CHARLA - Hoy 11 hs - Tema: "Chemical Self-Assembly Strategies for Nanoscale Devices"

[Marcelo Sandro Nazzarro]

Hoy martes 14 de mayo dará comienzo el Ciclo de Charlas del INFAP del año
2013. La primera charla estará a cargo del profesor invitado:

Ph.D. Wilfred T. Tysoe
CV: http://surface.chem.uwm.edu/tysoe.html

Department of Chemistry and Biochemistry and Laboratory for Surface Studies

University of Wisconsin-Milwaukee, Milwaukee, WI 53211 USA

http://surface.chem.uwm.edu/

Tema: "Chemical Self-Assembly Strategies for Nanoscale Devices"

Resumen: As the requirement for higher component densities in integrated
circuits increases, the size of the components will approach molecular
dimensions and will therefore require molecular-scale strategies for
fabricating them. Rather than assembling the components of nano-scale
devices individually, approaches will have to be devised in which the
components spontaneously organize, or “self assemble” to produce structures
with potential device applications. Many self-assembly strategies involve
growing molecules from surfaces as, for example, in alkyl thiolate
self-assembled monolayers (SAMs). A self-assembly strategy in which
extended structures grow parallel to a surface is proposed based on
isocyanide-containing molecules, illustrated using 1,4-phenylene
diisocyanide (PDI). It is shown that the isocyanide functionality binds
strongly enough to gold that it can extract gold atoms from
low-coordination sites on a Au(111) surface to form extended,
one-dimensional oligomeric Au-PDI structures. The π-conjugation is
maintained throughout the oligomeric species and that they are reasonably
mobile. This suggest that they can be used to make electrical contacts
between gold nanoparticles on surfaces, and this notion is tested by
exposing gold nanoparticles on a mica substrate to PDI. This results in a
significant reduction in resistivity of the films (by over two orders of
magnitude). Measuring the I/V curves of the films for various initial gold
coverages as a function of sample temperature suggests that electron
transport is via a thermally assisted tunneling mechanism.

The effects of an imposed electric field on the conductive properties of
the films are measured by growing similar structures on a 300 nm thick film
of silica grown on a conducting silicon substrate. It is also found that
the infrared spectrum of Au-PDI oligomers on Au(111) changes as a function
of exposure to carbon monoxide and the appearance of a free isocyanide
vibrational mode implies that one end of the isocyanide group decoordinates
from the gold. Such a decoordination would interrupt the conduction pathway
and lead to an increase in resistance with CO exposure, which is found
experimentally. This suggests that it might be possible to integrate
functionalities such as gas detection with potential nanoscale devices
based on diisocyanide chemistry.

Lugar y hora: Aula 34, Bloque II, 2º Piso a las 11 hs
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