Transition metal oxide nanocrystals and their interaction with light or with an alternating magnetic field

• Autores: Julia Natalia Majcherkiewicz
• Directores de la Tesis: Verónica Salgueiriño Maceira (dir. tes.)
• Lectura: En la Universidade de Vigo ( España ) en 2024
• Idioma: inglés
• Tribunal Calificador de la Tesis: María Luisa Fernández Gubieda (presid.), Lucas Vázquez Besteiro (secret.), Michael Farle (voc.)
• Programa de doctorado: Programa de Doctorado en Física Aplicada por la Universidad de A Coruña y la Universidad de Vigo
• Menciones:
  • Internacional
• Calificación: Sobresaliente Cum Laude
• Materias:
  • Física
  • Química
    • Química física
• Enlaces
  • Tesis en acceso abierto en: Investigo
• Resumen

  • The objectives of this PhD research are focused on the exploration and development of magnetic nanoparticles, specifically those composed of transition metal oxides. These nanoparticles, with a crystalline ionic configuration of metal cations with unfilled d-electron orbitals, have gained prominence in several emerging fields. This research makes emphasis in the optimization and functionalization of these magnetic nanocrystals, to render them suitable for diverse applications, including spintronics, targeted heat delivery, and bio-related uses. By studying these nanoparticles both in their pure form and as part of hybrid systems, we seek to demonstrate their versatility and efficacy in the pointed out fields.

    Besides an introductory chapter, this thesis contains three additional ones.

    In Chapter 2, we aimed to exert control over size and morphology of the chromium oxide (Cr2O3) nanocrystals considering various modifications of the synthetic pathway. The nanocrystals were investigated by means of Raman spectroscopy, X-Ray diffraction and Transmission Electron Microscopy. To provide more insights about the nucleation and growth, the structural analysis during the transition from an amorphous chromium hydroxide to crystalline chromium oxide with time at different temperatures of the calcination conducted. We explored the influence of N2 and O2 atmospheres on the nanocrystal growth as well as the effect of calcination times on morphology of chromia nanocrystals. Through mentioned modifications, we selected nanocrystals with tuned sizes exhibiting different magnetic properties for the analysis of a spin-phonon coupling effect via Raman spectroscopy.

    In Chapter 3, we examined cobalt and manganese ferrite nanoparticles to provide insights about calorimetric magnetic hyperthermia under non-adiabatic conditions. Firstly, we conducted structural and magnetic characterization and heating capability studies on these cobalt and manganese ferrite nanoparticles. We aimed to present useful insights for the usage of calorimetric magnetic hyperthermia devices, particularly addressing heat losses under non-adiabatic conditions. We examined the effects of initial sample temperature, chiller temperature, and sample concentration on the Specific Absorption Rate (SAR, heating capabilities) results, and proposed optimization strategies to minimize measurement errors. Secondly, we investigated the heating capabilities of large 260 nm iron oxide nanocrystals in powder form, highlighting their potential for heat delivery and optical tracking.

    In Chapter 4, we explored the integration of magnetic nanoparticles into hybrid systems for the enhancement of functionalities, such as magnetic manipulation and heat delivery, for biomedical applications. We investigated three hybrid systems, including hyaluronic acid microsponges, polyvinyl alcohol nanofiber-based membranes, and albumin protein microbubbles, incorporating two different shaped and sized iron oxide nanoparticles. Using microscopic techniques, we analyzed the morphology of these hybrid nanocomposites and expose them to alternating magnetic fields to evaluate their heating capabilities (magnetic hyperthermia) and/or their potential for magnetic guidance. This work underscored the potential of combining various structures to host magnetic nanoparticles and impart them with magnetic functionalities. This research was conducted collaboratively in the frame of three research stays at Nanofaber, ENEA (Rome, Italy), at the University of Melbourne (Melbourne, Australia), and at Universidad del Paí s Vasco (Bilbao, Spain).