Determination of functionalization rate of modified carbon nanotubes using resonant nuclear reactions

Multi-walled carbon nanotubes (MWCNTs) were functionalized by exposure to a RF vacuum plasma containing monomers (AllylAmine (AA), Methyl MethAcrylate (MMA), Styrene and Phenyl Glucidyl Ether (PGE). The Plasma Polymer modified CNTs (PPAA-CNT, PPMMA-CNT, PPS-CNT, and PPPGE-CNT) were characterized by means of Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) and revel that polymers were wrapped on CNTs. Resonant nuclear reactions (RNRA) were used to quantify nitrogen thanks to 14N (alpha, p0) 17O and hydrogen with H (15N,alpha-gamma) 12C. Both techniques have been coupled with Rutherford backscattering spectroscopy (RBS) for confirmation of nitrogen quantification and also for detection of eventual impurities. We show that all functionalized CNTs present considerable hydrogen concentration, however only functionalized plasma polymer CNTs with AA (PPAA-CNTs) show nitrogen peak due to the presence of amine (NH2) groups. During the hydrogen analysis, all samples were drastically affected by hydrogen desorption under ion beam irradiation; this behaviour has been rigorously corrected. The analysis of polymerized CNTs shows concentration varying from 22 % to 42 % of hydrogen and only PPAA-CNTs presents 3.5 % of nitrogen. The RBS measurements confirmed the 14N characterization. These results allowed us to determine for the first time in terms of atomic contribution the functionalization rate for each functionalized CNT.