Raman mapping as a tool for discrimination of blue writing inks and their cross lines

We examined surface enhanced Raman maps of blue writing inks received from commercially available refills and deposited on a rigid silver-nanocrystalline diamond–silicon heterostructure. The heterostructure constituted an active substrate providing a possibility to write directly on the surface and to record Raman maps. Based on rich data containing several thousands of spectra were discriminated between the inks in spite of slight spectral differences. Such discrimination would not be reliable by analyzing single spectra since a number of surface effects contribute to the evolution of Raman bands. We also successfully distinguished the order in which the cross lines of the inks were deposited on the substrate. Raman spectra could not be obtained by conventional Raman spectroscopy; this is why surface-enhanced Raman spectroscopy had to be employed.