Toward the DNA Electronics
Tomoji KAWAI
ISIR-Sanken, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
DNA is one of the most promising molecules as the scaffold for molecular nanotechnology and nanoelectronics. DNA has the special double helix structure with ¼-electron cores of well-stacking bases for the use of long-distance(e.g., 200Å) and one-dimensional charge transport. The investigations of DNA on the nanostructure, electrical conductivity and electronic states have significant implications for the application of DNA in electronic devices and in DNA-based electrochemical biosensors.
It is worthily noted that divergent and controversial conclusions were reported in DNA-mediated charge transport. The direct measurements of the intrinsic electrical characteristics of polynucleotides using a conducting probe atomic force microscope have been performed using self-assembled DNA network. Poly[d(A-T)]2 and poly(dA)€poly(dT) form the cross-interlaced mesh-like nanoscopic network and show the n-type rectification characters; Poly[d(G-C)]2 and poly(dG)€poly(dC), on the other hand, construct the uniform two-dimensional reticulate structure and show the p-type rectified behaviors, presumably due to the different redox potentials of DNA bases. The conductivity of these molecules has been successfully controlled by chemical doping. It is found that the poly(dG)€poly(dC) has the best conductivity and can act as a conducting nanowire. The conductive mechanism is discussed by the charge hopping model based on the SPM observation of DNA nanostructure.
For the advanced construction of DNA based molecular memories and circuits, gold particles have been assembled in two-dimensional DNA networks. Gold particles are arranged artificially with DNA molecular template as an average separation distance of 260nm. The pattern of the complex is controlled by changing the concentration of the DNA solution, suggesting that this method is effective in achieving the positional control of nano-scale molecular memories and circuits.
(references) T.Kawai et al; Appl.Phys.Lett.,77,3848(2000), Appl.Phys.Lett., 77,3105(2000), Surf.Sci.Lett,432,L611(1999), J.Vac.Sci.Technol.B17,1313(1999), Jpn.J.Appl.Phys. 39, 581(2000), 38,L606(1999), 38,L1211(1999)