Determination of Optical Band Gap Energies of CS/MWCNT Bio-nanocomposites by Tauc and ASF Methods

Abstract

In the quest for developing new and advanced technologies, semiconductor band gap engineering is critical. In this study, chitosan/multi-walled carbon nanotube (CS/MWCNT) bio-nanocomposite films were prepared using a simple, environmental-friendly and cost-effective method, and the changes occurring in optical band gap energies (Eg) were examined with Tauc and Absorbance Spectrum Fitting (ASF) methods. The results of both models were found to be very close to each other. The optical and electrical properties of the bio-nanocomposites were significantly improved, which make them promising materials for ultraviolet protection, coating and optoelectronic applications. In addition, Urbach energies (Eu) (Band tails) and optical parameters of CS/MWCNT bio-nanocomposites such as refractive index (n), absorption (α) and extinction (k) coefficient were investigated. Urbach energy levels and refractive index values were increased with the increase of MWCNT content in CS matrix. The obtained low band gap energies of the composites by adding MWCNT were interpreted as evidence that the electrical conductivity of the composites is increased and this behavior was found to be consistent with surface conductivity measurements of the composites.