Que et al. reported the synthesis of gold nanoparticles (Au NPs) sheltered in PEG-PS nanogels for the reduction of 4-nitrophenol (4NP) . Thiol functionalized PEG blocks were immobilized on Au NPs. PS segments improved the stability of the system and provided the necessary hydrophobic environment that is required to undertake the reduction reaction in water. The outcome of using Au@PEG-PS as nanoreactors was compared to those resulting from using both uncoated and PEG-coated Au NPs. While Au@PEG-PS resulted in quantitative conversions for 5 subsequent cycles, both uncoated and PEG45 coated Au NPs resulted in full and 61% conversions only for the first cycle, respectively. Recycling of uncoated and PEG45 coated Au NPs was not possible, highlighting the significance of the nanoreactor design (Figure 8).