Germ direct observation by AFM under crystallization of self-organized assemblies of mono-protonated meso-tetraphenylporphine dimers

Assemblies consisting of mono-protonated meso-tetraphenylporphine dimers and water have been investigated by UV–vis spectroscopy in solution and atomic force microscopy (AFM) in thin layers. These assemblies self-organized into domains produce microcrystals in thin layer. Morphology of the microcrystals and characteristic features of crystallization germ on the top found by contact AFM indicate that surface tension of an aqueous layer on the domain generates the crystallization process. Estimations of the pressure producing the germ and bulk modulus (Bm) of microcrystals give 26.3±2.6MPa and 3.72GPa and Bm=12.7GPa obtained for dried thin films. The former modulus is comparable with bulk modulus of water (2.174GPa) that implies liquid crystals formation. Absorptions of longitudinal optical (LO) phonons with ћωLO=0.3761 and 0.3577eV, which are arisen because of hole polaron moving through water, are found in the electronic spectra of the assemblies. The crystallization is suggested to occur due to Zundel cation (H5O2+) operation like the water–porphyrin matrix self-organization found earlier. •Microcrystals produced by self-organized assemblies of TPP2H+ and water have been found.•Their crystallization in thin layer starts from a germ formation on the top of domain.•The pressure producing the germ and therefore microcrystals is found to be 26.3MPa.•Bulk modulus estimated at final step of germ formation is comparable with that of water.•The findings attest liquid state of the microcrystals formed by the self-organized assemblies.