Stratified diffusion of HOD-D2O inside COOH- and NH2-functionalized multi-walled carbon nanotubes studied by NMR spectroscopy

Abstract

Functionalized multi-walled carbon nanotubes (MWCNTs) are potential systems for drug delivery applications like cancer therapy. By using NMR spectroscopy, we have demonstrated that 99.8% deuterated water, confined at nanoscale, splits into several components which flow with different diffusion coefficients through MWCNTs having an average diameter of 15 nm. Remarkably, we have highlighted the effect of the functionalization of MWCNTs with COOH- and NH2-molecules on the diffusion of water inside MWCNTs. Our results show that the specific choice of molecules used to functionalize the external surface of MWCNTs allows direct control of the diffusion coefficient. Raman and XPS spectroscopy were used to characterize the structure of MWCNTs after functionalization with COOH- and NH2-.