Marie Curie, Letter to her brother (1894) "Humanity stands... before a great problem of finding new raw materials and new sources of energy that shall never become exhausted. In the meantime, we must not waste what we have, but must leave as much as possible for coming generations." Svante Arrhenius, Chemistry in Modern Life (1925) v ACKNOWLEDGMENTS First, I would like to thank all my family for the support and for believing in my potential. Thanks Angelina Maria Lanna de Moraes and Fernando Machado Borges de Morais for bringing me to this existence and for educating me. Thanks, Rafael Lanna, for your unconditional brother support. Thanks to all my uncles Aurea, Zé Carlos, Iris, Rosana, Agrício (in memoriam), Léo and Daniel for all financial and emotional support. Special thanks to my life-partner Roberta Ferreira Monteiro for always being at my side, for believing in my mission and for your daily support. Thanks to my mother-in-law Rosália Ferreira Monteiro and my fatherin-law Maj. Idemar Monteiro (in memoriam) for everything. Thanks also to my brother-in-law Maj. Roberto Monteiro and all his family. I would like to acknowledge Prof a. Ana Claudia Queiroz Ladeira for the opportunity of studying at the CDTN under your supervision, for the trust in my work and for your important collaboration to the research. Thank you very much Prof a. Ascensión Murciego and Prof a. Esther Álvarez-Ayuso for the opportunity of studying at Salamanca under your supervision, for our partnership, for the unconditional help and for the unforgettable life experience. ¡Muchísimas gracias, Vale! Thanks to all my professors that shared their knowledge with me, contributing directly and indirectly to this thesis. Special thanks to Prof. Francisco Javier Rios (CDTN) and Clemente Recio (USAL) for creating the opportunity of double doctorate between the two institutions. Special thanks to Mr. Julius Martins for your high-quality proofreading. I would like to thank Indústrias Nucleares do Brasil (INB) for the partnership, the Comissão Nacional de Energia Nuclear (CNEN) for the scholarship, and CNPq, FINEP, Fapemig and Inct-Acqua for funding the research. I am also thankful to the Centro Nacional de Microscopía Electrónica-CNME (Madrid-Spain) for the TEM analysis, the Faculty of Chemistry of the Universidad Complutense de Madrid for the RMN analysis. I would like to thank the CDTN-Applied Physics Laboratory for the XPS analysis, especially to Prof. Pedro Lanna Gastelois and the CDTN Microscopy Laboratory for the and SEM analysis, especially to Dr. Tércio Assunção Pedrosa. Special thanks to Prof. José Domingos Ardisson (CDTN) for the 57 Fe Mössbauer spectroscopy analysis. Special thanks to the technicians and undergraduate internship students of all institutions, whose hard work and dedication were essential. Thanks to the undergraduate students Mariana Fadul, Ana Flávia Marinho Saraiva, Thales Augusto Carneiro and Augusto Alves Camargos for your unmeasurable contribution at the laboratory. Thanks to all my colleagues, especially Dr a. Elaine Fel...