First principles and MD simulation study of the interaction of functionalized carbon nanotubes with water molecules

The interactions between various single-walled carbon nanotubes (SWNTs) and water molecules have been studied using first principles calculations and molecular dynamics (MD) simulations. The SWNTs were modeled by varying the diameter ranging from the chiral vector (6,0) to (9,0), and by modifying the terminal ends with hydroxyl (-OH) and carboxyl (-COOH) functional groups for the nanotubes having chiral vector (9,0). Based on the potential energy surface study, it was found that movement of a water molecule into the tipmodified tubes is easier than that of the pristine tube. It was also found that the tubule diameter play an important role for solvation. The results from MD simulations indicate that the orientation of waters interacting with all of model tubes is rather similar. Water molecules prefer to occupy around the tip of carbon nanotubes than other parts. The hydrophilic behavior of functionalized SWNT is improved over the pristine tube as described by the first principles results.