We demonstrate in this joint experimental and theoretical study how one can alter electron transport behavior of a single melamine molecule adsorbed on a Cu (100) surface by performing a sequence of elegantly devised and well-controlled single molecular chemical processes. It is found that with a dehydrogenation reaction, the melamine molecule becomes firmly bonded onto the Cu surface and acts as a normal conductor controlled by elastic electron tunneling. A current-induced hydrogen tautomerization process results in an asymmetric melamine tautomer, which in turn leads to a significant rectifying effect. Furthermore, by switching on inelastic multielectron scattering processes, mechanical oscillations of an N-H bond between two configurations of the asymmetric tautomer can be triggered with tuneable frequency. Collectively, this designed molecule exhibits rectifying and switching functions simultaneously over a wide range of external voltage.hydrogen tautomerization ͉ melamine molecules ͉ rectifying effect ͉ switching property E lectron transport is a fundamental process that controls physical properties and chemical activities of molecular and biological systems. Over the years, different electron transport behaviors of a variety of molecules have been observed, and much effort has been made to elucidate the underlying mechanisms (1-12). Despite of these recent advances, it remains a great challenge to actively control the electron transport in a molecule and to systematically change its behavior from one type to another since this requires not only precise control of molecular structure, but also accurate activation of different electron tunneling processes. Controlling electron transport at the molecular level has important consequences for many applications, such as molecular electronics (13-26), biosensors (27), and solar cells (28,29). For certain molecules, change of electron transport properties could take place due to their specific response to the change of molecular conformation or orientation (19-25), chemical reactions (26), and tautomerization (18). The latter experiment (18) has attracted considerable attention owning to the facts that the switching process involved does not result in drastic molecular conformation changes as often occurring in mechanical molecular switches induced by cis-trans isomerization of azobenzene (23-25), making the process potentially more relevant to applications in memory devices.Although many studies have been conducted over the years, only a limited number of special molecules can be chosen for such experiments. In this joint experimental and theoretical study, we demonstrate the possibility of changing the electron transport behavior of an ordinary molecule, melamine, with the help of surface chemistry and scanning tunneling microscope (STM) in a controllable manner. It is shown that the involvement of a dehydrogenation process can make the molecule standing on a Cu (100) surface and behaving like a conducting molecule. By applying a high-voltage pulse, the energeti...

No abstract

Highlights d E. corollae larvae and adults sense EBF at different concentrations d OR3-expressing neurons and OBP15 mediate the attraction of E. corollae to EBF d E. corollae OR3 À/À mutants reduce attraction to EBF in both adults and larvae d OR3 mediates long-range detection in adults and short-range attraction in larvae