This first section aims to: (i) screen and investigate in a unified study the (co)influence(s) of different experimental parameters on the resulting properties of the colloidal Au NPs, (ii) clarify why the use of glycerol has been preferred to date to obtain Au NPs at RT with or without surfactants, and (iii) demonstrate the high throughput screening potential of surfactant-free colloidal syntheses of Au NPs. A high throughput is ultimately relevant to provide the missing large datasets required to implement machine learning in material discosery. Conveniently this is achieved here using a relatively green synthetic approach. A detailed explanation of the parameter space studied and a detailed analysis the results is provided in section S3. For clarity, a focus is given to the results of experiments performed with NaOH and discussion is focused on the parameter ʎspr. The results related to other bases (LiOH, KOH) and other parameters (Aspr/A450, ∆ʎ/ʎspr, A400, A380/A800 and A650/Aspr,) are provided in section S3. To help the discussion, the samples combining the desirable features according to the criteria detailed in section 2 are reported in orange and red. From Figure , it appears that the width of the experimental window for which the synthesis leads to NPs characterized by lower ʎspr values, i.e. the robustness of the synthesis, decreases in the order glycerol > EG > ethanol. This follows the relative speed at which a red color is observed during the synthesis but also the decreasing order of viscosity of the alcohols. The results could then be interpreted under the framework of the classical nucleation theory: To obtain small size Au NPs (lower ʎspr values), a fast nucleation should produce many seeds, and when follows by a slow growth, this would lead to small size monodispersed NPs. Alternatively, a burst-growth needs to be achieved, followed by a growth where smaller size NPs catch up in size, as suggested by recent work. The speed of reaction is then expected to be the key to achieve small size NPs. In this respect, It can be suggested that glycerol has been empirically preferred to date because (i) it is a more robust reducing agent, i.e. it leads to small size Au NPs across a larger parameter space, (ii) because the reaction seems fast (a red color indicative of the formation of Au NPs is observed within seconds or minutes) and (iii) the high viscosity of glycerol might contribute to the stabilization of the colloids. However, in light of the criteria defined above to develop an optimal synthesis, the use of ethanol is a promising alternative, especially considering that colloidal dispersions with relatively long term stability over months and even years are obtained, see section S4. Interestingly, the ethanol-mediated syntheses are apparently the slowest to proceed for the conditions of this screening without controlled light (turning red after ca. 1 hour), and yet, small size (below 10 nm) and stable NPs are obtained. This suggests that there is more at stake in the formation process of the Au NPs than controlling the kinetics of the reactions and viscosity. Importantly, by studying, the co-influences of the alcohol (ethanol, EG, glycerol), alcohol content (10-99 v.%), base (LiOH, NaOH, KOH) and base content (Base/Au molar ratios of 3-10) in a unified parametric study, it is established that the optimal conditions to obtain small size ca. 10 nm NPs are to use 20 v.% ethanol and 2 mM NaOH for 0.5 mM HAuCl4. No significant improvement compared to 20 v.% were observed using 15 or 25 v.% ethanol, as detailed in section S5.