Tailoring the CeO₂ morphology and its electrochemical reactivity for highly sensitive and selective determination of dopamine and epinephrine

Four CeO₂ nanomaterials with the morphologies of a nanoplate (CeO₂-p), a nanocube (CeO₂-c), a porous triangular microplate (CeO₂-t), and of a porous hierarchical rod-stacked nanobundle (CeO₂-b) were synthesized using a hydrothermal method. They were characterized by scanning and transmission electron microscopies, X-ray diffraction and X-ray photoelectron spectroscopy. Electrochemical characterizations reveal the tuning of their morphology and the presence of exposed crystal planes of CeO₂ that can be realized by changing the alkali sources. Among these materials, the CeO₂-b features the largest specific surface and lowest electron transfer resistance towards the redox probe Fe(CN)₆^3-/4-. The best voltammetric response to dopamine and epinephrine is thus achieved by using the Nafion-CeO₂-b coated electrode. A sensitive and selective method was developed that can voltammetrically detect dopamine (with a peak near 0.13 V vs. SCE), and epinephrine (with a peak near 0.25 V vs. SCE). The detection limits are 2.9 and 0.67 nM, respectively.