Development of Optical pH Sensor using Conducting Polyaniline -Wrapped Multiwalled Carbon Nanotubes (PANI-MWCNTs) Nanocomposite

摘要

Highly transparent and water soluble nanocomposite of conducting Polyaniline wrapped - Multi-Walled Carbon Nanotubes (PANI - MWCNTs) was synthesized by an in-situ chemical polymerization method using sulphonic acid as a dopant. MWCNTs were functionalized prior to their use and then polymerized using ammonium per sulphate as an oxidizing agent. The nanocomposite was subjected for physico-chemical characterization using spectroscopic (UV-Vis and FT-IR), FE-SEM and thermal analysis. The UV-Visible spectrum of the salt phase (dark green) of the PANI-MWCNTs nanocomposite shows a free carrier tail with increasing absorption at higher wavelength, which confirms the presence of conducting emeraldine salt phase of the polyaniline and is further supported by FT-IR analysis. However, the base form (deep blue) of the nanocomposite shows a sharp peak at 600 nm representing an insulating pemigraniline phase of the polymer. The FE-SEM image shows the uniform wrapping/coating of the polyaniline over functionalized MWCNTs. The synthesized nanocomposite was then successfully used for the determination of pH of the solution (pH 1-12) and found to be a potential candidate for optical pH sensing.