Synthesis of Fe3O4/CNT from discarded milk powder cans using diaphragm discharge plasma for sensing nitrite

Based on the harm of nitrite (NO 2 − ) to human health, quick, accurate, and sensitive detection is urgently demanded to guarantee food safety and public health. Herein, the Fe 3 O 4 /CNT nanocomposites were fabricated at 600 V in NaCl and carbon nano tube (CNT) mixed solution by one-step diaphragm discharge plasma, in which the graphite rod and metal sheet of discarded milk powder can were acted as the cathode and anode, respectively. A probable formation mechanism of Fe 3 O 4 /CNT was brought forth. Then, Fe 3 O 4 /CNT as a material of modified electrode to sense NO 2 − in pickled vegetable was presented. The results found that Fe 3 O 4 /CNT modified electrode shows outstanding performance for sensing NO 2 − in pH = 3.5 phosphate buffer saline (PBS), featuring a linear range of 8 μM-10.6 mM, the limit of detection (LOD) of 0.41 μM, and sensitivity of 1205.57 μA mM −1 cm −2 . The recovery for the detection of NO 2 − in pickled vegetable is 95.5%-106.7% with RSD less than 5%, confirming Fe 3 O 4 /CNT is an outstanding candidate for sensing NO 2 − . This work not only achieves the reuse of high-value waste materials, but also highlights the green advantages of diaphragm discharge plasma, such as simple device, few chemicals and no secondary pollution, offering a sustainable and effective strategy for preparing nanomaterials. Fe 3 O 4 /CNT nanocomposites were successfully fabricated in a mixed solution of NaCl and carbon nano tube (CNT) using discarded milk powder can as precursor of Fe 3 O 4 via the diaphragm discharge plasma technique, then employed as a material for electrochemical sensing nitrite (NO 2 − ) in pickled vegetable. • Fe 3 O 4 /CNT nanocomposites were fabricated via diaphragm discharge plasma. • The discarded milk powder can was used as precursor of Fe 3 O 4 . • A probable formation mechanism of Fe 3 O 4 /CNT was proposed. • Fe 3 O 4 /CNT as an electrode material can be sensed NO 2 − in pickled vegetable. • The sensitivity and LOD are 1205.57 μA mM −1 cm −2 and 0.41 μM, respectively.