Graphene nano-engine

    This week was fruitful for news related to applied applications of graphene and other nano-materials. At first there was an ultra-thin transistor , now in the same journal Nano Letters published an article on the development of a molecular nano-motor, in which the graphene layer plays a key role. This engine consists of a highly elastic membrane acting as a piston and ClF 3 molecules , which are the working fluid. The volume of the working fluid changes under the influence of a laser. The nano-engine develops pressure up to 10 6 Pa and withstands more than 10,000 cycles.

    The engine consists of graphene particles with ClF 3 inclusions . Between carbon atoms and ClF 3 molecules , CF chemical bonds arise that can easily dissociate. In particular, these bonds are destroyed by irradiation with a laser with a wavelength of 532 nm. The destruction of bonds leads to the fact that molecules are trying to "move away" from carbon atoms. As a result, the pressure under the graphene layer increases, graphene is separated from the substrate, and a blister (bubble) is formed. When the laser is turned off, graphene quickly returns to its initial flat state, since the reactivity of ClF 3very high, and it again forms bonds with carbon atoms. The rapid increase in volume under the graphene layer is equivalent to the expansion of the working fluid and the movement of the piston in the internal combustion engine. The key parameters that determine engine power are the pressure that it can withstand, which, in turn, depends on the modulus of elasticity of the membrane material, the gas permeability of the membrane, and its adhesion to the substrate.

    In graphene treated with liquid ClF 3 , ionic bonds between fluorine and carbon are formed, resulting in the formation of a positive charge of 1/6 hole for each fluorine atom. Such ionic bonds can be easily destroyed, since they have a very small energy of ~ 54 kJ / mol. This is about ten times less than the energy of the covalent bond CF. When a quasistable ClF 3 molecule loses its ionic bond, this leads to a transition of ClF 3into the gas phase and rapidly increasing pressure. According to researchers, the internal pressure is ~ 23 MPa. Such pressure is sufficient for local separation of graphene from the substrate. Due to the high strength of graphene, whose Young's modulus can reach 1 TPa, and low gas permeability, all gas remains inside the bubble. Structural analysis of graphene showed that even after 10 thousand cycles, no structural disturbances occur. The authors believe that the characteristics of such an engine can be significantly improved by optimizing the parameters of the laser pulse, beam diameter, and also by selecting the most efficient “working fluid”.

    Unfortunately, access to the full text of the article is paid, but additional materials are freely available on the journal’s website .
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