It is known that strongly interacting stabilizing agents might block the utilization and accessibility of the active sites on the surface of catalytic metal NPs, resulting in catalyst deactivation/poisoning. However, the stabilizers that electrostatically stabilize Au NPs typically do not interfere significantly with the mass transport processes towards the catalytic surface, thus allowing for high diffusion rates of the reactants and products without completely blocking the active sites. As a proof of concept, the catalytic activity of K,NaPHI2, KMel0.3, KCya0.3, and KCA0.3 was evaluated in the selective reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4, using the "naked" Au NPs electrostatically stabilized by excess NaBH4 (Au10) as a benchmark. The catalytic activity of all investigated samples was evaluated one day after their synthesis. The catalytic hydrogenation of nitroarenes has been extensively employed as a model reaction to evaluate the activity of Au NP catalysts, and it has the advantage of easy monitoring by UV-vis spectroscopy. As the reaction proceeds after the addition of the catalyst, the absorption peak at 400 nm decreases, while the absorption peak at 300 nm is increasing, showing the conversion of 4-NP to 4-AP (Fig. ). The time dependence of the relative absorbance (At/A0 %) of the 4-nitrophenolate peak at 400 nm in the presence of Au10, K,NaPHI2, KMel0.3, KCya0.3, or KCA0.3 is shown in ESI, Figure †, where At and A0 represent the absorbance at the reaction time t and at time t = 0, respectively. An important feature of the reduction of 4-NP catalyzed by ligand-stabilized nanoparticles is the induction period, an initial time interval needed until the reaction takes place. The induction period is related to either the formation of a diffusion pathway through the ligand shell on the NP surface or the restructuring of the NP surface induced by the adsorbed reactant molecules. Interestingly, very short (~2-20 s) induction times are observed for all investigated materials except for KCA0.3 (~45 s; Figure ), which indicates that especially the heptazine-based stabilizing agents can both effectively stabilize the Au NPs and allow for fast diffusion of reactants and products needed for effective surface catalysis.