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Manufacture • The preferred crystal face for alkanethiolate SAM preparation on gold substrates is the (111) direction, which can be obtained either by using single crystal substrates or by evaporation of thin Au films on flat supports, typically glass or silicon. A schematic outline of the SAM preparation procedure on such gold substrates is given in the Figure, together with a schematic of a mixed SAM (see below). Several different solvents are usable at the low thiol concentrations (typically 1-2 mM). The most commonly used solvent is ethanol. Even though a selfassembled monolayer forms very rapidly on the substrate, it is necessary to use adsorption times of 15 h or more to obtain well-ordered, defect-free SAMs. Multilayers do not form, and adsorption times of two to three days are optimal in forming highestquality monolayers. The substrate, Au on Si, is immersed in an ethanol solution of the desired thiol(s). Initial adsorption is fast (seconds); then an organization phase follows which should be allowed to continue for >15 h for best results. A schematic of a fully assembled SAM is shown to the right.
Tail Groups: Functionalization • As mentioned above, the tail group that provides the functionality of the SAM can be widely varied. CH3-terminated SAMs are commercially available; other functional groups can be synthesized by any well-equipped chemical laboratory, providing almost infinite possibilities of variation. In addition, chemical modification of the tail group is entirely possible after formation of the SAM, expanding the available range of functionalities even further.
Page 1 and 2: CHE499 : A Nanotechnology Course in
Page 3 and 4: History • Nuzzo, R. G.; Allara, D
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Page 9 and 10: Characterization: • Among the mos
Page 11 and 12: IRAS spectrum of a hexadecanethiola
Page 13: Lithography
Page 16 and 17: In Si(100), the anisotropic etch ch
Page 18 and 19: DNA SAMs
Page 21 and 22: Mercury Removal: SAMs in Mesopores
Page 23 and 24: Mercury Removal: SAM in Mesopores (
Page 25 and 26: • Molecular self-assembly is a un

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