Well-Defined Porphyrin Architectures From Self-Assembly and Dewetting - Molecular Self-Assembly: Advances and Applications - page 246

the fluorescence can only be detected when the detection is parallel
with the excitation configuration, suggesting that the absorption
and emission dipoles are parallel. Such an effect can only occur if the
porphyrins are oriented vertically with respect to the surface within
the rings, in a specific orientation as shown in Fig. 8.5, in which
stacks of porphyrin hexamers are oriented perpendicular to the
centre of the rings. Rings formed on a surface after self-assembly and
dewetting of porphyrin dodecamer 3 exhibited a similar anisotropic

fluorescence behaviour [13].

Figure 8.5 Schematic representation of the proposed ordering

of porphyrin hexamer molecules in the ring-shaped

assemblies, based on the AFM and NSOM studies. Copyright
Wiley-VCH Verlag GmbH & Co. KGaA. Reproduced with
permission.

2

The influence of the nature of the surface on the morphology
of the assemblies and their internal molecular ordering was
subsequently investigated in a systematic fashion [14]. A chloroform
solution of was allowed to evaporate on four different surfaces and

the formed assemblies were studied by fluorescence microscopy
(Fig. 8.6A-D). On the untreated glass, no defined rings were formed.
On the hydrophobic carbon-coated copper grids and on the glass
with a hydrophobic carbon coating, rings were formed that had a
rather large size dispersion (1-20

2

µ

m). In contrast, on the glass with
a hydrophilic carbon coating, rings with a highly monodisperse size
distribution were observed (1.5

± µ

1 m). Polarized fluorescence