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Stepwise preparation and characterization of molecular wires made of zinc octaethylporphyrin complexes bridged by 4,4-bipyridine on HOPG

Ferreira, Q. ; Alcácer, L. ; Morgado, J.

Nanotechnology Vol. 22, Nº 43, pp. 435604 - 435610, October, 2011.

ISSN (print): 0957-4484
ISSN (online): 1361-6528

Journal Impact Factor: 3,446 (in 2008)

Digital Object Identifier: 10.1088/0957-4484/22/43/435604

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Molecular-scale devices can be made using a step-by-step procedure, in a controllable and
highly versatile way. In this report, we describe the growth of molecular wires (MW) from zinc
(II) octaethylporphyrin (ZnOEP) assembled on highly oriented pyrolytic graphite (HOPG) by a
step-by-step approach using 4,4-bipyridine (BP) to bridge the porphyrin units, via coordination
of the nitrogen atom to zinc. In order to gain an insight into the molecular self-organization of
these wires, we carried out a detailed scanning tunnelling microscopy (STM) analysis of each
monolayer, using a solid/liquid interface technique, up to a complete
ZnOEP/BP/ZnOEP/BP/ZnOEP-assembled structure. The electrical properties of the MWs were
assessed by scanning tunnelling spectroscopy (STS) and by current-sensing atomic force
microscopy (CS-AFM), showing an increase of electrical resistance with the length of the MW.