*2.7. Raman Imaging*

Raman images were taken with a Jasco NRS-3100 Confocal Micro-Raman spectrophotometer from Jasco Inc. (Easton, MD, USA) using a short working distance 100× objective, which according to the manufacturer provides a lateral and depth resolution of ca. 1 and 2 μm, respectively under high confocal conditions. The source was a red laser in the visible excitation tuned at 632.8 nm. Raman chemical images were carried out in the point by point mode by plotting the added area of the two graphene peaks present in the spectral 1780–918 cm<sup>−</sup><sup>1</sup> area and were constructed by taking 15 × 15 spectra equally spaced along a similar flat and continuous sample area in the case of the samples from 0.1 to 1 wt.-% GNPs loading and 20 × 20 spectra for the sample with 2 wt.-% GNPs content. Averaged spectra were taken in the samples with the 40× objective in a non-confocal mode.
