Beyond the selective adsorption of polypyrrole-reduced graphene oxide nanocomposite toward Hg2Â +: Ultra-sensitive and -selective sensing Pb2Â + by stripping voltammetry

► We present a new insight in the ultra-sensitive and -selective sensing Pb2 + by stripping voltammetry. ► The method is based on the selective adsorption of polypyrrole-reduced graphene oxide (PPy-RGO) nanocomposite toward Hg2 +. ► A detection limit of 4 pM and a sensitivity of 0.642 μA nM− 1 were reached. ► The minimal interference with other ions at a high enough concentration could be observed.