Superassembled Hierarchical Asymmetric Magnetic Mesoporous Nanorobots Driven by Smart Confined Catalytic Degradation

Micro/nanoscale robotics has received great attention in many important fields. However, it is still a great challenge to construct nanorobots simultaneously possessing multifunctionality, well-controlled directionality, and fast and durable motion as well as fully compatible and biodegradable components. Here, a hierarchical, asymmetric, hollow, catalytic, magnetic, and mesoporous nanorobot has been fabricated through a multistep interfacial superassembly strategy. The multilayer composites consist of hollow silica nanoflasks sequentially coated with a highly magnetic responsive Fe₃ O₄ layer, a mesoporous silica layer with homogeneous vertical channels, and a layer of catalytic gold nanoparticles on both the inner and outer surfaces. Furthermore, para-nitrophenol was used as a model pollutant to trigger self-motility of the nanoflasks by confined catalytic degradation (CCD). We found that the bottleneck morphology and mesoporous surface both improved the catalytic nanoparticle loading capability and CCD effect, thus enabling efficient self-motility and a durable movement capacity of ∼100 h. In addition, the catalytic performance was improved by 180 % compared with that of solid spherical nanoparticles.