In situ preparation of gold nanoparticles of varying shape in molecular hydrogel of peptide amphiphiles

We have synthesized the gold nanoparticles (GNPs) of different shaped by in situ reduction within the structure-directing low molecular weight gel template of tryptophan-containing peptide amphiphiles in water without using any external reducing or capping agents. Gold nanocrystals with sheet, wire, octahedral, and decahedral shapes were modulated with the help of the different morphology of the supramolecular gel network. The gel morphology at minimum gelation concentration is the prime requirement to prepare such different nanocrystals of gold. We also elucidated that the seeding growth approach did not have any stimulating affect to control the shape of GNPs. The supramolecular template itself has the structure-directing capability. The formation of gold species in the aqueous solution was monitored by UV-vis spectroscopy, transmission electron microscopy, and X-ray diffraction studies. The tryptophan-based peptide hydrogelators are elegant hosts as structure-directing templates for in situ shape-controlled preparation and stabilization of GNPs.