All the Fe2p spectra generally show a main peak at a binding energy (BE) of around 710.3 eV, accompanied by a satellite line visible at a BE of around 718.3 eV, only indicative of the presence of Fe3+ cations.
The main peak at a binding energy of 285.3 eV is attributed to the C O or C C bonding, the peak at 287.6 eV is related to the carbonylate C (HO C=O), and the peak at 289.0 eV corresponded to O C=O components.
The main peak at a binding energy of 284.5 eV was assigned to sp2 hybridized C atoms in graphene, indicating the restoration of the C = C bonds after the hydrothermal reduction (~50%), whereas the other two peaks should be corresponded to sp2 C and sp3 C atoms bonded to O: epoxy/hydroxyls (C O, 285.5 eV) and carbonyl (C = O, 287.8 eV) [25].
The condition (Eq. 13) implies that the main contribution to the polaron binding energy is given by small values of the wave vector k such that (14).
The main component on the low binding energy side can be attributed to the O Zn bond, while the component with high binding energy is usually attributed to chemisorbed or dissociated OH or O species on the surface of ZnO material [22].
Regarding the N 1 s spectra (Figure 4), the addition of Ni produces a chemical shift of the main peak to a higher binding energy by 1.2 eV, which is a fingerprint of the binding of the N of bipyridine to the Ni2+ moiety [19, 20]. Figure 4d shows the Ni 2p3/2 region.
Hence, the nanoparticle is mostly composed of three elements, Zn, Cu, and O. Figure 3b shows Zn 2p XPS spectra; the two main peaks observed at the binding energy position of 1,021.8 and 1,044.9 eV correspond to the Zn 2p3/2 and Zn 2p1/2, respectively, verifying the existence of Zn2+.
As shown in Figure 3(a), four different peaks were identified on the aminated glass control; the main two peaks (binding energies of 285 eV and 284 eV) corresponded to carbon-carbon (C C) and carbon-silicon (C Si) bonding, respectively.
The absence of any excitonic absorption structure in the absorption spectra may have two main reasons: first, the weak exciton binding energy because of the strong Coulomb screening in narrow gap semiconductors and second, the existing size distribution of the nanocrystallites.
As illustrated in Figure 1a, e, the In3d5/2 core-level lineshapes are slightly asymmetric, with a high binding energy shoulder on the main peaks.
