Crystalline Dipeptide Nanobelts Based on Solid-Solid Phase Transformation Self-Assembly and Their Polarization Imaging of Cells.

Controlled phase transformation involving biomolecular organization to generate dynamic biomimetic self-assembly systems and functional materials is currently an appealing topic of research on molecular materials. Herein, we achieve by ultrasonic irradiation the direct solid-solid transition of bioinspired dipeptide organization from triclinic structured aggregates to  nanofibers and eventually to monoclinic nanobelts with strong polarized luminescence. It is suggested that the locally high temperature and pressure produced by cavitation effects cleaves the hydrophobic, π-π stacking or self-locked intramolecular interactions involved in one phase state and then rearranges the molecular packing to form another well-ordered aromatic dipeptide crystalline structure. Such a sonication-modulated solid-solid phase transition evolution is governed by distinct molecular interactions at different stages of structural organization. The resulting crystalline nanobelts are for the first time applied for polarization imaging of cells, which can be advantageous to directly inspect the uptake and fate of nanoscale delivery platforms without labeling of fluorescent dyes. This finding provides a new perspective to comprehend the dynamic evolution of biomolecular self-organization with energy supply by an external field and open up a facile and versatile approach of using anisotropic nanostructures for polarization imaging of cells and even live organisms in future.