Antimicrobial activity of zirconia (ZrO ₂) nanoparticles and zirconium complexes

The antimicrobial activities of zirconia (ZrO ₂) nanoparticles and zirconium mixed ligand complexes were studied on bacterial strains of E. coli, S. aureus and fungal strain of A. niger. The nanoparticles of zirconia and Zr(IV) complexes with different amino acids as ligands were synthesized by hydrothermal method. X-ray diffraction (XRD) and HRTEM confirmed the crystalline nature and morphology of the synthesized products. The antimicrobial studies revealed that the zirconia exhibits activity only against the E. coli, whereas, the Zr(IV) complexes exhibits activity against both the bacteria: gram -ve E. coli and gram +ve S. aureus as well as fungal strains. The Zr(IV) complexes are found to possess significant antifungal activity against A. niger. The results are indicative of crystal plane-dependent antimicrobial activity of zirconia nanoparticles and complexes. The observed difference in the antibacterial activity of ZrO ₂ crystals and Zr(IV) complexes may be ascribed to the atomic arrangements of different exposed surfaces. On the basis of the study, it could be speculated that the ZrO ₂ nanoparticles with the same surface areas but with different shapes i.e., different active facets will show different antimicrobial activity.