Adsorption analysis and mechanical characteristics of carbon nanotubes under physisorption of biological molecules in an aqueous environment using molecular dynamics simulations

The functionalisation of carbon nanotubes (CNTs) with biomolecules in an aqueous environment has found considerable potential applications in nanobiotechnology. To understand the structural properties under physical adsorption and mechanical characteristics of non-covalently functionalised CNTs with four important biomolecules in aqueous environment, i.e. l-alanine, guanine, thymine and uracil, molecular dynamics (MD) simulations are performed. It is demonstrated that, unlike l-alanine, the main factor of adsorption is pi-pi stacking together with van der Waals (vdW) interactions. Computation of gyration radius reveals that gyration radius increases linearly as the weight percentage of functional biomolecules increases. Also, it is shown that the presence of water molecules leads to more expansion of biomolecules around CNTs. Simulations show that Young's modulus of the adsorbed CNTs is slightly smaller than that of pure ones. Furthermore, it is demonstrated that the critical buckling force of functionalised CNT is higher than that of pure CNT. Also, for high aspect ratios, the critical strain of functionalised CNTs is found to be lower than that of pure ones and changes linearly by increasing the weight percentage of functional biomolecules. The buckling modes of functionalised CNTs in vacuum and aqueous environments are explored.