Fig. 3

Details of the visible image and spectral features of paints denoted as red1 and red2. a UV–Vis-NIR emission spectra (λ_ex = 445 nm); b FTIR spectra compared with the reference spectrum of PR3 (the rectangle evidences the small signals possibly related to an organic dye on red2); c Raman spectra (λ_exc = 785 nm) compared with the reference spectrum of PR3 (the Raman spectrum recorded from the PR3 standard was acquired with a portable device having a lower spectral resolution with respect to the system here employed, the laser excitation line is 785 nm); d UV–Vis-NIR reflectance spectra and e XRF spectrum representative of red2