Synthesis, characterization and potentials applications of highly ordered nanoporous materials

Author(s)

Luis Carlos Cides da Silva

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2007-06-22

Examining board members

Jivaldo do Rosário Matos; Hermi Felinto de Brito; Roy Edward Bruns; Ivana Conte Cosentino; Elson Longo da Silva

• Advisor: Jivaldo do Rosario Matos

Abstract

This work consists of the synthesis, characterization and potentials applications of highly ordered mesoporous silica, thermal and hydrothermally stable. These materials of cubic structure of type FDU-1 were synthesized, in acid media, using as silica source tetraetilortosilicate (TEOS) and as poly(ethylene oxide)-poly(butylene oxide)-poly-(ethylene oxide) triblock copolymer B50-6600 (EO39BO47EO39) and Vorasurf 504® templates. The synthesis gels were submitted the hydrothermal treatment in microwaves oven and after that the samples were calcined under N2 and air atmosphere or submitted to the solvent extration. The materials were characterized by thermogravimetry (TG), elementary analysis, infrared spectroscopy absorption, small-angle X ray diffraction (SAXRD), high-resolution transmission electronic microscopy (HRTEM), Nitrogen adsorption measurements and Rutherford Back-scattering spectrometry (RBS). FDU-1 materials were used for the development the following studies: i) application of the factorial design to define a new triblock copolymer as template, Vorasurf 504®, in order to substitute the triblock copolymer B50-6600, that is not more available in the market. The supplied answers were not significant in a reliable level of 95% for the selected variables (stirring time and microwave time). This study demonstrated that is possible to diminish the time of synthesis of the FDU-1 and still to get materials with good structural and texture properties. For the 22 and 23 factorial designs was observed that the most important variable was the microwave oven temperature used in the hydrothermal treatment. However, the concentration of HCl and the presence of etanol of the synthesis mixture did not show no significant effect in a reliable level of 95%; ii) encapsulation of luminescent europium complexes [Eu(DBM3.TPPO] e [Eu(pic)3.2Leu.5H2O] in the pure and/or modified silicas with 3-aminopropyltriethoxysilane (APTES). The encapsulated samples kept the optic properties and increased the thermal resistance of the complexes, both properties were measured for Excitation and emission spectra and TG; iii) incorporation of humic acid with different concentrations (1.0; 1.5 and 2.0 mmols) using microwave oven in the hydrothermal treatment. The samples were tested for removal of Cd2+ from aqueous solutions at pH=6. These materials presented high adsorption capacity for cadmium ions; iv) synthesis of the material using 1,3,5-trimethylbenzene (TMB) as pore expanding agent. This material with pore 11.7 nm was used for immobilization of the glucose oxidase (GOX) enzyme in the presence of glutaraldehyde. Its activity, measured by spectrofotometry and quimilumi-nescence, was very near close for the pure solutions, 601 and 629 µmol g-1, respectively. For immobilized glucose oxidase sample in silica FDU-1 the enzymatic activity, measured directly by quimiluminescence, was esteem in 233 µmol g-1; v) incorporation of TS-1 zeolite in the walls of mesoporous silica using hydrothermal treatment in microwave oven. The samples were submitted the thermal treatment for the zeolite crystallization. The test for the phenol catalysis in presence of UV radiation and H2O2 indicated that it had about 90% of phenol reduction after 120 minutes. (AU)