Flax fiber (Linum usitatissimum) is probably the earliest textile material and holds a great archaeological interest . The possibility to define a connection between ageing and molecular characteristics is thus a concrete purpose aiming to help indirect dating. The flax fibers mainly consist of cellulose, hemicellulose, lignin and pectic material. Vibrational spectroscopy, and in particular Raman spectroscopy, has been already used to give a non-destructive characterization of archaeological flax fabrics [2,3]. While larger acquisition areas and IR excitation (exc = 1064 nm) were used in , in the present work micro-Raman spectroscopy and visible-excited fluorescence spectroscopy were applied to 24 micrometric-sized fibers from historical linen (dating from about 3000 B.C. to the XVII cent.) and 12 crude or treated modern fibers. Micro-Raman and micro-fluorescence spectra were acquired respectively by means of a JASCO NRS-5000 Raman system (exc = 785 nm) and of a JASCO RMP-100 microprobe coupled with a Lot Oriel MS25 spectrometer and with a frequency-doubled Nd:YAG laser (exc = 532 nm). In the examined spectral range, from 70 cm-1 to 2600 cm-1, the ratio between 1121 cm-1 and 1096 cm-1 bands has been proved to be a possible signature of ageing [4,5]. Evaluating the above-mentioned band ratio (I1121 cm-1/ I1096 cm-1) after baseline correction, micro-Raman spectra show that modern samples exhibit a quite constant ratio value of 0.85±0.05, which diminishes (up to 0.7) if the linen fiber is heated or bleached. Fibers form archaeological linen show a reduced value for the ratio, that decreases to about 0.5 depending on the age and on the conservation conditions. It should be emphasized that for the most ancient samples or the most severely aged modern samples, the above ratio could not be determined due to the high fluorescence background overlapping the Raman signals. As the possible presence of non-cellulosic carbohydrates in the linen fiber can produce a different spectral pattern, especially in the 280-600 cm-1 region, with variations of relative signal intensities, multiple spectra relative to the same fibers must be acquired, selected and averaged, thus reducing also the possible contribution of extraneous material. A Pearson correlation value of about 0.7 between the intensity of the fiber fluorescence emission and the age of the flax samples is also obtained, showing variations mainly due to the possible influence of other features such as contamination from organic substances (balms, dyes etc.). In conclusion, this study opens a perspective on the possibility of a truly micro-destructive investigation of ancient textiles, exploiting the molecular specificity of spectroscopic techniques.  E.J.W. Barber, Prehistoric Textiles, Princeton University Press, Princeton, NY, USA, 1991, p.12  H. G.M. Edwards, D. W. Farwell, D. Webster, Spectrochemica Acta A, 53, 1997, 2383.  G. Fanti, P. Baraldi, R. Basso, A. Tinti, Vibrational Spectroscopy 67, 2013, 61.  H. G.M. Edwards, N. F. Nikhassan, D. W. Farwell, P. Garside, P. Wyeth, J. Raman Spectrosc. 37, 2006, 1193.  A. Jahan, M.W. Schröder, M. Füting, K. Schenzel, W. Diepenbrock, Spectrochemica Acta A, 58, 2002, 2271.
|Titolo:||Micro-Raman on flax fibers: ageing fingerprints in spectra|
|Data di pubblicazione:||apr-2015|
|Settore Scientifico Disciplinare:||Settore CHIM/01 - Chimica Analitica|
Settore CHIM/12 - Chimica dell'Ambiente e dei Beni Culturali
Settore FIS/07 - Fisica Applicata(Beni Culturali, Ambientali, Biol.e Medicin)
|Citazione:||Micro-Raman on flax fibers: ageing fingerprints in spectra / L. Bonizzoni, S. Bruni, G. Fanti, P. Tiberio, C. Zaffino. ((Intervento presentato al convegno Non-destructive and microanalytical techniques in art and cultural heritage tenutosi a Catania nel 2015.|
|Appare nelle tipologie:||14 - Intervento a convegno non pubblicato|