Science and Technology News

Trading places: Two new nonlinear optical materials, α‐ and β‐Ba₂[GaF₄(IO₃)₂](IO₃) (1 and 2), were designed via three‐site aliovalent substitution of VO₄F₂ in α‐ and β‐Ba₂[VO₂F₂(IO₃)₂](IO₃) by GaO₂F₄. The new materials display large second‐harmonic generation responses (≈6×KH₂PO₄ (KDP)), wide energy band gaps (4.61 and 4.35 eV), and high laser damage thresholds (29.7× and 28.3× relative to that of AgGaS₂).

Abstract

Two mixed‐metal gallium iodate fluorides, namely, α‐ and β‐Ba₂[GaF₄(IO₃)₂](IO₃) (1 and 2), have been designed by the aliovalent substitutions of α‐ and β‐Ba₂[VO₂F₂(IO₃)₂](IO₃) (3 and 4) involving one cationic and two anionic sites. Both 1 and 2 display large second‐harmonic generation responses (≈6×KH₂PO₄ (KDP)), large energy band gaps (4.61 and 4.35 eV), wide transmittance ranges (≈0.27–12.5 μm), and high relevant laser‐induced damage thresholds (29.7× and 28.3×AgGaS₂, respectively), which indicates that 1 and 2 are potential second‐order nonlinear optical materials in the ultraviolet to mid‐infrared. Our studies propose that three‐site aliovalent substitution is a facile route for the discovery of good NLO materials.

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Source:: Angewandte Chemie Int. edition

When the fearless Don Quixote was charging at windmills, he left his slow companion, Sancho Panza, behind. In their Communication (DOI: 10.1002/anie.201812937), J. Sun et al. describe a novel rhodium‐catalyzed dearomatization and rearrangement of O‐substituted pyridines to access N‐substituted 2‐pyridones, a challenging target since their straightforward synthesis by simple alkylation of 2‐pyridones is thwarted by their preferred O‐reactivity. The key to this transformation is the formation of the pyridinium ylide and subsequent 1,4‐acyl migratory rearrangement.

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Source:: Angewandte Chemie Int. edition

Gold nanorods, end‐grafted with achiral polymer ligands, show a new mechanism of chiral surface patterning giving a helicoidal morphology. This morphology is dictated by the relationship between the polymer grafting density and the ratio of the polymer length to the nanorod radius.

Abstract

Chiral packing of ligands on the surface of nanoparticles (NPs) is of fundamental and practical importance, as it determines how NPs interact with each other and with the molecular world. Herein, for gold nanorods (NRs) capped with end‐grafted nonchiral polymer ligands, we show a new mechanism of chiral surface patterning. Under poor solvency conditions, a smooth polymer layer segregates into helicoidally organized surface‐pinned micelles (patches). The helicoidal morphology is dictated by the polymer grafting density and the ratio of the polymer ligand length to nanorod radius. Outside this specific parameter space, a range of polymer surface structures was observed, including random, shish‐kebab, and hybrid patches, as well as a smooth polymer layer. We characterize polymer surface morphology by theoretical and experimental state diagrams. The helicoidally organized polymer patches on the NR surface can be used as a template for the helicoidal organization of other NPs, masked synthesis on the NR surface, as well as the exploration of new NP self‐assembly modes.

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Source:: Angewandte Chemie Int. edition

Electrocatalytic N₂ reduction under ambient conditions offers a promising carbon‐free strategy toward clean and sustainable NH₃ production. In their Communication (DOI: 10.1002/anie.201811728), J. Luo, R. R. Adzic, H. L. Xin et al. report single molybdenum atoms anchored on nitrogen‐doped porous carbon. The catalyst achieves a high NH₃ yield rate, Faradaic efficiency, and stability at room temperature because of a high density of active sites within a hierarchically porous carbon framework.

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Source:: Angewandte Chemie Int. edition