Pencil Graphite Electrocatalytic Sensors Modified by Pyrene Coated Reduced Graphene Oxide Decorated with Molybdenum Disulfide Nanoroses for Hydrazine and 4-Nitrophenol Detection in Real Water Samples.

Novel nanostructured platforms based on Pencil Graphite Electrodes (PGEs), modified with pyrene carboxylic acid (PCA) functionalized Reduced Graphene Oxide (rGO), and then decorated by chronoamperometry electrodeposition of MoS nanoroses (NRs) (MoSNRs/PCA-rGO/PGEs) were manufactured for the electrocatalytic detection of hydrazine (NH) and 4-nitrophenol, pollutants highly hazardous for environment and human health. The surface morphology and chemistry of the MoSNRs/PCA-rGO/PGEs were characterized by scanning electron microscopy (SEM), Raman, and X-ray photoelectron spectroscopy (XPS), assessing the coating of the PCA-rGO/PGEs by dense multilayers of NRs. NH and 4-nitrophenol have been monitored by Differential Pulse Voltammetry (DPV), and the MoSNRs/PCA-rGO/PGEs electroanalytical properties have been compared to the PGEs, as neat and modified by PCA-rGO. The MoSNRs/PCA-rGO/PGEs demonstrated a higher electrochemical and electrocatalytic activity, due to their high surface area and conductivity, and very fast heterogeneous electron transfer kinetics at the interphase with the electrolyte. LODs lower than the U.S. EPA recommended concentration values in drinking water, namely 9.3 nM and 13.3 nM, were estimated for NH and 4-nitrophenol, respectively and the MoSNRs/PCA-rGO/PGEs showed good repeatability, reproducibility, storage stability, and selectivity. The effectiveness of the nanoplatforms for monitoring NH and 4-nitrophenol in tap, river, and wastewater was addressed.