Reduced Graphene Oxide-Poly(3,4-ethylenedioxythiophene) Polystyrenesulfonate Based Dual-Selective Sensor for Iron in Different Oxidation States

A dual-selective sensor platform for detection of iron in ferrous (Fe²⁺) and ferric (Fe³⁺) oxidation states was developed. Upon dispersing reduced graphene oxide (rGO) sheets into poly­(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) polymer, we deposited a hybrid film of rGO-PEDOT:PSS onto a glassy carbon electrode (GCE) surface. Effective intercalation of rGO sheets in PEDOT:PSS film was observed by Raman spectroscopy, UV–vis-NIR spectroscopy, and scanning electron microscopy. The rGO-PEDOT:PSS/GCE sensor showed high electrocatalytic activity for Fe²⁺/Fe³⁺ redox reaction. Using amperometry with controlled applied potential, we demonstrated selective detection of both Fe²⁺ and Fe³⁺ with rGO-PEDOT:PSS/GCE. The sensor responded linearly to Fe²⁺ from 20–833 μM (at 0.6 V) and Fe³⁺ from 1–833 μM (at 0.4 V) in 0.5 M KCl + 0.05 M HCl. The presence of several common metal and organic interferents such as Cu²⁺, Co²⁺, Ag⁺, Pb²⁺, Cd²⁺, Zn²⁺, Mn²⁺, Ni²⁺, Hg²⁺, l-glycine, l-cysteine, l-tyrosine, glucose, KCN, guanine, uric acid, xanthan, salicylate, tartrazine, and naphthol yellow did not affect the selective detection of Fe²⁺ and Fe³⁺. In addition, detection of Fe²⁺ and Fe³⁺ ions in a red wine sample and iron supplement tablets were performed with satisfactory results. The sensor was also useful in determining oxidation kinetics of Fe²⁺ using hydrogen peroxide and measuring Fe³⁺ by differential pulse voltammetry. Thus, rGO/PEDOT:PSS hybrid film based electrode we developed can serve as a practical sensor for detecting iron in its different oxidation states in real samples for different applications.