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 CeO_2, Ag loaded CeO_2, and Au loaded CeO₂ NPs. In addition, the 100 μg mL^-1 of CeO_2, Ag/CeO_2, 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.