An atomic force microscopy study of self-assembled monolayers of calix[4]resorcinarene adsorbates on Au(111)

The structure and orientation of calix[4]resorcinarene receptor adsorbate self-assembled monolayers (SAMs) on Au(111) were studied with atomic force microscopy (AFM). In molecularly-resolved images, two hexagonal periodicities with lattice constants of 11.6 +/- 0.4 and 4.2 +/- 0.2 Angstrom, respectively, were observed. These two periodicities could be observed separately as well as simultaneously by changing the imaging force. The experimentally determined distances are assigned to different parts of the adsorbates; the 11.6 Angstrom repeat distance is related to the lattice of the calix[4] resorcinarene recognition sites of the adsorbates, while the smaller repeat length bts well with the interchain distance of a closest packing of alkyl chains. These measurements confirm our previous assumption regarding the high degree of order of the calix[4]resorcinarene SAMs on gold.