Fig. 4: Slow second reduction kinetics and more homogeneous Au NCs.
From: Critical roles of metal–ligand complexes in the controlled synthesis of various metal nanoclusters
a, d UV–vis absorption spectra, b, e MALDI-TOF mass spectra in the linear mode, and c, f Digital photographs of Au NCs during the second reduction using precursors obtained applying 1:3, 15 s (from 0 m of second reduction, light turquoise to 3 h of second reduction, bold turquoise) and 1:2, 7 d conditions (from 0 m of second reduction, light pink to 3 h of second reduction, bold pink), respectively. Dashed lines in UV–vis absorption and mass spectra indicate the evidence of Au25 NCs. Arrows in (a, d) indicate an increasing fraction of Au25 with increasing second reduction time. Arrows in (b, e) indicate the existence of Au NCs smaller than Au25. Evidence of Au NCs smaller than Au25 also appears in UV-vis absorption spectra (black asterisks). g Reaction mechanism schematic when the degree of the first reduction is high (Au: yellow, S: magenta, non-sulfur anions: lime). Source data are provided as a Source Data file.
