Julich researchers use a scanning tunneling microscope [ 3 ] to analyze the Nanoscale . The thin metal tip of the microscope traverses the sample surface like a needle of a gramophone and records by using small electric currents and surface roughness height differences of approximately one nanometer. But even with a microscope tip reduced to the size of an atom , it was hitherto impossible to have an image of the inside molecules .

” To increase the sensitivity for organic molecules, we placed a sensor and a signal converter to the microscope tip , ” said Dr. Ruslam Temirov . These two functions are fulfilled by a small molecule consisting of two atoms of deuterium (also known as heavy water) . This molecule is moving at the tip, it can follow the contours of the sample and affects the currents that pass through this point.

The first molecule that Temirov and his colleagues have studied is perylene – tetracarboxylic acid dianhydride ( APTCD ) [4] . It is composed of 24 carbon atoms , eight hydrogen atoms and six oxygen atoms , with seven cyclic structures of about one nanometer. In the images acquired previously, she was represented by a task of about one nanometer without precise contours . The scanning tunneling microscope Jülich can represent the inner structure honeycombed due to the seven carbon cycles .

“The simplicity of this method gives it great value for future research ” says Prof . Stefan Tautz, director of the Institute for Bio -and Nanosystems Centre Jülich. This method is patent pending and will pair easily with commercial scanning tunneling microscopes . ” Just a few minutes to determine the spatial dimensions of molecules inside , and preparedness of the sample is largely based on standard processes , ” says Tautz . The next step is to calibrate the measured currents . If it works, different types of atoms and molecules could be identified by the value of the measured currents .

After publishing in 2008 the first images acquired using this method, researchers were able to explain the quantum mechanical principle of action of deuterium in the microscope tip . That with the help of a computer calculation of the group of Prof. . Rohlfing , University of Osnabrück . According to the principle of Pauli repulsion , the quantum force short distance between the deuterium molecule and modulates the conductivity and thus allows very precise measurement of fine structures .

By improving the method , it might even be possible to analyze large biomolecules in three dimensions.

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[ 4] perylene – tetracarboxylic acid dianhydride is a pigment used in the development of organic components of semi- conductors. It is produced by the dye industry for commercial applications.

- [1] ” in Scanning Imaging Pauli Repulsion Tunneling Microscopy ” : C. Weiss , C. Wagner, C. Kleimann , M. Rohlfing , F. S. Tautz and R. Temirov – Phys. Rev. Lett. 105 , 086103 ( 2010 ) – http://link.aps.org/doi/10.1103/PhysRevLett.105.086103
- [2] Website of the Research Centre Jülich : http://www.fz-juelich.de
- [3 ] Web page of wikipedia on tunneling microscope : http://fr.wikipedia.org/wiki/Microscope_ % C3% A0_effet_tunnel

Source:

News Research Centre Jülich – 08.20.2010 – http://www.fz-juelich.de/portal/index.php?cmd=show&mid=788&index=163