Continuum modelling of fullerene encapsulation inside two-section carbon and boron nitride nanotubes

In this study, semi-infinite two-section nanotubes of different radii are used as nanocontainers to encapsulate spherical fullerenes. In particular, the encapsulation behaviours of C₆₀ and B₃₆N₃₆ fullerenes inside carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) are investigated. In order to determine the van der Waals (vdW) interactions between fullerenes and two-section nanotubes, the continuum approximation along with the classical 6-12 Lennard–Jones (LJ) potential function is employed. The proposed continuum model provides explicit analytical expressions for the evaluations of total potential energy and interaction force. Moreover, the suction energy, a measure of the total increase in the kinetic energy experienced by the core, is derived as a function of geometrical parameters and materials of fullerene and nanotube. For C₆₀-CNT, C₆₀-BNNT, B₃₆N₃₆-CNT and B₃₆N₃₆-BNNT mechanisms, the distributions of vdW interactions as well as the nature of suction energy are studied in detail. It is demonstrated that the weakest and strongest interactions are related to C₆₀-CNT and B₃₆N₃₆-BNNT mechanisms. In addition, the interaction of B₃₆N₃₆-CNT mechanism is found to be stronger than that of C₆₀-BNNT one. It is further found that the length of the first section of the nanotube has a negligible effect on the vdW interactions and suction energy. The results of this study also suggest that for a given type of fullerene, the suction radius of CNTs is smaller than that of BNNTs. By contrast, the optimal radius that gives rise to maximum suction energy is unique for all considered mechanisms. The present theoretical study presents deep insights into the basic concepts of encapsulation behaviour and it could be useful to guide the design of novel nanodevices where the nanocapsule may be utilized as a drug container.