Novel Nanoscroll Structures from Carbon Nitride Layers
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Novel Nanoscroll Structures from Carbon Nitride Layers Eric Perim and Douglas S. Galvao Instituto de Física ‘Gleb Wataghin’, Universidade Estadual de Campinas, 13083-970, Campinas, São Paulo, Brazil. ABSTRACT Nanoscrolls consist of sheets rolled up into a papyrus-like form. Their open ends produce great radial flexibility, which can be exploited for a large variety of applications, from actuators to hydrogen storage. They have been successfully synthesized from different materials, including carbon and boron nitride. In this work we have investigated, through fully atomistic molecular dynamics simulations, the dynamics of scroll formation for a series of graphene-like carbon nitride (CN) two-dimensional systems: g-CN, triazine-based (g-C3N4), and heptazine-based (gC3N4). Carbon nitride (CN) structures have been attracting great attention since their prediction as super hard materials. Recently, graphene-like carbon nitride (g-CN) structures have been synthesized with distinct stoichiometry and morphologies. By combining these unique CN characteristics with the structural properties inherent to nanoscrolls new nanostructures with very attractive mechanical and electronic properties could be formed. Our results show that stable nanoscrolls can be formed for all of CN structures we have investigated here. As the CN sheets have been already synthesized, these new scrolled structures are perfectly feasible and within our present-day technology. INTRODUCTION Nanoscrolls are nanostructures that consist of layered structures rolled up into papyrus-like form [1]. Graphene, carbon nanotubes (CNTs), and carbon nanoscrolls (CNSs) (Figure 1) can be considered, from a topological point of view, as closely related structures, as tubes and scrolls can be formed from rolling up graphene sheets. In fact, scroll can be considered as sheets rolled up into Archimedean spirals [1]. CNTs and CNSs differ only by the fact the CNSs present both ends open, since the edges of the scrolled membranes are not fused. CNSs are remarkable structures sharing some of the graphene and CNTs properties, and also exhibiting unique ones [2,3]. Due to their open topology their diameter can be easily tuned, which can be the basis for a large variety of applications, from hydrogen storage [4] to electromechanical nanodevices [5], among others [1]. CNSs have a long history, with their first observation dating back to 1960s [6]. Difficulties in synthesis and characterization [7] have precluded their wide investigations. Recent advances in synthesis [8] have renewed the interest in these nanostructures. Similarly to CNTs, nanoscrolls of different materials are possible. In fact hexagonal boron nitride nanoscrolls were theoretically predicted [9], and recently experimentally realized [10]. In principle, any layered structure is a good candidate for scrolls, as the mechanisms for the scroll formation and stability is an interplay between van der Waal interactions (energetic gain associated with the overlap regions) and mechanical deformations (energetic cost assoc
