A synergistic promotion strategy for selective trapping and sensing of lead(II) by oxygen-vacancy and surface modulation of MnO2 nanoflowers

Abstract

Designed and fabricated electrochemical sensing materials with high electrical conductivity, sufficient number of active sites, and good selectivity to target analytes are highly desirable for sensitive determination of heavy metal ions in water. In this work, MnO2 nanoflowers with enriched oxygen vacancies and surface phosphate ions (P-MnO2-x) were prepared by a simple phosphorization process. For this novel electrode modifier, oxygen vacancies increased the electrical conductivity, thereby improving the signal-to-noise ratio of sensors. Phosphate ions acted as ligand molecules for trapping Pb(II) and thus enhanced the selectivity toward Pb(II), and through (PO4)3− bridge, a fast charge-transfer channel was formed and promoting the redox cycles between Mn(III)/Mn(IV) and Pb(II)/Pb(0). Thus, these multiple synergistic effects endowed P-MnO2-x with a high detection sensitivity of 50.11 μA μM−1 and a low limit of detection of 0.0012 μM. More impressively, after phosphorization treatment, P-MnO2-x showed ultra-high selectivity toward Pb(II) while did not change the stripping signals obviously toward other common metal ions. This synergistic oxygen-vacancy and surface modulation strategy demonstrates a new way to construct high-performance electrode materials for electroanalysis.