Nanoparticles Assemblies on Demand: Controlled Aggregation of Ag(0) Mediated by Modified Peptoid Sequences

Assemblies of metal nanoparticles (NPs) have been broadly used for the construction of materials with distinct spectroscopic properties towards sensing applications. On the other hand, well-dispersed NPs are exploit for applications in catalysis and medicine. Biopolymers or biomimetic oligomers can serve both as efficient stabilizers of NPs and as useful aggregation mediators that can lead to assemblies with unique properties. Controlling aggregation processes, however, is still challenging and often relies on trial and error rather than on defined thumb rules. Herein we develop specific guidelines for the controlled aggregation of Ag(0) NPs at room temperature in water near neutral pH and without any additives. We use relatively short peptide mimics, N-glycine oligomers named "peptoids" as mediators. Spectroscopic and electron microscopy data reveal that both the monomer identity and their capping ligand have an effect on the NPs aggregation morphology. Thus, we demonstrate that we can control on the aggregate`s morphology by tuning these properties. Specifically, we show that a peptoid heptamer consisting 1,10-Phenanatrolin capping ligand directly bounded to the peptoid, as well as aromatic side chains, is required for the formation of uniform spherical NP-assemblies. In contrast, a peptoid heptamer, having 2,2`-bipyridine capping ligand attached via a flexible linker to the peptoid, in addition to aromatic side chains, can mediate the formation of rod like NP-assemblies.

References

Hagar Tigger-Zaborov, Galia Maayan, Journal of Colloid and Interface Science, 2017, 508, 56–64