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SERS analysis of basic and acid early synthetic dyes on wool

AutorCañamares, María Vega ; Deriu, Chiara; Mazzeo, Rocco; Prati, Silvia; Sánchez-Cortés, Santiago
Palabras claveSERS
Anionic dyes
Cationic dyes
Fecha de publicación21-mar-2016
CitaciónINART (2016)
ResumenWhat makes it possible for such dyes to directly fix to a substrate is the presence of functional groups able to interact with the constituting chemical units of a textile. In the case of wool its amphoteric character allows the efficient use of both anionic (Acid) and cationic (Basic) dyes. The acidic groups confer the molecule water-solubility and negative charge, the latter being the major driving factor of the dying mechanism. Acid dyes are applied to the fibres in acidic conditions. In such environments, the protein components of wool acquire a positive charge, due to the protonation of the basic side-chain moieties and to the neutralization of the acid functions. As far as basic dyes are concerned, the way in which they are applied to wool resembles the one just seen for acid dye. The analysis of dyes in cultural heritage samples is a well-known challenging task, due to their inherent high tinting strength and consequent low concentration in the carrying matrix. This fact severely limits the number of analytical techniques that can be efficiently and micro-destructively employed for their detection and unambiguous identification. The introduction of Surface-Enhanced Raman Spectroscopy (SERS) to the field of conservation science has made the study of such materials possible and more straightforward, both as free molecules and as dyed fibres. This is possible due to the SERS ability to yield good signal-to-noise ratio spectra from minute amounts of sample, as well as to the quenching of the fluorescence emission. Such advantages have been exploited for the elaboration of a quick and pre-treatment-less methodology based on SERS, for the analysis of three early synthetic dyes (Acid Orange 7, CI 15510; Basic Violet 14, CI 42510; and Basic Violet 3, CI 42555) in minute wool yarns fragments. A small amount of dyed wool fibre was placed inside a glass tube along with a triply washed modification of the standard Lee-Meisel silver colloid and KNO3 0.5M as aggregating agent. Such dispersion was analysed in a macro Raman arrangement. A further modification of colloid by adjusting the pH value to 4 with diluted HNO3 was established as the SERS substrate for the analysis of anionic dyes on wool. This methodology was satisfactorily applied to the detection of AO7, a very difficult SERS probe due to its anionic character and to the presence of Cl- ions deriving from its synthesis, which are known to negatively affect SERS experiments.
Descripción2nd International Conference on Innovation in Art Research and Technology, Ghent, Belgium, 21-25 March, 2016
Aparece en las colecciones: (CFMAC-IEM) Comunicaciones congresos
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