Advances in techniques for the nanoscale manipulation of matter are important for the realization of molecule-based miniature devices with new or advanced functions. A particularly promising approach involves the construction of hybrid organic-molecule/silicon devices. But challenges remain--both in the formation of nanostructures that will constitute the active parts of future devices, and in the construction of commensurately small connecting wires. Atom-by-atom crafting of structures with scanning tunnelling microscopes, although essential to fundamental advances, is too slow for any practical fabrication process; self-assembly approaches may permit rapid fabrication, but lack the ability to control growth location and shape. Furthermore, molecular diffusion on silicon is greatly inhibited, thereby presenting a problem for self-assembly techniques. Here we report an approach for fabricating nanoscale organic structures on silicon surfaces, employing minimal intervention by the tip of a scanning tunnelling microscope and a spontaneous self-directed chemical growth process. We demonstrate growth of straight molecular styrene lines--each composed of many organic molecules--and the crystalline silicon substrate determines both the orientation of the lines and the molecular spacing within these lines. This process should, in principle, allow parallel fabrication of identical complex functional structures.
The relative contributions of vitamin E, urate, ascorbate and proteins to the total peroxyl radical-trapping antioxidant activity of human blood plasma Wayner, D. D. M.; Burton, G.W.; Ingold, K. U.; Barclay, L. R. C.; Locke, S. J.
A thorough understanding of reaction thermochemistry is essential in order to distinguish between mechanistic possibilities. In the gas phase, thermodynamic relationships between molecules, radicals, and 283-285.
The oxidation and reduction potentials of a variety of carbon-centered radicals have been measured by a technique that makes use of modulated photolysis for radical generation and phase-sensitive voltammetry for their detection. The measured half-wave potentials were close to the thermodynamically significant E°values for the arylmethyl radicals and led to estimates of pATa(RH) and pATR(ROH) as well as data for the solvation energies of these ions and radicals.The electron donor and acceptor properties of a molecule in the gas phase are characterized by the ionization potential, IP,2 and electron affinity, EA.3 However, these properties are not directly relevant to the liquid phase where solvation of ions becomes important. In fact, the solution analogues of the ionization potential and electron affinity of a molecule are the electrochemical oxidation and reduction potentials4 which, for the vast majority of persistent molecules, are easily measured by standard techniques.
Two new methods for the formation of Si−C monolayers from reactions with Si(111)−H are reported.
Besides the photochemical method previously reported by Chidsey, Lewis acid-catalyzed hydrosilylation
of alkenes and direct reaction of alkylmagnesium bromide produce a surface with similar chemical
composition. These processes are demonstrated and compared using reactions of a C10 precursor. The
surfaces are chemically stable and can be stored for several weeks without measurable deterioration. The
availability of a variety of synthetic approaches leading to the same chemical product is key to the development
of flexible surface synthetic strategies. It is expected that these approaches will underpin the development
of stepwise solid-phase-like syntheses of more complex organic/bioorganic species on these surfaces.
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