Water-soluble gold nanoclusters with pH-dependent fluorescence and high colloidal stability over a wide pH range via co-reduction of glutathione and citrate

We present a simple strategy for synthesis of water-soluble, monodisperse, highly fluorescent gold nanoclusters (Au NCs) with sizes of 1.8 nm by co-reduction of glutathione and citrate for 24 h at 50 °C. The fluorescence intensity of the GS/C–Au NCs obtained is pH-dependent and can be reversibly adjusted in the pH range from 4.1 to 8.6.