Nanoparticles, nanotubes and nanowell-array films via solvent diffusion-induced self-assembly

The two most common methods to grow single crystals are the evaporation of solvent and the diffusion of one kind of solvent to solution. Evaporation-induced self-assembly has been widely used to make nanostructures, but to date there is no report on the nanostructures from solvent diffusion-induced self-assembly. In this work, different morphologies of porphyrin self-assembly were achieved by controlling the diffusion rate of water into organic solution. When water was mixed and homogenized with the porphyrin solution immediately, AFM measurements showed that porphyrin nanoparticles approximately 250 nm formed. On the other hand, when porphyrin DMF solution was diffused into water slowly, long nanotubes up to several hundred micrometers in length were observed. In particular, porphyrin macroscopic nanowell-array films, which may consisted of vertically-aligned porphyrin nanotube arrays, were obtained by diffusing water vapor into porphyrin organic solution. The methodology and results reported here may provide a novel, simple and efficient approach to obtain well-defined self-assembly structures.