Green synthesis of Ce³⁺ rich CeO₂ nanoparticles and its antimicrobial studies

Cerium oxide nanoparticles (CeO₂-np) with Ce³⁺ rich surfaces were synthesized by ecofriendly route using tannic acid. XRD and SAED patterns confirm the cubic structure of CeO₂-np. A semi-quantitative XPS analysis revealed the presence of 34 % Ce³⁺ ions. Tannic acid not only mediates the CeO₂-np synthesis, but also helps in reduction of surface states from Ce⁴⁺ to Ce³⁺. Oxygen vacancies were evidenced from XPS and photoluminescence studies. The synthesized nanoparticles showed good antimicrobial activity towards both gram positive (Bacillus subtilis) and gram negative (Escherichia coli) bacteria. The toxicity of CeO₂-np towards tested bacteria is due to production of Reactive oxygen species (ROS). The presence of Ce³⁺ ions and rich surface oxygen vacancies may lead to excellent production of ROS and simultaneously causing cell wall damage. Present findings show that tannic acid assisted CeO₂-np with obtained properties acts as good antibacterial agent.