Spectroscopic and morphological studies of polyaniline (PANI) — Carbon nanotubes (CNTs) nanocomposite synthesized via dynamic, liquid-liquid interfacial polymerization process and its application as optical pH sensor

Herein, we report the development of highly water dispersible nanocomposite of conducting polyaniline and multiwalled carbon nanotubes (PANI-MWCNTs) via novel, `dynamic' or `stirred' liquid-liquid interfacial polymerization method using sulphonic acid as a dopant. MWCNTs were functionalized prior to their use and then dispersed in water. The nanocomposite was further subjected for physico-chemical characterization using spectroscopic (UV-Vis and FT-IR), FE-SEM analysis. The UV-VIS spectrum of the PANI-MWCNTs nanocomposite shows a free carrier tail with increasing absorption at higher wavelength. This confirms the presence of conducting emeraldine salt phase of the polyaniline and is further supported by FT-IR analysis. The FE-SEM images show that the thin layer of polyaniline is coated over the functionalized MWCNTs forming a `core-shell' like structure. The synthesized nanocomposite was found to be highly dispersible in water and shows beautiful colour change from dark green to blue with change in pH of the solution from 1 to 12 (i.e. from acidic to basic pH). The change in colour of the polyaniline-MWCNTs nanocomposite is mainly due to the pH dependent chemical transformation /change of thin layer of polyaniline.