Hierarchical assembly-dynamic gel-nanoparticle hybrid soft materials based on biologically derived building blocks

This article reports the interaction between cysteine-functionalised organogelators and gold nanoparticles. It is clearly demonstrated by transmission electron microscopy that for these gelators, where S-Au interactions can form, the nanoparticles align directly on top of, inside, and along the gel fibres. On the other hand, for a tryptophan functionalised gelator, which cannot form direct interactions with gold nanoparticles, the nanoparticles tend instead to simply cluster loosely around the fibrillar objects as a consequence of sample drying effects. Dependent on the ligand initially present as a stabiliser on the nanoparticle surface, some rearrangement of the nanoparticles on exposure to the gelator and sonication conditions can be observed. On thermal treatment, the nanoparticle-doped xerogel undergoes significant rearrangement: the gel fibres become smaller in diameter and the gold nanoparticles undergo enlargement by Ostwald ripening. This demonstrates how supramolecular nanohybrid assembled materials can evolve in response to stimulus as a consequence of the non-covalent interactions which underpin them, and their resulting dynamic nature.