Use of nano gold obtained by laser ablation for SEIRA analyses of colorants

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 a fact that severely limits the number of analytical techniques that can be efficiently and micro-destructively employed for their detection and unambiguous identification. In the present study, an advanced and alternative SEIRA based analytical protocol for the analysis of small quantities of synthetic colorants has been proposed. The method has been set up for the identification of Acid Orange 7 (AO7) using Au nanoparticles obtained by laser ablation in solution (LASiS). Analyses have been performed applying a drop containing a mixture between the colorant and the Au colloidal solution in its unaggregated state on a gold coated glass slide for RAS (Reflection Absorption Spectroscopy) analysis. The first results showed that, thanks to the enhancement produced by the nanoparticles, it is possible to analyze small amount of diluted solutions containing the colorant. Thus, the method has been successfully applied for the analysis of few pieces of dyed wool, after the development of a suitable micro extraction procedure.