Síntese, caracterização espectroscópica e termogravimétrica do precursor Difenil-4-amina sulfonato de európio: conversão de Eu2O2SO4/Eu2O2S

• Main Author: Carvalho, Maria Aparecida de
• Publication Date: 2010
• Format: Master thesis
• Language: por
• Source: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Download full: http://repositorio.ufes.br/handle/10/4656
• topic: Sulfonates; Europium; Thermogravimetry; Oxysulfate; Oxysulfide; Spectroscopy; Sulfonatos; Oxissulfato; Oxissulfeto; Espectroscopia; Química; Európio; Análise espectral; Termogravimetria; 54

In this work we studied the synthesis and characterization of europium diphenylamine-4-sulfonateat different reaction media and their behavior of two techniquesof thermal analysis(TG/DTG and DSC). The compounds synthesized in aqueous solution (Compound A) and in water-ethanol (Compound B), were characterized by the following techniques: microanalysisof C, H, N andS, absorption spectroscopy in the infrared regions and ultraviolet-visible, complexometric titration with EDTA, SEM and X-ray diffraction (powder method). The elemental analyses data of C, H, N and S, complexometric titration suggestedthe general formulasEu(C12H10NSO3)3.7H2O for the compound obtained in aqueous solution (Compound A) and Eu(C12H10NSO3)3.5H2O forcompound B obtained in aqueous/ethanolsolution. The infrared spectra indicated thatthe complexes are hydrated and that the coordination of the sulfonate to the Eu+3ions occurs through the oxygen atoms of the sulfonate group. The SEM showed that the compound B has a more defined morphology in relation to compound A, which was attributed to the presence of alcohol in the synthesis. The TG/DTG curves corroborated with data from the IR spectra with regardto the absence of water coordinated to the metal ion in the compound A, while in the compound B there are water molecules coordinatedto the metal. The emission spectra of thesecomplexes displayed mainly the narrowbands arising from intraconfigurationaltransition4FN5D0? 7F1, 2, 3, 4,extended, indicating that the Eu+3ion occupies more than one symmetry site. Furthermore, these spectra are consistent with a centrosymmetric environment for the Eu+3ion and allowed to suggest the microsymmetrymore likely, as Ohfor bothcompound A and B compounds.The emission spectra show a significant decrease of the radiative processes in the B complex by the presence of suppressor OH. The results of TG curves obtained in a dynamic atmosphere of air and XRD showed Eu2O2SO4as a product of decomposition. The emission spectra of these products displayed mainly the narrowbands arising from intraconfigurational transitions4FN5D0? 7F1, 2, 3, 4,. These bands were a little wider, indicating more than one symmetry site for Eu+3ion. The unfolding transitions allowed to suggest the most likely microssimetria as C3vfor both products of thermal decomposition in air. In the thermal decomposition using dynamic atmosphere of N2, it was observed that was not possible to establish any level indicative of formation of intermediate thermostable up to 1000°C. The thermal 18decomposition processes were followed by DSC in N2atmosphere to 600°C, showing small exothermic peak followed by endothermic peaks, relating to consecutive reactions. Regarding the decomposition of the precursor under an atmosphere of gas mixture (H2/Ar), data from TG/DTG together with data from XRD showed Eu2O2S as product ofthermal decomposition at 1150°C. Regarding the conversion of oxysulfate the oxysulphide under H2/Aratmosphere to the product of the conversion at 950°C of oxysulfate of the compound A, the results showed the presence of oxide, while for the conversion ofoxysulfateof thecompound B, obtaining oxysulphideas single phase occurs at 1150°C. The recovery of the reduction products under a dynamic atmosphere of air shows reoxidation. The results of different tests showed that the presence of alcohol in the synthesis influences the structure, symmetry and morphology of precursors, which also contributed to the formation of morphologically different decomposition products.