SERS for the analysis of objects of art and archaeology

Abstract

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 [1]. This fact severely limits the number of analytical techniques that can be efficiently and micro-destructively employed for their detection and unambiguous identification. Vibrational spectroscopic techniques such as infrared and Raman spectroscopies have been employed with consistent difficulties associated to the sample typology itself and the amount necessary to obtain good quality spectra [2]. The introduction of Surface-Enhanced Raman Spectroscopy (SERS) [3] to the field of conservation science has made the study of such materials possible and more straightforward, both as free molecules [4] and as in artworks [1, 5]. This is possible thanks to SERS ability to yield good signal-to-noise ratio spectra from a very low amount of sample, as well as to the quenching of the fluorescence emission, an additional obstacle when working with traditional Raman spectroscopy. SERS is a very sensitive technique that gives rise to a huge Raman emission due to the giant intensification of the radiation intensity in the presence of metal nanoparticles mediated by the plasmon resonance of selected metals such as Au and Ag [6].