Effects of dynamic polarization on boron-doped NCD properties and on its performance for electrochemical-analysis of Pb (II), Cu (II) and Hg (II) in aqueous solution via direct LSV

Boron-doped diamond films electrode has been effectively applied in electroanalysis to detect numerous kinds of electroactive chemicals including heavy metals. The success of this application not only depends on the original quality of the films, but more than that, surface treatment or activation and analytical method applied play important role. Fabricated boron-doped nanocrystalline diamond (BD-NCD) in this work were electrochemically pretreated prior to the measurement of heavy metal ions in the solution. The surface properties of the films were evaluated with FE-SEM, AFM, Raman spectroscopy and XPS. The technique chosen for heavy metal measurement was linear sweep voltammetry (LSV) after comparing with differential pulse and square wave voltammetry. In this study, dynamic polarization applied on the BD-NCD electrode was proven to enhance its surface properties. The result of XPS analysis shows that polarized electrode exhibits diminution of Csp² and possess minimum adventitious carbon content on its surface. This leads to an increase of electrode kinetic and promotes its capability for Pb, Cu and Hg ions measurements in the aqueous solution using LSV technique without pre-concentration step. The linearity of current response with increasing heavy metals concentration in an acetate buffer is ranging from 1 to 22.5 μM for Pb and Cu ions and 1 to 10 μM for Hg ion. The detection limit and sensitivity are 1.339, 0.102 and 0.666 μM, and 0.014, 0.104 and 0.057 μA μM^-1 mm² for Pb, Cu and Hg, respectively. The BD-NCD electrode also exhibits capability in simultaneous multi-metals determination although the presence of Cu ion was found to be a disturbance in the system as well. On the other hand, the high content of organics in the real water sample such as lake water also demonstrated to hinder heavy metals measurement. Thus, this study confirms that the BD-NCD after undergoing dynamic polarization are capable of direct determination of Pb, Cu and Hg ions both individually and simultaneously either in the acetate buffer solution or natural water system, within μM level.