Redox-mediated negative differential resistance behavior from metalloproteins connected through carbon nanotube nanogap electrodes.

A reproducible negative differential resistance (NDR) behavior with symmetric peaks was observed from the planar-type metalloproteins (ferritins) devices utilizing metallic single walled carbon nanotube (SWNT) nanogap electrodes. The SWNT nanogap electrodes were fabricated by electrically cutting metallic SWNTs, between which ferritins were captured by electrostatic or hydrogen-bonding interactions. Upon the bias voltage sweeps, both positive and negative NDR peaks were observed. The origin of NDR behavior is attributed to the reversible redox reactions between Fe(III) and Fe(II) states since no such NDR peak was observed when ferritin did not contain Fe ionic species, that is, when apoferritin was used. However, in vitro inclusion of Fe(III) or Co(III) ions into the pores of apoferritins promptly induced the emergence of both positive and negative NDR peaks