[10p-Z25-1~17] 12.2 Characterization and Materials Physics

[10p-Z25-13] Single-Molecule Conductance of An Acid/base-Responsible Molecule

〇(M1)Yuki Yoshihara¹, Shintaro Fujii¹, Shuhei Higashibayashi², Tomoaki Nishino¹ (1.Tokyo Tech, 2.Keio Univ.)

Keywords:single molecule, break junction, acid/base responsible molecule

In this study, we studied a single-molecule switch of a biphenothiazine derivative that can operate in response to an acid-base reaction. The single-molecule switch driven by such reactions can also be applied to pH sensing on a single-molecule scale. Using the scanning tunneling microscopy-based break junction technique, individual single molecules before and after the reaction were trapped between Au electrodes, and its electrical conductance was measured. The conductance of the single-molecule junctions of the biphenothiazine derivative before the reaction was found to be 0.2 G₀ (G₀=2e²/h). In constant, that of a radical cation generated in response to the acid stimulus increased to 0.4 G₀. Current-voltage responses of this particular switch revealed that the conductance increase after the reaction stems from energy shift of the molecular orbital level toward the Fermi energy of the Au electrode. Furthermore, we succeeded in reversibly operating the single-molecule switch by dropping acidic or basic solution onto the Au substrate on which the molecules were adsorbed.