Optimized porous carbon-fibre microelectrode for multiplexed, highly reproducible and repeatable detection of heavy metals in real water samples.

This work demonstrates the simultaneous identification of four hazardous heavy metals in water samples, namely copper, lead, cadmium, and mercury. A simple yet selective electrode with the simplest fabrication procedure was used. The modified porous carbon threads coated with gold nanoparticles (AuNPs) was employed as a working electrode. The surface chemistry and morphology of the AuNPs deposited porous carbon thread surface were examined. The electrocatalytic activity of the metals on the Au-modified thread surface was observed using the differential pulse voltammetry (DPV) technique. Furthermore, all four metal ions were detected simultaneously, and no interference was observed. Individual and simultaneous experiments to test the impact of concentration revealed that the limit of detection (LoD) was observed to be 1.126 μM, 1.419 μM, 0.966 μM, 0.736 μM for the Cd, Pb, Cu, and Hg metal ions respectively in a linear concentration range of 10-110 μM of each. Subsequently, the study of pH, interference with coexisting metal ions, repeatability study, and stability analysis was also performed. A real sample analysis utilising three different lake water samples is also carried out to further understand the application of the proposed sensor. A good recovery rate is achieved, and the results are reported. This work paves way for the on-field applicability of the present heavy metal detection platform.