Self-assembled peptide nanorods as building blocks of fractal patterns

Hierarchical self-assembly of peptide molecules has become an attractive approach of fabricating multifunctional advanced materials. Here we report fractal structures hierarchically self-assembled from a simple dipeptide derivative, Fmoc-phenylalanine-tyrosine-phosphate (FPTP). Scanning electron microscopy (SEM) analysis revealed that dipeptides first self-assembled into nanorods with length on the order of one micrometre in solution, which are prerequisite for the formation of fractals on a solid substrate. The fractal dimension analysis indicated that fractals were assembled following the diffusion-limited aggregation (DLA) mechanism. We present for the first time the evidence of nanorods as diffusion units for forming fractals on a surface. This nanorod-mediated DLA model explains and suggests a new strategy for forming fractal patterns from self-assembling molecules.