PHOIBOS 150 hemispherical energy analyzer with 2D DLD detector) using the Al Kα (hν = 1486.6 eV) radiation. The spectra were collected at 200 W with a pass energy of 10 eV and a step-size of 0.1 eV in a fixed analyzer transmission mode. The collected spectra were later calibrated to the signal of C-C/C-H sp3 at 284.8 eV as a reference on CasaXPS software.