Bovine serum albumin assisted preparation of ultra-stable gold nanoflowers and their selective Raman response to charged dyes.

In this work, we demonstrated a facile, one-pot approach for preparation of gold nanoflowers by using tetrachloroauric acid as a gold precursor, ascorbic acid as a reductant, and bovine serum albumin (BSA) as a ligand. It was found that the morphology of the as-prepared gold nanoparticles (Au NPs) was dependent on the concentration of BSA introduced into the reaction solutions. It is identified that BSA directed the preferential growth along the 〈111〉 direction, which contributed to the anisotropic growth of Au NPs and thus the formation of Au nanoflowers. An increased concentration of BSA reduced the reactivity of the gold precursor, leading to the formation of Au nanoflowers with increased size, which could also be obtained by decreasing the amount of reductant added. The Au nanoflowers were ultra-stable in the presence of chloride ions under acidic pH, making them suitable for selective detection of oppositely charged dyes via surface-enhanced Raman scattering according to the isoelectric point (∼4.7) of BSA capped on their surface.