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nanotimes News in Brief

double hydroxides (LDH) via one-step route, In: Transac- tions of Nonferrous Metals Society of China, Vol. 19(2010), Issue 6, December 2009, Pages 1479-1482, DOI:10.1016/ S1003-6326(09)60055-8: http://dx.doi.org/10.1016/S1003-6326(09)60055-8

Researchers from the McGill University, Canada, and Institute for Microstructural Sciences, National Research Council of Canada,Canada, show how electrostatic force detection using atomic force mi- croscopy reveals the electronic structure of indivi- dual and coupled self-assembled quantum dots. An electron addition spectrum results from a change in cantilever resonance frequency and dissipation when an electron tunnels on/off a dot. The spectra show clear level degeneracies in isolated quantum dots, supported by the quantitative measurement of predicted temperature-dependent shifts of Cou- lomb blockade peaks. Scanning the surface shows that several quantum dots may reside on what topo- graphically appears to be just one. Relative coupling strengths can be estimated from these images of grouped coupled dots. © PNAS Lynda Cockins, Yoichi Miyahara, Steven D. Bennett, Aashish A. Clerk, Sergei Studenikin, Philip Poole, An- drew Sachrajda, and Peter Grutter: Energy levels of few-electron quantum dots imaged and characterized by atomic force microscopy, In: PNAS, Vol. 107(2010), No. 21, May 10, 2010, Pages 9496-9501, DOI:10.1073/ pnas.0912716107:

http://dx.doi.org/10.1073/pnas.0912716107

By computer simulation studies, a consortium of theoretical chemists and physicists from the Ruhr- University Bochum, Germany, and King’s College

10-05/06 :: May/June 2010

London, U.K., has now managed to reconstruct the exact course of the light-driven molecular changes and gain insight into the switching pro- cess. This enables targeted chemical design of light- controllable nanotechnological devices.

Chemically modified azobenzene was used for the computer simulation based on the laws of quantum mechanics. The azobenzene molecule can have two forms and vary between them, different co- loured light triggering the switching processes. The researchers carried out a detailed computer simu- lation study of the switchover processes of the two molecular forms, attaining unprecedented insight into the atomic resolution. Dr. Markus Böckmann explained that it is important that the switching process is fast and highly efficient in all devices in which it is used. Recent experiments have shown that particular chemical modifications in azoben- zene can significantly enhance this process. Howe- ver, to date the reasons for this improvement have not been understood. The computer simulation study could explain the experimental results for the first time. The researchers reported that they have been able to establish a clear relationship between the structure and switching properties of the mole- cule. This is a decisive step for the chemical design of azobenzene-based light-driven nanotechnologi- cal devices and thus the development of improved light-controlled materials. Marcus Böckmann, Nikos L. Doltsinis and Dominik Marx: Unraveling a Chemically Enhanced Photoswitch: Bridged Azobenzene, In: Angewandte Chemie International Edi- tion, Volume 49(2010), Issue 19, April 26, 2010, Pages 3382-3384, DOI: 10.1002/anie.200907039 http://dx.doi.org/10.1002/anie.200907039

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