Mechanism of hierarchical plasmonic biomaterials engineered through peptide-directed self-assembly.

Hierarchical plasmonic biomaterials constructed from small nanoparticles (NPs) that combine into larger micron-sized structures exhibit unique properties that can be harnessed for various applications. Using diffusion-limited aggregation (DLA) and defined peptide sequences, we developed fractal silver biomaterials with a Brownian tree structure. This method avoids complex redox chemistry and allows precise control of interparticle distance and material morphology through peptide design and concentration. Our systematic investigation revealed how peptide charge, length, and sequence impact biomaterial morphology, confirming that peptides act as bridging motifs between particles and induce coalescence. Characterization through spectroscopy and microscopy demonstrated that arginine-based peptides are optimal for fractal assembly based on both quantitative and qualitative measurements. Additionally, our study of diffusion behavior confirmed the effect of particle size, temperature, and medium viscosity on nanoparticle mobility. This work also provides insights into the facet distribution in silver NPs and their assembly mechanisms, offering potential advancements in the design of materials for medical, environmental, and electronic applications.