Nitrogen-doped carbon spheres surface modified with in situ synthesized Au nanoparticles as electrochemical selective sensor for simultaneous detection of trace nitrophenol and dihydroxybenzene isomers

Using polydopamine as nitrogen-doped carbon precursors, adsorbent and reducing agent of HAuCl4, nitrogen and Au nanoparticle could be in situ doped and surface modified successively into/onto carbon spheres. The conductivity, electrons transfer ability, and electrocatalytic activity of carbon sphere were improved by the synergistic effect of surface modification with Au nanoparticle and nitrogen doping and then the sensitivity of this electrochemical sensor was enhanced. The synthesized nanocomposite was characterized by transmission electron microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. Based on the difference of adsorption rates and oxidation potentials, both nitrophenol isomers (o-nitrophenol, m-nitrophenol, p-nitrophenol) and dihydroxybenzene isomers (hydroquinone, catechol, resorcinol) could be identified, separated successfully, and determined simultaneously by differential pulse voltammetry. This proposed method with wide linear range (0.05–600 μmol L−1) and low detection limit (24–98 nmol L−1) was successfully applied for simultaneous detection of nitrophenol and dihydroxybenzene isomers in wastewater and natural water.