The reaction was performed in disposable 1 cm wide rectangular polystyrene (PS) UVvis cuvettes (340-900 nm, VWR, 634-0675) containing a magnet (unless otherwise specified), de-dusted with a flow of compressed air prior to the addition of the chemicals. The chemicals were added from the stock solutions (NaOH: 50 mM in mQ, HAuCl4: 50 mM in mQ, ethanol as received, methanol as received, glycerol from a 60 v.% stock solution in mQ to facilitate the handling of this otherwise viscous chemical) in the order water < base < alcohol(s) < HAuCl4. HAuCl4 was added last, under stirring in a photo-box (Puluz LED portable Photo Studio, PU5060EU, 60 cm x 60 cm x 60 cm, 60 W) to control the light environment. The samples were capped with dedicated stoppers and left to react for 2 hours in the photo-box with stirring. Alternatively the samples were subjected to a 365 nm light (OFK-8000 OptimaxTM Multi-LiteTM inspection kit, Spectroline), illuminated from the top and without capping, for 2 hours, as described elsewhere, or kept under dark conditions for 2 hours (capped) using aluminum foil. The samples were then left for a day at room temperature and ambient light without stirring. The samples were then stored at room temperature in a drawer.