Amino acid-capped gold nanoparticles (AuNPs) are a promising
tool
for various applications, including therapeutics and diagnostics.
Most often, amino acids are used to cap AuNPs synthesized with other
reducing agents. However, only a few studies have been dedicated to
using α-amino acids as reducing and capping agents in AuNPs
synthesis. Hence, there are still several gaps in understanding their
role in reducing gold salts. Here, we used 20 proteinogenic α-amino
acids and one non-proteinogenic α-amino acid in analogy to sodium
citrate as reducing and capping agents in synthesizing AuNPs using
the Turkevich method. Only four of the twenty-one investigated amino
acids have not yielded gold nanoparticles. The shape, size distribution,
stability, and optical properties of synthesized nanoparticles were
characterized by scanning electron microscopy, differential centrifugal
sedimentation, the phase analysis light scattering technique, and
UV–vis spectroscopy. The physicochemical characteristics of
synthesized AuNPs varied with the amino acid used for the reduction.
We proposed that in the initial stage of gold salts reduction most
of the used α-amino acids behave similarly to citrate in the
Turkevich method. However, their different physicochemical properties
resulting from differences in their chemical structures significantly
influence the outcomes of reactions.