In-operando electrochemical detection of hydrogen peroxide during bacteria damage using ZIF-67 derived electrocatalysts

In this study, ZIF-67 derived materials were obtained calcinating the ZIF-67 from 500 °C to 700 °C, and they were employed for the in-operando electrochemical detection of hydrogen peroxide formed during the bacterial damage of E. coli induced by the ZIF-67 as antibacterial agent. Transmission electron microscopy (TEM) micrographs revealed a shape transition during the calcination of ZIF-67 from a Co@C core@shell structure (500 °C) to a hollow carbon structure (600 °C). At 700 °C, the hollow structure unfolded to a laminar structure, forming a Co-N-C structure with Co-aggregated particles. The activity for H₂O₂ detection was shape-sensitive, finding that Co-N-C at 700 °C performed better by displaying a lower detection limit (LOD) of 1.64 ppm (48 μM) and a limit of quantification (LOQ) of 5.47 ppm (in phosphate buffer). The in-operando electrochemical tests confirmed that bacterial death can be followed by the detection of H₂O₂, finding a significant antibacterial activity until 1.5 h, after which the current dropped. These results were corroborated using the spread-plate method. Further tests with S. Aureus as a Gram-positive bacterium indicated that the proposed method can be extended to other bacteria.