Carbon-dot liposome–based synthesis of gold nanocatalysts for efficient reduction of 4-nitrophenol in wastewater

Supported metal nanoparticles (NPs) having high catalytic activity and stability hold great promise in many fields including catalytic wastewater treatment. These NPs can be effectively stabilized by the suitable carriers to achieve satisfactory long-term stability and increased recyclability. Compared with common solid-state supports, catalyst supports with dynamic behavior are expected to endow active sites with additional degrees of freedom for enhanced catalytic performance. Here, a novel dynamical nanocatalyst support utilizing lamellar vesicles formed via self-assembly of lipid-like carbon dots was devised for in situ growth of gold NPs decorated carbon-dot liposomes (AuNPs@CDLs) in catalytic reduction application. CDLs with abundant carbon domains and surface functional groups are ideal hosts for carrying high-density Au NPs, which are beneficial for providing large number of active sites. CDLs also endow high substrate entrapment and adsorption capacity and thereby improve the overall catalytic performance. Our results reveal that AuNPs@CDLs exhibited superior catalytic activity than unsupported Au NPs for catalytic reduction of 4-nitrophenol (4-NP) with sodium borohydride. The increased fluidity in the vesicle membrane also leads to an enhancement of catalytic efficiency. AuNPs@CDLs have been successfully applied in industrial wastewater treatment, with results of almost complete degradation of 4-NP within 3 min. As a dynamically self-assembled support, CDLs can not only improve the stability against salt-induced aggregation and reusability of immobilized metal nanocatalysts, but also enhance the accessibility of active sites through the intrinsic fluidity of vesicle membranes.