Molecular conformation and UV–visible absorption spectrum of emeraldine salt polyaniline as a hydrazine sensor

Abstract

ABSTRACTA study on the molecular conformation and electronic properties of different degrees of polymerisation of emeraldine salt polyaniline (ES PANI) has been explored using ab-initio calculations in order to have an insight into the optoelectronic properties, such as band gap, molecular orbital distribution, and UV–visible absorption spectrum conductivity mechanism. The optimization was done with DFT and TD-DFT for calculated UV-visible spectrum using B3LYP/6–31 g(d,p) basis set. Systematic conformational search has been done to find the suitable monomer and dimer model of ES PANI. The monomer model tends to keep a coplanar conformation for π-π interaction where a dimer structure ES PANI has the twist angle between two central rings about 63 degrees. The UV-vis absorption spectrum has one peak in the visible range. A significant red-shift with more degree of polymerisation has the better prediction of experimental UV-visible spectrum.