Creating Two-Dimensional Electron Gas in Polar/Polar Perovskite Oxide Heterostructures: First-Principles Characterization of LaAlO₃/A⁺B⁵⁺O₃

By using first-principles electronic structure calculations, we explored the possibility of producing two-dimensional electron gas (2DEG) at the polar/polar (LaO)⁺/(BO₂)⁺ interface in the LaAlO₃/A⁺B⁵⁺O₃ (A = Na and K, B = Nb and Ta) heterostructures (HS). Unlike the prototype polar/nonpolar LaAlO₃/SrTiO₃ HS system where there exists a least film thickness of four LaAlO₃ unit cells to have an insulator-to-metal transition, we found that the polar/polar LaAlO₃/A⁺B⁵⁺O₃ HS systems are intrinsically conducting at their interfaces without an insulator-to-metal transition. The interfacial charge carrier densities of these polar/polar HS systems are on the order of 10¹⁴ cm^–2, much larger than that of the LaAlO₃/SrTiO₃ system. This is mainly attributed to two donor layers, i.e., (LaO)⁺ and (BO₂)⁺ (B = Nb and Ta), in the polar/polar LaAlO₃/A⁺B⁵⁺O₃ systems, while only one (LaO)⁺ donor layer in the polar/nonpolar LaAlO₃/SrTiO₃ system. In addition, it is expected that, due to less localized Nb 4d and Ta 5d orbitals with respect to Ti 3d orbitals, these LaAlO₃/A⁺B⁵⁺O₃ HS systems can exhibit potentially higher electron mobility because of their smaller electron effective mass than that in the LaAlO₃/SrTiO₃ system. Our results demonstrate that the electronic reconstruction at the polar/polar interface could be an alternative way to produce superior 2DEG in the perovskite-oxide-based HS systems

A Macromolecule Cathode for High-Performance Li-Ion and Na-Ion Batteries

Organic macromolecules have a molecular weight (Mw) between small molecules (Mw –1) and polymers (Mw > 5000 g mol–1). In this work, we design a novel organic macromolecule, namely, 1,1′-(1,4-phenylene)-bis[N,N′-bis(2-anthraquinone)]-bis[perylene-3,4,9,10-tetracarboxydiimide] (2PTCDI-4AQ). 2PTCDI-4AQ has a definite molecule structure and a large Mw value of 1679.59 g mol–1, thus showing good insolubility against most organic liquids. Meanwhile, 2PTCDI-4AQ can deliver a 12-electron redox mechanism and a theoretical specific capacity (CT) of 189 mAh g–1. Consequently, 2PTCDI-4AQ exhibits high cathode performances in Li-ion and Na-ion half/full cells. For instance, 2PTCDI-4AQ can show the discharge capacities of 174–188 mAh g–1 with a highly stable cycling retention of 93–97% during 100 cycles. Meanwhile, 2PTCDI-4AQ can also exhibit good rate performances of 130–148 mAh g–1 at the large current of 5 A g–1. As far as we know, this is the first example of macromolecule organic electrodes reported in Li-ion and Na-ion batteries

Synthesis and Biological Activity Evaluation of Novel α‑Amino Phosphonate Derivatives Containing a Pyrimidinyl Moiety as Potential Herbicidal Agents

To find novel high-activity and low-toxicity herbicide lead compounds with novel herbicidal mode of action, series of novel α-amino phosphonate derivatives containing a pyrimidinyl moiety, <b>I</b>, <b>II</b>, <b>III</b>, and <b>IV</b>, were designed and synthesized by Lewis acid (magnesium perchlorate) catalyzed Mannich-type reaction of aldehydes, amines, and phosphites. Their structures were clearly identified by spectroscopy data (IR, ¹H NMR, ³¹P NMR, EI-MS) and elemental analyses. The bioassay [in vitro, in vivo (GH1 and GH2)] showed that most compounds <b>I</b> exhibited good herbicidal activities; for example, the activities of compounds <b>Ib</b>, <b>Ic</b>, <b>Ig</b>, <b>Ii</b>, <b>Ik</b>, and <b>Im</b> were as good as the positive control herbicides (acetochlor, atrazine, mesotrione, and glyphosate). However, their structural isomers <b>II</b> and <b>III</b> and analogues <b>IV</b> did not display any herbicidal activities in vivo, although some of them possessed selective inhibitory activity against Arabidopsis thaliana in vitro. Interestingly, it was found that compounds <b>IVs</b>, <b>IVt</b>, and <b>IVl</b> showed selective insecticidal activities against Aphis species or Plutella xylostella, respectively. Their preliminary herbicidal mode of action and structure–activity relationships were also studied