Development of Au-Pd@UiO-66-on-ZIF-L/CC as a self-supported electrochemical sensor for in situ monitoring of cellular hydrogen peroxide.

Integrating metal-organic frameworks (MOFs) of different components or structures together and exploiting them as electrochemical sensors for electrochemical sensing has aroused great interest. Furthermore, the incorporation of noble metals with MOFs is conducive to the improvement of catalytic performance. In this work, Pd@UiO-66-on-ZIF-L nanomaterials were successfully synthesised onto a self-supported flexible carbon cloth (Pd@UiO-66-on-ZIF-L/CC) through a novel strategy called MOF-on-MOF. Then, Au nanoparticles were electrodeposited onto Pd@UiO-66-on-ZIF-L/CC to obtain Au-Pd@UiO-66-on-ZIF-L/CC, which can serve as an excellent electrocatalyst for the reduction of hydrogen peroxide (H2O2). The obtained flower-like Pd@UiO-66-on-ZIF-L/CC hybrid MOF changes the structure of the monomeric MOF alone and adds more attachment sites. The synergy of the bimetals greatly improved the catalytic performance of the as-developed sensor. Electrochemical experiment results show that the proposed sensor based on Au-Pd@UiO-66-on-ZIF-L/CC has an extended linear range from 1 μM to 19.6 mM with a sensitivity of 390 μA mM-1 cm-2, and a low limit of detection (LOD) of 21.2 nM (S/N = 3). Moreover, it has good anti-interference, reproducibility, repeatability and excellent stability. Furthermore, the real-time in situ detection of H2O2 secreted from human adenocarcinomic alveolar basal epithelial cells (A549 cells) was achieved by culturing cells on Au-Pd@UiO-66-on-ZIF-L/CC, which indicates the potential of the sensor for applications in cancer pathology. Both the synthesis strategy and the sensor design provide new methods and ideas for the production of ultrasensitive H2O2 electrochemical sensors.