Abstract
<jats:p>The controlled synthesis of nanomaterials remains a general bottleneck, often related to challenges in reproducibility. A range of seemingly non-relevant parameters can crucially impact the outcome of a synthesis. In particular, gold nanoparticles can be very easily obtained at room temperature in seconds by simply using water, HAuCl4 and NaBH4 without the need for other chemicals. Despite the very promising features of this surfactant-free colloidal approach, its potential remains largely under-exploited. Here, we first detail the strong influence of the type of the reaction vessel used, the impact of different suppliers of the chemicals, the influence of direct or sequential addition of NaBH4, the effect of using inert gas and the impact of temperature on the resulting size of the gold nanoparticles obtained. It is found that the synthesis is rather reproducible but particularly sensitive to the geometry of the vessel used, mixing of the chemicals and chemicals used. There is no benefit to use a controlled gas atmosphere or high temperatures to achieve small size nanoparticles. The sequential addition of NaBH4 is a convenient original approach to achieve size control for this synthesis. Finally, the nanoparticles are shown to be readily active catalysts for Congo Red degradation and to study size effects. The results clarify important pitfalls for improved reproducibility in this synthesis strategy for a wider use of this convenient approach and to make the most of the resulting materials.</jats:p>