A copper-based metal-organic framework decorated with electrodeposited FeO nanoparticles for electrochemical nitrite sensing.

An amperometric nitrite sensor is reported based on a screen-printed carbon electrode (SPCE) modified with copper(II)-benzene-1,4-dicarboxylate (Cu-BDC) frameworks and iron(III) oxide nanoparticles (FeO NPs). First, copper(I) oxide (CuO) nanocubes were synthesized, followed by a solvothermal reaction between CuO and HBDC to form square plate-like Cu-BDC frameworks. Then, FeO NPs were electrodeposited on Cu-BDC frameworks using a potentiostatic method. The FeO@Cu-BDC nanocomposite benefits from high conductivity and large active surface area, offering excellent electrocatalytic activity for nitrite oxidation. Under optimal amperometric conditions (0.55 V vs. Ag/AgCl), the sensor has a linear range of 1 to 2000 µM with a detection limit of 0.074 µM (S/N = 3) and sensitivity of 220.59 µA mM cm. The sensor also provides good selectivity and reproducibility (RSD = 1.91%, n = 5). Furthermore, the sensor exhibits long-term stability, retaining 91.4% of its original current after 4 weeks of storage at room temperature. Finally, assessing nitrite in tap and mineral water samples revealed that the FeO@Cu-BDC/SPCE has a promising prospect in amperometric nitrite detection.