Voltammetric sensing of Pb(II) using a glassy carbon electrode modified with composites consisting of Co3O4 nanoparticles, reduced graphene oxide and chitosan

A sensitive Pb(II) sensor was fabricated based on Co 3 O 4 /reduced graphene oxide/chitosan (Co 3 O 4 /rGO/chitosan) nanocomposite modified glassy carbon electrode (GCE). The Co 3 O 4 /rGO material was synthesized through in situ growth of Co 3 O 4 nanoparticles (NPs) on GO and subsequent hydrazine reduction process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that Co 3 O 4 NPs with a diameter of around 100   nm are attached on rGO sheets. The structures and compositions of Co 3 O 4 /rGO were further characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Many experimental parameters, such as pH value, deposition time and deposition potential were optimized. Under optimal conditions, the calibration plot for Pb(II), with data acquired at −   0.556   V ( vs . SCE) is linear in the concentration range from 1.0 to 200.0   nM. Combining the good conductivity and high surface area of rGO, strong Pb(II) adsorption ability of Co 3 O 4 NPs, and excellent Pb(II) complex-forming ability of chitosan, the nanocompsite provides a sensitive Pb(II) senor with a detection limit of 0.35   nM. Moreover, the positively charged chitosan can interact with the negatively charged rGO to increase the stability of Co 3 O 4 /rGO nanocomposite. The hybrid nanocomposite Pb(II) senor provides new opportunity for vegetable analysis.