Dual-Redox Responsive Interfaces Based on Donor–Acceptor Interactions

Nanoparticle surfactant (NPS) is a highly competitive means for stabilizing liquid–liquid interfaces, endowing interfacial assemblies with functionalities, and enabling the construction of all-liquid devices. Integrating different types of supramolecular interactions into NPSs would open possibilities to generate interfaces that are responsive to multiple stimuli. Here, by using donor–acceptor interactions between polydopamine nanoparticles (PDA NPs) and methyl viologen (MV2+) terminated polystyrene, the formation, assembly, and jamming of a supramolecular NPS at the water–toluene interface is demonstrated. Harnessing the redox properties of both catechol and MV2+, the dual-redox responsiveness can be achieved, allowing the reconfiguration of NPS-based structured liquids. Using NPS as an emulsifier, oil-in-water (O/W), water-in-oil (W/O), and oil-in-water-in-oil (O/W/O) Pickering emulsions can be obtained in one step, which exhibit smart responsiveness to redox reagents. Taking advantage of the adsorption capacity of PDA NPs, the purification of dye-polluted water can be achieved through O/W Pickering emulsions. We envision that this unique dual-redox responsive biphasic system would hold great potential for developing sophisticated controlled-release systems as well as other intelligent, functional materials.