Fig. 1: Structural characterization and optical properties of AuH₂O NCs.
a Chemical structures of thione and thiol 6-MPR isomers. b Schematic illustration of two 6-MPR isomers protected AuH₂O NCs. c Schematic illustration of the isomerization of the surface terminal for AuH₂O NCs. R represents the ribosyl at the terminal of the 6-MPR ligand. d High-resolution N 1 s XPS and S 2p XPS spectra of AuH₂O NCs synthesized in pH = 6.5 and 13.5 aqueous solutions, respectively. For N 1 s XPS, the yellow, gray, and reddish-brown shaded areas represent the N-H, pyrrolic N, and pyridinic N, respectively. For S 2p XPS, the yellow, gray, and reddish-brown shaded areas represent the Au-S, C = S, and C-S bonds, respectively. e Positive MALDI-TOF mass spectra of AuH₂O NCs synthesized in different pH aqueous solutions (from bottom to top: pH = 6.5, 7, 9, 11, 13, and 13.5). The gray shaded areas represent the location of the MALDI-TOF mass spectrometry signal. f PL spectra of serial NCs synthesized at pH = 6.5, 7, 9, 11, 13, and 13.5, respectively (λex = 365 nm). Illustrations are the evolution of terminal ligands in the surface motifs on the AuH₂O NCs. The gray and reddish-brown shaded areas represent the PL I and PL II bands, respectively. g Comparison of UV-vis absorption spectra of AuH₂O NCs synthesized in different pH aqueous solutions (from bottom to top: pH = 6.5, 7, 9, 11, 13, and 13.5). The pink shaded area represents the surface absorbance of AuH₂O NCs. The gray shaded area represents the core absorbance of AuH₂O NCs. Source data are provided as a Source Data file.
