76 nanotimes News in Brief

A team of scientists at the National Physical Laboratory (NPL) and University of Cambridge has made a significant advance in using nano-devices to create accurate electrical currents. They have developed an electron pump - a nano-device - which picks these electrons up one at a time and moves them across a barrier, creating a very well-defined electrical current. The device drives electrical current by manipulating individual electrons, one-by-one at very high speed. This technique could replace the traditional definition of electrical current, the ampere, which relies on measurements of mechanical forces on current-carrying wires.

SEM image of the electron pump. The arrow shows the direction of electron pumping. The hole in the middle of the electrical control gates where the electrons are trapped is about 0.0001mm (100nm) across. © NPL, UK

The key breakthrough came when scientists experimented with the exact shape of the voltage pulses that control the trapping and ejection of electrons. By changing the voltage slowly while trapping electrons, and then much more rapidly when ejecting them, it was possible to massively speed up the overall rate of pumping without compromising the accuracy. By employing this technique, the team were able to pump almost a billion electrons per second, 300 times faster than the previous record for an accurate electron pump set at the National Institute of Standards and Technology (NIST) in the USA in 1996.

S.P. Giblin, M. Kataoka, J.D. Fletcher, P. See, T.J.B.M. Janssen, J.P. Griffiths, G.A.C. Jones, I. Farrer & D.A. Ritchie: Towards a quantum representation of the ampere using single electron pumps, In: Nature Communications, Vol. 3, July 03, 2012, Article number: 930, DOI:10.1038/ncomms1935:

http://dx.doi.org/10.1038/ncomms1935

http://www.npl.co.uk/science-technology/quantum-detection/

German HZB scientists have apply a new method - "inverse Partial Fluorescence Yield" (iPFY) on micro-jet – which will enable them to probe the electronic structure of liquids free of sample damages. The experiments are performed in vacuum conditions at the LiXEdrom experimental chamber, where a fluid stream of micrometer diameter is moving freely through vacuum and is continuously irradiated with X-ray radiation. These kinds of experiments are important as they reveal the interaction strength of the X-rays with the liquids and therefore allow for the structural analysis of substances dissolved in solution. 

"The method will achieve its absolute apprehension when will be applied to metal ions that are part of  chemical catalysts used for clean energy production and biocatalysts (protein enzymes) used in biochemical transformation inside the living cells" - the team leader Prof. Aziz stated, "which is the next milestone in our research progress. Previously, these types of experiments were so far only possible if the fluid was contained between two membranes."

Malte D. Gotz, Mikhail A. Soldatov, Kathrin M. Lange, Nicholas Engel, Ronny Golnak, René Könnecke, Kaan Atak, Wolfgang Eberhardt, and Emad F. Aziz: Probing Coster–Kronig Transitions in Aqueous Fe2+ Solution Using Inverse Partial and Partial Fluorescence Yield at the L-Edge, In: Journal of Physical Chemistry Letters, Vol. 3, Issue 12, Pages 1619-1623, DOI: 10.1021/jz300403nDOI:10.1021/jz300403n:

http://dx.doi.org/10.1021/jz300403n