Revealing the Effect of Synthesis Conditions on the Structural, Optical, and Antibacterial Properties of Cerium Oxide Nanoparticles

Abstract

Cerium oxide nanoparticles were prepared by a precipitation method using Ce(IV) sulphate as precursor dispersed in glycerol with varying synthesis parameters such as temperature or precipitating agent. The structural and morphological characteristics of the obtained nanoparticles were investigated by X-ray diffraction, transmission electron microscopy, and diffuse reflectance spectroscopy. The crystallite size of the nanoparticles varied between 13 and 17 nm. The presence of Ce3+ and Ce4+ was proved by XPS data in the CeO2 samples and the conservation of the fluorite structure was evinced by X-ray diffractograms with a contraction of the lattice parameter, regardless of the size of the nanoparticle. From diffuse reflectance spectra, two band gap energy values for the direct transition were observed. Depending on the synthesis condition, the red shift of gap energy and the blue shift of Urbach energy with increasing content of Ce3+ were ascertained. The antibacterial tests revealed that the cerium oxide nanoparticles show good antimicrobial activity towards the common pathogens Escherichia coli and Staphylococcus aureus.

Investigating the Vibrational, Magnetic and Dielectric Properties, and Antioxidant Activity of Cerium Oxide Nanoparticles

“…These values are comparable to those of some earlier reported data for pure cerium oxide or doped cerium oxide nanoparticles [11,43,55,56]. From our XPS analysis, the development of oxygen vacancies on the nanostructure surface and the presence of Ce 3+ ions were confirmed [42]. In this way, the ferromagnetic behavior of the CeO-1 sample may have been the result of interactions between oxygen vacancies and Ce 3+ ions which determine the alignment of spins in the local environment.…”

“…In the case of CeO-3, the mixed ferromagnetic and paramagnetic phase indicated that the presence of the adsorbed oxygen decreased the oxygen deficiency and lowered the antioxidant properties. XPS studies also proved that even though CeO-1 had a lower content of Ce 3+ than CeO-3, the former was oxygen deficient while the latter was rich in oxygen, i.e., with an oxygen content higher than stoichiometric value [42]. The oxygen deficient sites in CeO-1 were the active sites that increased the possibility of Ce 3+ oxidation, thereby also increasing the scavenging ability of the sample as compared to CeO-3.…”

“…Cerium oxide nanoparticles were prepared by the precipitation method using cerium(IV) sulphate (>99% Sigma-Aldrich/Merck, Darmstadt, Germany) as a precursor and sodium hydroxide (>98%, Sigma-Aldrich/Merck, Darmstadt, Germany) or ammonium hydroxide (25%, Chemical Company, Iasi, Romania) as a precipitating agent (Table 1), as previously described [42,43]. Raman measurements were made on a micro-Raman system (inVia Reflex, Renishaw, New Mills, United Kingdom) with an excitation wavelength of 633 nm, provided by a 633 nm He-Ne laser at room temperature.…”

“…It was demonstrated that the presence of surface oxygen deficiency determines the magnetic ordering within cerium oxide nanostructures [11,13,18,62,63]. The XPS data indicated a higher content of oxygen vacancies in CeO-1, which exhibited a dominant ferromagnetic response, whereas in the CeO-2 sample having a higher content of adsorbed oxygen the ferromagnetism was diminished [42].…”

“…In our previous paper, we successfully obtained cerium oxide nanoparticles by the precipitation method using glycerol as a dispersion medium for cerium sulphate and with modified synthesis parameters (temperature, precipitating agent) [42]. The prepared nanostructures were characterized by X-ray diffraction, diffuse reflectance spectra, emission spectra, XPS, and transmission electron microscopy.…”