Lone pair–π interactions in naphthalene diimide π-acid dyes

The electron-deficient naphthalene diimides (NDIs) are ideal π-Lewis acid dyes for studies of lone pair–π interactions but remain unexplored. By a crystal engineering approach, herein we report that lone pair–π interactions between C = O and π-acceptors indeed have been found not only in free NDIs but also in their coordination networks. Interestingly, the lone pair–π interactions between C = O in the including solvents and NDIs are stronger than those found in the own C = O of imides, but weaker than the hydrogen-bonding interactions between solvent C = O and H-acceptors. In addition, the coordination by metal cation, the directionality and number of the lone-pair-bearing molecules play a crucial role on the lone-pair–π-interaction strength. These findings are undoubtedly of considerable significance for the development of NDI catalytic materials.     

Electrochemical performance of grown layer of Ni(OH)2 on nickel foam and treatment with phosphide and selenide for efficient water splitting

Active nanocomposites synthesized by the electrochemical approach play a vital role in energy generation, conversion, and storage technologies. Recently, scientists began to explore the use of earth-rich transition metal-based materials to replace precious metal-based catalysts. Transition metals (TMs) based nickel (Ni) and their pnictides compounds such as phosphides and selenides exhibit good activity for hydrogen evaluation reaction (HER) and the entire water electrolysis process. In this study, we first prepared Ni(OH)₂ and grown its layer on Ni foam (NF) and treated it with selenide (Se) and phosphide (P) then nickel-based selenide-phosphide catalyst (Ni–P–Se) was prepared by simultaneous selenization and phosphidation process for the first time. The as-obtained composite was then analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), elemental mapping and transmission electron microscope (TEM) means to study the composition, structure, and micro-morphology of materials. Furthermore, we also observed electrocatalytic water splitting activity using electrochemical cell. The results of electrochemical tests depicted that the selenization and phosphidation treatments significantly enhanced the electrocatalytic HER activity of the starting materials. The overpotentials required for Ni–P–Se to reach 10 ?mA ?cm^?2 and 100 ?mA ?cm^?2 were only 242 ?mV and 282 ?mV. The Tafel slope of Ni–P–Se is 151 ?mV dec^?1, which is lower than that of nickel phosphide, selenide, and hydroxide indicating that selenide-phosphide enhances the HER reaction kinetics of the material, which in turn increases hydrogen output rate as compared with previous studies.     

Recent advances in synthesis of ketenimines

Ketenimines are a kind of reactive species that can be used as synthetic intermediates. In the last two decades, there has been a surge of interest in this class of building blocks and their applications, which has led to extensive research on ketenimine derivatives such as fluorine ketenimine, metal complexes of ketenimines, and the various methods of their preparation. Ketenimines have been prepared by a variety of methods, including photolysis, elimination, or rearrangement reactions. As well as, ketenimines can be prepared using a variety of useful reagents, including isocyanates, copper acetylide, amides, organometallic compounds, and metal complexes. An overview of these achievements is presented here.     

Generalized spherical Aluthge transforms and binormality for commuting pairs of operators

In this paper, we introduce the notion of generalized spherical Aluthge transforms for commuting pairs of operators and study nontrivial joint invariant (resp. hyperinvariant) subspaces between the generalized spherical Aluthge transform and the original commuting pair. Next, we study the norm continuity through generalized Aluthge transform maps. We also study how the Taylor spectra and the Fredrolm index of commuting pairs of operators behave under the spherical Duggal transform. Finally, we introduce the notion of Campbell binormality for commuting pairs of operators and investigate some of its basic properties under spherical Aluthge and Duggal transforms. Moreover, we obtain new set inclusion diagrams among normal, quasinormal, centered, and Campbell binormal commuting pairs of operators.     

A differential graded approach to the silting theorem

A silting theorem was established by Buan and Zhou as a generalisation of the classical tilting theorem of Brenner and Butler. In this paper, we give an alternative proof of the theorem by using differential graded algebras.     

