Lying-Down Metallic Single-Walled Carbon Nanotubes as Efficient Linkers for Metalloprotein-Based Nanodevices

Metalloproteins recently emerged as good candidates for signal transduction in bionanodevices, but the feasibility of such novel devices is strongly connected to the achievement of an efficient charge transport between single metalloproteins and metal electrodes. In this work, we propose the use of metallic single-walled carbon nanotubes as efficient linkers between metalloproteins and metal surfaces. By means of a conductive atomic force microscopy investigation, we compare the conduction across single yeast cytochrome c molecules covalently bound both to bare gold and to functionalized metallic single-walled carbon nanotubes lying on gold. At comparable forces applied by the microscope tip (i.e., comparable physical contact), the measured current is higher when a metallic single-walled carbon nanotubes is in between the metalloprotein and the gold surface. The analysis of the single molecule current responses by means of a non-resonant tunneling transport model suggests that the increasing in the conduction is due both to the strong electronic conjugation existing at the nanotubes/gold interface and to the participation of the nanotube electronic bands to the charge transport.