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Recently, chiral metal‐organic coordination materials have emerged as promising candidates for a wide range of applications in chiroptoelectronics, chiral catalysis, and information encryption, etc. Notably, the chiroptical effect of coordination chromophores makes them appealing for applications such as photodetectors, OLEDs, 3D displays, and bioimaging. The direct synthesis of chiral coordination materials using chiral organic ligands or complexes with metal‐centered chirality is very often tedious and costly. In the case of ionic coordination materials, the combination of chiral anions with cationic, achiral coordination compounds through noncovalent interactions may endow molecular materials with desirable chiroptical properties. The use of such a simple chiral strategy has been proven effective in inducing promising circular dichroism and/or circularly polarized luminescence signals. This concept article mainly delves into the latest advances in exploring the efficacy of such a chiral anion strategy for transforming achiral coordination materials into chromophores with superb photo‐ or electro‐chiroptical properties. In particular, ionic small‐molecular metal complexes, metal clusters, coordination supramolecular assemblies, and metal‐organic frameworks containing chiral anions are discussed. A perspective on the future opportunities on the preparation of chiroptical materials with the chiral anion strategy is also presented.

 

Epitaxial thin films of cobalt ferrite (CoFe2O4) are grown on two isostructural substrates, (001)-oriented MgGa2O4 and ZnGa2O4, using pulsed laser deposition. The substrates have a lattice mismatch of 1.26% and 0.70% with bulk CoFe2O4 (CFO) crystal. We have systematically investigated the structural and magnetic properties of the epitaxial CFO films on these substrates. X-ray diffraction and transmission electron microscopy result analysis reveal that the films deposited on spinel ZnGa2O4 are essentially free of defects and are under a small compressive strain, while films on MgGa2O4 show partial strain relaxation along with defect formation. Room temperature magnetization data indicate that CFO grown on ZnGa2O4 substrates have a bulk-like saturation magnetization of 420 emu/cc and a uniaxial substrate-induced anisotropy value of −22.9× 106 erg/cm3 with an anisotropy field as low as 60 kOe.

 

Also available at https://arxiv.org/abs/2110.12271 

Abstract Piezoelectric polymers hold great potential for various electromechanical applications, but only show low performance, with | d 33  | < 30 pC/N. We prepare a highly piezoelectric polymer ( d 33  = −62 pC/N) based on a biaxially oriented poly(vinylidene fluoride) (BOPVDF, crystallinity = 0.52). After unidirectional poling, macroscopically aligned samples with pure β crystals are achieved, which show a high spontaneous polarization ( P s ) of 140 mC/m 2 . Given the theoretical limit of P s,β  = 188 mC/m 2 for the neat β crystal, the high P s cannot be explained by the crystalline-amorphous two-phase model (i.e., P s,β  = 270 mC/m 2 ). Instead, we deduce that a significant amount (at least 0.25) of an oriented amorphous fraction (OAF) must be present between these two phases. Experimental data suggest that the mobile OAF resulted in the negative and high d 33 for the poled BOPVDF. The plausibility of this conclusion is supported by molecular dynamics simulations. 

Protein splicing is a post-translational process by which an intein catalyzes its own excision from flanking polypeptides, or exteins, concomitant with extein ligation. Many inteins have nested homing endonuclease domains that facilitate their propagation into intein-less alleles, whereas other inteins lack the homing endonuclease (HEN) and are called mini-inteins. The mini-intein that interrupts the DNA PolII ofPyrococcus horikoshiihas a linker region in place of the HEN domain that is shorter than the linker in a closely related intein fromPyrococcus abyssi. TheP. horikoshiiPolII intein requires a higher temperature for catalytic activity and is more stable to digestion by the thermostable protease thermolysin, suggesting that it is more rigid than theP. abyssiintein. We solved a crystal structure of the intein precursor that revealed a domain-swapped dimer. Inteins found as domain swapped dimers have been shown to promote intein-mediated protein alternative splicing, but the solvedP. horikoshiiPolII intein structure has an active site unlikely to be catalytically competent.

 

Ligand‐controlled regiodivergence has been developed for catalytic semireduction of allenamides with excellent chemo‐ and stereocontrol. This system also provides an example of catalytic regiodivergent semireduction of allenes for the first time. The divergence of the semireduction is enabled by ligand switch with the same palladium pre‐catalyst under operationally simple and mild conditions. Monodentate ligand XPhos exclusively promotes selective 1,2‐semireduction to afford allylic amides, while bidentate ligand BINAP completely switched the regioselectivity to 2,3‐semireduction, producing (E)‐enamide derivatives.

 

In response to the stringent requirements for future DC-link capacitors in electric vehicles (EVs), it is desirable to develop dielectric polymer films with high-temperature tolerance (at least 105 °C) and low loss (dissipation factor, tan δ < 0.003). Although the biaxially oriented poly(ethylene terephthalate) (BOPET) film has an alleged temperature rating of 120 °C, its dielectric performance in terms of breakdown strength and lifetime cannot satisfy the stringent requirements for power electronics in EVs. In this work, we carried out a structure–electrical insulation property relationship study to understand the working mechanism for various PET films, including a commercial BOPET film, an amorphous PET (AmPET) film, and two annealed PET films (AnPET, i.e., cold-crystallized from AmPET). Structural analyses revealed a uniform edge-on crystalline orientation in BOPET with the a* axis in the film normal direction. Meanwhile, a high content of the rigid amorphous fraction (RAF) was identified for BOPET, which resulted from biaxial stretching during processing. On the contrary, AnPET films had a random crystal orientation with lower RAF contents. From dielectric breakdown and lifetime studies, the high-crystallinity AnPET film exhibited better electrical insulation than BOPET, and AmPET had the worst electrical insulation. Electrical conductivity results revealed that the high RAF content in BOPET led to reasonably high breakdown strength and long lifetime only at low temperatures (<100 °C). Meanwhile, PET crystals were more insulating than the amorphous phase, whether mobile, rigid, or glassy. In particular, the flat-on lamellae in the AnPET film were more effective than the edge-on lamellae in BOPET in blocking the conduction of charge carriers (electrons and impurity ions). This understanding will help us design high-temperature semicrystalline polymer films for DC-link capacitors in EVs.