Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) synthesis was monitored by resonance Raman (RR) and surface-enhanced resonance Raman scattering (SERRS) spectroscopies and both the oxidation of the polymer and the effects of chain length were assessed by vibrational analysis. It was supported by theoretical models of oligomers, with charge ranging from 0 to +6 and size varying from 2 to 16 3,4-ethylenedioxythiophene (EDOT) repeat units, described through density functional theory. The symmetric CαCβ stretching band observed at ca. 1426 cm-1 shifts to higher wavenumbers for reaction times varying from 2 to 9 hours and stabilizes at intermediate wavenumbers for longer times. The former behavior was ascribed to the increase of concentration of oxidized species, which was corroborated by calculated wavenumbers for oligomer models when their charges changed from neutral to +6. The behavior observed for longer reaction times was associated with the growth of chains. It was also observed through SERRS spectroscopy that small chains of the polymer, obtained in the early time of the synthesis, adsorbs on gold nanoparticle surfaces through interactions via oxidized residues. In this way, RR and SERRS spectroscopies were valuable tools to follow the synthetic procedures of PEDOT:PSS, allowing the determination of the structural evolution of the polymer.

The present work shows the temperature dependence of the Raman spectra of two conjugated polymers: poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). In situ resonance Raman spectra of PEDOT from 77 to 423 K at 633 nm and of MEH-PPV from 77 to 473 K at 785 nm suggest that, for both polymers, as the temperature increases there is a decrease in the chain conjugation length. Raman bands of PEDOT assigned to the νsim Cα-Cβ are the most sensitive to temperature while bands due to oxyethylene rings do not show significant shifts in this temperature range. Raman and FT-IR spectra of MEH-PPV recorded above the thermal decomposition temperature provide some insights about the thermal degradation.

This paper proposes a method for chicken tissues preparation using tetramethylammonium hydroxide (TMAH) for Pb determination by graphite furnace atomic absorption spectrometry employing multivariate approaches. Combining Raman spectroscopy with scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy to monitor the solubilization process it was possible to show that TMAH acts in the solubilization of proteins, amino acids and lipids. Besides, this investigation showed that the small residual masses of samples have organic and inorganic compounds. Accuracy tests indicated that such residues have not interfered in the analytical results (recovery between 90-95%). The obtained limits of detection (0.099 µg g -1) and quantification (0.33 µg g -1) are compatible with the detectability required for regulatory purposes. Linearity (R2 = 0.9925) and characteristic mass (13 pg) were also reported. Considering the set of 15 samples comercialized in Brazil, any Pb contamination was successfully observed and this was confirmed by the analysis of digested samples.

Nanocompósitos à base de amido de mandioca, argila sintética hectorita e açúcar invertido (plastificante) foram preparados por processo em meio aquoso (casting) produzindo filmes transparentes e homogêneos. Pequenas quantidades de argila (5-15% em massa) produzem principalmente nanocompósitos esfoliados, enquanto grandes quantidades (30% em massa) promovem a formação de nanocompósitos intercalados. Os espectros FT-Raman mostram que bandas sensíveis à ligação de hidrogênio em grânulos de amido são progressivamente deslocadas para frequências menores quando o teor de argila é aumentado. Os nanocompósitos mostram um comportamento térmico semelhante até 320 ºC, enquanto a decomposição da biomolécula em cerca de 500 ºC é dependente do teor de argila. A liberação de CO2 em aproximadamente 300 ºC (decomposição não oxidativa das cadeias poliméricas) diminui se comparada com o desprendimento desse gás em 500 ºC quando a quantidade de argila é aumentada. Filmes com teor de argila maior que 10% não mostram melhora substancial nas propriedades de alongamento ou resistência.

Polymer-clay nanocomposites (PCN) based on cassava starch, synthetic hectorite clay and inverted sugar cane syrup (plasticizer) were prepared by solvent-assisted (casting) process producing transparent and homogeneous films. Small amounts of clay (5-15 wt.%) resulted mainly in exfoliated nanocomposites while large amounts (30 wt.%) promote the intercalated nanocomposites formation. FT-Raman bands sensitive to hydrogen bonding in starch granules are progressively shifted to lower wavenumbers as the clay content is raised. Nanocomposites show a similar thermal behavior up to 320 ºC while the biomolecule decomposition at about 500 ºC is dependent on the clay content. CO2 release at about 300 ºC (non-oxidative decomposition of polymeric chains) decreases if compared to the gas delivery at ca. 500 ºC, as the clay content is increased. Films with clay content higher than 10 wt.% show no substantial benefit for either elongation or resistance properties.