DNA self-assembly on graphene surface studied by SERS mapping

The self-assembly of double-stranded DNA (dsDNA) segments on two variations of graphene surfaces having nano-platelets with different lateral sizes and thicknesses was investigated using surface-enhanced Raman spectroscopy (SERS) and electrical impedance spectroscopy (EIS) techniques. Due to the strong local field-enhancement, the SERS signals from functional molecules bound to the graphene edges and from DNA moieties were recorded. Relative intensities of specific Raman modes were used as contrast parameters to build Raman signal intensity maps. The observed variation in the SERS signal intensity was related to the different configuration (tilted or flattened) in which dsDNA segments are assembled on the carbon surface, depending on the graphene platelet size. EIS was used to characterize the conductive properties of nano-structured films containing pristine or DNA-functionalized graphene nano-platelets. Results from the EIS analysis supported the SERS findings and confirmed that SERS mapping is a reliable method for a rapid monitoring of the procedures used to interface DNA with graphene surfaces. The present study, linking DNA anchoring morphology to the conductive properties of nano-structured hybrid films, contribute to define a new approach in the optimization of biosensor design.