“…Two types of spectra were obtained that include low-resolution spectra from 0 to 1,100 eV binding energy to determine elemental composition (O and C ratios) and high-resolution spectra from 280 to 300 eV to analyze C. For the quantitative analysis, the spectra were baseline corrected, normalized, and curve fit using IGOR Pro 5.05 software (WaveMetrics, Inc.). The area of each peak identified by curve fitting was mathematically computed (Fabiyi et al 2009). The following data processing restrictions were made: (1) the full widths at half height (FWHM), for C1 (C-C or C-H), C2 (C-O), C3 (C=O or O-C-O), and C4 (O-C=O) peaks (285, 286.5, 288, and 289.5 eV) were kept constant (1.6 eV); (2) the fitted peaks were made using Voigt; (3) the third restriction is that a peak C0 (C=C), at 283.5 eV, was fitted when the residual of the band indicating the presence of this peak (FWHM of 1.6 EV); and (4) therefore, with these restrictions in place, a peak-fitting routine was then used to minimize and randomize the residual signal.…”