Ionic liquid functionalized biogenic synthesis of AgAu bimetal doped CeO2 nanoparticles from Justicia adhatoda for pharmaceutical applications: Antibacterial and anti-cancer activities.

The noble metal such as Ag and Au doped CeO2 nanoparticles was successfully prepared by ionic liquid assisted hydrothermal method in the presence of Justicia adhatoda leaves extract and were used as an antibacterial and anticancer agent. The FT-IR and Raman spectrum exhibit the peaks at 460 and 464 cm-1 assigned to CeO stretching vibrations of NPs. The electron microscopic micrographs confirmed the spherical shaped morphology of prepared NPs. The insertion of Ag and Au ions into the CeO2 surface creates lattice defects the leads to reduce the band gap energy of Ag-Au/CeO2 at 3.15 eV. The XRD results suggested the average crystalline size of the silver‑gold loaded CeO2 was 28 nm. From the elemental mapping images, we have visualized that existence and uniform distribution of Ag, Au, Ce, and O in the prepared nanomaterials. The antibacterial activity of unloaded and bimetal loaded CeO2 NPs was evaluated with Gram-positive and Gram-negative bacteria using disc diffusion assay. The AgAu loaded CeO2 NPs exhibited the highest zone of inhibition against E. coli and S. aureus strains when compared with pristine CeO2, Ag loaded CeO2, and Au loaded CeO2 NPs. In addition, the 100 μg mL-1 of CeO2, Ag/CeO2, Au/CeO2 and Ag-Au/CeO2 NPs exposed the 50, 51, 52 and 56% of anticancer activity against the HeLa cells respectively. Overall, this study concludes that the ionic liquid functionalized green synthesized bimetal loaded cerium oxide NPs showed potent antibacterial and anticancer activities.