Exploiting differential electrochemical stripping behaviors of Fe ₃O₄ nanocrystals toward heavy metal ions by crystal cutting

This study attempts to understand the intrinsic impact of different morphologies of nanocrystals on their electrochemical stripping behaviors toward heavy metal ions. Two differently shaped Fe₃O₄ nanocrystals, i.e., (100)-bound cubic and (111)-bound octahedral, have been synthesized for the experiments. Electrochemical results indicate that Fe ₃O₄ nanocrystals with different shapes show different stripping behaviors toward heavy metal ions. Octahedral Fe₃O ₄ nanocrystals show better electrochemical sensing performances toward the investigated heavy metal ions such as Zn(II), Cd(II), Pb(II), Cu(II), and Hg(II), in comparison with cubic ones. Specifically, Pb(II) is found to have the best stripping performance on both the (100) and (111) facets. To clarify these phenomena, adsorption abilities of as-prepared Fe ₃O₄ nanocrystals have been investigated toward heavy metal ions. Most importantly, combined with theoretical calculations, their different electrochemical stripping behaviors in view of facet effects have been further studied and enclosed at the level of molecular/atom. Finally, as a trial to find a disposable platform completely free from noble metals, the potential application of the Fe₃O₄ nanocrystals for electrochemical detection of As(III) in drinking water is demonstrated.