Programa da Pos graduacao em Ciencia e Engineering de Materiais

São Cristóvão, Brazil

Programa da Pos graduacao em Ciencia e Engineering de Materiais

São Cristóvão, Brazil
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Nascimento C.C.,Programa da Pos graduacao em Ciencia e Engineering de Materiais | Nascimento C.C.,Instituto Federal Of Educacao | Andrade G.R.S.,Programa da Pos graduacao em Ciencia e Engineering de Materiais | Santos O.S.,Federal University of Bahia | And 4 more authors.
Materials and Design | Year: 2017

This work reports the use of diatomite biosilica as support to deposition of homogeneously dispersed CdS nanoparticles by aqueous reaction. Time evolution of the process revealed that 30 min are sufficient to obtain well dispersed hexagonal CdS nanoparticles, without formation of external particles. Characterization by UV/visible reflectance spectroscopy allowed estimating nanocrystal size as ranging from 4 to 6 nm, while TEM and STEM images showed that those primary CdS nanocrystals formed aggregates with 14.2–71.8 nm depending on the reaction time. Photocatalysis in flow setup through glass column under solar light, under UVA irradiation and adsorption in dark conditions showed that the process under solar light was the most efficient. Photocatalytic tests in dry phase under solar light revealed that the presence of CdS favors dye degradation when compared to diatomite containing the adsorbed dye. Finally, photocatalysis of aqueous suspensions under solar light was also more efficient than adsorption or photolysis, following pseudo-first order kinetics with a half time of 46.2 min. © 2017


Santana Andrade G.R.,Programa da Pos graduacao em Ciencia e Engineering de Materiais | Da Cunha Nascimento C.,Programa da Pos graduacao em Ciencia e Engineering de Materiais | Da Cunha Nascimento C.,Instituto Federal Of Educacao | Xavier P.A.,Programa de Pos graduacao em Quimica | And 3 more authors.
Optical Materials | Year: 2014

CdS and ZnS nanocrystals were grown over specific binding sites onto a thiolated silica-gel aiming to favor defect emission processes. This strategy was found to be effective in yielding ZnS nanocrystals with simultaneous blue and blue-green emissions owing to different types of defects. The effects of doping with copper ions have been observed on the photoluminescence properties. The intensity of defect-related emissions from both semiconductor nanocrystals increased with increasing dopant concentration from 0.25% to 1.5% copper, consistent with the presence of sulfur vacancies. Higher dopant concentrations lead to concentration quenching. © 2014 Elsevier B.V. All rights reserved.


Vasconcelos D.A.,Programa de Pos graduacao em Quimica | Kubota T.,Programa de Pos graduacao em Quimica | Kubota T.,Laboratorio Of Sintese Of Polimeros Derivados Of Carboidratos | Santos D.C.,Programa da Pos graduacao em Ciencia e Engineering de Materiais | And 3 more authors.
Carbohydrate Polymers | Year: 2016

Here we report the use of β-cyclodextrin polyurethane nanosponges cross-linked with 1,6-hexamethylene diisocyanate as a template for the preparation of Aun quantum clusters, by the core-etching of glutathione-capped Au nanoparticles. The study of temporal evolution of the core-etching process using different Au concentrations indicated that formation of Aun clusters embedded in the nanosponge is favored by the use of lower Au concentrations, since it began at shorter times and lead to higher cluster loading. An estimation of the number of Au atoms based on the maximum photoluminescence wavelength suggested that, depending on the Au concentration and the core etching time, clusters with 11-15 atoms were formed. After excluding the possibility of an inclusion complex formation, evaluation of the catalytic activity of nanosponge-loaded Aun clusters toward the reduction of 4-nitrophenol has shown that the reaction is catalyzed by the Aun clusters with no induction time, following the Langmuir-Hinshelwood kinetic model. © 2015 Elsevier Ltd. All rights reserved.


PubMed | Programa de Pos graduacao em Quimica, Programa da Pos graduacao em Ciencia e Engineering de Materiais and Laboratorio Of Sintese Of Polimeros Derivados Of Carboidratos
Type: | Journal: Carbohydrate polymers | Year: 2015

Here we report the use of -cyclodextrin polyurethane nanosponges cross-linked with 1,6-hexamethylene diisocyanate as a template for the preparation of Aun quantum clusters, by the core-etching of glutathione-capped Au nanoparticles. The study of temporal evolution of the core-etching process using different Au concentrations indicated that formation of Aun clusters embedded in the nanosponge is favored by the use of lower Au concentrations, since it began at shorter times and lead to higher cluster loading. An estimation of the number of Au atoms based on the maximum photoluminescence wavelength suggested that, depending on the Au concentration and the core etching time, clusters with 11-15 atoms were formed. After excluding the possibility of an inclusion complex formation, evaluation of the catalytic activity of nanosponge-loaded Aun clusters toward the reduction of 4-nitrophenol has shown that the reaction is catalyzed by the Aun clusters with no induction time, following the Langmuir-Hinshelwood kinetic model.


Moreira M.P.,Programa da Pos graduacao em Ciencia e Engineering de Materiais | Andrade G.R.S.,Programa da Pos graduacao em Ciencia e Engineering de Materiais | De Araujo M.V.G.,Laboratorio Of Sintese Of Polimeros Derivados Of Carboidratos | Kubota T.,Laboratorio Of Sintese Of Polimeros Derivados Of Carboidratos | Gimenez I.F.,Programa da Pos graduacao em Ciencia e Engineering de Materiais
Carbohydrate Polymers | Year: 2016

Synthesis of ternary polyurethanes (PUs) from hexamethylenediisocyanate, β-cyclodextrin and β-glycerophosphate (acid and calcium salt) was studies varying synthesis parameters such as monomer proportion, heating method (reflux and microwave), and catalyst amount. Favorable conditions were provided by microwave irradiation and use of β-glycerophosphoric acid although the results suggest that it is possible to obtain ternary PUs with the calcium salt. FTIR data indicated the existence of secondary urea linkages. After characterization of ternary PUs by FTIR spectroscopy, XRD and thermal analysis, as well as evidences that the cyclodextrin cavities remained active toward inclusion of guest molecules, the possibility of inclusion of the antibiotic ciprofloxacin was evaluated. Absence of ciprofloxacin melting peak in DSC curves indicated that it is molecularly dispersed within the polymer, possibly included in the cyclodextrin. In vitro release experiments suggested additional non-inclusion interactions, showing also that the use of dialysis membranes may mask the actual release profile. © 2016 Published by Elsevier Ltd.


Rezende T.S.,Federal University of Sergipe | Andrade G.R.S.,Programa da Pos graduacao em Ciencia e Engineering de Materiais | Barreto L.S.,Programa da Pos graduacao em Ciencia e Engineering de Materiais | Costa Jr. N.B.,Federal University of Sergipe | And 2 more authors.
Materials Letters | Year: 2010

Here we report on the preparation of gold nanoparticles supported on an insoluble thiolated chitosan derivative, which acted both as reducing and as a stabilizing agent. The material (QT/Au nano) was characterized by suitable techniques and was tested as a catalyst for the reduction of methylene blue (MB). The MB reduction was found to be faster in the presence of QT/Au nano than the reduction by ascorbic acid in solution without the catalyst. A kinetic evaluation showed that the reaction changed from reversible first-order in the absence of the catalyst to a second-order process in its presence, probably by following a different reaction mechanism. © 2010 Elsevier B.V. All rights reserved.

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