Ceria nanoparticles are important catalyst and nanozymes accompanied with a strong affinity for many harming species. As ceria can scavenge such species, it is defined a nanozymes when they have an enzymatic mimetic activity. Here, we have studied the interaction of ceria with important molecules that can be harmful. We focus on arsenate, phosphate and reactive oxygen species (ROS) to prove the strong interaction they have with ceria and how provide insights from the modelling. The arsenate water pollution has been reported as a burning issues in many countries and can harm humans and the wildlife causing several serious health issues. Many different metabolic pathways to breakdown arsenate can produce ROS, which in high concentration can cause oxidative stress to the cells. Cerium oxide can be used to remove arsenate as it can adsorb such species. Furthermore, ceria can also adsorb phosphate strongly, which in high concentrations causes eutrophication, but they are also bodily electrolytes and constituents of biological molecules. Ceria has been shown to have a strong affinity for phosphate and phosphatase activity. Alongside the species that ceria can scavenge are also ROS such as the superoxide radical and hydrogen peroxide. These ROS enter catalytic superoxide dismutase and catalase activities when interacting with ceria. This thesis begins with an introduction (Chapter 1) to provide the background information about the advanced applications of ceria nanoparticles in various fields, alongside literature reviews of the different topics. The methodology follows, presenting density functional theory and relevant background details (Chapter 2). The first result chapter covers the effect of the surface chemistry (i.e., concentration of Ce(III) and oxygen stoichiometry) on the arsenate and phosphate adsorption (Chapter 3) on the three most stable ceria surfaces ({100}, {110}, and {111}). Phosphate is stronger than arsenate adsorption, which both preferring pristine and oxygen deficient surfaces at low and high concentrations of Ce(III), respectively. This is followed by the vibrational fingerprint, in the form of simulated IR and Raman spectra, of the arsenate (Chapter 4) and phosphate (Chapter 5) adsorbed on the surfaces of ceria. The vibrational fingerprints for the phosphate and arsenate adsorption on ceria surfaces are in range of 500-1500 cm-1 and 200-1200 cm-1, respectively. Then, we study the catalytic superoxide dismutase (SOD) and catalase (CAT) activities of ceria surfaces, at different stoichiometry (Chapter 6). We find that SOD is preferable on the surface sub-layer oxygen deficient surfaces, while CAT is preferable on the pristine surfaces. Higher concentrations of Ce3+ favour SOD while lower concentrations favour CAT. Non-catalytical activities expressed by ceria are also studied as they can only occur on surface layer oxygen deficient surfaces, but they alter the surface chemistry of ceria surfaces, ultimately hindering the catalytic activities. Finally, all main findings and future developments are highlighted in Chapter 7.
| Date of Award | 12 Mar 2025 |
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| Original language | English |
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| Supervisor | Marco Molinari (Main Supervisor) |
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