A class of spectral self-affine measures with four-element digit sets

The self-affine measure _μM,D${\mu }_{M,D}$ associated with an expanding matrix M∈_Mn(Z)$M\in M_n(\mathbb{Z})$ and a finite digit set D⊂Zⁿ$D\subset {\mathbb{Z}}^n$ is uniquely determined by the self-affine identity with equal weight. In this paper we construct a class of self-affine measures _μM,D${\mu }_{M,D}$ with four-element digit sets in the higher dimensions (n≥3$n\ge 3$) such that the Hilbert space L²(_μM,D)$L^2({\mu }_{M,D})$ possesses an orthogonal exponential basis. That is, _μM,D${\mu }_{M,D}$ is spectral. Such a spectral measure cannot be obtained from the condition of compatible pair. This extends the corresponding result in the plane.     

Unraveling the nature of carrier-mediated ferromagnetism in diluted magnetic semiconductors

After more than a decade of intensive research in the field of diluted magnetic semiconductors (DMS), the nature and origin of ferromagnetism, especially in III–V compounds, is still controversial. Many questions and open issues are under intensive debates. Why after so many years of investigations, Mn-doped GaAs remains the candidate with the highest Curie temperature among the broad family of III–V materials doped with transition metal (TM) impurities? How can one understand that these temperatures are almost two orders of magnitude larger than that of hole-doped (Zn,Mn)Te or (Cd,Mn)Se? Is there any intrinsic limitation or is there any hope to reach room-temperature ferromagnetism in the dilute regime? How can one explain the proximity of (Ga,Mn)As to the metal–insulator transition and the change from Ruderman–Kittel–Kasuya–Yosida (RKKY) couplings in II–VI compounds to double-exchange type in (Ga,Mn)N? In spite of the great success of density functional theory-based studies to provide accurately the critical temperatures in various compounds, till very lately a theory that provides a coherent picture and understanding of the underlying physics was still missing. Recently, within a minimal model, it has been possible to show that among the physical parameters, the key one is the position of the TM acceptor level. By tuning the value of that parameter, one is able to explain quantitatively both magnetic and transport properties in a broad family of DMS. We will see that this minimal model explains in particular the RKKY nature of the exchange in (Zn,Mn)Te/(Cd,Mn)Te and the double exchange type in (Ga,Mn)N and simultaneously the reason why (Ga,Mn)As exhibits the highest critical temperature among both II–VI and III–V DMS's.     

Application of coordinate transformation and finite differences method for electron and hole states calculations

In this work we are particularly interested for GaAs/Ga_1−xAl_xAs V-groove quantum wires. The paper presents an efficient and simple method for energy spectra and wave function calculations of electrons and holes in V-groove quantum wires. The method is based on the coordinate transformation of the V-groove quantum wire structure and the computational domain using a function proposed by Inoshita. Then, the Hamiltonian followed by implementation of the FDM (Finite Difference Method) in the new computational space leads to an eigenvalues problem resolved using specialized LAPACK’s routines. The influence of the parameters introduced in the mathematical function, is studied on the energy levels of electrons and holes as well as the oscillator strengths.     

Compounds with π(loc) → π*(deloc) electronic transitions and their solvatochromism

Molecular structures possessing atomic sites that contribute a non‐bonding electron pair to their π system (e.g. nitrogen atoms with sp² hybridization in pyrroles and anilines) usually exhibit a first absorption band whose solvatochromism is, surprisingly, sensitive only to the polarizability of the medium even though they are dipolar. As shown here, this solvatochromic behavior is a result of the first electronic transition in these compounds occurring from a substantially localized π orbital to a substantially delocalized π* orbital in the molecular structure. The high electronic delocalization present leads to a marked bathochromic band shift as the polarizability of the medium increases. It is especially relevant that this solvatochromism, which is because of the polarizability of the medium, explains the spectral shift that is only because of the redistribution of the electrons of the solvent molecules. It is important to take into account that this electronic redistribution happens instantaneously in this process. Copyright © 2015 John Wiley & Sons, Ltd.