Porphyrin/Graphene-Based Electrochemical Nanosensors for the Detection of Nerve Agent Simulant Dimethyl Methylphosphonate (DMMP)

Nerve agent simulant DMMP was detected electrochemically in aqueous solution using pristine graphene (PG), reduced graphene oxide (RGO), graphene oxide (GO), tetraphenylporphyrin (TPP), zinc tetraphenylporphyrin (Zn-TPP), RGO/TPP, and RGO/Zn-TPP modified glassy carbon electrode (GCE) systems. Nanocomposites were prepared by non-covalent π-π stacking interactions. The prepared materials were characterised using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and ultraviolet visible spectroscopy (UV-Vis). In addition, the electrochemical performance of DMMP was estimated by means of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The optimum results are obtained at the RGO/Zn-TPP/GCE system, which was used to check the effect of variable scan rate (10-210 mVs⁻¹), pH (4-8), and concentration (100-900 µM). Thus, an increase in anodic (I pa) and cathodic peak current (I pc) response was observed at a high scan rate and with the increase in DMMP concentration up to 900 µM. Also, the best results were obtained at pH 6 for the electrochemical analysis of DMMP. Selectivity studies were carried out at RGO/Zn-TPP/GCE for DMMP and glyphosate through CV. Hence, the proposed sensor showed a large peak current response, low potential peaks, a large linear response range of 100-900 µM, a low limit of detection (LOD) of 0.2540 µM, suitable conductivity, excellent sensitivity of 0.90 µA µM-1 cm-2 and good stability, repeatability, and reproducibility towards DMMP.