pH robust electrochemical detection of 4-nitrophenol on a reduced graphene oxide modified glassy carbon electrode

Abstract A glassy carbon electrode modified with reduced graphene oxide (GCE/rGO) is proposed as a novel electrochemical platform for detecting 4-nitrophenol (4-NP). The examined rGOs were synthesized using a straightforward reduction route under hydrothermal conditions (120, 150 and 180 °C). The rGOs were characterized by X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy, X-ray diffraction, field-emission scanning electron microscopy and atomic force microscopy. A higher reduction degree was achieved after thermal treatment at 180 °C, as demonstrated by the significant decrease in the oxygen content of the starting GO (from 35.4 to 16.7 at.%) and by the marked restoration of the Csp 2 domains (from 16.1 to 62.4 at.%). The electrochemical activity of GCE/rGOs towards 4-NP was investigated using cyclic voltammetry experiments in a 0.1 M acetate buffer solution (ABS). rGO-180 was selected as the active electrode material of the electrochemical sensor for detecting 4-NP because of the highest measured cathodic reduction current. The results demonstrated an enhancement of the corresponding cathodic currents measured after modification of the GCE and slight changes over the pH range of 4.0–5.0. These results are beneficial for real sample analysis. The sensor worked linearly in the range of 50 to 800 μM and had a detection limit of 42 μM. Interferences of other pollution compounds, such as hydroquinone, catechol and bisphenol A, did not affect the sensing towards 4-NP. The electrode demonstrated good recoveries in real samples and excellent long-term stability (98.98% of the original signal value after 14 days).