Effect of Zr doping on photoantioxidant and antibiofilm properties of CeO2 NPs fabricated using aqueous leaf extract of Pometia pinnata.

Synthesized cerium oxide nanoparticles (S-CeO2 NPs) and 1%, 5% and 10% zirconium doped CeO2 (Zr-doped CeO2) NPs were fabricated using aqueous leaf extract of Pometia pinnata. The synthesized NPs were characterized using standard techniques which confirmed successful synthesis of NPs with particle size ranging from 12 to 23 nm and band gap energy of 2.54-2.66 eV. Photoantioxidant activities showed enhanced activities under visible light irradiation in comparison to the dark condition in the dose-dependent study. Biofilm inhibition studies showed ~ 73% biofilm inhibition of Staphylococcus aureus at 512 µg/mL for S-CeO2, whereas 10% Zr-doped CeO2 NPs showed biofilm inhibition of 52.7%. The bactericidal tests showed killing properties at 1024 µg/mL of S-CeO2 NPs and at 512 µg/mL of 1% Zr-doped CeO2. Reduced bactericidal activities were observed for 5% and 10% Zr-doped CeO2. These studies showed that the fabricated NPs have both good photoantioxidant and antibacterial properties.

Green-synthesized CeO2 nanoparticles for photocatalytic, antimicrobial, antioxidant and cytotoxicity activities.

Cerium oxide nanoparticles (CeO2 NPs) are a sought-after material in numerous fields due to their potential applications such as in catalysis, cancer therapy, photocatalytic degradation of pollutants, sensors, polishing agents. Green synthesis usually involves the production of CeO2 assisted by organic extracts obtained from plants, leaves, flowers, bacteria, algae, food, fruits, etc. The phytochemicals present in the organic extracts adhere to the NPs and act as reducing and/or oxidizing agents and capping agents to stabilize the NPs, modify the particle size, morphology and band gap energy of the as-synthesized materials, which would be advantageous for numerous applications. This review focuses on the green extract-mediated synthesis of CeO2 NPs and discusses the effects on CeO2 NPs of various synthesis methods that have been reported. Several photocatalytic, antimicrobial, antioxidant and cytotoxicity applications have been evaluated, compared and discussed. Future prospects are also suggested.

Green synthesis of CeO2 and Zr/Sn-dual doped CeO2 nanoparticles with photoantioxidant and antibiofilm activities.

Cerium oxide (CeO2) and 1%, 5% and 10% zirconium/tin-dual doped CeO2 nanoparticles (Zr/Sn-dual doped CeO2 NPs) were synthesized using an aqueous leaf extract of Pometia pinnata. By using UV-visible diffuse reflectance spectroscopy, the band gap energies of these materials were found to be in the range of ∼2.49 to 2.66 eV. The average crystallite sizes of the fluorite phase obtained from X-ray diffraction were between 7 and 16 nm. X-ray photoelectron spectroscopy (XPS) analysis further confirmed the synthesis of CeO2 and Sn-doped CeO2 NPs. Almost spherical shapes of the nanomaterials with an average particle size of 12-17 nm were determined using scanning electron microscopy and transmission electron microscopy studies. Photoantioxidant activities of the synthesized materials showed enhanced photoantioxidant response under visible light irradiation in comparison with those under dark conditions in both dose- and time-dependent manner. The CeO2 NPs exhibited a significant concentration-dependent antibiofilm activity against the Gram-positive bacteria Staphylococcus aureus (S. aureus) and Listeria monocytogenes (L. monocytogenes). Only the 10% Zr/Sn-dual doped-CeO2 NPs were found to inhibit S. aureus biofilm formation at higher concentrations. All Zr/Sn-dual doped CeO2 NPs exhibited a concentration-dependent biofilm inhibition of L. monocytogenes and also bactericidal activity towards S. aureus. These nanomaterials exhibited enhanced photoantioxidant activities and antibacterial properties, which make them suitable for various biological applications.