Homogeneously mixed porphyrin J-aggregates with rod-shaped nanostructures via zwitterionic self-assembly

To tailor functional nanomaterials, the co-assembly of self-assembling dyes in a homogeneous way would be a promising approach because the electronic properties can be tuned by the mixing ratio. Although porphyrins are important supramolecular building blocks with unique optical properties, a homogeneously mixed J-aggregate system of porphyrins has not been reported yet. Herein, we focused on three kinds of zwitterionic porphyrin diacids, H(4)TSPP(2-), H(4)T(5-STh)P(2-) and H(4)T(4-STh)P(2-), due to their capability to form J-aggregates with distinguished optical properties and well-defined nanostructures. In this study, we investigated the co-assembly behaviours of the zwitterionic porphyrins in aqueous solution by UV-vis and RLS, and investigated the morphology of the resultant homogeneously mixed J-aggregates by AFM. In the case of the combination of H(4)TSPP(2-) and H(4)T(5-STh)P(2-), they readily co-assemble to form homogeneously mixed J-aggregates with different types of binary excitonic bands, whereas the combination of H(4)T(4-STh)P(2-) and other porphyrins results in the dominant formation of the individual pure J-aggregates. Deposited homogeneously mixed J-aggregates of H(4)TSPP(2-) with H(4)T(5-STh)P(2-) consist of rod-shaped nanostructures, whose height changes discontinuously upon varying the mixing ratio. These results would provide new insights into the electronic properties and the nanostructure of self-assembled multicomponent materials.