Dual Control of Molecular Conductance through pH and Potential in Single-Molecule Devices

Abstract

One of the principal aims of single-molecule electronics is to create practical devices out of individual molecules. Such devices are expected to play a particularly important role as novel sensors thanks to their response to wide ranging external stimuli. Here we show that the conductance of a molecular junction can depend on two independent stimuli simultaneously. Using a scanning tunnelling microscope break-junction technique (STM-BJ), we found that the conductance of 4,4'-vinylenedipyridine (44VDP) molecular junctions with Ni contacts depends on both the electrochemically applied gate voltage and the pH of the environment. Hence, not only can the Ni|44VDP|Ni junction function as a pH-sensitive switch, but the value of the pH at which switching takes place can be tuned electrically. Furthermore, through the simultaneous control of pH and potential the STM-BJ technique delivers unique insight into the acid-base reaction, including the observation of discrete proton transfers to and from a single molecule.

Achieving Efficient Multichannel Conductance in Through‐Space Conjugated Single‐Molecule Parallel Circuits

“…By careful survey of the traces of f-4Ph-4SMe, it can be seen that there are typically four kinds of traces with different plateau features, as indicated by different colors in Figure 3 A. Accordingly, different conductance states are unveiled by automated conductance-trace selection [19] (details are provided in the Supporting Information). In the one-dimensional histogram (Figure 3 B), three conductance peaks are found at 10 À4.44 G 0 , 10 À4.69 G 0 , and 10 À4.94 G 0 .…”

Achieving Efficient Multichannel Conductance in Through‐Space Conjugated Single‐Molecule Parallel Circuits

“…By careful survey of the traces of f ‐4Ph‐4SMe, it can be seen that there are typically four kinds of traces with different plateau features, as indicated by different colors in Figure A. Accordingly, different conductance states are unveiled by automated conductance‐trace selection (details are provided in the Supporting Information). In the one‐dimensional histogram (Figure B), three conductance peaks are found at 10 −4.44 G 0 , 10 −4.69 G 0 , and 10 −4.94 G 0 .…”

Electrical and spin switches in single‐molecule junctions

“…By smartly designing the molecular structure, several functions can be integrated into the same single‐molecule junction. Several groups have reported single‐molecule switches controlled by different external stimuli . As shown in Figure A, a spiropyran derivative that undergoes rapid and reversible isomerization under either UV light or chemical stimuli was incorporated into a single‐molecule device via the STM‐BJ technique, providing a bifunctional electrical switch .…”