"Memory catalysis": Extending the photocatalytic antibacterial performance of a palladium-modified ZnO nanocomposite

In this study, Pd-ZnO nanocomposite was synthesized via the facile solvothermal method. Then, PdO-ZnO was obtained by continuing calcination of the synthesized Pd-ZnO. X-ray Diffraction (XRD), Transmission Electron Microscope (TEM), and X-ray Photoelectron Spectroscopy (XPS) tests showed that Pd was converted to PdO in the process of calcination. The photocatalytic sterilization experiment showed that in the 3 % Pd-ZnO system, 2 x 107 CFU/mL of E. coli was completely killed within 3 h, while 3 % PdO-ZnO took 1.5 h. In electron spin resonance (ESR) tests on PdO-ZnO, The & BULL;OH and & BULL;O2- signals can be detected under light and within 20 min after the end of light. 1 x 105 CFU/mL of E. coli were killed within 1 h by the optical "memory" effect of PdO-ZnO. PdO-ZnO inactivates E. coli by disrupting the membrane structure of bacteria as demonstrated by scanning electron microscopy (SEM) test. PdO-ZnO is non-toxic and can be demonstrated through cytotoxicity experiments on HTT2.