Double-layer carbon nanocapsules with radioiodine content and its interaction with calcium, phosphorus, and strontium

First principles calculations have been performed for C60@C180 carbon double-layer endofullerenes with up to: three diatomic radioiodine molecules (131I2), two potassium radio-iodide (K131I), and three sodium radio-iodide (Na131I) inside. The plane-wave pseudopotential (PP) method within the general gradient approximation (GGA) in the framework of the density functional theory (DFT) and time-dependent DFT (TD-DFT) was used to perform geometric optimizations (GOs) and molecular dynamics (MD) at 310 K and atmospheric pressure. We found that the double-layer carbon nanocapsules formed by two concentric fullerenes (C180 surrounding C60) are very stable and may contain a radiodosis, without altering their configuration; that is, the 3(131I2)@C60@C180, 2(K131I)@C60@C180, and 3(Na131I)@C60@C180 systems constitute stable nanocapsules. We analyzed the interaction of double-layer endofullerene with radioactive content with some calcium, phosphorus, and strontium atoms, [n(X131I)@C60@C180 + mY], for X = I, K, Na; Y = Ca, P, Sr; n = 1, 2, 3; m = 1, …, 20. Our calculations show that up to m = 20 calcium atoms can easily be physisorbed by the outer surface of the double-layer endofullerene, maintaining their integrity and shielding the radiodosis of any interaction that can proceed from the outside. It is thus concluded that these double-layer endofullerenes can be functionalized as vectors to deliver radiodosis with structural advantages over the single layer systems; as they are more robust, stable, and possess a larger surface to functionalize with some atoms serving as molecular recognizers.