Juiz de Fora, Brazil
Juiz de Fora, Brazil

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Silva M.A.P.,Campus Universitario Martelos | Franco D.F.,Campus Universitario Martelos | Brandao A.R.,Campus Universitario Martelos | Barud H.,São Paulo State University | And 3 more authors.
Materials Chemistry and Physics | Year: 2010

Transparent amorphous bulk materials have been prepared through the coacervation process of sodium polyphosphate and Ni2+ and Co 2+ chloride solutions. Structural and spectroscopic properties were analyzed by X-ray diffraction, thermogravimetric analysis, UV-vis, infrared and Raman spectroscopic techniques. Different optical properties and water absorption tendencies were observed for the polyphosphate coacervates. The symmetric P-Ob and P-Ot stretching modes on the Raman spectra for the coacervates and the sodium polyphosphate revealed the coordination processes of the polyphosphate chains to the metal ions, including the effects of the water coordination outside the polyphosphate cages, connecting the adjacent chains. Based on data collected from the electronic spectra, these materials can present important technological applicability. Being transparent materials, these glasses can be used as absorption filters with pass-band between 600 and 500 nm for the Ni coacervate, and above 600 nm for the Co coacervate. © 2010 Elsevier B.V. All rights reserved.

Dos Santos H.F.,Campus Universitario Martelos | De Souza L.A.,Lqc Mm Laboratorio Of Quimica Computacional E Modelagem Molecular | De Almeida W.B.,Lqc Mm Laboratorio Of Quimica Computacional E Modelagem Molecular | De Almeida W.B.,University of Sao Paulo | Heine T.,Jacobs University Bremen
Journal of Physical Chemistry C | Year: 2014

Capped carbon cones, known as carbon nanohorns (CNHs), are currently considered to be promising drug carrier agents. To explore the drug-carrying ability and other properties for practical use, the chemistry of production, functionalization, and characteristics of CNHs must be elucidated. To this end, molecular modeling can complement the experimental results by providing the molecular properties for single idealized molecules. In the present study, distinct structures for CNHs are proposed, and their equilibrium geometries, stability, and infrared spectrum are discussed. In addition to the opening angle of the cone, the topology of the tips was also changed, giving rise to 12 distinct geometries, which were analyzed by using the density functional-based tight binding approach (DFTB). © 2014 American Chemical Society.

De A. MacHado A.E.,Campus Universitario | Dos Santos H.F.,Campus Universitario Martelos | De Almeida W.B.,Campus Universitario
Chemical Physics Letters | Year: 2011

B3LYP/6-31G(d) DFT calculations of static first hyperpolarizability (β) were performed for armchair (5,5) single wall carbon nanotube (CNT) functionalized with diethynylsilane (PDES) oligomers having electron-donor (D) or acceptor (A) groups attached to their ends. PDES oligomers were introduced longitudinally and transversely to the CNT external surface. Remarkable β values were obtained for all substituted CNT (>2000 × 10-30 cm5 esu-1). Furthermore, all chemically modified CNT presented very large polarizability values and very small HOMO-LUMO energy gap, indicating their possible use as conducting materials. Our results demonstrated that CNT hybrid materials containing Si might be promising applied in opto-electronics and photonics. © 2011 Elsevier B.V. All rights reserved.

De Castro M.M.,Campus Universitario Martelos | Guimaraes D.L.,Campus Universitario Martelos | Prezoto F.,Campus Universitario Martelos
Sociobiology | Year: 2011

The social wasp Mischocyttarus cassununga is easily found in the southeast and southern Brazil. However, their foragingbehavior is little known. The aim of this study was to examine the foragingbehavior and its variation over the seasons. The study was conducted in Juiz de Fora, Brazil, from July/2007 to June/2008. Apre-emergent colony andapost-emergent colony were observed monthly, from 7am to 5pm. The number of wasps that left and arrived to the nest, as well as information about temperature, air humidity, intensity of light and speed wind was recorded. In the rainy season, foraging activity was observed for the whole observation time. This activity was increased in the afternoon. Spearmans correlation showed that temperature was the only variable that was positively correlated with departures and multiple linear regression analysis showed that about 50% of departures were influenced by temperature and wind speed. In the dry season, the wasps left the nest later and the flow of individuals was only intense in the middle of the day. The departures showed positive correlation with temperature and humidity (Spearman's correlation). Multiple Linear Regression analysis showed that about 70% of exits were influenced by wind speed. Therefore, individual behavior can be influenced by environmental changes that promote activities in the warmer periods throughout the day and seasons.

Anconi C.P.A.,Federal University of Lavras | Da Silva Delgado L.,Centro Universitario Of Caratinga | Alves Dos Reis J.B.,Centro Universitario Of Caratinga | De Almeida W.B.,Campus Universitario | And 2 more authors.
Chemical Physics Letters | Year: 2011

Quantum mechanics theoretical methodology has been applied in order to access and compare the relative stability of inclusion compounds formed by α-CD and the platinum (II) based drugs carboplatin, oxaliplatin and nedaplatin. The relative stability of the studied inclusion compounds has been discussed based on the number and type of hydrogen bonds identified between host and guest molecules. The evaluated energies at B3LYP/6-31G level of theory strongly indicates that α-CD forms stable supramolecular systems with all studied cisplatin analogues, being the carboplatin α-CD found as the most favorable inclusion complex among the platinum (II) derivatives studied in the present paper. © 2011 Elsevier B.V. All rights reserved.

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