Synthesis of nanostructured CeO2 by chemical and biogenic methods: Optical properties and bioactivity

Synthesis of nanostructured CeO2 by chemical and biological methods has been performed. Oxalic acid and polyethylene glycol have been utilized for the chemical synthesis, while, Simarouba glauca leaf extract is used for the synthesis of biogenic CeO2 nanoparticles. The synthesized nanoparticles have been characterized using UV-visible, PL, XRD, TEM, EDAX, FTIR and Raman techniques. TG-DTG analysis has revealed an annealing temperature above 420 degrees C to be suitable for the complete conversion of the synthesized materials into nanostructured CeO2 NPs. UV-visible spectra give band gap energies of 3.41, 3.65 and 3.81eV for the synthesized bare, polymer capped and biogenic nanostructures, respectively. Biogenic nanoparticles show a striking average particle size of approximate to 9.9 nm imparting them superior optical and bioactivities in comparison to the other samples. Intensity of PL emission peak at 467 nm arising due to the charge transfer from the 4f conduction band to the 2p valence band of CeO2 is found to increase with a decrease of particle size depicting better crystallinity of the biogenic sample. Particle sizes calculated from Raman line broadening at 461 cm(-1) representing F-2g mode of cubic fluorite structured CeO2 are found to coincide with those from XRD and TEM. The bio fabricated CeO2 NPs at the concentration of 100 mu g/mL shows significant bactericidal activity against E. coli and S. aureus due to the direct interaction of CeO2 NPs on the membrane surface of the microorganisms. The biogenic CeO2 NPs exhibited prominent wound healing activity on L929 fibroblast cell line in comparison with the control. Further, complete wound healing has been observed for cells treated with all the synthesized samples after 24 h. The simple, costeffective and eco-friendly biogenic method for the synthesis of nanostructured CeO2 exposes superior properties enabling their utilization in biomedical field.