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Environmentally harmful and high-priced initiators such as azodiisobutyronitrile, perchloric acid and butyllithium are usually essential for most of the polymerization technologies such as radical, cationic and anionic polymerizations. Besides, it is also troublesome to achieve complete separation of initiators from the obtained polymers. Herein, a recyclable catalytic system for the generation of hydroxyl radicals by catalyzing hydrogen peroxide based on bi-nano-bionic enzymes (refers to the bionic enzymes constructed from two kinds of enzymes, Fe3O4@Au NPs) was successfully constructed. The magnetic and flower-like Fe3O4 NPs provided a recyclable and well-dispersed scaffold for immobilization of Au NPs, leading to enhanced catalytic activity of Au bionic enzymes. The designed catalytic system showed excellent catalytic activity for hydroxyl radical generation under various working conditions (pH 7–11, 15–100 °C). Impressively, the catalytic system was then employed as a novel initiating system (Fe3O4@Au NPs/H2O2) for reversible addition–fragmentation chain transfer (RAFT) polymerization of a wide range of functional monomers using different RAFT agents in both aqueous and organic solvents. The established initiating system provided an effective method for RAFT polymerization with a real-time control feature in a recyclable way by magnetic separation. It was found that over 93.9% catalytic activity of Fe3O4@Au was still retained after 4 consecutive operations of RAFT polymerization.

Discovering the relationship of structure and rheological behaviors remains challenging. In this study, the TiO2 nanoparticle decorated magnetic MoS2 nanosheets (Fe3O4@MoS2@TiO2 nanoparticles) exhibited unique rheological behaviors under external electric and magnetic fields owing to their special hierarchical structures. The constructed core–shell structures of the Fe3O4@MoS2@TiO2 nanoparticles were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The magnetic behaviors were studied using a vibrating sample magnetometer (VSM). The Fe3O4@MoS2@TiO2 nanoparticles exhibited both electrorheological (ER) and magnetorheological (MR) properties that result from the decoration of high dielectric TiO2 nanoparticles on the MoS2 shell and paramagnetic behavior of Fe3O4 nanoparticles in the core, respectively. The MoS2 nanosheets act as superb lubricant at a high shear rate due to their weak interlayer van der Waals forces. The abrupt decrease of shear stress at a critical shear rate was observed under the external magnetic field and the proposed mechanism was also discussed. The unique rheological behaviors of the Fe3O4@MoS2@TiO2 nanoparticle based suspensions highlight the great promise of MoS2-based materials for cornerstone applications in rheological fields.