Thiacalixarene Covalently Functionalized Multiwalled Carbon Nanotubes as Chemically Modified Electrode Material for Detection of Ultratrace Pb2+ Ions

This paper presents the preparation of novel thiacalixarene (TCA) covalently functionalized multiwalled carbon nanotubes (MVVCNTs) and an enhanced differential pulse anodic stripping voltammetric procedure for the determination of trace amounts of Pb2+ ions, which relies on the selective accumulation of the metals at a TCA-MWCNT-modified glassy carbon electrode. Through a combination of thiacalixerene's excellent selective recognition and the outstanding electronic properties of MWCNTs, this electrode material shows excellent selectivity and high sensitivity for electrochemical detection of Pb2+ ions. The stripping response is highly linear (R = 0.999) over a Pb2+ concentration range of 2 x 10(-10) to 1 x 10(-8) mol/L, and the limit of detection is 4 x 10(-11) mol/L. Furthermore, the determination of Pb2+ (10(-7) mol/L) in the presence of an equal amount of interfering Sn2+ ions yielded well-separated signals. To understand the molecular interaction mechanism between the TCA molecules and metal ions (Pb2+ and Sn2+), theoretical computations were performed. The results demonstrate that the Pb2+/Sn2+ ions could stably adsorb onto the TCA molecules, and there is significant electron delocalization between Pb2+/Sn2+ and sulfur atoms in the TCA molecule.