Duque de Caxias, Brazil
Duque de Caxias, Brazil

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Marletta A.,Federal University of Uberlandia | Silva G.B.,Federal University of Uberlandia | Silva R.A.,Federal University of Uberlandia | Silva R.A.,Instituto Nacional Of Materologia | And 2 more authors.
Journal of Luminescence | Year: 2010

The discovery of an alternative route to convert poly(xylyliden tetrahydrothiophenium chloride) (PTHT) into poly(p-phenylene vinylene) (PPV) using dodecylbenzenesulfonate (DBS) has allowed the formation of ultrathin films with unprecedented control of architecture and emission properties. In this work, we show that this route may be performed with several sufonated compounds where RSO3 - replaces the counter-ion (C1-) of PTHT, some of which are even more efficient than DBS. Spin-coating films were produced from PTHT and azo-dye molecules, an azo-polymer and organic salts as counter-ions of PTHT. The effects of the thermal annealing step of PTHT / RSO3 - films at 110 and 230 °C were monitored by measuring the absorption and emission spectra. The results indicate that the exchange of the counter-ion Cl- of PTHT by a linear long chain with RSO3 - group is a general procedure to obtain PPV polymer at lower conversion temperature (ca. 110 °C) with significant increase in the emission efficiency, regardless of the chemical position and the number of sulfonate groups. With the enhanced emission caused by Congo Red and Tinopal as counter-ions, it is demonstrated that the new synthetic route is entirely generic, which may allow accurate control of conversion and emission properties. © 2010 Elsevier B.V. All rights reserved.

Alliprandini-Filho P.,Federal University of Uberlandia | Borges G.F.,Federal University of Uberlandia | Calixto W.B.,Federal University of Uberlandia | Bechtold I.H.,Federal University of Santa Catarina | And 7 more authors.
Chemical Physics Letters | Year: 2010

This Letter reports about the molecular alignment effects on absorbance and emission properties of a new compound based on 2,1,3-benzothiadiazole guested in liquid crystals. The molecular ordering is available for different chromophore concentrations. Despite of the increasing in molecular disorder above the concentration of 0.20%, samples always present a high degree of linear polarization in fluorescence. A considerable amount of polarized emission is observed during the isotropic phase (T > 58 °C), which is attributed to emission of light by aligned molecules before loosing the coherence among them. Finally, we demonstrate the feasibility of ellipsometry technique to investigate phase transitions in fluorescent systems. © 2010 Elsevier B.V. All rights reserved.

Marletta A.,Federal University of Uberlandia | Campos K.R.,Federal University of Uberlandia | Nogueira S.L.,Federal University of Uberlandia | Andrade A.A.,Federal University of Uberlandia | And 3 more authors.
Journal of Non-Crystalline Solids | Year: 2010

This work addresses the new synthesis of poly(styrene sulphonate) (PSS) films doped with neodymium ion (Nd 3+) and co-doped with chromium ion (Cr 3+). NdCr-PSS films were obtained by using the sulphonated polystyrene acid (H-PSS), neodymium nitrate (Nd(NO 3) 3), and chromium nitrate (Cr(NO 3) 3) in aqueous solution. Absorption spectrum of NdCr-PSS film shows the characteristic transition bands of Nd 3+ and Cr 3+ in UV-Vis-NIR region. Infrared spectra indicate that the dopant is bounded to the PSS lateral groups SO 3 -. The selective photoluminescence displays spectra blue shift when Nd and Cr ions are incorporated on PSS films. The behavior results corroborate to decrease the interaction between aromatic rings for adjacent PSS monomers, i.e., the aggregation formation. © 2010 Elsevier B.V. All rights reserved.

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