“…As evident in Figure 7a, the high-resolution XPS spectrum of Zn2p3/2 is fitted by two peaks located at a binding energy of 1021.21 and 1022.18 eV, and can be attributed to the ZnO and Zn(OH)2, respectively [23,27,29]. It can be clearly seen in Figure 7b that the highresolution XPS spectrum of O1s is fitted by four peaks located at 530.75, 531.72 532.78, and 533.79 eV, corresponding to the Zn-O bonding of the ZnO structure, Zn(OH)2, C-O or C=O, and C-O-C, respectively [23,26,29]. The high-resolution XPS spectrum of C1s is shown in Figure 7c.…”