X-Ray Diffraction Analysis by Modified Scherrer, Williamson–Hall and Size–Strain Plot Methods of ZnO Nanocrystals Synthesized by Oxalate Route: A Potential Antimicrobial Candidate Against Foodborne Pathogens

In the present study, highly pure zinc oxide nanocrystals were successfully synthesized by thermal decomposition in an air atmosphere at 400 °C of pre-prepared ZnCO⋅2HO. The purity of both compounds was confirmed through Fourier Transform Infrared Spectroscopy, Energy Dispersive X-ray Spectroscopy and X-Ray Powder Diffraction (XRPD). Scanning Electron Microscopy shows that powder particles are organized in micron-aggregates. Diffuse reflectance measurements and photoluminescence investigation, performed for ZnO, confirmed the presence of point surface defects. XRPD peak broadening analysis using modified Scherrer equation, Williamson-Hall and Size-Strain plot (SSP) methods was performed in order to calculate the average crystallite size (D) and lattice strain (ε). The SSP model reflects the best agreement between the experimental and fitted data with R = 0.999 (D ≈ 25 nm and ε = 8.57 × 10). Antimicrobial activity of ZnO against four foodborne pathogens (Listeria monocytogenes ATCC 19117, Staphylococcus aureus ATCC 6538, Salmonella typhimurium ATCC 14028 and Escherichia coli ATCC 8739) was discussed based on qualitative and quantitative assays consisting of agar well diffusion method, microdilution and time-kill kinetic assays. The obtained results are quite promising and suggest the possibility to use the as-synthesized zinc oxide as an antimicrobial agent in food preservation.