Self-assembled porphyrin microrods and observation of structure-induced iridescence

Abstract

Self-assembled microrods {based on 5-nitro-10,15,20-trialkylporphyrins [(CnH2n+1)3-NO2P]} and microplates {based on 5,10,15,20-tetraheptylporphyrin [(C7H15) 4-P]} are fabricated and characterised using optical microscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The length of the alkyl chains and the deposition surface are found to influence the optical properties and microrod self-assembly. When the deposition surface is silica (α-quartz), 5-nitro-trialkylporphyrins, (C5H 11)3-NO2P, (C7H15) 3-NO2P and (C11H23) 3-NO2P all form microrods of 0.7-0.8 micron diameter; the average length of the microrods varies from 170 microns for (C5H 11)3-NO2P to about 11 microns ..