Single molecule detection using graphene electrodes
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abstract
It is shown using density functional theory that the trapping of molecules between graphene electrode plates can be used to sense molecules through their vibrational fluctuations. This hypothesis is tested using water trapped in two graphene molecules connected to a potential difference. The electric current fluctuations generated through the junction correspond to the fluctuations of the vibrational modes. Since this system yield currents in a range workable by present electronic devices, there is no need for further 'molecular amplification'. Fluctuations of the three modes of water yield similar changes of potentials in the neighbourhood accessible to other molecules; therefore, vibrations from a single water molecule, as an example, or vibrations from any other molecule can be transduced into electrical currents of magnitude compatible with present silicon technology. In the particular case of the water molecule, a rectified potential signal is obtained from the fluctuations of the antisymmetric stretching mode and a simple transduction is obtained from the symmetric stretching and bending modes. It is argued that the high sensitivity is due to the strong delocalization of the frontier molecular orbitals or molecular plasmons on graphene electrodes, which guarantees the detection based on molecular potentials or molecular vibrations; these plasmon-like molecules are of major importance for the development of molecular and nano electronics. 2010 IOP Publishing Ltd.
