© 2004 Robert A. Freitas Jr. and Ralph C. Merkle. All Rights Reserved.

Robert A. Freitas Jr., Ralph C. Merkle, Kinematic Self-Replicating Machines, Landes Bioscience, Georgetown, TX, 2004.

B.4.3.3.1 Nature of the Physisorbed Monolayer

Although n-octane molecules exhibit numerous vibrational modes and surface conformations on diamond [3218, 3219], experiments and molecular dynamics simulations have shown that an n-octane monolayer deposited on hydrogen-terminated diamond C(111):H(1x1) [3220], simulated hydrocarbon-like waxy substrate [3232], hydroxylated a-Al₂O₃(0001) [1109], Cu(111) [3221, 3222], Cu(100) [3222], or Au [3223] surfaces adsorbs octane molecules with their C-C-C plane oriented parallel to the substrate. Other studies [3224-3230] have confirmed that for straight chain molecules such as the n-alkanes and for various linear polymer melt molecules, the molecules align parallel to the solid surfaces. A surface monolayer of n-octane on diamond has an areal density of a_octane ~ 0.60 nm²/molecule [3231] and a thickness of d_monolayer ~ 0.3-0.6 nm [3173, 3180, 3194, 3232-3234]. A molecular dynamics study by Gupta, Koopman, et al [3173, 3176] of liquid n-octane at 360.6 K physisorbed on a planar fcc surface having a solid-liquid adhesive energy parameter equivalent to the basal plane of graphite found that the population of octane molecules nearest the surface showed only 36% of adsorbed molecules with 8 hydrogen-surface contacts, 22% with 5-7 contacts, and 42% with 1-4 contacts, and rotational relaxation times of order ~0.01 nanosec.

Consistent with related studies [3187-3189], we assume that van der Waals physisorption by n-octane induces no reconstruction of the underlying hydrogen-terminated diamond wall surface structure.

Last updated on 13 August 2005