It is known that the stabilization mechanism of pristine Au NPs (Au10) stabilized by the excess of NaBH4 relies on the formation of a layer (incorporating water molecules) of anions (BH surface of Au NPs. Hence, to evaluate the true stabilization ability of K,Na-PHI, the prepared suspensions of the Au NPs were dialyzed against water to remove the NaBH4 hydrolysis products. The results unambiguously show that K,Na-PHI can efficiently stabilize ultrafine AuNPs also in the absence of the NaBH4 hydrolysis products; for details see ESI, Fig. and Fig. , as well as Table and S4 †.