Supramolecular Polyaniline-Metal Ion as Chiral Nanozymes for Enantioselective Catalysis.

Understanding origin of asymmetric information encoded on chiral nanozymes is important in mediating enantioselective catalysis. Herein, the supramolecular chiral nanozymes constructed from P/M-polyaniline (P/M-PANI) nanotwists and metal ions (M2+ , M = Cu, Ni, Co, and Zn) are designed through thioglycolic acid (TA) without chiral molecules to show the regulated catalytic efficiency and enantioselectivity. With combination of chiral environment from supramolecular scaffolds and catalytic center from metal ions, the P-PANI-TA-M2+ as nanozymes show preference to 3,4-dihydroxy-S-phenylalanine (S-DOPA) oxidation while the M-PANI-TA-M2+ show better selectivity to R-DOPA oxidation. Among them, though the Cu2+ doped supramolecular nanotwists show the highest catalytic efficiency, the Co2+ doped ones with moderate catalytic efficiency can exhibit the best enantioselectivity with select factor as high as 2.07. The molecular dynamic (MD) simulation clarifies the mechanism of enantioselective catalysis caused by the differential kinetics with S/R-DOPA enantiomers adsorbed on chiral PANI surface and free in solution. This work systematically studies the synergistic effect between the chiral supramolecular nanostructures assembled by achiral species and metal ions as peroxidase-like catalytic centers to regulate the enantioselectivity, providing deep understanding of the origin of asymmetric catalysis and serving as strong foundation to guide the design of nanozymes with high enantioselectivity.

Dumbbell-like Pt-Fe3O4 Nanoparticles Encapsulated in N-Doped Carbon Hollow Nanospheres as a Novel Yolk@Shell Nanostructure toward High-Performance Nanocatalysis.

Noble metal-Fe3O4 dumbbell-like nanoparticles have aroused considerable attention because of their high potential as heterogeneous nanocatalysts. The designed synthesis of the advanced architecture of noble metal-Fe3O4 dumbbell-like nanoparticles with both improved catalytic activity and stability is still a challenge. Herein, through the combination of yolk@shell and dumbbell-like nanostructures, dumbbell-like Pt-Fe3O4 nanoparticles encapsulated in N-doped carbon hollow nanospheres (Pt-Fe3O4@N-carbon) as a special yolk@shell nanostructure were developed. In comparison with Pt-Fe3O4 dumbbell-like nanoparticles, Pt-Fe3O4@N-carbon yolk@shell nanoparticles showed improved catalytic activity and stability toward the liquid-phase 4-nitrophenol reduction and ß-ionone oxidation, making them a promising candidate for catalysis applications.

Implantation of Fe3O4 Nanoparticles in Shells of Au@m-SiO2 Yolk@Shell Nanocatalysts with Both Improved Recyclability and Catalytic Activity.

Multifunctional nanocatalysts of Au@Fe3O4/m-SiO2 yolk@shell hybrids had been developed through a template-assisted synthesis, where Fe3O4 nanoparticles (∼12 nm) and m-SiO2 shells were sequentially assembled on surfaces of Au/SiO2 core/shell templates, followed by selective etching of the inner SiO2 cores, leading to the formation of Au@Fe3O4/m-SiO2 yolk@shell hybrids. The Fe3O4 nanoparticles were implanted in the inner surfaces of m-SiO2 shells with partially exposed surfaces to the inner cavity. The novel design not only ensures a high surface area (540.0 m2/g) and saturation magnetization (48.6 emu/g) of the hybrids but also enables interaction between Au and Fe3O4 nanoparticles. Catalytic tests toward the reduction of 4-nitrophenol in the presence of NaBH4 indicated that Au@Fe3O4/m-SiO2 yolk@shell nanocatalysts not only showed high stability and recyclability but also maintained improved catalytic activity as a result of the synergetic effect resulting from Au and Fe3O4 interactions.

Dictating catalytic performance of platinum-iron nanoparticle by regulating its heterogeneous interface and stability.

Innovative design of nanocatalyst with high activity remains to be great challenge. Platinum (Pt) nanoparticle has already demonstrated to be excellent candidates in the field of catalysis. However, the scarcity and high price significantly hinder its large-scale production. In this work, dumbbell-like alloying nanoparticle of platinum-iron/ferroferric oxide (PtFeFe3O4) was prepared. On one hand, the design of the alloying nanoparticle can manipulate the d-band center of Pt, in further, the interaction with substrates. In addition, the dumbbell-like structured PtFeFe3O4 can offer heterogeneous interface, of which the interaction between PtFe and Fe3O4, supported by the X-ray photoelectron spectroscopic (XPS) results, leads to the enhanced catalytic efficiency. On the other hand, the introduction of Fe (iron) composition largely decreases the necessary amount of Pt, leading to efficient cost reduction. Moreover, to avoid the aggregation related activity attenuation problem, PtFeFe3O4 nanoparticle located in cavity of nitrogen heteroatom-doped carbon shell (PtFeFe3O4@NC) as yolk@shell nanostructure was constructed and its improved catalytic performance was demonstrated towards the reactions of 4-nitrophenol (4-NP) reduction, ß-ionone and benzhydrol oxidation.