Antibacterial and biocompatibility potentials of zinc oxide quantum dots via Nd: YAG laser ablation

Current study report the preparation of zinc oxide quantum dots (ZnO QDs) by Nd: YAG laser ablation in water at different laser energies. The structural properties were investigated using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The XRD studies reveal that the synthesized ZnO QDs are crystalline in nature with a hexagonal structure. The optical energy gap of the ZnO QDs decreased from 4.15 to 3.4 eV as laser energy increased from 60 mJ to 120 mJ. The morphological properties of the prepared nanosized particles and QDs were investigated by transmission electron microscopy (TEM), which confirms the formation of spherical ZnO QDs with diameters in the range of 3–6 nm prepared at a laser energy of 60 mJ. While the TEM investigation shows that the ZnO prepared with laser energy of 120 mJ has nanoparticles of sizes ranging from 16 to 22 nm. The antibacterial activity of the prepared ZnO QDs and NP colloids was investigated against two types of pathogens: one gram-negative Escherichia coli (E. coli) and one gram-positive Streptococcus pyogenes (S. pyogenes) using nutrient broth and nutrient agar. The results indicate that the ZnO QDs with a mass concentration of 110 µg/mL have higher antibacterial activity than ZnO NPs of 430 µg/mL for both kinds of bacteria. Application of ZnO QDs also potentially reduced E. coli and S. pyogenes biofilm formation and had minimal effects on normal rat embryonic fibroblast (REF) cells, suggesting a satisfactory therapeutic index. According to current findings, this study suggests that the size and concentration of the zinc oxide nanoparticles play a crucial role in their effectiveness as antibacterial agents.