| dc.description.abstract | This project focuses on the simple, fast and highly sensitive adsorptive stripping voltammetry
detection of Nickel and Cobalt complexed with DMG and Nioxime respectively at a Reduced
Graphene Oxide modified pencil graphite electrode in water samples. This research as well
demonstrates a novel electrochemically reduced graphene oxide (ERGO)/mercury film (MF)
nanocomposite modified PGE, prepared through successive electrochemical reduction of graphene
oxide (GO) sheets and in-situ plated mercury film. The GO and graphene were characterized using
FT-IR, HR-SEM, HR-TEM, XRD and Raman spectroscopy. The FT-IR results supported by Xray
diffraction analysis confirmed the inclusion of oxygen moieties within the graphitic structure
during the chemical oxidation step. Microscopic and spectroscopic analysis was used to confirm
the stackings of graphene on the pencil electrode. The ERGO-PG-MFE, in combination with a
complexing agents of [dimethylglyoxime (DMG) and Nioxime] and square-wave cathodic
stripping voltammetry (SW-CSV), was evaluated towards the individual determination of Ni2+
and Co2+ respectively and simultaneous determination of both metals from the combination of
DMG and Nioxime mixture. A single-step electrode pre-concentration approach was employed for
the in-situ Hg-film electroplating, metal-chelate complex formation and its non-electrolytic
adsorption at – 0.7 V for the individual analysis of Ni2+ and Co2+. The current response due to
metal-ligand(s) complex reduction were studied as a function of experimental variables;
deposition/accumulation potential, deposition/accumulation time, rotation speed, frequency and
amplitude and carefully optimized for the individual determination of Ni2+and Co2+ and
simultaneous determination of Ni2+ and Co2+ at low concentration levels (μg L-1) in 0.1 M NH3-
NH4Cl buffer solution (pH 9.4) solution. The recorded limit of detection for the individual analysis
of Ni2+and Co2+ was found to be 0.120 μg L-1 and 0.220 μg L-1 respectively, at an accumulation
time of 120 s for both metals. The recorded limit of detection of the simultaneous analysis of Ni2+
and Co2+ was found to be 6.1 μg L-1 and 1.8 μg L-1 respectively. The ERGO-PG-MFE further
demonstrated a highly selective stripping response toward all trace metal analysis. The testing of
the applicability of graphene-based sensor and method in laboratory tap water samples was
evaluated. This electrode was found to be sensitive enough to detect metal ions in the tap water
samples at the 0.2 μg L-1 level for individual analysis and 0.001 μg L-1 for simultaneous, well
below WHO standards. | en_US |
