Preparação e caracterização estrutural de nanopartículas de tio2 dopado com lantanídeos (Ti1-xGdxO2 e Ti1-xLaxO2) para aplicações fotocatalíticas.

Abstract

In this dissertation we presente the studies related to the preparation and the structural characterization of nanostructured TiO2 samples doped with Gd3+ (Ti1-xGdxO2) and La3+ (Ti1-xLaxO2) via the polymeric precursor method in the nominal concentrations of xN = 0,0; 0,02; 0,04 e 0,06. The structural characterization was performed by using the techniques: thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction (XRD) and Rietveld structural refinement, Raman spectroscopy, scanning and transmission electron microscopy (SEM and TEM), energy-dispersive X-ray spectroscopy (EDS) and diffuse reflectance spectroscopy (DRS). The preparation parameters were determined in order to obtain the samples Ti1-xGdxO2 and Ti1-xLaxO2 in the anatase crystallographic phase of the TiO2 with the better possible crystallinity and powder grains at the nanoscale. The experimental results confirm the synthesis of nanostructured samples and indicate the incorporation of the dopants into the TiO2 matrix without formation of secondary or spurious phases. Increasing the doping concentration, the band gap remains unchanged. There are also evidences pointing that the spatial distribution of the dopants and the related structural defects mainly located near/at the surface of the nanoparticles. These results, in spite of the optical absorption still been at the UV region of the electromagnetic spectrum, indicate a potential higher catalytic efficiency of the doped samples as compared to the pure TiO2 sample.