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Dynamics of porphyrin adsorption on highly oriented pyrolytic graphite monitored by scanning tunnelling microscopy at the liquid/solid interface

Ferreira, Q. ; Bragança, A. ; Oliveira, O. N. O. ; Moura, N.M.M. Moura ; Faustino, M.A.F.Faustino ; Alcácer, L. ; Morgado, J.

Applied Surface Science Vol. 273, Nº n.a., pp. 220 - 225, May, 2013.

ISSN (print): 0169-4332
ISSN (online):

Scimago Journal Ranking: 0,96 (in 2013)

Digital Object Identifier: 10.1016/j.apsusc.2013.02.017

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Scanning tunnelling microscopy (STM) at solid/tetradecane interface is used to study the dynamics of
zinc(II)-octaethylporphyrin (ZnOEP) and zinc(II)-meso-tetradodecylporphyrin (ZnTDP) adsorption on the
surface of highly oriented pyrolytic graphite (HOPG). ZnOEP exhibits a polymorphic behaviour, with a first
metastable phase remaining for the first 2 h. This initial ˛-phase is then converted into a ˇ-phase, where
all porphyrins lie parallel to the substrate with a hexagonal arrangement, in agreement with previous
reports. At variance with this behaviour, no metastable phases are found during ZnTDP adsorption under
the same conditions. We consider that this different behaviour is due to the combination of a stronger
interaction and lower mobility of ZnTDP on the HOPG surface.