Surfactant-Free Synthesis of Melon Seed–Like CeO<sub>2</sub> and Ho@CeO<sub>2</sub> Nanostructures with Enriched Oxygen Vacancies: Characterization and Their Enhanced Antibacterial Properties
Kanwal Javed, Yufang Ren, Zhenhao Cao, Bushra Begum, Yifan Liu, Aamad Ullah Zafar, Xue Li
Abstract
High Resolution Image Download MS PowerPoint Slide To overcome the poor antibacterial performance of cerium oxide (CeO 2 ) nanoparticles at low concentrations, melon seed–shaped CeO 2 (MS-CeO 2 ) and holmium (Ho)-doped CeO 2 (Ho@MS-CeO 2 ) nanoparticles were synthesized using a simple precipitation method without the addition of any surfactants. The surface morphology, phase structure, crystallinity, Ce 3+ and Ce 4+ valence, lattice defects, and reactive oxygen species (ROS) production of both synthesized nanostructures were examined using different techniques, i.e., scanning electron microscopy (SEM), energydispersive X-ray (EDX), resolution transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), Raman spectroscopy, ultraviolet (UV) spectra, fluorescence spectra, and zeta potential (ζ). The results show that under certain stirring and aging temperatures, CeO 2 and Ho-doped CeO 2 nanoparticles with a melon seed–like morphology can be prepared in a short period. Both nanoparticles were tested as antiseptic agents against G + and G – bacteria ( E. coli and S. aureus ), and the results confirmed that the Ho@MS-CeO 2 nanostructures exhibited remarkable antimicrobial activity at a low concentration (0.5 mg/L) compared with the control group, which is attributed to the reversible conversion of Ce 3+ and Ce 4+ in the ceria crystal lattice, enriched oxygen vacancy, ROS species production, and positive surface charge.