Modification of multi-walled carbon nanotubes by plasma treatment and further use as templates for growth of CdS nanocrystals

Abstract

In this study, we present a novel method for preparing multi-walled carbon nanotubes (MWCNTs) grafted with a poly(2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA)-cadmium sulfide complex (CNTs-G-ICdS complex) through plasma-induced grafting polymerization. The characteristics of the MWCNTs after being grafted with the GMA-IDA polymer were monitored by a Fourier transform infrared (FT-IR) spectroscope. Scanning electronic microscopy (SEM) shows that the amount of GMA-IDA grafted onto the MWCNTs increases with the concentration of GMA-IDA monomer. The complex resulting from GMA-IDA polymer grafting onto the MWCNTs, CNTs-G-I (15%), shows excellent dispersion properties in aqueous solution and has high Zeta potential values over a wide range of pH values, from 2 to 12. Moreover, Raman spectroscopy was used to confirm the successful chemical modification of MWCNTs through the plasma treatment. The chelating groups, -N(CH(2)COO(-))(2) in the GMA-IDA polymer grafted on the surface of the CNTs-G-I, are the coordination sites for chelating cadmium ions, and are further used as nano-templates for the growth of CdS nanocrystals (quantum dots). Moreover, TEM microscopy reveals that the size of the CdS nanocrystals on the CNT surfaces increases with increasing S(2-) concentration. In addition, high resolution x-ray photoelectron (XPS) spectroscopy was used to characterize the functional groups on the surface of the MWCNTs after chemical modification by the plasma treatment and grafting with GMA-IDA polymer.