Interplay and competition between the lithium bonding and halogen bonding: R3C···XCN···LiCN and R3C···LiCN···XCN as a working model (R = H,CH3; X = Cl,Br)

UMP2 calculations with aug-cc-pVDZ basis set were used to analyse intermolecular interactions in R₃C···XCN···LiCN and R₃C···LiCN···XCN triads (R = H, CH₃; X = Cl, Br) which are connected via lithium bond and halogen bond. To understand the properties of the systems better, the corresponding dyads are also studied. Molecular geometries and binding energies of dyads, and triads are investigated at the UMP2/aug-cc-pVDZ computational level. Particular attention is paid to parameters such as cooperative energies, and many-body interaction energies. All studied complexes, with the simultaneous presence of a lithium bond and a halogen bond, show cooperativity with energy values ranging between ?1.20 and ?7.71 kJ mol^?1. A linear correlation was found between the interaction energies and magnitude of the product of most positive and negative electrostatic potentials (V_S,maxV_S,min). The electronic properties of the complexes are analysed using parameters derived from the atoms in molecules (AIM) methodology. According to energy decomposition analysis, it is revealed that the electrostatic interactions are the major source of the attraction in the title complexes.     

Synthesis, spectral characterization, and crystal structure of mononuclear mercury(II) complex [Hg((3,4-MeO-Bza)2En)I2]

Mercury(II) complex, [Hg((3,4-MeO-Bza)₂En)I₂] (I), where (3,4-MeO-Bza)₂En = N,N′-bis(3,4-dimethoxybenzaldehyde)ethylenediimine, has been synthesized from the reaction of HgI₂ with (3,4-MeO-Bza)₂En in methanol as solvent at 50°C. It was characterized by elemental analysis (CHN), ¹H-NMR spectroscopy and confirmed by single-crystal X-ray diffraction analysis. The complex I crystallizes in the monoclinic system, with space group P2₁/c, having one symmetry-independent Hg²⁺ ion coordinated in a distorted tetrahedral geometry by two N atoms of the Schiff base ligand and by two I atoms. The Schiff base ligand (3,4-MeO-Bza)₂En acts as a chelating ligand and coordinates via two N atoms to the mercury center. It adopts an (E, E) conformation.     

Surfactant-Free Fabrication of Copper Sulfides (CuS, Cu2S) via Hydrothermal Method

Copper sulfide nanoparticles have been synthesized from copper salicylate and thioglycolic acid by a hydrothermal method. The obtained product was analyzed by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and photoluminescence spectroscopy. The effect of reaction time, temperature, solvent and sulfur sources was investigated.     

Enlargement of absolute photonic band gap in modified 2D anisotropic annular photonic crystals

We analyze the absolute photonic band gap in two dimensional (2D) square, triangular and honeycomb lattices composed of air holes or rings with different geometrical shapes and orientations in anisotropic tellurium background. Using the numerical plane wave expansion method, we engineer the absolute photonic band gap in modified lattices, achieved by addition of circular, elliptical, rectangular, square and hexagonal air hole or ring into the center of each lattice unit cell. We discuss the maximization of absolute photonic band gap width as a function of main and additional air hole or ring parameters with different shapes and orientation.     

Controlled Electrodeposition of Au‐Copper Oxide Nanocomposite on a Renewable Carbon Ceramic Electrode for Sensitive Determination of NADH in Serum Samples

In this study, a sensitive nicotinamide adenine dinucleotide (NADH) biosensor based on Au‐Copper oxide nanocomposite modified carbon ceramic electrode (Au?CuO/CCE) was introduced. The developed NADH biosensor was prepared by controlled electrodeposition of copper and Au nanoparticles on the surface of a renewable CCE and was turned to Au?CuO/CCE by cycling the potential in alkaline media. The prepared electrode was carefully characterized with scanning electron microscopy, X‐ray diffraction, atomic force microscopy and cyclic voltammetry techniques. According to scan rate study, surface coverage (Γ) of the fabricated Au?CuO/CCE was calculated to be 1.54×10^?8 mol cm^?2 which was 3 time more than CuO/CCE. The fabricated electrode is well stable which could be reliably utilized for the determination of NADH with amperometry technique over the concentration range of 1–29 μM with sensitivity and detection limit (S/N=3) of 0.1025 μA μM^?1 and 0.09 μM respectively. The prepared biosensor was used for NADH determination in serum samples with fast response time and satisfactory analytical results.     

Preparation of electrospun shape memory polyurethane fibers in optimized electrospinning conditions via response surface methodology

Herein, the electrospinning method, as an effective approach, was utilized to fabricate poly (ε‐caprolactone)‐based polyurethane (PCL‐based PU) fibers. PCL was synthesized by ring‐opening polymerization, and characterized by proton nuclear magnetic resonance (¹H NMR) and Fourier‐transform infrared (FTIR) spectroscopies. Afterward, PU was prepared by step‐growth polymerization. The effects of solution concentration and solvent type on fibers' diameter were investigated. Scanning electron microscopy (SEM) images revealed that the optimum solution was N, N‐dimethylformamide(DMF): chloroform with a ratio of 60:40. In addition, results showed that bead‐less nanofibers could be achieved by a concentration of 5 w/v% (polymer to solvent). Various optimum practical parameters, such as applied voltage, feeding rate, and needle‐to‐collector distance, were obtained and compared with the results of response surface methodology (RSM). On the other hand, the mechanical evaluations indicated that the porous structure of scaffolds caused them to possess lower mechanical properties, as well as shape fixity ratios than those of bulk samples.     

Effects of graphene quantum dot (GQD) on photoluminescence,mechanical, thermal and shape memory properties of thermoplastic polyurethane nanocomposites

A group of shape memory polyurethane‐based nanocomposites containing graphene quantum dot nanoparticles (GQDs) were prepared via in‐situ polymerization method. GQD nanoparticles were synthesized by a facile and rapid microwave‐assisted method and characterized by Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction pattern, field emission scanning microscopy, transmission electron microscopy, and fluorescence analysis. Chemical structure and hydrogen bonding index (HBI_[C=O]) of the nanocomposites were analyzed via FTIR spectra. The results show that the incorporation of GQDs in PU matrix reduces HBI_(C=O) of nanocomposites. Crystalline structure and thermal properties of the nanocomposites were investigated by differential scanning calorimetry. As results indicate, nucleation effect of GQDs raises crystallinity content of the samples. Mechanical examinations indicate that incorporation of GQDs improves Young's modulus of the nanocomposites, while their elongation at break values are reduced. In addition, shape memory analyses reveal that the presence of GQDs in PU matrix increases the shape fixity ratios in nanocomposites.     

Urchin-like double-shelled Pd–PdO/ZnO hollow sphere as an efficient catalyst for the Suzuki-Miyaura reaction

In recent years, the modi?cation of metal oxides with noble metals to decrease the loading amount of expense of noble metal catalyst and amend the stability of nanocatalyst in chemical reactions has attracted signi?cant attention. Here in this study, the urchin-like double-shelled Pd–PdO/ZnO hollow sphere is successfully prepared by using a simple hydrothermal method and carbon sphere as a hard template. The structure of the catalyst was confirmed by using field-emission scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, energy-dispersive X-ray spectroscope, and BET. The total amount of palladium particles on ZnO was determined by induced coupled plasma analysis. The prepared catalyst gave high catalytic activity for the Suzuki reaction of aryl halides to afford biphenyls under milder conditions. Furthermore, the stability and reusability of catalyst were investigated, and all of the data proved that urchin-like double-shelled Pd–PdO/ZnO hollow sphere could be recycled five times without marked loss of activity.