Spectroscopic studies on sidewall carboxylic acid functionalization of multi-walled carbon nanotubes with valine

• The convenient and simple method for sidewall carboxylic acid functionalization of MWCNTs with valine was demonstrated.
• The enhanced XRD peak (0 0 2) intensity was observed for valine functionalized MWCNTs.
• The blue shift was observed in the UV–Vis spectra of valine functionalized MWCNTs.
• The EPR absorption spectral data were found to be best fit for the Gaussian lineshape.
• SEM images show that the increase in the diameter of the MWCNTs was observed for valine functionalized MWCNTs.

The valine functionalized multi-walled carbon nanotubes (MWCNTS) were prepared and characterized by using XRD, UV–Vis, FT-IR, EPR, SEM, and EDX, spectroscopic techniques. The enhanced XRD peak (0 0 2) intensity was observed for valine functionalized MWCNTs compared with oxidized MWCNTs, which is likely due to sample purification by acid washing. UV–Vis study shows the formation of valine functionalized MWCNTs. FT-IR study confirms the presence of functional groups of oxidized MWCNTs and valine functionalized MWCNTs. The ESR line shape analysis indicates that the observed EPR line shape is a Gaussian line shape. The g-values indicate that the systems are isotropic in nature. The morphology study was carried out for oxidized MWCNTs and valine functionalized MWCNTs by using SEM. The EDX spectra revealed that the high purity of oxidized MWCNTs and valine functionalized MWCNTs. The functionalization has been chosen because, functionalization of CNTs with amino acids makes them soluble and biocompatible. Thus, they have potential applications in the field of biosensors and targeted drug delivery.

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