Molecular order affecting electron transport through ssDNA

DNA is considered to be the ideal model for studies of electron transport in molecule/conductor systems due to its stability, easily controlled structure and the presumed electrical properties. Scanning tunnelling microscope (STM) studies of single-stranded DNA bound to Au (1 1 1) or Au nanodots with a thiol linker were carried out under ambient conditions. The results show that the electron transfer between the STM tip and the gold is governed by the serial resistance of the oligomer strands and a water film. Electron transfer properties also depend on the alignment of the DNA strands. Measurements show that well-ordered parallel arrangement of the molecules protruding from flat crystalline surfaces is favourable for electron transport compared with unordered arrangements of molecules on spherical nanodots. Nanodots are good candidates for effective charge production by absorption of light allowing chemical reactions to happen at the dots, which can be used for storing the light energy. Understanding electron transport through molecular structures is of crucial importance for the development of such novel photovoltaic devices.