Au-I: an alternative and potentially better precursor than Au-III for the synthesis of Au nanostructures

This article provides an overview of current developments with regard to the use of Au-I compounds as precursors in the synthesis of Au nanostructures with controlled shapes or morphologies. We begin with a brief description of the difference between Au-I and Au-III compounds, followed by a discussion on how the solubility and stability of a Au-I compound can be improved by forming a coordination complex with a ligand (X). We then focus on a range of recent studies that have been directed towards the use of Au-I-X complexes as precursors to elemental Au, in an effort to produce Au nanostructures with a variety of shapes, including icosahedral nanoparticles, truncated decahedrons, nanowires or nanorods, branched nanostructures, hybrid nanostructures, nanoboxes, nanocages, and nanoframes. In these syntheses, the Au-I-X complexes offer a number of attractive features for generating Au nanostructures as compared to the conventional Au-III compounds, mostly due to their differences in oxidation state and aurophilic effect. The ability to control Au-I chemistry therefore provides a great opportunity to systematically investigate the syntheses, physical properties, and applications of Au nanostructures.