No abstract

Due to the extremely small dimensions and super high frequency of the rotor in a thermally driven rotary nanomotor made from carbon nanostructures, measuring the rotational frequency of the nanomotor is still an open issue. To this end, a measuring system is constructed in which a spring wing is connected with the rotor to provide collisions with a probe tip whose deflection reflects the rotational frequency of the rotor. The spring wing is formed by connecting an end-tube from a carbon nanotube and a graphene with differently hydrogenated surfaces. Due to the alternative hydrogenation of the two surfaces, the graphene shrinks like a spring. When the rotational frequency increases, the centrifugal force applied on the wing increases and then the spring is stretched (becoming longer). As the end-tube rotates with the rotor and reaches the probe tip, a collision occurs between the end-tube and the probe tip. After collision, the probe tip undergoes a variation of vertical deflection that can be measured through atomic force microscopy. The relation between the maximal deflection of the probe tip and the rotational frequency of the rotor is determined via numerical experiments. The effects of the configuration (namely hydrogenation and length) of graphene on the rotation of the rotor are investigated. The results provide some insight into the fabrication of nanomachines.

Nanotube synthetizing from black phosphorous (BP) is still challenging in laboratory. Fabricating a BP nanotube by self-assembling of a BP nanoribbon seems promising. To estimate the feasibility of such fabrication method, this study performs numerical experiments of self-assembling a jammed BP ribbon on a fixed carbon nanotube using molecular dynamics simulation. The study is based on following two facts: phosphorus-phosphorus (P-P) bond is weaker than the bond of carbon-carbon (C-C), and van der Waals interaction among non-bonding phosphorus atoms is stronger than that between phosphorus atoms and carbon atoms. The results show that when a longer BP ribbon is jammed by a shorter BP ribbon, the self-assembling result depends on the relative positions of CNT and the two BP ribbons. Only when the shorter BP ribbon is on the outside of the longer ribbon, the longer BP ribbon can be wound on the CNT to forms an ideal BP nanotube. The finding is helpful for practical applications of BP nanotubes in nanodevices.

A nanotube from single-layer black phosphorus (BP) has never been discovered in experiments. The present study proposed a method for the fabrication of a BP nanotube (BPNT) from a parallelogram nanoribbon self-assembled on a carbon nanotube (CNT). The nanoribbon has a pair of opposite sides along the third principal direction. According to the numerical simulation via molecular dynamics approach, we discover that a wider BP nanoribbon can form into a series of chiral nanotube by self-assembly upon CNTs with different radii. The radius of a BPNT from the same ribbon has a wide range, and depends on both geometry of the ribbon and the CNT. One can obtain a BPNT with the specified radius by placing the ribbon nearby a given CNT. The method provides a clue for potential fabrication of BPNTs.

As a low dimensional material, black phosphorus (BP) continues to attract much attention from researchers due to its excellent electric properties. In particular, the one-dimensional material, in the form of a ring or tube formed from BP, has been extensively studied and found to be a perfect semiconductor. But the BP ring has never been reported in laboratories. To form an ideal ring from a rectangular BP ribbon, we choose a carbon nanotube (CNT) bundle to attract the ribbon and move one or more CNTs in the bundle to induce the unsaturated ends of the BP ribbon to become covalently bonded. Numerical experiments are applied to BP ribbons with lengths either equal to, shorter, or longer than the perimeter of the CNT bundle, to investigate the formation of a BP ring. Experiments show that if one end of the BP ribbon is attracted by a CNT, moving the other CNTs away endows the ribbon with high probability of forming an ideal ring. The conclusions drawn from these results will benefit future in situ experiments involving forming a ring from a BP ribbon.