N-Alkanethiols

Liu G-Y and Salmeron M B 1994 Reversible displacements of chemisorbed n-alkanethiol molecules on Au(111) surface an atomic force microscopy study Langmuir 10 367... 

Flahner G, Wdll C, Buok M and Grunze M 1993 Investigation of intermediate steps in the self-assembly of n-alkanethiols on gold surfaoes by soft-x-ray speotrosoopy Langmuirs 1955-8... 

Li W, Virtanen J A and Penner R M 1995 Self-assembly of n-alkanethiolate monolayers on silver nanostructures protective encapsulations Langmu/r 11 4361... 

Hostetler M J, Stokes J J and Murray R W 1996 Infrared speotrosoopy of three-dimensional self-assembled monolayers n-alkanethiolate monolayers on gold oluster oompounds Langmuir M 3604... 

Laibinis PE, Whitesides GM, Allara DL, Tao Y-T, Parikh AN, Nuzzo RG (1991) Comparison of the structures and wetting properties of self-assembled monolayers of n-alkanethiols on the coinage metal surfaces, copper, silver, and gold. J Am Chem Soc 113 7152-7167... 

C.A. Widrig, C. Chung, and M.D. Porter, The electrochemical desorption of n-alkanethiol monolayers from polycrystalline gold and silver electrodes. J. Electroanal. Chem. 310, 335-359 (1991). 

P7 We will begin with a study of the topography of an n-alkanethiol self-assembled monolayer (SAM) anchored to a Au(lll) substrate. Alkanethiols will be attached to a Au(lll) substate by published methods. The SAM will be imaged by atomic force microscopy (AFM) to assure that the known structure is observed. (From Spain, 1997)... 

Based on cp-AFM evidence for the simple case of an n-alkanethiolate/Au SAM, the M structures show no evidence for penetration of metal to form conducting filaments that can cause shorts. The resultant junctions, however, do show extensive formation of reaction product layers with complex chemical compositions which may lead to unfavorable characteristics for molecular device operation. Indeed, in recent reports the use of Ti deposition on LB films, which contain water and inorganic salts at the bottom Pt electrode/LB film interface, leads to formation of inorganic titanium oxide type species in the junction but these complex inorganic layers have also been reported to impart fortuitously quite useful device... 

McGuiness CL, Blasini D, Masejewski JP, Uppili S, Cabarcos OM, Smilgies D, Allara DL (2007) Molecular self-assembly at bare semiconductor surfaces characterization of a homologous series of n-alkanethiolate monolayers on GaAs(OOl). ACS Nano l(l) 30-49... 

Porter and coworkers [98] who have used pc-Au electrodes and have examined monolayers of -alkanethiols CnH2n+lSH with n = 3-10, 12, 16, and 18, have found the surface coverage to be independent of n and equal to 9.3 ( 0.6) xl0 mol cm . Assuming that the real surface area of pc-Au electrode is 1.2 times larger than the geometric surface area, this is consistent with structures proposed on the basis of different experiments in which monolayers of various long-chain n-alkanethiols were found to form a (. 3 X overlayer structure on Au... 

Self assembly of monolayers on gold electrodes provided a viable approach to sensor construction (see below), as well as permitted electrochemical characterization of the mechanism involved in chemisorption [233,236-239]. Electrochemical investigation of the spontaneous adsorption of n-alkanethiols onto a gold electrode and the subsequent desorption of the monolayer were rationalized in terms of oxidation and reduction of the sulfur atom [233]. More intimate details concerning the chemical fate of all species involved in the chemisorption process have not yet been elucidated. 

Fig. 28. Schematic diagram of an all-trans chain in an n-alkanethiols monolayer on a surface. The coordinate system used to define the orientations of the chain, the cant angle tx, and the chain twist fi are shown along with their relationship to the surface coordinates [218]...

Double-tail derivatives were sometimes prepared by short syntheses thus, dithioacetals 9 were obtained by condensation of a free carbohydrate with the corresponding n-alkanethiol [50] whereas the 6,6-di-O-alkyl derivatives 29 were synthesized by the reaction of alkyl magnesium bromide with l,2 3,4-di-0-iso-propylidene-D-galacturonic acid [62]. 

Figure 6.4. Illustration of the canted structure formed upon adsorption of the n-alkanethiols, CH3(CH2) SH, on copper and silver.

Dip-pen nanolithography (DPN) is a variety of scanning probe lithography (direct-write) developed by Mirkin and coworkers, where components of interest are transferred from an AFM tip to a substrate.201 DPN has been used to pattern a wide variety of materials on surfaces, including small organic molecules (most commonly n-alkanethiols), DNA, nanoparticles, proteins, viruses, and precursors for inorganic thin films. 

Figure 3. Structure elucidation of n-alkanethiol SAMs on gold by techniques excluding diffrac-tometry, STM and AFM.

As a final note concerning solvent effects, amphiphilic alcohols added to hydro-phobic electroactive n-alkanethiol SAMs in aqueous solution appear to aggregate on the monolayer surfaces, decreasing the capacitive envelope and enhancing the barrier properties [109, 110]. However, the formal potentials of the redox couples are shifted positively, and the electrochemical reversibility is decreased. This effect had previously been used by Becka and Miller to determine the pinhole current in the presence of a freely diffusing redox probe (see above) [96]. 

The results from selected studies in which P has been determined for n-alkanethiol self-assembled monolayers are presented in Table 1. The measurements made on... 

Table 1. Summary of electron-transfer distance decay constants for n-alkanethiol SAMs and related bilayer systems.

Majda and co-workers provided an elegant demonstration of through-bond and chain-chain hopping processes as parallel mechanisms for electron transfer across SAMs [46, 133]. In n-alkanethiol monolayers formed on hanging drop mercury electrodes, the adsorbate coverage T is measured by chronocoulometry of the mercuric thiolate formed upon adsorption. For the as-adsorbed films, geometric con-... 

Lestelius, M. Engquist, I. Tengvall, P. Chaudhury, M. K. Liedberg, B., Order/disorder gradients of n-alkanethiols on gold, Colloids Surf., B Biointerfaces 1990, 15, 57-70... 

This le electrode reaction implies the loss of the thiol hydrogen and the oxidation of the S to a formal oxidation state of — 1 upon adsorption of n-alkanethiol (RSH) at Au. 

---