Adsorption structures of catechol on the ZnO(10-10) surface

Coverage- and Temperature-Dependent Adsorption of Phenol on the ZnO(101̅0) Surface

“…As reported in our previous works, the prepared clean ZnO­(10 0) surface in Figure a is characteristic of wide terrace and free of identifiable surface oxygen vacancies. ,,,− Due to the main contribution of 4s states of Zn to the conduction band edge of ZnO, the Zn ion rows along the [110] direction generally present as bright lines at short tipsurface distances . Under even harsher imaging conditions (such as lower bias or higher current), each Zn ion can be resolved as a bright spot so that the precise surface sites can be unambiguously determined (see the inset of Figure a).…”

“…To obtain more binding details of each distinct phenol configuration, we tried to resolve the ZnO lattice while maintaining the characteristic morphologies of the phenol molecules. We maintained a normal tunneling current (∼50 pA) to scan the phenol, while adopting a sufficiently large current (∼5 nA) to scan the bare surface. ,, As shown in Figure a–c, by doing so, we can extend the black grids that represent the Zn lattice to the molecular region so as to accurately determine where the phenol molecule binds. Based on the derived information, we propose in Figure d–i the corresponding models of the adsorbed phenols to each characteristic morphology shown in Figure a–c, respectively.…”

“…In the models of Figure e,h, the dissociated phenol and hydrogen bind to the Zn and O ions belonging to the same surface Zn–O pair, while in the models of Figure f,i, the dissociated segments bind to the Zn and O ions belonging to adjacently different surface Zn–O pairs. The latter case has a stronger binding to the surface than the former similar to other OH-containing molecules such as methanol, H 2 O, and catechol on the same surface. ,, In both of the configurations described above, the benzyl ring lies down and orientates roughly along the [110] direction. More careful examination finds that in Figure e, the benzyl rings are slightly shifted to the [000] direction.…”

“…We also performed DFT calculations to corroborate the STM-derived adsorption models and found that the aggregated phenol structures show a reversed charge-transfer direction to the ZnO surface as compared with single-phenol molecules, which is similar to the case of catechol on the same surface. 22 These results provide fundamental details for understanding how phenol or its derivative molecules interact with the ZnO material.…”

“…The latter case has a stronger binding to the surface than the former similar to other OH-containing molecules such as methanol, H 2 O, and catechol on the same surface. 22,35,39 In both of the configurations described above, the benzyl ring lies down and orientates roughly along the [12̅ 10] direction. More careful examination finds that in Figure 2e, the benzyl rings are slightly shifted to the [0001̅ ] direction.…”