CeO2-encapsulated gold nanoparticles (AuNPs) were anchored to reduced graphene oxide (RGO/Au@CeO2) by an interfacial auto-redox reaction in a solution containing tetrachloroauric acid and Ce(III) on a solid support. The resulting material was placed on a glassy carbon electrode (GCE) and used as an electrochemical hydrazine sensor at trace levels. The electrocatalytic activity of the modified GCE towards hydrazine oxidation was significantly enhanced as compared to only RGO/CeO2, or CeO2-encapsulated AuNPs, or AuNPs loaded on CeO2 modified with RGO. This enhancement is attributed to the excellent conductivity and large surface area of RGO, and the strong interaction between the reversible Ce4+/Ce3+ and Auδ+/Au0 redox systems. The kinetics of the hydrazine oxidation was studied by electrochemical methods. The sensor, best operated at a peak voltage of 0.35 V (vs. saturated calomel electrode), had a wide linear range (that extends from 10 nM to 3 mM), a low detection limit (3.0 nM), good selectivity and good stability. It was successfully employed for the monitoring of hydrazine in spiked environmental water samples and to in-vitro tracking of hydrazine in cells with respect to its potential cytotoxicity. Graphical abstract CeO2-encapsulated gold nanoparticles anchored on reduced graphene oxide with the strong interaction between the reversible Ce4+/Ce3+ and Auδ+/Au0 reductions can be used for sensitive detection of hydrazine with detection limit of 3 nM and good selectivity in environmental and biological samples.
Keywords: Electrochemical sensor; Encapsulation structure; In vitro cell detection; Solid-solution interfacial autoredox reaction.