Spectromicroscopic determinations of chemical environments of Ni in MoS2-Ag-Ni ternary systems

Using heterogeneous photocatalysts for harvesting sunlight and converting it for water remediation and splitting are promising to mitigate the possible crisis of environment and energy. Among various composites, the MoS₂-based heterostructures and Ni-based systems exhibit unique electronic, optical properties and redox capabilities, enabling their roles as photocatalysts. Herein, the impacts of chemical environments on the Ni electronic structures within the MoS₂-Ag-Ni ternary systems are studied via X-ray photoemission electron spectroscopy (X-PEEM). Ni nanoparticles with two different sizes of 70 and 200 nm were loaded to MoS₂ flakes with silver buffers as bridges. Heterostructures with a nominal mol percentage of (MoS₂)₇₇Ag_3.7Ni_19.3 were synthesized through an ultrasound-assisted wet method. The oxidation states and various interfacial interactions of Ni with MoS₂ in MoS₂-Ag-Ni ternary composite are spectromicroscopically determined, combining the X-ray absorption spectroscopy near Ni L-edges and the imaging capability of the X-PEEM. Results showed that Ni mainly retrains its chemical states of metal and native oxidizations without observable electronic features subjected to bonding with the sulfur from the MoS₂ flakes. The charge migration channel set up by the Ag buffer thus contributes to electron–hole migrations that facilitate the photocatalytic performance of the ternary system eventually.     

Unexpected Efficiency of a Luminescent Samarium(III) Complex for Combined Visible and Near‐Infrared Biphotonic Microscopy

An original samarium(III) complex based on a triazacyclononane platform functionalized with a charge‐transfer antenna chromophore exhibited optimized brightness and was successfully used as an emissive species for two‐photon microscopy experiments in both the visible and near‐infrared spectral ranges.     

Copper(I)‐Catalyzed Amination of Halogenopyridines with Polyamines

Cu^I‐Catalyzed amination of 2‐bromo‐, and 2‐, 3‐, and 4‐iodopyridines with tri‐ and tetraamines aimed at the synthesis of N,N′‐diheteroaryl derivatives was studied. A strong dependence of the product yields on the nature of starting compounds and the ligand used was observed. The increase in the number of ethene‐1,2‐diamine fragments in the polyamine structure led to the increase in the yields of polyheteroarylated compounds, whereas propane‐1,3‐diamine fragments favored the formation of monopyridinyl derivatives and promoted the heteroarylation of the secondary amino groups. 2‐Iodopyridine, as a more reactive compound, readily formed N,N‐diarylated products. The best yields of the target N,N′‐dipyridin‐2‐yl derivatives were 76% in the case of the triamine and 68% in the case of the tetraamine. A comparison of Cu^I‐ and Pd⁰‐mediated heteroarylation of polyamines was also presented.     

The images of Lie polynomials evaluated on matrices

Kaplansky asked about the possible images of a polynomial f in several noncommuting variables. In this paper, we consider the case of f a Lie polynomial. We describe all the possible images of f in M₂(K) and provide an example of f whose image is the set of non-nilpotent trace zero matrices, together with 0. We provide an arithmetic criterion for this case. We also show that the standard polynomial s_k is not a Lie polynomial, for k>2.     

Thin films of the composition 8% Y<Subscript>2</Subscript>O<Subscript>3</Subscript>–92% ZrO<Subscript>2</Subscript> (8YSZ) as gas-sensing materials for oxygen detection

The synthesis of hydrolytically active heteroligand precursors of the composition [M(O₂C₅H₇) _x ( ⁱ OC₅H₁₁) _y ] (M = Zr⁴⁺ and Y³⁺) using zirconium and yttrium acetylacetonates was investigated. It was shown that the reactivity of the obtained precursors in hydrolysis and polycondensation depends on the composition of the coordination sphere. It was studied how thin films of their solutions are applied by dip coating to the surface of Al₂O₃ substrates with platinum interdigital electrodes and a microheater. A study was made of the effect of the crystallization conditions and thickness of the oxide coatings of the composition 8 mol % Y₂O₃–ZrO₂ on their microstructure and sensor characteristics in oxygen detection.     

Reduction of the Search Space for the Folding of Proteins at the Level of Formation and Assembly of Secondary Structures: A New View on the Solution of Levinthal′s Paradox

The complete volume of the protein conformation space is, by many orders of magnitude, smaller at the level of secondary structure elements than that at the level of amino acid residues; the latter, according to Levinthal′s estimate, scales approximately as 10^{2 L}, with L being the number of residues in the chain, whereas the former, as demonstrated in this paper, scales no faster than ～L^N, with N being the number of the secondary structure elements, which is approximately equal to L/15. This drastic decrease in the exponent (L/15 instead of 2 L) explains why sampling of the conformation space does not contradict the ability of the protein chain to find its most stable fold.     

Rheological properties of nonfunctional derivatives of hyperbranched polycarbosilanes

The rheological properties of melts of nonfunctional hyperbranched polycarbosilane polymers differed in regularity of the structure and chain length between the branch points were studied for the first time. Unlike melts of linear polymers, the studied hyperbranched systems are Newtonian fluids, and the viscosity and activation energy of their viscous flow depend substantially on the molecular parameters and regularity of the molecular structure.     

Increasing entanglement between Gaussian states by coherent photon subtraction

We experimentally demonstrate that the entanglement between Gaussian entangled states can be increased by non-Gaussian operations. Coherent subtraction of single photons from Gaussian quadrature-entangled light pulses, created by a nondegenerate parametric amplifier, produces delocalized states with negative Wigner functions and complex structures more entangled than the initial states in terms of negativity. The experimental results are in very good agreement with the theoretical predictions.