Simultaneous multi-angle AR-XANES for surface-sensitive chemical speciation of gold nanolayers in wall painting replica†

Wall paintings from the world heritage site Petra-Jordan contain gilding remnants, which show various types of degradation. To investigate the deterioration processes as well as assess the conservation treatment, non-destructive (ND) and non-invasive (NI) analyses of the chemical species of gold are mandatory. In this work, simultaneous multi-angle angle-resolved X-ray absorption near-edge spectroscopy (AR-XANES) measurements were performed to assess gold species variations in depth. Experimental validation proved the method to be successful in differentiating between gold species in nanolayered structures. Technical advantages and limitations of the method are discussed. The application of a conservation material containing Nano Gold Gel (NGG) applied underneath a gold layer to regenerate adhesion with its support layer was also examined.