Quasi one-dimensional assembly of gold nanoparticles templated by a pH-sensitive peptideamphiphile from silk fibroin

Abstract

One dimensional (1-D) assembly of gold nanoparticles (AuNPs) plays critical roles in fabricating linear optical and electronic devices. Herein, a novel pH-sensitive template formed by C₁₂-GAGAGAGY, a peptide amphiphile based on the sequence of Bombxy mori silkworm silk fibroin, was employed to generate gold nanoparticles (AuNPs) in situ and direct their aggregation. Due to the incorporation of tyrosine, C₁₂-GAGAGAGY was able to reduce Au³⁺ to AuNPs and further stabilize them at pH 11 without any external reducing or capping reagents. In addition, these AuNPs could reversibly assemble/disassemble by varying pH due to the pH-sensitive assembly of the template, C₁₂-GAGAGAGY. These templates were cylindrical nanofibers at pH 11 and stacking nanoribbons at pH 4. AuNPs were well-dispersed among the networks formed by cylindrical nanofibers of C₁₂-GAGAGAGY at pH 11, while they aggregated on both sides of the stacking nanoribbons at pH 4. Interestingly, unlike traditional pre-defined templates, the pH-induced assembly of C₁₂-GAGAGAGY and assembly/disassembly of AuNPs occurred simultaneously. These results present us with the potential to utilize such smart peptide amphiphile templates for the fabrication of 1-D inorganic nanostructures with promising applications in nano-scale optical devices.