Green chemistry synthesis of gold nanoparticles using lactic acid as a reducing agent

A method of green chemistry synthesis of gold nanoparticles using lactic acid as a reducing agent is reported. The size and shape of gold nanoparticles are modulated by varying the ratio of metal salt and lactic acid in the reaction medium. The nanoparticles obtained are characterised by UV-vis, transmission electron microscopy (TEM) and X-ray diffraction (XRD). Crystalline nature of the nanoparticles in the face-centred cubic structure is confirmed by the peaks in the XRD pattern corresponding to (1 1 1), (2 0 0), (2 2 0) and (3 1 1) planes, which are bright circular spots in the selected area electron diffraction (SAED) and clear lattice fringes in the high-resolution TEM image. It is found that the size and shape of gold nanoparticles are strongly influenced by the molar ratio of HAuCl₄ to lactic acid. Based on these results, a potential mechanism of this method of gold nanoparticle synthesis is also discussed. In future, more biological and medical applications of gold nanoparticles prepared by this method could be found based on their biocompatibility and solubility in aqueous solutions of lactic acid.