Biomimetic fabrication of gold nanoparticles on templated indole-3-acetic acid based nanofibers

Self-assembly of the phytohormone indole-3-acetic acid (IAA) was examined in aqueous solutions of varying pH values. Further, it was observed that IAA biomimetically reduced Au ions leading to the formation of Au nanoparticles at a pH range of 4–9. It was found that at a pH range of 4–7, uniform spherical gold nanoparticles in the size ranges of 20–30 nm were obtained, while under basic conditions, a high degree of aggregation was observed. In addition, we conjugated IAA with the organic linker 1,4-diaminobutane in order to enhance the attachment of Au ions to the IAA moiety via the free amino group and examined its self-assembly. In general, higher yields of nanofibers were formed upon self-assembly of the amide conjugate, with lengths in the micron range. Further, it was observed that the Au nanoparticles formed in the presence of the self-assembled amide conjugates were uniformly coated, leading to the formation of uniform gold nanowires. Thus, a new class of materials based on IAA and IAA-amide conjugates could be efficiently used for formation of gold nanoparticles using environmentally friendly mild synthetic methods in the absence of harsh reducing agents. Such materials may have potential applications in optoelectronics, bioimaging and sensing.