A high–selectivity electrochemical sensor for ultra-trace lead (II) detection based on a nanocomposite consisting of nitrogen-doped graphene/gold nanoparticles functionalized with ETBD and Fe3O4@TiO2 core–shell nanoparticles

Abstract A sensor made of Fe 3 O 4 @TiO 2 @NG@Au@ETBD was developed to specifically detect Pb 2+ in a significantly toxic aqueous environment. Nitrogen–doped graphene (NG) was utilized as the substrate material of the sensor by a self–assembly method. The synergistic effect of the Fe 3 O 4 @TiO 2 as well as the expanded activated surface and good electrical conductivity of the gold nanoparticles enhanced the detection of Pb 2+ . 2, 2′–((1E)–((4–((2–mercaptoethyl) thio) −1, 2–phenylene) bis (azanylylidene)) bis (methanylylidene)) diphenol (ETBD) was employed as the capture probe for the label–free detection. The electrical characteristics of the Fe 3 O 4 @TiO 2 @NG@Au@ETBD sensor were monitored to measure and investigate the performance of the sensor. Compared with conventional detection technologies and electrodes, this sensor enabled a wide linear range from 4 × 10 −13  mol/L to 2 × 10 −8  mol/L. Lower limits of detection and quantification for Pb 2+ , 7.5 × 10 −13 and 2.5 × 10 −12  mol/L, respectively, were achieved. Furthermore, the Fe 3 O 4 @TiO 2 @NG@Au@ETBD sensor could distinguish Pb 2+ from other metal ions despite the interfering metal ions with concentrations 10 3 –fold higher than that of Pb 2+ . The proposed sensor could potentially be used in heavy–metal detection.