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.