| AVS 64th International Symposium & Exhibition | |
| Scanning Probe Microscopy Focus Topic | Tuesday Sessions |
| Session SP+AS+MI+NS+SS-TuM |
| Session: | Probing Chemical Reactions at the Nanoscale |
| Presenter: | Parisa Yasini, Temple University |
| Authors: | P. Yasini, Temple University S. Afsari, Temple University P. Pikma, Temple University E. Borguet, Temple University |
| Correspondent: | Click to Email |
Single molecules are possible components of miniaturized electronic devices. Interconversion between states using external stimuli is a convenient way to generate single molecule devices such as switches and sensors. In this study, we have devised an electromechanical single molecule junction where molecular orientation is controlled by the working electrode potential in an electrochemical environment. We used the scanning tunneling microscopy (STM)-break junction method to measure the electrical properties of benzene derivatives, e.g., tetrafluoroterephthalic acid (TFTPA ), terephthalic acid (TPA) and trimesic acid (TMA), bridged between two gold electrodes (the conducting substrate and STM tip). At potentials more negative than zero charge potential, direct contact between the π –system of a benzene ring and the Au (111) electrode results in the formation of a highly ordered monolayer and a high conductance of 0.24 G˳, 0.22 G˳ and 0.15 G˳ are detected for TFTPA, TPA and TMA, respectively. Moving to potentials more positive than the potential of zero charge triggers an order-disorder transition as revealed by STM. Our results show that charge transport through the π conjugated benzene ring increases by fluorination of TPA and decreases by an addition of a carboxylic acid functional group to the TPA. Accordingly, these results suggest that using functional groups, charge transport can be modified by manipulation of the electronic structure of molecules.