radiation dose and simpler operation.

Peiping Zhu, Kai Zhang, Zhili Wang, Yijin Liu, Xiaosong Liu, Ziyu Wu, Samuel A. McDonald, Federica Marone, and Marco Stampanoni: Low-dose, simple, and fast gra- ting-based X-ray phase-contrast imaging, In: PNAS, Vol. 107(2010), No. 31, August 3, 2010, Pages 13576-13581,

10-09 :: September 2010

DOI:10.1073/pnas.1003198107: http://dx.doi.org/10.1073/pnas.1003198107

In order to accelerate the discovery of optimal catalysts, the working group led by Prof. Bernhard Breit, Internal Senior Fellow of the FRIAS School of Soft Matter Research, has now developed an enti- rely new concept which allows catalysts to be found much more easily than before. The new process for generating and identifying catalysts uses a combi- natorial approach where catalyst libraries are produ- ced by simply mixing complementary components. In this case, catalytically active rhodium(I) centres are modified with phosphine ligands which bond to them. Here, precisely two phosphine ligands always bond to one rhodium centre, a process that the Freiburg chemists have been able to ensure by designing special phosphine ligands. Similar to the adenine (A) - thymine (T) base pair in DNA, these ligands can form complementary hydrogen bonds with one another. By mixing twelve phosphine ligands with ten different complementary phosphine ligands and a metal salt, 120 self-assembling, de- fined molecular catalysts will form without any ad- ditional synthesis steps. In order to identify the most active and the most selective candidates from this catalyst library, the new principle of iterative decon- volution (unravelling) was developed. For this pur- pose, the entire library is divided into sub-libraries. These sub-libraries of catalysts now compete against one another in each test reaction, with activity and, in this case, enantioselectivity as the competition criteria. In the next step, the researchers focused exclusively on the sub-library which had achieved the best result in this competition (it must contain the most active and most selective catalysts), and