The spatial structure of the J-aggregates of meso-tetra(4-sulfonatophenyl)porphine (TPPS4) formed in acidic
aqueous solutions and coated on silicon substrates was analyzed by means of atomic force microscopy (AFM).
The AFM experiments indicate the presence of the stripelike J-aggregate structures on the surface. The size
of the individual stripes ranged from 4.5 × 40 × 200 to 4.5 × 40 × 1000 nm3 (height × width × length).
The length of the stripelike structures varied, whereas stripe width and thickness remained unchanged. The
stripes stacked into larger domains, “fibers”, containing typically 2−20 stripes aligned parallel with a
longitudinal shift with respect to each other. The size of individual stripes remained the same when interacting
side-by-side in fibers. At lower magnification it is clearly seen that fibers form a network-like structure. The
J-aggregates assemble into large (up to several millimeters) bushlike structures. It takes several weeks to
form such structures in acidic aqueous solutions. On the basis of our experimental findings, it is also suggested
that the stripes consist of rings that form nanotube-like TPPS4 J-aggregates, which are flattened as a result of
attractive interactions with the substrate.
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