The results detailed in section S11 suggests the rapid formation of the first small size NPs followed by a relatively slow autocatalytic growth for the alcohol-mediated syntheses. The fast formation could be related to the absence of surfactants and the slow autocatalytic growth can be attributed to the RT process. Further advanced characterization such as in situ small angle X-ray scattering (SAXS) will be required to fully understand the formation pathway of these surfactant-free Au NPs. Nevertheless, the results presented highlight the potential benefits of surfactant-free colloidal Au NPs synthesis in alkaline water-alcohols mixtures as a promising alternative model system to the citrate-based Turkevich-Frens synthesis, given for instance the strong differences here documented using ethanol or glycerol.