Abstract: The molecular electronics as well as molecular scale optics (via plasmonics), have long been visualized to pose the next huge leap in technology development. Even not fully realized yet, the promises of these nanotechnologies are certainly getting closer to be fulfilled. The most crucial issues in realization of functional molecular scale electrical devices is to find both molecular conductors as well as suitable building blocks and scaffolds, for nanoscale assembly. For nano-optics the plasmonic nanostructures have shown high potent due to their unique optical properties such as field enhancement and possibilities for subwavelength optics. However, due to limitations of the conventional nanofabrication methods, nanostructures with tunable plasmonic/optical activity in visible range are hard to realize, especially in large amounts. At the moment, DNA has proven to be a very versatile and promising molecule for nanoscale patterning. Quickly developing techniques based on DNA self-assembly provide precise and programmable ways to form electrical molecule scale devices as well as plasmonic nanoscale structures, even in large quantities. Yet, in the respect of the long history and debate on the possibly conductivity of DNA itself, the electrical properties of DNA-based structures are also of a great interest.
We have studied the conductance of several types of individual DNA nanostructures and found that even the electrical conductivity of DNA-helix as such, seems to be too fragile to be directly utilized, the multilayered 3D DNA origami structures may have improved properties. However, more robust realization of DNA-based electrical devices, relies on other components and uses DNA as only a scaffold. Hence, we have utilized DNA nanostructures to assemble a row of gold nanoparticles (AuNP). The whole entity is further trapped between metallic electrodes where AuNPs act as metallic islands to form a single electron transistor (SET). Due to small size of the islands, this SET could work even at room temperature in contrast to the usually needed kryogenic temperatures. For nanoscale optics, we have developed a novel method, which takes advantage of the DNA origami constructions and together with conventional nanofabrication processes enabling fabrication of high quality sub-100-nanometer plasmonic nanostructures with desired shapes. As a demonstration, we have fabricated optical bowtie antennas with a tunable plasmonic resonance in visible range. The method is highly parallel, which enabled us to fabricate also optically chiral surface with high coverage. This ability to fabricate metallic nanoparticles with designed shape in high quantities provides great potential in various applications, especially sensing and metamaterial fabrication.