Long-chain alkanethiols on gold

Fujishima et al. found that SAMs prepared of azobenzene-terminated long chain alkanethiols on gold surfaces show a herring-bone structure in which the long axes of the azobenzene moieties are parallel to each other and the short axes of neighbouring molecules are perpendicular to each other (Fig. 27) [183,184], In contrast, phenylazonaphthol alkanethiol mono-layers are densely packed as a J-aggregate and well oriented with a tilt angle of 28° [185]. 

The third question in 3D MESA - the dimension of the smallest pieces that can self-assemble - motivated experiments with metallic, polyhedral, 10- xm-sized plates [ref. 63]. The fabrication of 10- xm-sized polyhedra is difficult, so these experiments examined the self-assembly of flat plates, which were easily obtained at this scale. Photolithography, electrodeposition, and electron beam evaporation provided a convenient way to form plates having surfaces whose properties could be modified selectively. The surfaces of these plates consisted of either gold or chromium. Treatment with a long-chained alkanethiol formed a hydrophobic SAM on the gold with a phosphonic acid-terminated thiol, a hydrophilic one. Similarly, a phosphonic acid-terminated thiol formed a hydro-phobic SAM on chromium (through coordination of the acid with surface Cr... 

Whitesides and coworkers developed a procedure to estimate the density of defects in gold-thiol monolayers. The monolayer surface is exposed to the gold-etching solution, the pits obtained are transferred into pits on the Si surface through further chemical treatment and the number of pits per unit area counted. Long-chain alkanethiolate monolayers prepared by the standard technique show pit densities of ca 100 pits mm . The number of pits sharply increase if the gold surface is stored for a long time in air prior to monolayer deposition . 

Formation of SA monolayers of phospholipids [217,242] and surface-active viologens [244, 245] on gold substrates, those of long-chain zirconium-phosphonates on silicon substrates [243], and those of alkanethiols on gallium arsenide substrates [246] have also been reported. 

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