Raman and surface enhanced Raman scattering of a black dyed silk

Abstract

Artículo de publicación ISIThe Raman and surface enhanced Raman scattering (SERS) spectra of a black dyed silk sample (BDS) were registered. The spectral analysis was performed on the basis of Raman and SERS spectral data of isolated samples of Bombyx mori silk fibroin, its motif peptide component (GAGAGS) and the synthetic reactive black 5 dye (RB5). The macro FT-Raman spectrum of the silk sample is consistent with a silk II-Cp crystalline fraction of Bombyx mori silk fibroin; the SERS spectrum is highly consistent with conformational modifications of the fibroin due to the interactions with the Ag nanoparticles. The GAGAGS peptide sequence dominates the Raman spectrum of the silk. The SERS spectrum of the peptide suggests a random coil conformation imposed by the surface interaction; the serine residue in the new conformation is exposed to the surface. Quantum chemical calculations for a model of the GAGAGS–Ag surface predict a nearly extended conformation at the Ag surface. The Raman spectrum of the dye was analysed, and a complete band assignment was proposed; it was not possible to propose a preferential orientation or organization of the molecule on the metal surface. Quantum chemical calculations for a model of the dye interacting with a silver surface predict a rather coplanar orientation of the RB5 on the Ag metal surface. The Raman spectrum of the BDS sample is dominated by signals from the dye; the general spectral behaviour indicates that the dye mainly interacts with the silk through the sulphone (–SO2–) and sulphonate (–SO2–O–) groups. Besides the presence of dye signals, mainly ascribed to the sulphone and sulphonate bands, the SERS spectrum of the BDS sample also displays bands belonging to the amino acids alanine, glycine, serine and particularly tyrosine

A vibrational approach for the study of historical weighted and dyed silks

“…As shown in our previous work [8], the GAGAGS sequence is highly expressed in the cocoon fibroin. The Raman spectrum of the raw Bombyx mori silk (CS) has many similarities with the spectral profile of the peptide GAGAGS; thus, the crystal fraction dominates the spectrum.…”

“…In our recent publication concerning the RB5 dyed silk we observed that the Raman spectrum is dominated by the dye [8]. Three historic samples of dyed silks were analysed.…”

“…Spectroscopic, chromatographic and chemical data were analysed in order to infer about the physical deterioration of silk during the aging process [7]; it has been found that the amorphous region broke down and the crystallites progressively lost their strong alignment with the fibre axis but stayed intact until the ultimate stage. Samples of Bombyx mori silk fibroin, and its motif peptide component (GAGAGS) were already studied by using mainly Raman and surface enhanced Raman scattering (SERS) techniques [8]. A complete spectral analysis was performed and conformational modifications of the peptide by temperature and surface effect were inferred; the amorphous fragments are exposed to the Ag metal surface as indicated by the predominance of Tyr spectral signals.…”

Vibrational spectroscopy for the study of Chilean cultural heritage

“…A second group includes samples of dark silk belonging to the same period as the light samples, but differentiated by a lesser degradation with respect to the stability of the textiles. Samples of Bombyx mori silk fibroin, and its motif peptide component (GAGAGS) were also studied by using mainly Raman and surface enhanced Raman scattering (SERS) techniques [67]. Silk degumming, weighting and dyeing processes effects on the degradation of Bombyx mori silk fibroin were investigated through the ATR-IR and Raman techniques along with SEM/EDS microscopy.…”

“…The Raman spectrum of the raw Bombyx mori silk (CS), has many similarities with the spectral profile of the peptide GAGAGS, the crystal fraction dominating the spectrum [67]. The ATR-IR spectrum of the raw silk shows two strong bands at 1617 and 1511 cm −1 .…”