Metallization of DNA Origami to Form Electrically Conductive ~10 Nm Diameter Nanowires

Abstract

DNA based bottom-up nanotechnology is seen as a promising technology for the development of future generations of nanodevices. The bottom-up approach takes advantage of molecular self-assembly to create useful architectures of nanometer dimensions. DNA, with its small size, functional groups and complementary base pairs, is a powerful template for nanodevice fabrication via bottom-up assembly. Recent advances in the field of “DNA origami” have enabled fabrication of nanostructures by folding single-stranded DNA into a variety of 2- and 3-D shapes. However, electrically conductive structures are required for many nanodevice applications. In this study, we report the fabrication of electrically conductive DNA origami-templated nanowires with the use of gold nanorods (Au NR’s) as a step towards DNA nanodevices. Our process begins with a seeding step where Au NR’s bind to the DNA origami backbone. The seeds are then connected by electroless deposition to make continuous wires. The use of nanorods as seeds provides two key advantages over previous work with particulate seeds. First, the surfactant-enabled anisotropic growth used to initially fabricate the nanorods appears to persist through the electroless plating process on the DNA template. This permits improved control of the width of the final metallized structure since growth in the axial direction is preferred. The average final width of our Au-metallized DNA wires was ~10nm. Continuous 400 nm long DNA wires were obtained by filling gaps between seed particles that ranged from 10.6 nm on average to gaps as wide as 25 nm. The second advantage of nanorods is the reduction in the number of connection points between seed particles by a factor of three relative to that observed for 5 nm seed particles. The reduced number of connection points is expected to increase the conductivity of the wires. Initial electrical characterization of the DNA wires shows that they are conductive, and more detailed measurements are in progress. Site-specific placement of Au NR's on a DNA origami template, demonstrated in this study, is capable of providing the controlled placement needed to enable future nanodevice applications. In summary, we have demonstrated a metallization process to fabricate thin, high aspect ratio, conductive wires on DNA-origami templates with the use of Au NR’s and electroless plating. Continuing efforts seek to interface these thin nanowires with appropriate semiconducting elements to enable fabrication of self-assembled nanoscale devices.