Supramolecular Microfibrils of O-Phenylenediamine Dimers: Oxidation-induced Formation of Au Nanoparticle-decorated Nanoplates for H ₂ O ₂ Detection

The direct mix of aqueous FeCl<sub>3</sub> and o-phenylenediamine (OPD) solutions at room temperature leads to supramolecular microfibrils of OPD dimers generated by the oxidation of OPD monomers by FeCl<sub>3</sub>. In this paper, we demonstrate that the subsequent treatment of such microfibrils with a HAuCl<sub>4</sub> aqueous solution leads to Au nanoparticle (AuNP)-decorated nanoplates. The possible formation mechanism involved is also discussed. It is found that such nanocomposites can effectively catalyze both oxidization and reduction of H<sub>2</sub>O<sub>2</sub>. The sensor constructed with these nanocomposites exhibits a fast amperometric response time of less than 4 s. The linear detection range is estimated to be from 100 μM to 170 mM (r=0.997), and the detection limit is estimated to be 8 μM at a signal-to-noise ratio of 3.