EPR Spectroscopy for the investigation of materials of technological and industrial interest

The research presented in this Doctoral Thesis discusses mainly the use of Electron Paramagnetic Spectroscopy for the characterization of materials of technological interest. The longitudinal relaxation properties of a vanadyl porphyrin complex have been investigated using pulse EPR experiments at Q (34 GHz) and J-band (263 GHz) frequencies, and the molecule proposed as suitable candidate for quantum processors engineering. The experimental knowledge developed through these relaxation studies, have been transferred to the field of melanins biopigments characterization. The interest for this class of biopigments was derived from the vast amount of applications melanin can cover in the electrochemical and optoelectronic field (e.g. low immunoresponse coating for medical electroanalytical devices, or UV-Vis radiation absorber for solar energy harvesting devices). A novel bacterial melanin from Streptomyces cyaneofuscatus bacteria, and melanin pigments of enzymatic origin, were first studied through S (4 GHz), X (9 GHz) and Q-band (34 GHz) multifrequency EPR. The composition of the bacterial and enzymatic pigments was described, with the support of computer simulation and existing literature in the field. The relaxation properties of these melanin pigments were investigated by means of X and Q-band continuous wave EPR, as well as with Q-band pulse EPR experiments. Differences in terms of longitudinal relaxation times were observed for the melanin pigments of different origin, so that pulse EPR could be proposed either as a tool to distinguish among different melanin species, as well as probe to investigate the structure and dynamics of the radical species present in these natural pigments. A last chapter on the use of computer simulations for the modeling of the electrochemical devices that could be designed to host melanin coated electrodes is presented. In that context, a general model for the evaluation of electrodic currents generated under different geometrical and physical parameters of the systems has been proposed. The physical description was carried out using a dimensionless form of the governing equations, so that the findings of that research can be adapted to particular cases of study. The diverse content of the thesis is thought to reflect the multidisciplinary nature of materials research.