Molecular Motor Regulated By Charge State

Scanning tunneling microscope(STM) is the tool of possessing strongest amplifying power at the time on the world. It’s imaging principle is not the same of the previous magnifier, it image depending on the tunnel current through tip scanning on surface, then which reflects the surface fluctuation and contour, what’s more, the resolution can reach 0.1 nm. It not only possesses an amplifying power but also no damage to the surface, and high scanning rate. In addition, the use of STM can also obtain surface electronic state density distribution, surface transportation and some other current information.The study in this paper is collecting and scanning information on solid surface by scanning tunneling microscopy, and characterization of nano materials. At the beginning of the experiment, the highly oriented pyrolytic graphite(HOPG) is pasted on the copper sheet by conductive glue, and baked for 2-3hours at 90 degrees Celsius, so that the conductive glue turns to solidification, which can fix the HOPG on the copper sheet. And mechanically dissociating the HOPG, then a clean HOPG surface is obtained. In ultra high vacuum, a small amount of ethanol molecules is placed on the HOPG surface by a micro leakage valve, and then scanned in the environment of the liquid nitrogen.Because there is the existence of a vacuum between the tip and the molecule, and is other existence of a vacuum between the molecule and the HOPG surface, this two vacuum form a double-barrier tunnel junction, so ethanol molecules are easily influenced by tip to negatively charged, which is charging phenomena. Ethanol charged will get larger and brighter, and the Ⅰ-Ⅴ spectrum, gathering on the ethanol molecule, also shows a conductance "lag" phenomena. In this structure, ethanol clusters will be also charged, the charged molecular clusters will form a non-uniform local electric field around themselves, and attract polar molecular or clusters in certain distance surrounding themselves, even to the extent that them can attract a certain length ethanol molecular chains surrounding themselves. Interestingly, if this clusters or molecular chains are also subject to a certain disturbances at the same time when they are attracted, the clusters or chains will be around with the charged cluster to rotate, and the orbit of cluster surrounding the charged cluster is a circular or elliptical like the one of the planetary surrounding the sun; the orbit of molecular chain surrounding the charged cluster shows a motor disc, forming a supramolecular motor.It is worth pointing out, this supramolecular is different with previous molecular motor. Because the previous molecular motor is supramolecular motor in liquid environment, or single molecular motor on solid surface. However, the molecular motor in this finding is a supramolecular motor on solid surface, between the motor "stator" and "rotor" are connected by the electrostatic, but the previous motor’s are connected by chemical covalent bond, this connection mode is helpful to decrease the molecular motor rotation resistance. More interestingly, power source of this molecular motor is the driving of the tunneling electron. The I-t spectrum gathered on the molecular motor shows that the tunneling current keeps a beating between two values versus time. The relevant calculation and statistics shows that the injection of a tunneling electron from tip means a step rotation of the molecular chain. This explains that the molecular motor maintains continuous rotation in this electronic driven. It is not same with the shocking of previous molecular motor, because thermal vibration is not rule and assured rotation. But it can realize unidirectional rotation while in the electronic driving, and we fortunately have observed the supramolecular motor which unidirectionally rotated. This provides a feasible basis and reference for manufacturing supramolecular engine or motor.