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Papers by Roberto Medeiros Silveira
Journal of the Australian Ceramic Society
In this study, we report on a novel and reactive synthesis of highly ordered cubic mesoporous sil... more In this study, we report on a novel and reactive synthesis of highly ordered cubic mesoporous silica that is able to tailor different symmetries of pores and morphologies through a two-step procedure carried out in relatively low temperatures (20–60 °C) using a single type of surfactant. We systematically examined the effects of reaction parameters such as pH, times of hydrolysis and condensation, concentration of Pluronic F-127 surfactant, and aging temperature, by using characterization techniques such as small-angle X-ray scattering (SAXS), analysis of surface area and porosity by adsorption of N2 (BET isotherms), and scanning and transmission electron microscopy (SEM and TEM). Our investigations found that, at 20 °C, the shape of particles is sensitive to changes in surfactant concentration which means that it is possible to tune spherical to polyhedral particles by simply increasing the amount of surfactant. In addition, at low concentrations of F-127, the size of the particles is temperature-dependent, with an inversely proportional pattern of behavior. The protocol also enables the production of well-ordered pores, particularly with 3D-cubic symmetries Fm3̅m and Im3̅m, and some hexagonal, as well as to control the sizes of the pores.
RSC Advances, 2017
The current density of glycerol electrooxidation on Pd/SiO2reached twice the values found for Pd/... more The current density of glycerol electrooxidation on Pd/SiO2reached twice the values found for Pd/C. Mesosporous silica support works as a trap that confines the reactant.
Journal of Nanomaterials, 2013
In this work we have synthesized and characterized new hybrid nanoplatforms for luminescent biola... more In this work we have synthesized and characterized new hybrid nanoplatforms for luminescent biolabeling based on the concept of Eu3+complexes encapsulation in mesoporous silica nanoparticles (≈100 nm). Eu complexes have been selected on the basis of their capability to be excited at 365 nm which is a currently available wavelength, on routine epifluorescence microscope. For Eu complexes encapsulation, two different routes have been used: the first route consists in grafting the transition metal complex into the silica wall surface. The second way deals with impregnation of the mesoporous silica NPs with the Eu complex. Using the second route, a silica shell coating is realized, to prevent any dye release, and the best result has been obtained using Eu-BHHCT complex. However, the best solution appears to be the grafting of Eu(TTA)3-Phen-Si to mesoporous silica NPs. For this hybrid, mSiO2-Eu(TTA)3(Phen-Si) full characterization of the nanoplatforms is also presented.
Journal of the Australian Ceramic Society
In this study, we report on a novel and reactive synthesis of highly ordered cubic mesoporous sil... more In this study, we report on a novel and reactive synthesis of highly ordered cubic mesoporous silica that is able to tailor different symmetries of pores and morphologies through a two-step procedure carried out in relatively low temperatures (20–60 °C) using a single type of surfactant. We systematically examined the effects of reaction parameters such as pH, times of hydrolysis and condensation, concentration of Pluronic F-127 surfactant, and aging temperature, by using characterization techniques such as small-angle X-ray scattering (SAXS), analysis of surface area and porosity by adsorption of N2 (BET isotherms), and scanning and transmission electron microscopy (SEM and TEM). Our investigations found that, at 20 °C, the shape of particles is sensitive to changes in surfactant concentration which means that it is possible to tune spherical to polyhedral particles by simply increasing the amount of surfactant. In addition, at low concentrations of F-127, the size of the particles is temperature-dependent, with an inversely proportional pattern of behavior. The protocol also enables the production of well-ordered pores, particularly with 3D-cubic symmetries Fm3̅m and Im3̅m, and some hexagonal, as well as to control the sizes of the pores.
RSC Advances, 2017
The current density of glycerol electrooxidation on Pd/SiO2reached twice the values found for Pd/... more The current density of glycerol electrooxidation on Pd/SiO2reached twice the values found for Pd/C. Mesosporous silica support works as a trap that confines the reactant.
Journal of Nanomaterials, 2013
In this work we have synthesized and characterized new hybrid nanoplatforms for luminescent biola... more In this work we have synthesized and characterized new hybrid nanoplatforms for luminescent biolabeling based on the concept of Eu3+complexes encapsulation in mesoporous silica nanoparticles (≈100 nm). Eu complexes have been selected on the basis of their capability to be excited at 365 nm which is a currently available wavelength, on routine epifluorescence microscope. For Eu complexes encapsulation, two different routes have been used: the first route consists in grafting the transition metal complex into the silica wall surface. The second way deals with impregnation of the mesoporous silica NPs with the Eu complex. Using the second route, a silica shell coating is realized, to prevent any dye release, and the best result has been obtained using Eu-BHHCT complex. However, the best solution appears to be the grafting of Eu(TTA)3-Phen-Si to mesoporous silica NPs. For this hybrid, mSiO2-Eu(TTA)3(Phen-Si) full characterization of the nanoplatforms is also presented.