Raman spectroscopy was performed using a confocal Raman microscope (Renishaw InVia) using a 532 nm laser (max power 50 mW), a 20× objective (Zeiss) and a 1800 lines mm -1 grating. The exposure time was 3 seconds for a laser power of 5%, and spectra were recorded between 1237 and 2796 cm -1 and averaged over 10 accumulations. Spectra were corrected for background effects by subtracting a linear function that compensates for autofluorescence of the cellulose paper. Peaks were analysed by fitting a Lorentzian function with four components for the D-, G-, 2D-(double, 2D1 & 2D2) bands respectively , i.e.