α-Fe2O3 nanoparticles (NPs) with morphologies varying from shuttle to drum were synthesized through an anion-assisted and surfactant-free hydrothermal method by simply varying the ratios of ethanol and water in solvent. Control experiments show that the structural evolution can be attributed to a small-molecular-induced anisotropic growth mechanism in which the growth rate of α-Fe2O3 NPs along the a-, b-, or c-axis was well-controlled. The detailed structural analysis through the high-resolution transmission electron microscope (HRTEM) indicated that shuttle-like Fe2O3 NP surface was covered by high-density atomic steps, which endowed them with the enhanced adsorption and sensor ability toward dopamine (DA). The XPS characterizations indicated that the percentages of the OC component follow the order of shuttle-like Fe2O3 (S-Fe2O3 for short) > pseudoshuttle-like Fe2O3 (Ps-Fe2O3 for short) > polyhedron-like Fe2O3 (Ph-Fe2O3 for short) > drum-like Fe2O3 (D-Fe2O3 for short). Benefits from these structural advantages, the S-Fe2O3 NPs-Nafion composite electrode exhibited remarkable electrochemical detection ability with a wide liner range from 0.2 μM to 0.107 mM and a low detection limit of 31.25 nM toward DA in the presence of interferents.
Keywords: chemical absorption; dopamine; electrochemical biosensor; hematite; shape evolution.