Resumen de Designing advanced nanocatalysts: Synthesis of complex ceo2-based nanostructures
The main objective of this dissertation has been to stablish a bridge between materials science and its fields of application. The scope of this thesis work, under this premise, is aimed towards understanding the catalytical properties of CeO2 nanocrystals and the applications arising from them. In order to tackle it, the chemist labour consists in providing a cutting-edge nanosynthesis technology able to improve efficiencies of the chemical processes, reducing energy consumption and minimizing the environmental impact of both activity and waste products. At the same time, research on nanomaterial synthesis involves the design and formulation of nanomaterials under total control of their physicochemical, morphological, and colloidal properties. Coupled with the appropriate description of the structure-activity relations, the current aim of nanomaterial synthesis is an application-oriented design strategy towards programmable properties of the products.
Within this framework, this thesis work is divided into two parts. The first part revolves around nanomaterial synthesis. It pursues the optimised formulation of nanostructured CeO2, a semiconductor material that holds a broad set of intrinsic catalytic properties, describing the synthesis of the minimal stable size for colloidal monocrystalline particles of the material and its complete physicochemical characterization (size, composition, morphology, crystal structure, optical and colloidal properties). It is followed by the extension of the material¿s functionality through different derivation strategies, such as doping with different trivalent lanthanide ions and coupling to plasmonic metal domains (Au and Ag) via different synthetic approaches to produce several types of hybrid architectures (core-shell, heterodimers, hollow structures, and other anisotropic shapes) of controlled size.
The second part of this work involves the characterization of structure-activity relations of the CeO2-based nanomaterials synthesised in the first part. These are evaluated first through the catalytic performance of each nanomaterial. It has been carried out for two different processes. As a heterogeneous catalyst for methanol production and as ROS scavenger for biomedical applications, coupled with the correspondent assessment of the nanomaterials¿ toxicity through in vitro assays. To complete the description of the structure-activity relations, the characterization of the singular electronic structure of CeO2, that confers its characteristic catalytical properties, has been also carried out. Employing core-level spectroscopic techniques, the differences between bulk and nanosized CeO2 have been evaluated through the Ce 3d and O 1s spectra in XPS and Ce L3 edge in XANES.
