One-step synthesis of porous cuprous oxide microspheres on reduced graphene oxide for selective detection of mercury ions

In this paper, we report on the facile one-step synthesis of porous cuprous oxide microspheres on reduced graphene oxide (Cu2OMS–rGO) by synchronously reducing Cu2+ ions and GO with ascorbic acid sodium, followed by their application as electrochemical biosensors for the detection of mercury ions in water. After detailed characterization of the basic chemical components, crystal structure, surface morphology, and electrochemical properties of the Cu2OMS–rGO composites, single-stranded and thymine (T)-rich oligonucleotides were successively immobilized onto the surface of the composite electrode modified by Cu2OMS–rGO. Upon introduction of the target analyte, Hg2+ ions were intercalated into the DNA polyion complex membrane based on T–Hg2+–T coordination chemistry. The results show that the Cu2OMS–rGO composite has high sensitivity for the detection of Hg2+, with a detection limit of 8.62 pM within the range of 0.05 nM to 40 nM. Therefore, the Cu2OMS–rGO composite could be utilized as a novel biosensor for the detection of heavy metal ions in water or in the environment. The strategy yielded excellent selectivity of Hg2+ against other interfering metal ions. In addition, the developed DNA sensor for the determination of Hg2+ ions could be reproduced up to 10 cycles, and the recovery was approximately 95%.