Facile fabrication of zinc phosphate-based nanocomposites for high-performance electrochemical sensing of Hg(II)

Two novel nanocomposites of zinc phosphate [Zn 3 (PO 4 ) 2 ] and Hg 2+ -targeted DNA [Zn 3 (PO 4 ) 2 @DNA] and Zn 3 (PO 4 ) 2 and multi-wall carbon nanotubes (MWCNTs) modified with Hg 2+ -targeted DNA [Zn 3 (PO 4 ) 2 @MWCNTs-DNA] were fabricated by the assembly of Hg 2+ -targeted DNA strands with Zn 2+ ions. Two as-prepared nanocomposites were subsequently used as electrochemical biosensors for sensitively detecting Hg 2+ due to the combination effect of the formation of T–Hg 2+ –T coordination between DNA strands and Hg 2+ and the direct adsorption of Hg 2+ onto porous nanocomposites. In comparing with Zn 3 (PO 4 ) 2 @DNA nanocomposite, the crystallization degree of Zn 3 (PO 4 ) 2 @MWCNTs-DNA was improved due to the presence of MWCNTs, which further enhance electrochemical activity of the nanocomposite. As a result, Zn 3 (PO 4 ) 2 @MWCNTs-DNA nanocomposite-based electrochemical biosensor showed a higher sensitivity toward Hg 2+ detection in aqueous solution than Zn 3 (PO 4 ) 2 @DNA-based biosensor. It showed a detection limit of 0.071   nM within the range of 0.1–50   nM of the concentration of Hg 2+ . This newly developed biosensor also presented excellent selectivity, repeatability, and applicability in Hg 2+ detection. Therefore, the fabricated Zn 3 (PO 4 ) 2 -based nanocomposite using this novel strategy showed their considerable potential use in water or environmental treatment.