Swiss physicists have created a molecular motor of 16 atoms, which comprises the stator of a three-layer cluster compounds of palladium with gallium and the adsorbed molecules of acetylene as the rotor. The rotation of the acetylene occurs under the combination of quantum tunneling and classical kinetics is dependent on the external parameters. The results of a study published in the journal Proceedings of the National Academy of Sciences.
The creation and study of molecular machines is not only important in order to them to arrange a race, but to study the processes that occur during their movement. Though many artificial molecular machines start using quantum effects, their movement is mainly determined by the laws of classical kinetics, almost without affecting the phenomena of quantum tunneling. The size reduction of molecular machines increases the probability of quantum effects.
Samuel Stolz (Stolz Samuel) with colleagues from the Federal Polytechnic school of Lausanne has created the world’s smallest to date, the molecular rotor and investigated its behavior by scanning tunneling microscopy (STM) at a temperature of five Kelvin and a pressure of below 50 femtobarn. Researchers synthesized a chiral surface of the crystal intermetallic compounds of palladium and gallium in the ratio 1:1 (PdGa), which can adsorb compounds with defined geometric parameters and played the role of a stator. The rotor of this molecular motor was a small adsorbed molecule of acetylene C2H2.
A single molecular motor consists of 16 atoms: three-layer cluster PdGa layer of the trimer of palladium, a layer of six atoms of gallium and another, top layer of three atoms of palladium, which sorbed the spinning part of chetyrehstennoy of acetylene molecule. The STM image of the rotor looks like a dumbbell in the three symmetrically identical orientations.
Researchers have shown that the structure of the microscope probe has no determining influence on the movement of the rotor, noting the independence of rotation of the acetylene from the distance to the probe, both theoretically and in experiment. The direction of rotation is determined solely by the stator. More than 96 percent of cases, the rotation was in one direction. 100 seconds, the molecule actylene could scroll 23 times anti-clockwise.
The authors found two regimes of rotation of the tunnel, when the rotation frequency does not depend on temperature (below 15 Kelvin), voltage and current, and classic, when the frequency depends on these parameters. Molecular motor spinning only in one direction under the action of a single electron, continuously moving between the six cyclical conditions.
Mainly unidirectional movement even in tunnel mode, the authors could not explain. They argue that further investigation of such effects will allow in the future to convert the energy of external excitation into directed movement and to study these processes in a minimal spatial scales.
Last year an international group of researchers have created a molecular propeller, the direction of rotation of the blades, which also determined the chiral stator. More about molecular machines can be found in our article “the Machine is out of the tube”.