Search

Sulfoxides are remarkably useful in asymmetric synthesis and drug development. Herein, we propose a new electroenzymatic cascade route to selectively synthesize methyl phenyl sulfoxide rather than methyl phenyl sulfone by the oxidation of thioanisole. Chloroperoxidase (CPO) functionalized with 1-ethyl-3-methylimidazolium bromide (ILEMB) is encapsulated into dendritic N-doped mesoporous carbon nanospheres (NMCNs) modified with polyethyleneimine (NMCNs-PEI) to form a biohybrid (CPO-ILEMB@NMCNs-PEI). The in situ generation of hydrogen peroxide (H2O2) species by the two-electron oxygen reduction reaction (2e−ORR) on NMCNs-PEI initiates the subsequent selective oxidation of thioanisole by CPO-ILEMB. NMCNs-PEI shows not only high electroactivity for the 2e−ORR but also good biocompatibility for CPO-ILEMB immobilization. The mesopores in NMCNs-PEI can provide a protective space for the encapsulated enzyme, ensuring the operational stability of the enzyme and avoiding the escape of H2O2, which result in high catalytic activity. The experimental results suggest that the catalytic efficiency of the electroenzymatic cascade system with the CPO-ILEMB@NMCNs-PEI biohybrid is up to 4.5 times higher than that of the free CPO-ILEMB catalytic system with H2O2 generated by NMCNs-PEI for the oxidation of thioanisole to produce methyl phenyl sulfoxide. [ABSTRACT FROM AUTHOR]

Symmetry‐breaking synthesis of colloidal nanocrystals with desired structures and properties has aroused widespread interest in various fields, but the lack of robust synthetic protocols and the complex growth kinetics limit their practical applications. Herein, a general strategy is developed to synthesize the Au–Cu Janus nanocrystals (JNCs) through the site‐selective growth of Cu nanodomains on Au nanocrystals, which is directed by the substantial lattice mismatch between them, with the assistance of judicious manipulation of the growth kinetics. This strategy can work on Au nanocrystals with different architectures for the achievement of diverse asymmetric Au–Cu hybrid nanostructures. Of particular note, the obtained Au nanobipyramids (Au NBPs)‐based JNCs facilitate the conversion of CO2 to C2 hydrocarbon production during electrocatalysis, with the Faradaic efficiency and maximum partial current density being 4.1‐fold and 6.4‐fold higher than those of their monometallic Cu counterparts, respectively. The excellent electrocatalytic performances benefit from the special design of the Au–Cu Janus architectures and their tandem catalysis mechanism as well as the high‐index facets on Au nanocrystals. This research provides a new approach to synthesize various hybrid Janus nanostructures, facilitating the study of structure‐function relationship in the catalytic process and the rational design of efficient heterogeneous electrocatalysts. [ABSTRACT FROM AUTHOR]

To determine the effects of Ti and mixing entropy (ΔSmix) on the structure and mechanical proper-ties of Zr-Ta alloys and then find a new potential energetic structural material with good me-chanical properties and more reactive elements, TixZr2.5−xTa (x = 0, 0.5, 1.0, 1.5, 2.0) alloys were investigated. The XRD experimental results showed that the phase transformation of TixZr2.5−xTa nonequal-ratio ternary alloys depended not on the value of ΔSmix, but on the amount of Ti atoms. With the addition of Ti, the content of the HCP phase decreased gradually. SEM analyses revealed that dendrite morphology and component segregation increasingly developed and then weakened gradually. When x increases to 2.0, TixZr2.5−xTa with the best mechanical properties can be ob-tained. The yield strength, compressive strength and fracture strain of Ti2.0Zr0.5Ta reached 883 MPa, 1568 MPa and 34.58%, respectively. The dependence of the phase transformation and me-chanical properties confirms that improving the properties of Zr-Ta alloys by doping Ti is feasible. [ABSTRACT FROM AUTHOR]

Plasmonic hot electrons have shown great potential in photocatalysis, but little is known about the hot hole-driven chemical reactions due to the lack of desired plasmonic metal/p-type semiconductor architectures. Herein, we describe a general and robust strategy for the site-selective growth of a p-type semiconductor, Cu 2 O on Au nanocrystals (NCs), to produce diverse spatially separated Au/Cu 2 O heterostructures. The preferential growth of Cu 2 O on the tips/ends/edges of Au NCs is directed by the sparse coverage of the surfactant molecules at the high-curvature sites of Au NCs. The obtained dumbbell-shaped nanostructures serve as the ideal platforms for probing the hot-hole-mediated CO 2 reduction reaction. Benefiting from the hot-hole injection, a new reaction pathway is unlocked, and the C 2 product activity and selectivity are significantly improved. This study demonstrates the genuine superiority of the dumbbell-shaped nanostructures in photocatalysis, offering a new unique avenue to explore the underlying mechanism of hot-hole-mediated chemical reactions.