Biological synthesis of gold nanoparticles using the aqueous extract of the brown algae Laminaria japonica

In this study, the extracellular biosynthesis of self-assembled gold nanoparticles (GNPs) was accomplished using the aqueous extract of the brown algae Laminaria japonica. The optical, physical, and chemical properties of the GNPs were investigated to identify their average shape and size, crystal nature, and surface chemistry, via UV-visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The sizes of the spherical self-assembled cores of the GNPs ranged from 15 to 20 nm. The XRD patterns showed a (111) preferential orientation and the crystalline nature of the GNPs. The results of the FTIR analysis suggested that the peptides and/or proteins carried out the dual function of effective AuIII reduction and successful capping of the GNPs. Thus, the biomolecular synthesis, stabilization, and self-assembly of the GNPs by L. japonica extract can be an example of green chemistry and extracellular biomineralization.