News

Transfer of chirality
Feb/17 Paper published in Nature Chemistry including News&Views. »more info

Towards chemical recognition of molecules
Aug/16 Paper published in ACS Nano. »more info

Odehnal award
June/16 O. Stetsovych received Odehnal award »more info

Praemium Academiae
June/16 P. Jelinek received CAS award »more info

Imaging electrostatic field
May/16 paper in Nature Comm. »more info

O. Wichterle prize
May/16 P. Hapala received O. Wichterle prize for outstanding young scientists at the AS CR. »more info

On-surface chemical synthesis
Apr/16 paper in JACS »more info

Structural and Electronic Properties of Nitrogen-Doped Graphene
Mar/16 Paper in Phys. Rev. Lett. »more info

Role of the electrostatic force in AFM images
Mar/16 Paper in Phys. Rev. Lett »more info

Charge transport between two molecules
Sep/15 Paper in Phys. Rev. Lett »more info

The best poster ECOSS-31
Sep/15 Our work has been selected as the best poster in the ECOSS-31 conference. »more info

Paper in ACS Nano
Aug/15 Novel way of B,N-co doping of graphene demonstrated. »more info

paper in PRL and Physics
Aug/15 Our work has been published in Phys. Rev. Lett highlighted as Synopsis in Physics. »more info

Paper in Nature Comm.
Jul/15 High-resolution AFM images reported at room temperature. »more info

Paper in Nano Letters
Jun/15 The current and the force used for controlled atomic switching of silicon tetramer. »more info

O. Wichterle prize
May/15 M. Ondracek received O. Wichterle prize for outstanding young scientists at the AS CR. »more info

paper in PRL and Physics

So far, the charge distribution was mostly studied by so-called Kelvin probe force microscope (Kelvin Probe Force Microscopy = KPFM), which detects change in the local work function (i.e. the energy that is needed for removal of just one electron from the surface of a solid), at the atomic level, However, for achieving the sub-molecular resolution of the charge distribution it is necessary to bring the probe close to the investigated surface. Unfortunately, the proximity of the scanning probe near the surface induces undesired artifacts in KPFM measurements that prevent precisely determine the charge distribution within a single molecule.

To solve this problem we have proposed a new measuring protocol that allows remove the aforementioned artifacts. In an article published in the journal Physical Review Letters, scientists have described a new method of detecting charge distribution, which is based on measuring the Kelvin probe force spectroscopy (Kelvin probe force spectroscopy = KPFS) for two different voltages applied to the scanning probe. The new KPFS method overcomes the shortcomings of the original KPFM method and it allows mapping the distribution of charge in the individual chemical bonds within the same molecule. Scientists have demonstrated the potential detecting the bond polarization on two very similar molecules. Namely, they investigated trimeric perfluoroortho-phenylenemercury (F12C18Hg3) and its derivate, which contains hydrogen instead of fluorine atoms (H12C18Hg3) on periphery of the molecule. Consequently, different electronegativity of hydrogen (H) or fluorine (F) gives rise to different bond polarization between carbon and hydrogen atoms (C-H) and fluorine (C-F), respectively, as shown on Fig.

The new method was published in the article in the journal Physics Review Letters, and it received a lot of attention soon. For example, the work was a subject of paper published in the journal Physics, which highlights the most important papers published in scientific journals of the American Physical Society. The importance of the work is underlined by positive reviews issued by Scientific Publishing IOP Publishing and the Royal Society of Chemistry on their websites.

 

Fig. (a) atomically resolved atomic force microscope image of molecules, trimeric perfluoroortho-phenylenemercury (F12C18Hg3) and its hydrogen-terminated counterpart (H12C18Hg3) on the surface of Cu (111). (b) The charge distribution simulated using quantum mechanical calculations. (c) Image of the sub-molecular charge distribution of the studied molecules obtained by the new KPFS method showing the different polarity of the chemical C-H and C-F bonds, respectively.
 

F. Albrecht, J. Repp, M. Fleischmann, M. Scheer, M. Ondracek, and P. Jelinek Probing Charges on the Atomic Scale by Means of Atomic Force Microscopy
Phys. Rev. Lett. 115 (2015) 076101-1 - 076101-5.