STM Studies on Molecular Rotors and Motors

Abstract

Molecular motor is a nanoscale machine that consumes energy to produce work via the unidirectional and controlled movement. They are universal in nature and essential to numerous processes of life. When mounted onto solid surfaces, scanning tunneling microscopy (STM) is a powerful technique to characterize the molecular rotors and motors due to the atomic-scale resolution coupled with its ability to track the motion of molecular rotor and motor over time. Moreover, the molecular rotors and motors can be powered by STM tip through injecting tunneling electrons. This review addresses recent advances in the STM studies of the structure, motion, and manipulation of molecular rotors and motors. The developments of surface-mounted azimuthal and altitudinal rotor and motors, large-scale array of molecular rotors, as well as the molecular motors with translational motion will be addressed.

Plasmon-Driven Motion of an Individual Molecule

“…Controlled activation of molecular motion and conformational changes is vital for creating molecular devices, motors, and machines. , To this end, molecular motion can be induced by a variety of physical and chemical stimuli, depending on the desired functionality . While nonlocal stimuli, such as an external light source, can address many molecular machines simultaneously, − it is ultimately desirable to create molecular devices where molecules can be addressed individually. − Controlled on-surface manipulation of single atoms and molecules has been successfully demonstrated using a scanning tunneling microscope (STM), typically via electronic or inelastic (vibrational or vibronic) excitation mechanisms. − ,− Within the tip–sample junction, nanocavity plasmons can also be excited, as seen in STM-induced light emission (STM-LE). − While plasmon-induced chemical reactions have been reported, to date there has been no demonstration that local nanocavity plasmon–molecule coupling can also be utilized to induce single-molecule motion.…”

Rotation of Ethoxy and Ethyl Moieties on a Molecular Platform on Au(111)

“…Switches and motors are essential engineering components in our macroscopic world as well as at the molecular level. , Considerable effort is made to synthesize artificial motors that mimic biological examples or offer prospects in nanotechnology . Rotor molecules deposited on surfaces may be investigated at a submolecular scale using scanning tunneling microscopy (STM). , The compounds thus studied fall into two classes. Either molecular adsorbates serve as a rotor and the substrate is used as a stator − or the stator and the rotor are subunits of the same molecule. − Besides rotors there are also rotary switches that alternate between two rotation angles − and consequently do not enable studies on the directionality of the motion, which is essential for using a rotor in a motor. , …”

“…3 Rotor molecules deposited on surfaces may be investigated at a submolecular scale using scanning tunneling microscopy (STM). 4,5 The compounds thus studied fall into two classes. Either molecular adsorbates serve as a rotor and the substrate is used as a stator 6−21 or the stator and the rotor are subunits of the same molecule.…”

Molecular rotor based on an oxidized resorcinarene

“…Molecular rotors [1][2][3][4][5][6][7] are a class of molecular machine [8][9][10][11][12][13] containing two key components, the stator and the rotor, which undergo facile relative rotation. 14 The operation of rotors might be an important factor in the development of synthetic molecular machines where they would be integrated with other molecular components having different operational activities.…”