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Rio de Janeiro, Brazil

De Almeida Pereira L.,Federal University of Minas Gerais | Windmoller C.C.,Federal University of Minas Gerais | Borba Da Silva J.B.,Federal University of Minas Gerais | Neto W.B.,University Federal Of Uberla
Quimica Nova | Year: 2011

This paper describes the development of methods for the determination of Pb and Mn in fishes by GF AAS after solubilization with tetramethylamonium hidroxide. The optimization of the operational conditions and the choice of modifier were made using multivariated optimization. Analytical Figures of Merit were adequately to propose. The Limit of Quantification obtained were 150 and 18.5 μg kg 1- to Mn and Pb, respectively. No significant difference was found between the slope values obtained for the aqueous and standard addition calibration curves. The D.P.R. was always lower than 12% and the analysis of the SRM NRCC TORT2 showed 80-120% of recovery.

Vivas M.G.,University of Sao Paulo | Nogueira S.L.,University Federal Of Uberla | Silva H.S.,University Federal Of Uberla | Barbosa Neto N.M.,University Federal Of Uberla | And 7 more authors.
Journal of Physical Chemistry B | Year: 2011

In this article, we investigate the linear and nonlinear optical properties of the thiophene/phenylene-based oligomer (SL128G) and polymer (FSE59) chemically modified with alquilic chains, which allow greater solubility and provide new optical properties. These compounds present a strong absorption in the UV-visible region, providing a wide transparence window in visible-IR, ideal for applications in nonlinear optics. Employing the Z-scan technique with femtosecond pulses, we show that these compounds exhibit considerable two-photon absorption (2PA), with two 2PA allowed states located at 650 and 800 nm for SL128G and 780 and 920 nm for FSE59. Moreover, we observe the resonance enhancement effect as the excitation wavelength approaches the lowest one-photon-allowed state. By modeling the 2PA spectra considering a four-energy-level diagram within of the sum-over-essential states approach, we obtained the spectroscopic parameters of the electronic transitions to low-energy singlet excited states. Additionally, photoluminescence excited by femtosecond and picosecond pulses were performed to confirm the order of the multiphoton process and estimate the fluorescence lifetime, respectively. © 2011 American Chemical Society.

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