Spectroscopic studies on covalent functionalization of single-walled carbon nanotubes with glycine

Single-walled carbon nanotubes (SWCNTs) have a great potential in a wide range of applications, but faces limitation in terms of dispersion feasibility. The functionalization process of SWCNTs with the amino acid, glycine involves oxidation reaction using a mild aqueous acid mixture of HNO₃ and H₂SO₄ (1:3), via ultrasonication technique and the resulted oxidized SWCNTs were again treated with the amino acid glycine suspension. The resulted glycine functionalized carbon nanotubes have been characterized by XRD, UV-Vis, FTIR, EPR, SEM, and EDX, spectroscopic techniques. The enhanced XRD peak (002) intensity was observed for glycine functionalized SWCNTs compared with oxidized SWCNTs, which is likely due to sample purification by acid washing. The red shift was observed in the UV-Vis spectra of glycine functionalized SWCNTs, which reveals that the covalent bond formation between glycine molecule and SWCNTs. The functional groups of oxidized SWCNTs and glycine functionalized SWCNTs were identified and assigned. EPR results indicate that the unpaired electron undergoes reduction process in glycine functionalized SWCNTs. SEM images show that the increase in the diameter of the SWCNTs was observed for glycine functionalized SWCNTs, which indicates that the adsorption of glycine molecule on the sidewalls of oxidized SWCNTs. EDX elemental micro analysis confirms that the nitrogen element exists in glycine functionalized SWCNTs. The functionalization has been chosen due to CONH bioactive sites in glycine functionalized SWCNTs for future applications.