Robust and selective electrochemical sensing of hazardous photographic developing agents using a MOF-derived 3D porous flower-like Co3O4@C/graphene nanoplate composite

• An electrochemical sensing platform for the quantification of hazardous photographic developing agents. • Simultaneous and individual detection of MT, HQ and CC with high reproducibility, sensitivity and selectivity. • The MOF-derived Co 3 O 4 @C/GNP composite is formed using a two-steps procedure involving a solvothermal process and a calcination treatment. Here we present a facile, rapid and reliable electrochemical sensor for quantitative analysis of hazardous photographic developing agents, including metol (MT), hydroquinone (HQ) and catechol (CC). They have been identified as usual contaminants in environment and water samples. This sensor is based on a nanocomposite of three-dimensional (3D) porous flower-like Co 3 O 4 @C hybrid and graphene nanoplates (Co 3 O 4 @C/GNP). The Co 3 O 4 @C/GNP compoiste is prepared by a two-steps procedure, consisting of the composite synthesis of a Co-MOF precursor and GNPs in the first step and subsequently direct calcination process in the N 2 atmosphere. The morphology, composition, and electrochemical behavior of the Co 3 O 4 @C/GNP composite is characterized by using microscopic methods and electrochemical techniques, revealing its 3D porous structure, abundant pores, a large electrode active area, a high conductivity, outstanding electrocatalytic and sensing performance toward MT, HQ, and CC. Taking advantages of a huge electroactive surface area and a fast electron transfer rate of GNPs and strong electrical catalytic ability of the Co 3 O 4 @C hybrid, the fabricated Co 3 O 4 @C/GNP sensor displays high sensitivity for quantitative analysis of MT, HQ and CC. Their detection limits are as low as 5.1, 14.7 and 169 nM (S/ N = 3), respectively. Beyond that, the proposed Co 3 O 4 @C/GNP electrochemical sensor shows strong reproducibility, good stability and selectivity in the voltammetric quantitation of these analytes. It has been also successfully applied in measuring these photographic developing agents in water environment. Consequently, the fabricated Co 3 O 4 @C/GNP composite is expected to be an excellent electrode material in the applications of electrochemical sensing.