Porphyrin nanofibers were fabricated by acidifying tetra(p-carboxyphenyl)porphyrin (TCPP) using hydrochloric acid in aqueous solution. The results of absorption spectroscopy and atomic force microscopy (AFM) show that once the solution passed the equivalence point at around pH 5, the structures of TCPP assemblies were pH dependent. After the carboxylate groups of TCPP were protonated, the porphyrin forms nanoplates via J-aggregation. At lower pH, the absorption spectrum of the porphyrin nanofibers shows the collapse of the Q bands, revealing the protonation of the core nitrogen of the porphyrin occurred and form TCPP diacids. XPS of the samples indicate that the interaction between the TCPP diacids and the chlorides plays a key role in the assembly. The formation of fibers on surfaces show a distinct difference in their assembly dimension than those formed in solution.  The pH dependent structural changes and resulting optical properties will be described.

Directed assembly of porphyrin nanofibers

242nd National Meeting (2011)

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