November 4, 2014 at 11:15 pm

NanoForum: Scanning Tunneling Microscopy Study of Artificial Dipolar Molecular Rotors and Dipolar Molecule Self-Assembly Mechanisms, Nov. 4

Yuan Zhang

Yuan Zhang

NQPI NanoForum presents Yuan Zhang on “Scanning Tunneling Microscopy Study of Artificial Dipolar Molecular Rotors and Dipolar Molecule Self-Assembly Mechanisms” on Tuesday, Nov. 4, at 4 p.m. at Clippinger 259.

Abstract: One of the goals of nanotechnology is to assemble billions of nanomachines packed in a tiny area that can be operated under control; their rotation can be synchronized and information can be coherently transferred to multiple destinations within nanometer range. Realizing this goal requires developing a system in which nanomachines can communicate each other. Here we show that by exploiting dipolar interactions between the rotor arms of self-assembled double-decker class molecular motors in a hexagonal network, synchronized and coordinated rotations of the motors can be performed using an electric field of a scanning tunneling microscope tip as an energy source. Remarkably, all the rotors can be simultaneously rotated when the applied bias is above 0.9 V at 80K due to the degeneracy of the ground state rotational energy in the hexagonal dipole network. Below this bias, slight reorientations of individual rotors can occur. A careful analysis reveals that the rotor reorientations here are not random, but they are coordinated to minimize the energy within the hexagonal dipole network, and the rotation direction is dependent on the initial rotor alignment. This work is a step forward for the development of solid state compatible and responsive multi-component molecular machines.

Molecular self-assembly happens in a pre-defined manner. Self-assembled structure and properties are pre-defined by the nature of molecular chemistry, and this imposes nano engineering limitations. Therefore, an important objective of molecular self-assembly research is to seek possibilities to control or even alter molecular self-assembly processes. To achieve this goal, a comprehensive understanding of the forces responsible for the individual molecules to self-assemble  is required. By introducing a slight atomic modification (replacing two hydrogen atoms with two fluorine atoms), 6Ps self-assembly structure can be completely altered. The assembly structures of two isomers meta-2F-6Ps and ortho-2F-6Ps reveals that by positioning two fluorine atoms at different sites isomer molecule assembly behavior can be altered completely. This study reveals that atom-atom interaction at interfaces plays a more dominant role over the localized dipole interactions in this system.

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