Figure 3: Specific adsorption demonstrated on an array of gold squares on an aluminum surface. The sample is shown in (a). The smaller square is the gold surface and at the background is the aluminum substrate. In (b and d) the gold and aluminum substrates, respectively, are shown with molecules adsorption only. In (b) It is possible to observe the gold grains but the surface is clean from NCs. (c) shows the gold area of the sample after dipping the sample in the NCs solution. The surface is covered with NCs at a density of about  NCs/cm2. By comparing these results to the adsorption of NCs on the Al2O3 surface (d) with molecules only and (e) after dipping in NCs solution, we can see the selectivity.