A thiol and magnetic polymer-based electrochemical sensor for on-site simultaneous detection of lead and copper in water

In this study, a magnetic electrochemical sensor, Fe3O4@PDA-DMSA, was triumphantly fabricated by covalently modifying dimercaptosuccinic acid (DMSA) around magnetic polydopamine (Fe3O4@PDA). PDA with many functional groups can act as the starting points for covalent modification with desired molecules, and DMSA containing abundant sulfhydryl and carboxyl groups can be used as an excellent candidate. This magnetic nanocomposite synergistically exhibits several functions (especially high magnetic susceptibility), which can own unique advantages in electrochemical sensing applications. It was employed to enrich target analytes to design a novel electrochemical sensor for reliably monitoring of Pb(II) and Cu(II) in environmental samples, resulting from the specific chelation mechanisms between metal ions and functional groups. X-ray photoelectron spectral data demonstrate the main chelation mechanisms of this process. The synergistic effect among Fe3O4, PDA, and DMSA enhances the electrochemical sensitivity and accelerates the electron transfer. Under optimized conditions, the linear responses to Pb(II) and Cu(II) within the concentration range of 0.5-50 mu g L-1 was obtained with the detection limits of 0.1 and 0.2 mu g L-1, respectively. The little to no interference generated from common coexisting anions/cations allows the designed sensor to operate in diverse environmental conditions for practical applications. Such method of covalent modification can be used for designing sensitive electrochemical sensors for monitoring heavy metal ions.