Tethering Catalytic Nanoparticles to Supramolecular Nanostructures for Improved Recyclability

Nano-sized catalysts are promising due to their high catalytic activity originating from ultra-large surface-to-volume ratios. However, nanoscale suspensions are also inseparable, hampering the reusability and recyclability of nano-sized catalysts. While depositing the nano-sized catalysts on supporting materials offers an approach to overcome this challenge, the surface of supporting materials often has little flexibility to harness the surface chemistry, which leads to limited loading ratios and uncontrolled nucleation growth of the catalysts on the surface. Here we show that nano-sized catalysts may be anchored to self-assembled nanostructures, offering tunable surface chemistry which can be harnessed to promote affinity with and recyclability of catalysts. In this study, we use sub-10nm gold nanoparticle (AuNP) catalysts and L-cysteine-functionalized aramid amphiphile nanotubes which exhibit a strong affinity with AuNPs, as a model system. We observe that sub-10nm AuNPs bind evenly on the surface of the nanotubes without precipitation. We confirm that the AuNP-CysAA system is capable of reducing 4-nitrophenol. Unlike only AuNPs suspension, the reacted mixture of the AuNP-CysAA system can be easily separated by filtration to reuse due to the high-aspect-ratio of the nanotubes.