Self-Assembly
of Porphyrins on a Single Crystalline Organic Substrate
Fieke J. van den Bruele, Johannes A. A. W. Elemans, Alan E. Rowan,
Willem J. P. van Enckevort* and Elias Vlieg
Langmuir, 2010, 26 (1), pp 498-503
Abstract:
Layers of a free base porphyrin have been deposited from n-heptane
solution onto single crystalline potassium acid phthalate substrates
and the self-assembled structures have been characterized by atomic
force microscopy and X-ray diffraction. Depending on the concentration
of the porphyrin solution, different anisotropic structures are found
that are epitaxially related to the substrate, with the length axis
parallel to the [001] direction of the (010) substrate surface. For
undersaturated solutions, islands, cellular structures, and a hole
pattern of monolayers of approximately 2.5 nm height are formed, which
correspond to porphyrin molecules stacking approximately perpendicular
to the substrate surface. From supersaturated solutions, multilayers
are formed. At the highest concentrations, nanosized needles develop,
which cover the whole substrate, creating a “monocrystalline” film with
a length scale of several millimeters.