In this work, Raman spectroscopy and density functional theory (DFT) calculations have been used in order to understand the nature of the interaction between the carotenoid bixin and organic solvents with dielectric constant varying from ca. 2 (toluene) to ca. 47 (dimethyl sulfoxide). Raman shifts registered for the main carotenoid marker band, the C=C stretching mode (1525-1533 cm-1), were used as a probe to monitor spectral changes due to chemical interaction between bixin in the solid state with the analogous solvated species. Raman spectra of bixin in solution showed significant bathochromic shifts in the wavenumber position of ν(C=C) when compared with the solid state. Among the solutions, subtle differences were observed and the polarizability rather than dielectric constant of the solvents seems to be a more appropriate parameter to explain the differences in Raman shifts which could be correlated with the solvation degree of bixin. Correlation between DFT analysis and molecular dynamics simulations obtained for cis-bixin in DMSO and CHCl3 demonstrated that the interaction of the solute with the respective solvents occurs in specific portions of the molecule, however, this result was not confirmed by the experimental data since bixin is solvated by larger numbers of solvent molecules.

In this work specimens of chitosan which have been cross-linked covalently and ionically with different oxocarbon and pseudo-oxocarbon anions have been synthesised and characterized using infrared and Raman spectroscopic techniques, solid state 13C nuclear magnetic resonance (NMR) and by thermogravimetry. According to the spectroscopic and thermal results, ionically crosslinked chitosans are obtained with squarate, croconate and rhodizonate ions as crosslinking agents, whereas covalently crosslinked chitosan can be obtained when squaric acid is used as the crosslinking agent; the same products are not observed when the pseudo-oxocarbon anion croconate violet is used, which can be attributed to the low basic strength of the crosslinking species.

Guias de luz planares foram obtidos a partir de um sol de um novo híbrido Ti4+-acetilacetona (acac)-Ureasil depositado na forma de filmes finos sobre substratos de vidro. A estrutura foi investigada por medidas espectroscópicas (absorção no infravermelho, fotoelétrons de raios-X e espalhamento Raman) e espalhamento de raios-X a baixos ângulos (SAXS). Para a adição do complexo Ti-acac ao ureasil na razão molar Ti:Si de 1:1 interações entre o complexo Ti-acac e grupos siloxanos foram identificadas. Quantidades maiores de Ti4+ (razão molar Ti:Si de 5:1) levam também à formação de nanoagregados ricos em titânio. Os parâmetros ópticos dos guias, como índice de refração, espessura, modos propagados e coeficiente de atenuação foram medidos para 632,8, 543,5 e 1550 nm pela técnica de acoplamento de prisma. O índice de refração pode ser controlado pela quantidade relativa de titânio. Guias de poucos micra de espessura suportam modos de propagação com baixas perdas para todas as composições.

Hybrid planar waveguides were prepared from Ti4+-acetylacetone (acac)-Ureasil sols deposited on glass substrates. Structural features have been investigated by spectroscopic measurements (Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Raman scattering) and Small Angle X-ray Scattering (SAXS). Addition of Ti4+-acac to the ureasil (Ti:Si molar ratio 1:1) leads to the formation of bonds between the Ti complex and the siloxane groups, whereas further addition of Ti4+ (Ti:Si molar ratio 5:1) leads to the additional formation of titanium-rich nanoclusters. The optical parameters of the waveguides such as refractive index, thickness, propagating modes and attenuation coefficient were measured at 632.8, 543.5 and 1550 nm by the prism coupling technique. The refractive index can be tuned by the Ti4+ relative content. The few microns thick planar waveguides support well confined propagating modes with low attenuation loss for all compositions.