Eco-Friendly Synthesis of CeO2 Nanoparticles Using Air Microdischarge Plasma for Efficient Photocatalytic Degradation of Norfloxacin

Abstract

Nonthermal plasma (NTP) is an emerging technique for nanoparticle (NP) synthesis due to its ability to generate highly reactive species under mild conditions. Microdischarge plasma (MDP) is a type of NTP that offers various advantages over standard synthesis processes, including a single-step process, short processing time, atmospheric operating conditions, and elimination of surfactant or other additional chemicals. Herein, CeO₂ NPs were synthesized using air MDP in a short time without the need for high-temperature post treatment. Reactive species generated by air plasma, including hydroxyl radicals (OH•) and other reactive oxygen species (ROS), play a major role in the nucleation and growth of NPs. The as-prepared CeO₂ NPs displayed a cubic fluorite crystal structure, with a small crystallite size of 1.74 nm and spherical morphology. The optical band gap of as-synthesized CeO₂ NPs was found to be 2.6 eV, indicating that defect states introduced during the MDP process reduced the band gap, thereby enhancing the visible light absorption. The photocatalytic potential of the synthesized CeO₂ NPs was assessed by the degradation of norfloxacin. The maximum degradation efficiency of 91.91% was achieved using a low catalyst dosage of 0.1 g/L^-1, and the degradation process follows pseudo-first-order kinetics. Antibacterial assays confirmed that the photodegraded samples did not affect both gram-negative and gram-positive bacteria, indicating effective degradation of the antibiotic without inducing toxicity. Therefore, the MDP technique is a rapid and eco-friendly approach for large-scale production of functional metal oxide NPs for water treatment and environmental remediation.