Dual-Redox\nResponsive Interfaces Based on Donor–Acceptor\nInteractions

Nanoparticle\nsurfactant (NPS) is a highly competitive means for\nstabilizing liquid–liquid interfaces, endowing interfacial\nassemblies with functionalities, and enabling the construction of\nall-liquid devices. Integrating different types of supramolecular\ninteractions into NPSs would open possibilities to generate interfaces\nthat are responsive to multiple stimuli. Here, by using donor–acceptor\ninteractions between polydopamine nanoparticles (PDA NPs) and methyl\nviologen (MV<sup>2+</sup>) terminated polystyrene, the formation,\nassembly, and jamming of a supramolecular NPS at the water–toluene\ninterface is demonstrated. Harnessing the redox properties of both\ncatechol and MV<sup>2+</sup>, the dual-redox responsiveness can be\nachieved, allowing the reconfiguration of NPS-based structured liquids.\nUsing NPS as an emulsifier, oil-in-water (O/W), water-in-oil (W/O),\nand oil-in-water-in-oil (O/W/O) Pickering emulsions can be obtained\nin one step, which exhibit smart responsiveness to redox reagents.\nTaking advantage of the adsorption capacity of PDA NPs, the purification\nof dye-polluted water can be achieved through O/W Pickering emulsions.\nWe envision that this unique dual-redox responsive biphasic system\nwould hold great potential for developing sophisticated controlled-release\nsystems as well as other intelligent, functional materials.