Abstract
The conventional key steps for seed mediated growth of noble metal nanostructures involve classical and nonclassical nucleation. Furthermore, the surface of the seed catalytically enhances the secondary nucleation involving Au+ to Au0reduction, thus providing in-plane growth of seed. In contrast to this well-established growth mechanism, herein we report the unique case of methionine (Met) controlled seed mediated growth reaction, which rather proceeds via impeding secondary nucleation in presence of citrate stabilized gold nanoparticle (AuNP). The interaction between the freshly generated Au+ and thioether group of Met in the medium restricts the secondary nucleation process of further seed catalyzed Au+ reduction to Au0. This incomplete conversion of Au+, as confirmed by X-ray photoelectron spectroscopy (XPS), results in a significant enhancement of the zeta (z) potential even at low Met concentration. Nucleation of in situgenerated small-sized particles (nAuNPs) takes place on the parent seed surface followed by their segregation from the seed. Self-assembly process of these nAuNPs arises from the aurophilic interaction among the Au+. Furthermore, the time dependent growth of smaller particles to larger sized particles through assembly and merging within the same self-assembly validates the non-classical growth. This strategy has been successfully extended towards the seed mediated growth reaction of AuNP in presence of three bio-inspired decameric peptides having varying number of Met residues. The study confirms the nucleation strategy even in presence of single Met residue in the peptide and also the self-assembly of nucleated particles with increasing Met residues within the peptide.
Mathematical modelling of seed-mediated size-specific growth of spherical silver nanoparticles using Azadirachta indica leaf extract
