Molecular Devices Using Artificial Protein and LB Films Based on Quantum Electron Transfer in Flavin-Porphyrin Molecular Heterojunction

To investigate the molecular electronic function of artificial flavocytochrome (FC), STM and STS measurement were performed on FC molecules adsorbed on Au (111) surface. At positive bias, many spherical particles with diameter of 3-4 nm were observed. These are considered to correspond to FC. At-900 mV bias at substrate, FC was not observed at all, while the structure of Au substrate was similar to the positive bias images. After changing the bias voltage to positive one, the sane FC images were obtained as before with good reproducibility. This bias dependence of the FC images can be attributed to the rectification function between flavin and heme in FC. In STS measurement, tunneling current increased in positive bras on adsorbed FC area. This rectification result corresponds with the STM images of FC.