Porphyrin nanofiber patterning was generated by air/water interfacial assembly. The air/water interfacial aggregation behavior of two prophyrins, both of which contain two hydrophobic alkyl chains and two carboxylic acid substituent groups at different positions, was investigated using UV spectra, FT-IR spectra, and AFM measurements on the corresponding transferred films. The porphyrin nanofiber patterning can only be produced on ionic liquid (IL) doped water subphases by the assembly of the building blocks with two carboxylic acids located at the para-position (TPPA2b-A). The results suggest that the bulky cations of ionic liquids (ILs) can interact with the carboxylate of porphyrin electrostatically. The appropriate molecular geometries, ionic liquid (IL) doped water subphases, and relatively high surface pressures help the TPPA2b-A to form nanofiber patterns. (C) 2011 Elsevier Inc. All rights reserved.