Preparação e estudo das propriedades fotoluminescentes de nanoestruturas de In2O3 puro e dopado com íons La3+ e Er3+

Abstract

In this study were obtained pure and doped indium oxide (In2O3) nanoparticles with different concentrations of La3+ and Er3+, rare-earth ions (RE), from the preparation of the hydroxide indium (In(OH)3) by microwave hydrothermal method followed by calcination in a microwave oven. The precursors, pure In(OH)3 and RE-doped In(OH)3, were synthesized at 140 °C with a short time reaction of 2.0 minutes, and from the calcination of such materials in a microwave oven at 350 °C for 2.0 min particles were obtained pure and doped In2O3. The X-ray diffraction showed the formation of the cubic phase for the pure In2O3 and two phases, cubic and rhombohedral, for the samples doped with different concentrations of La3+ and Er3+ ions, indicating that the addition of the RE ions in the In2O3 lattice leads to a structural rearrangement with the formation of the second phase. The characteristic Raman modes for the cubic and rhombohedral In2O3 structures were observed for the pure and doped samples, respectively, and the presence of RE ions generates local distortions, causing a disorder to short range in the In2O3 structure. The structural changes resulting from the effect of the incorporation of the Er3+ and La3+ were also observed in the images of electron diffraction patterns. Nanoparticles around 10 nm from rounded to cubic shapes, wherein the sample doped with a higher concentration of La3+ ions exhibited a more regular cubic morphology, was observed by scanning and transmission electronic microscopy. Uv-vis spectra revealed absorption bands resulting from the Er3+ f-f transitions, which are intensified with increasing concentration of these ions incorporated into the In2O3 network, while the samples doped with La3+ ions were characterized by the absence of absorption in the visible region. All samples showed photoluminescent properties with a broad band emission in the visible region and maximum peak in the orange region mainly attributed to the presence of oxygen vacancies. The photoluminescence phenomenon is related to structural defects on medium and short ranges that may be generated during the preparation of the materials in the presence of different concentrations of La3+ and Er3+ added in the crystalline In2O3 lattice. These defects exert important role related to semiconductor features, in this study the influence of doping on photocatalytic performance of the synthesized materials was verified.