Figure 2

µATR-FTIR spectra performed on the wallpapers. The spectra were collected on the selected sampling points (as indicated in the legend) of (a) INV_11, (b) INV_13, (c) INV_15, and (d) INV_20. For clarity, the µATR-FTIR spectra were offset of 0.10 arbitrary units (a.u.).