Based on our previous studies, the NPs likely form at RT via a fast nucleation, likely promoted by the absence of surfactant and the high redox potential of HAuCl4, followed a relatively slow growth, likely promoted by a RT process . The different sizes observed are to be related to the initial formation of Au NPs seeds, by analogy with other syntheses methods of Au NPs . Here the reaction is initiated fast by using a sonic bath (A), a bit slower by adding the HAuCl4 under stirring (B, C), even slower when only a manual shake is performed (D). This is to be related to the fact that the reaction is best performed when concentrated HAuCl4 is used and added last to initiate the reaction. The redox potential of the acid form of HAuCl4 is higher than the hydroxy-substituted species. However, the alkaline conditions here needed to promote the formation of the alkoxides from the alcohol that will then play the role of reducing agent , would favour the formation of the hydroxy substituted species. A way to by-pass this dilemma is to add HAuCl4 last from concentrated stock solution to locally reduce the precursor then more likely in its acidic form. The way the precursor is then mixed to the alkaline alcohol and water mixture is then expected to impact the formation of the Au NPs, as observed here. A poorer mixing will lead to larger NPs because the initial reduction of the HAuCl4 might be slower. For samples E and F the difference in size comes from using different precursor or reducing agent, respectively (see also details in SI).