Figure 4 Experimental and simulated I – V curves. (a) I-V characteristics for the ZnO wire-gold junctions obtained experimentally (empty circles), in comparison with the simulated curves, where ZnO is either placed on the gold electrodes (straight line) or between them (dot line). Atomistix toolkit (ATK) scheme of ZnO between the gold electrodes (b, top view) or on them (c, lateral view). (d) Experimental and (e) simulated I-V of the ZnO-gold junction (black line) and of ZnO-NH2-gold one (red line). The current from the ZnO-NH2-gold junctions is remarkably lower than

that of the unfunctionalized ZnO-gold ones). The flattening of the I-V curve is attributed to the high resistive #HSP inhibitor randurls[1|1|,|CHEM1|]# behavior of the Citarinostat solubility dmso propyl chain (as depicted in Figure 1) grafted to the zinc oxide surface. The ATK simulation of the I-V

characteristics was carried out by positioning the bare ZnO structure both between the gold electrodes (Figure 4b) and on them (Figure 4c). The transport properties are determined by the electronic structures of the wires and electrodes. We assumed a two-probe device with ZnO wire connected to two semi-infinite Au(001) electrodes. The initial hexagonal cross-section of ZnO was cut from a large wurtzite supercell along the [0001] c-direction. The two-probe device was an open system, consisting of three parts: the two electrodes and the ZnO scattering region. The left and right regions consisted of Montelukast Sodium four layers of Au(001)-6?×?6 surface atoms, repeated periodically, forming the infinite electrode. The scattering region included a portion of the semi-infinite electrodes where all the screening effects take place. Therefore, the charge distribution of the electrodes corresponded to the bulk gold phase with a prescribed numerical accuracy. Figure 4b shows a three-cell wire sandwiched between the electrodes, where each unit cell of ZnO consists of 20 O– and 20 Zn atoms (more details in the Additional file). This method was similar to those used in the literature for carbon and boron nitride nanotubes, and OPVn molecules [42–44], maintaining fixed distances to compare the transport

properties of 1D nanostructures with different lengths. The simulated I-V plot shows a semiconducting-like behavior (Figure 4a, dot line), confirming both the experimental results and those reported in the literature [45]. With the same bulk configuration, we performed a second simulation with the wire placed on the gold electrodes (Figure 4a, solid line, and scheme in Figure 4c), also reflecting the Schottky-type electronic structure discussed above. This second configuration shows a current decrease for the same applied voltage with respect to the first case (wire between). This occurred because the interface was reduced and deflected about 20%. Both simulated I-V curves show a higher current at the same voltage with respect to the experimental I-V.