Sustainably Synthesized CeO₂ Nanoparticles from Lemon Juice and Sucrose for Antibacterial Applications

Green synthesis of metal oxide nanoparticles is a promising route to reduce toxic reagents and energy consumption while enabling biocompatible nanomaterials for biomedical use. In this work, cerium oxide (CeO₂) nanoparticles were synthesized using lemon juice and sucrose as bio-based chelating, capping and stabilizing agents. Three synthesis routes were designed by varying the use of lemon juice, sucrose, or their combination. The synthesized materials were characterized using thermal analysis (DSC-Differential Scanning Calorimetry and TGA-Thermogravimetric Analysis), X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). Additionally, their antibacterial activity was assessed against Gram positive bacterium Staphylococcus aureus (S. aureus). Thermal analysis showed that heat treatment at 600 °C promotes high crystallinity, as evidenced by the development of sharp diffraction peaks associated with the cubic fluorite CeO₂ structure, and a dominant F_2g Raman mode at 463 cm^-1. SEM micrographs revealed nanometric particles and highlighted that combining lemon juice and sucrose effectively suppresses coalesced structures, yielding more homogeneous morphologies. Crystallite size calculations gave average sizes of 17.2 nm, with the lemon juice-only route producing the largest crystallites. Antibacterial tests revealed a clear dose-dependent inhibition of S. aureus, with marked inhibition of bacterial growth at concentrations ≥5 mg/mL and a plateau effect above 25 mg/mL. This study confirms the feasibility of using plant-based extracts as sustainable reagents for CeO₂ nanoparticle synthesis, with promising structural and biological performance for potential biomedical applications.