Conductive AFM Characterization of Gold Coated DNA Wires

Over the past decades, DNA, which is the carrier of genetic information, has been used by researchers also as a structural material. Watson-Crick base pairing enables formation of complex 2D and 3D structures from DNA through self-assembly, and various methods have been developed for additional functionalization of DNA these structures. Metallization of DNA has attracted much attention as means of forming conductive nanostructures. The conductivity of these structures hasn’t, however, yet been fully characterized due to shortage of reliable charge transport measurements through structures tens to hundreds of nanometers in length at the single molecule/wire level. In order to supply this shortage, a novel measurement setup was recently developed in our lab that is suitable for measurement of molecules and wires of these lengths. This setup involves a stationary gold electrode that is evaporated over the molecules/wires of interest and a conductive AFM tip serving as a second mobile electrode that contacts single molecules protruding from the gold electrode. We used this technique to characterize the conductivity of gold coated DNA molecules. Our measurements show that thicker gold coating leads to longer conductive lengths. These results indicate larger distances between defects in the formed gold wire as the gold coating is increased.