Octadecanethiolate

Several striking examples demonstrating the atomically precise control exercised by the STM have been reported. A "quantum corral" of Fe atoms has been fabricated by placing 48 atoms in a circle on a flat Cu(lll) surface at 4K (Fig. 4) (94). Both STM (under ultrahigh vacuum) and atomic force microscopy (AFM, under ambient conditions) have been employed to fabricate nanoscale magnetic mounds of Fe, Co, Ni, and CoCr on metal and insulator substrates (95). The AFM has also been used to deposit organic material, such as octadecanethiol onto the surface of mica (96). New appHcations of this type of nanofabrication ate being reported at an ever-faster rate (97—99). 

Thiols range over the gamut of physical properties. Most of the important thiols ate Hquids, however methanethiol is a gas, and 1-hexadecanethiol and 1-octadecanethiol ate waxy soflds. Tables 2 and 3 Hst a variety of physical properties for the mote important thiols. 

Fig. 32. Cyclic current-potential curve for Au(l 11), covered with an octadecanethiol SAM, in 0.1 M H2SO4 + 1 mM CUSO4. Scan rate 10 mV s-1. The C18-SAM blocks Cu deposition up to very high overpotentials. Inset Current response of a bare Au(lll) electrode for the same potential cycle [98],...

Fig. 9 Scheme of different Hg-drop LAJs incorporating (a) SAMs of octadecanethiols (Cl8) on both electrodes (b) SAMs of C18 on the Hg electrode and of HBCS on an Au electrode (c) SAMs of HBCS on both electrodes (d) i—V curves measured for the three a, b, c junctions... 

Octadecanethiol Octadecyl Mercaptan Octadecylthiol Octafluoroisobutene Octamethyl... 

OCTADECYNE OLEIC ACID DIBUTYL SEBACATE DI HEXYL ADIPATE 1-CYCOPENTYLTRIDECANE 1-CYCLOHEXYLDOOECANE 1-OCTADECENE STEARIC ACID n-OCTADECANE DINONYL ETHER 1-OCTADECANOL BUTYL-TETRADECYL-SULFIDE ETHYL-HEXADECYL-SULFIDE HEPTADECYL-HETHYL-SULFIDE NONYL-SULFIDE PENTADECYL-PROPYL-SULFIDE 1-OCTADECANETHIOL NONYL-DISULFIDE 1-n-NONYLNAPHTHALENE n-TRIDECYLBENZENE... 

A simple and general method for the preparation of surfactant-free, thiol-functionalized iridium nanoparticles was reported by Ulman and coworkers in 1999 [11], The synthesis consisted of a reduction of the dihydrogen hexachloroiri-date (IV) H2lrCl6 H20 precursor by lithium triethylborohydride ( super-hydride ) in the presence of octadecanethiol (C18H37SH) in tetrahydrofuran (THF) (Scheme 15.1). The obtained iridium nanoparticles were crystaUine with fee (face-centered cubic) packing, and showed a wider size distribution with diameters ranging from 2.25 to 4.25 nm. 

Controlled delivery of collections of molecules onto a substrate with nanometre resolution can be achieved with the tip of an AFM. This positive printing mode technique is called dip-pen nanolithography (DPN) and its working principle is illustrated in Fig. 3.27. DPN uses an AFM tip as a nanopencil, a substrate as the paper and molecules with a chemical affinity for the substrate as the ink. Capillary transport of molecules from the AFM tip to the solid substrate is used in DPN to directly write patterns consisting of a relatively small collection of molecules in submicrometre dimensions. The hrst example introducing the technique was the transfer of octadecanethiol onto gold surfaces (Piner et al, 1999). 

Tarlov MJ (1992) Silver metalization of octadecanethiol monolayers self-assembled on gold. Langmuir 8 80-89... 

Colavita PE, Doescher MS, Molliet A, Evans U, Reddic J, Zhou J, Chen D, Miney PG, Myrick ML (2002) Effects of metal coating on self-assembled monolayers on gold. 1. Copper on dodecanethiol and octadecanethiol. Langmuir 18(22) 8503-8509... 

Kolipaka S, Aithal RK, Kuila D (2006) Fabrication and characterization of an indium tin oxide-octadecanethiol-aluminum junction for molecular electronics. Appl Phys Lett 88 (23) 233104-233113... 

Widrig CA, Alves CA, Porter MD (1991) Scanning tunneling microscopy of ethanthiolate and n-octadecanethiolate monolayers spontaneously adsorbed at gold surfaces. J Am Chem Soc 113 2805-2810... 

Brett etal. [103] have studied selfassembling of 1-decanethiol at the fixed positive potentials of pc-Au electrode in chronoamperometry and quartz crystal microgravimetry. The obtained layers appeared to have improved quality and were produced faster than in the open-circuit deposition. The factors possibly influencing the fine structure of monolayers observed in voltammetric reductive desorption and oxidative redeposition of long-chain alka-nethiolates, for example, hexadecanethiol (HT) and octadecanethiol on smooth Au electrodes have been discussed [104]. It has been shown that the local order of adlayer has a role to play in the formation of that fine structure. 

Passivating behavior of self-assembled octadecanethiol on pc-Au electrodes has been tested by CV using Ru(NH3)6Cl3, K4Fe(CN)6, and benzoquinone [106] as the redox probes. Inhibiting properties toward these reactants were found to be different. 

Inhibiting properties may be influenced by the solvent molecules trapped within the monolayer during self-assembly of octadecanethiol molecules on gold electrodes [107]. 

---