Designing Sequence-Defined Peptoids for Bio-Inspired Synthesis of Plasmonic Nanomaterials

In nature, biomolecules (e.g. proteins) play significant roles in the assembly of hierarchical structures and delivering sequence-specific functions ranging from photosynthesis, to molecular separation, selective ion transport, and tissue mineralization. Inspired by nature, many sequence-defined polymers have been designed and exploited for the bio-inspired materials synthesis.¹ While bio-inspired synthesis offers great potential for controlling nucleation and growth of inorganic particles, precisely tuning polymer-particle interactions has been a long-standing challenge.² On the other hand, despite that the morphology-dependent physical and chemical properties of plasmonic nanomaterials are significant for applications in sensing, photonics and catalysis, achieving the high-level of control over morphology seen in biomineral formation controlled by proteins and peptides is still a significant challenge and the rules governing bio-controlled formation of plasmonic nanomaterials remain to be exploited.³ Among various peptide mimetics, peptoids have received particular attention for achieving predictive materials synthesis because they offer unique opportunities for tuning inter-molecular and molecule-particle interactions solely through variations in side-chain chemistry, while still emulating the capacity of peptides and proteins for molecular recognition.⁴<br/>In this talk, I will report our recent progress in designing sequence-defined peptoids for controlled synthesis of well-defined plasmonic nanomaterials. By engineering peptoid sequences and investigating resulting particle formation mechanisms, we developed a rule of thumb for designing peptoids that predictively enabled the morphological evolution from spherical to nanocoral-shaped metallic nanoparticles. We demonstrate that the individual nanocoral-shaped gold particles exhibit a plasmonic enhancement as high as 10⁵fold. Our study shows that tuning peptoid-peptoid and peptoid-particle interactions and peptoid amphiphilicity are crucial for driving particle attachment during the early stages of formation of the branched nanostructures.³ In another study,⁵ we used variations in peptoid sequence to manipulate peptoid-Au interactions, leading to the synthesis of concave five-fold twinned, five-pointed Au nanostars <i>via</i> a process of repeated particle attachment and facet stabilization. Control over peptoid-particle interactions provides diverse possibilities for directed formation of plasmonic nanomaterials. These mechanistic studies will offer molecular level understanding of peptoid-induced plasmonic nanomaterials formation and guide the design of new peptoid sequences that enable the precise tuning of peptoid-peptoid and peptoid-particle interactions for particle attachment and facet-specific stabilization.<br/><br/>References: 1). C. L. Chen, N. L. Rosi, Peptide-based methods for the preparation of nanostructured inorganic materials. <i>Angew. Chem., Int. Ed.</i> <b>49</b>, 1924-1942 (2010). 2) B. Cai, Z. Li, C.-L. Chen, Programming Amphiphilic Peptoid Oligomers for Hierarchical Assembly and Inorganic Crystallization. <i>Acc. Chem. Res.</i> <b>54</b>, 81-91 (2021). 3) F. Yan<i> et al.</i>, Controlled synthesis of highly-branched plasmonic gold nanoparticles through peptoid engineering. <i>Nat. Commun.</i> <b>9</b>, 2327 (2018). 4) W. Yang, Q. Yin, C.-L. Chen, Designing Sequence-Defined Peptoids for Biomimetic Control over Inorganic Crystallization. <i>Chem. Mater.</i> <b>33</b>, 3047-3065 (2021). 5) Z. Li, B. Cai, W. Yang, C.-L. Chen, Hierarchical Nanomaterials Assembled from Peptoids and Other Sequence-Defined Synthetic Polymers. <i>Chem. Rev.</i> <b>121</b>, 14031-14087 (2021). 6) B. Jin<i> et al.</i>, Peptoid-Directed Formation of Five-Fold Twinned Au Nanostars through Particle Attachment and Facet Stabilization. <i>Angew. Chem., Int. Ed.</i> <b>61</b>, e202201980 (2022).