The Influence Of Redox Active Center On The Conductance Of Molecular Junction And Their Gating By Electrochemical Approch

Metal-molecule-metal junctions have attracted extensive attention due to their specific functions and quantum transport properties, such as negative differential resistance, field effect transistor, molecular rectifier, storage and molecular switches, etc., A key question is how to control the charge transfer in single molecule to reach the requirements of making specific molecular electronic devices, while molecular junctions with redox active center have received increasing interest due to its electrochemical gating properties. STM-BJ could construct molecular junction quickly and effectively, and measure its conductivity. What’s more, it could be also performed under electrochemical environment. Based on this point, this thesis mainly adopts the STM-BJ method to investigate the effect of redox active center on the conductance of molecule junctions and their electrochemical gating. The redox active center includes ferrocene, Ru and Pt. The main achievements are outlined as following:1. We investigated the effect of redox active center ferrocene on the conductance of molecule junctions. By comparing the measured conductance of1,1’-dipropyl carboxyl ferrocene and1,6-hexane dicarboxylic acid, it can be found that the insertion of a ferrocene center could enhance the conductance of molecule junction. We further investigated their HOMO and LUMO levels through the theoretical calculation. The results demonstrated that the enhancement of molecule conductance is attributed to the reducing tunneling barrier and the HOMO-LUMO gap. At the same time, we also investigated the influence of the substituent group on the unconjugated backbone. Interestingly, the absence of a substituent effect is found in the conductance measurements. 2. The effect of redox active centers Ru and Pt on the conductance of molecule junctions were also carried out. Our results demonstrated that the conductance could be enhanced by the insertion of redox active centers Ru and Pt.3. We investigated the electrochemical gating of Ru complex under electrochemical environment. We found that the conductance of molecule junction remained almost unchanged with potential.