Toward DNA electrochemical sensing by free-standing ZnO nanosheets grown on 2D thin-layered MoS₂

Very recently, the 2-dimensional MoS₂ layer as base substrate integrated with other materials has caused people's emerging attention. In this paper, a thin-layered MoS₂ was prepared through an ultrasonic exfoliation method from bulk MoS₂ and then the free-standing ZnO nanosheet was electrodeposited on the MoS₂ scaffold for DNA sensing. The ZnO/MoS₂ nanocomposite revealed smooth and vertical nanosheets morphology by scanning electron microscopy, compared with the sole MoS₂ and sole ZnO. Importantly, the partially negative charged MoS₂ layer is beneficial to the nucleation and growth of ZnO nanosheets under the effect of electrostatic interactions. Classic methylene blue, which possesses different affinities to dsDNA and ssDNA, was adopted as the measure signal to confirm the immobilization and hybridization of DNA on ZnO nanosheets and pursue the optimal synthetic conditions. And the results demonstrated that the free-standing ZnO/MoS₂ nanosheets had low detection limit (6.6×10^-16M) and has a positive influence on DNA immobilization and hybridization.