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Graphene nanochannels and nanostructures have been of great interest to applications like nanofluidics and solar-thermal evaporation since nanoconfinement can lead to altered liquid properties. In this article, we employ molecular dynamics simulations combined with the free energy perturbation method to study the influence of external electric fields on the free energy of water molecules in graphene nanochannels. We observe a decrease in the water free energy difference ([Formula: see text], where 0 is the reference vacuum state and 1 is the solvated state) with the increasing electric field, suggesting that the application of an electric field may reduce the thermal energy needed to evaporate water from graphene nanochannels. Our analysis reveals that the reduction in free energy difference is related to more aligned water molecules along the electric field direction in the nanochannels, which leads to a decrease in the water inter-molecular potential energy and, thus, reduces the free energy difference. 

Plasma-enhanced chemical vapor deposition (PECVD) provides a low-temperature, highly-efficient, and catalyst-free route to fabricate graphene materials by virtue of the unique properties of plasma. In this paper, we conduct reactive molecular dynamics simulations to theoretically study the detailed growth process of graphene by PECVD at the atomic scale. Hydrocarbon radicals with different carbon/hydrogen (C/H) ratios are employed as dissociated precursors in the plasma environment during the growth process. The simulation results show that hydrogen content in the precursors significantly affects the growth behavior and properties of graphene ( e.g. , the quality of obtained graphene, which is indicated by the number of hexagonal carbon rings formed in the graphene sheets). Moreover, increasing the content of hydrogen in the precursors is shown to reduce the growth rate of carbon clusters, and prevent the formation of curved carbon structures during the growth process. The findings provide a detailed understanding of the fundamental mechanisms regarding the effects of hydrogen on the growth of graphene in a PECVD process. 

Abstract Directed high-speed motion of nanoscale objects in fluids can have a wide range of applications like molecular machinery, nano robotics, and material assembly. Here, we report ballistic plasmonic Au nanoparticle (NP) swimmers with unprecedented speeds (~336,000 μm s⁻¹) realized by not only optical pushing but also pulling forces from a single Gaussian laser beam. Both the optical pulling and high speeds are made possible by a unique NP-laser interaction. The Au NP excited by the laser at the surface plasmon resonance peak can generate a nanoscale bubble, which can encapsulate the NP (i.e., supercavitation) to create a virtually frictionless environment for it to move, like the Leidenfrost effect. Certain NP-in-bubble configurations can lead to the optical pulling of NP against the photon stream. The demonstrated ultra-fast, light-driven NP movement may benefit a wide range of nano- and bio-applications and provide new insights to the field of optical pulling force.