The detection of toxicants in different matrices have attracted much attention due to the detrimental effects they pose on humans and wildlife. As a result, different analytical techniques have been and are being developed for their detection and identification. However, most of these techniques require the use of instruments that are bulky, expensive and sophisticated; hence, needing highly skilled personnel for their operation. In addition, their bulky nature makes field measurements unattractive. In some cases, the techniques are either not sensitive or selective and rely on tedious pre-sample preparation protocols. Therefore, there is a need for detection techniques that address these drawbacks.
In this study, reusable, disposable as well as conductive and plasmonic nanostructured substrates for the detection of toxicants at trace and high concentrations by surface enhanced Raman spectroscopy (SERS) and electrochemistry was fabricated. The nanostructures were developed on a gold disc, Indium Tin Oxide (ITO) and carbon fiber. Their sensitivities for toxicant detection by SERS were enhanced by incorporating surface Plasmon resonance (SPR) – surface Plasmon polariton (SPP) coupling (which amplified the electromagnetic enhancement effect) and noble metal-semiconductor nanocomposites concept (which increased the charge transfer effect). The fabricated substrates were then used for the selective detection of Hg(II), Pb(II) and melamine at an LOD of 0.51 pM, 0.69 pM and 57.4 pM to 1.89 fM respectively by SERS. Electrochemical application of the developed substrates were also demonstrated by detecting Hg(II) and melamine at 1µM and 0.1µM respectively.
The SERS and electrochemical based substrate and detection technique developed in this work provide a relatively cheaper, faster, yet highly sensitive, selective and field deployable means of detecting and identifying toxicants within a wide range of concentration. The research outcome will potentially assist toxicant monitoring, forensics analysis and environmental law enforcement.