Phosphorene Supported Single-Atom Catalysts for CO Oxidation: A Computational Study

Single-atom catalysts (SACs) have attracted extensive attention owing to their high catalytic activity. The development of efficient SACs is crucial for applications in heterogeneous catalysis. In this article, the geometric configuration, electronic structure, stabilitiy and catalytic performance of phosphorene (Pn) supported single metal atoms (M=Ru, Rh, Pd, Ir, Pt, and Au) have been systematically investigated using density functional theory calculations and ab initio molecular dynamics simulations. The single atoms are found to occupy the hollow site of phosphorene. Among the catalysts studied, Ru-decorated phosphorene is determined to be a potential catalyst by evaluating adsorption energies of gaseous molecules. Various mechanisms including the Eley-Rideal (ER), Langmuir-Hinshelwood (LH) and trimolecular Eley-Rideal (TER) mechanisms are considered to validate the most favourable reaction pathway. Our results reveal that Ru−Pn exhibits outstanding catalytic activity toward CO oxidation reaction via TER mechanism with the corresponding rate-determining energy barrier of 0.44 eV, making it a very promising SAC for CO oxidation under mild conditions. Overall, this work may provide a new avenue for the design and fabrication of two-dimensional materials supported SACs for low-temperature CO oxidation.     

Spatiotemporal dynamics of a predator-prey model incorporating a prey refuge

In this paper, we investigate the spatiotemporal dynamics of a ratio-dependent predator-prey model with cross diffusion incorporating proportion of prey refuge. First we get the critical lines of Hopf and Turing bifurcations in a spatial domain by using mathematical theory. More specifically, the exact Turing region is given in a two parameter space. Also we perform a series of numerical simulations. The obtained results reveal that this system has rich dynamics, such as spotted, stripe and labyrinth patterns which show that it is useful to use the predator-prey model to reveal the spatial dynamics in the real world.     

Stability and Hopf bifurcation of a diffusive predator‐prey model with hyperbolic mortality

The dynamics of a reaction‐diffusion predator‐prey model with hyperbolic mortality and Holling type II response effect is considered. The stability of the positive equilibrium and the existence of Hopf bifurcation are investigated by analyzing the distribution of eigenvalues without diffusion. We also study the spatially homogeneous and nonhomogeneous periodic solutions through all parameters of the system which are spatially homogeneous. To verify our theoretical results, some numerical simulations are also presented. © 2015 Wiley Periodicals, Inc. Complexity 21: 34–43, 2016     

Antitumour and antioxidant activity of Scutia myrtina against Ehrlich ascites carcinoma in Swiss albino mice

The aim of this study is to investigate the antitumour and antioxidant activities of the ethanol extract of Scutia myrtina (EESM) against Ehrlich's ascites carcinoma (EAC) in mice. Twenty-four hours after tumour inoculation, EESM was administered at doses 100, 200 and 300?mg?kg?1 bodyweight/mice/day for 21 days. EESM caused a significant (p?相似文献   

Construction of frustrated Lewis pair from nitride and phosphine for the activation and cleavage of molecular hydrogen

Activation and cleavage of molecular hydrogen (H₂) to proton and hydride is an important task for several reasons, especially as a reagent in hydrogenation. In this scenario, with the support of density-functional theory methods, a novel strategy has been devised for the conversion of coordinated nitride into ammonia using molecular hydrogen in the presence of tri-tert-butylphosphine (P^tBu₃). The proposed methodology is based on the formation of frustrated Lewis pair (FLP) from [Os^VI(tpy)(Cl)₂(N)]⁺ (tpy = 2,2′:6′,2′′-terpyridine ) and P^tBu₃ followed by reaction with molecular hydrogen to form an FLP–H₂ adduct. The FLP–H₂ adduct can further undergo H–H bond cleavage heterolytically to produce proton and hydride which can be eventually used for the functionalization of coordinated nitride to ammonia. The calculated energy profile comprising all possible intermediates and transition-state molecules suggests that the proposed reaction pathway is energetically viable at elevated temperatures.     

Hydroxylamine synthesis by oxygen insertion into ReNH2 bond via Baeyer–Villiger oxidation: a Theoretical study

A novel scheme has been proposed by computational methods (B3LYP and CCSD(T)) to produce hydroxylamine under normal experimental conditions using [O₃Re‐(NH₂)] and H₂O₂ under basic conditions. This particular reaction may proceed similar to Baeyer–Villiger oxidation and μ‐peroxo type pathways to insert oxygen into the Re?NH₂ bond to yield NH₂OH; nevertheless, Baeyer–Villiger type oxidation is seems to be more viable. The calculated energy barriers further revealed that the introduction of different solvent medium does not affect significantly the energies of intermediates and transition state molecules. The calculated Gibbs free energies show that this reaction is perhaps viable experimentally to produce NH₂OH from the our choice of reagents. Copyright © 2015 John Wiley & Sons, Ltd.     

Understanding the stability, electronic and molecular structure of some copper(III) complexes containing alkyl and non alkyl ligands: Insights from DFT calculations

DFT calculations have been performed for some Cu(III)-alkyl complexes. Complexes 1-19 were optimized to the square planar (sq) geometry and observed no imaginary frequencies. Although formally copper adopts d⁸ configuration (Cu(III)) in all the complexes, the Natural Population Analysis (NPA) revealed that the copper actually in d¹⁰ (Cu(I)) configuration, Bond order calculation suggested that the Cu(III)-Et_trans bond gets more bond order in the presence of poor π-acidic co-ligand (probe ligand). Relatively smaller bond order was calculated for Cu(III)-Me_cis bond than Cu(III)-Et_trans bond and therefore Cu(III)-Et_trans bond is the strongest bond in all the complexes. Calculated less Chemical hardness (η) of complexes 1-19 suggested that all these complexes are less stable in nature. Energy Decomposition Analysis (EDA) revealed that the Cu(III)-Et_trans bond is relatively more stable than the Cu(III)-Me_cis and Cu(III)-L (L = co-ligand/probe ligand) bonds. And also the Cu(III)-alkyl (Cu(III)-Me_cis and Cu(III)-Et_trans) bond in complexes 1-17 is more of ionic in nature. However, Cu(III)-Et_trans bond is relatively more ionic than Cu(III)-Me_cis bond.     

Colorimetric sensing of fluoride ion by new expanded calix[4]pyrrole through anion-π interaction

Three new expanded calix[4]pyrroles were synthesized, where the two dialkylldipyrromethane units are linked via C-C double bonds. One of them, calix[2]bispyrrolylethene, colorimetrically senses fluoride ion only, owing to anion-π interaction in polar aprotic solvents.     

Bifurcations in a diffusive predator–prey model with predator saturation and competition response

A diffusive predator–prey model with predator saturation and competition response subject to homogeneous Neumann boundary conditions is considered in this paper. We find that the spatially homogeneous and non‐homogeneous periodic solutions through all parameters of the system are spatially homogeneous. To verify our theoretical results, some numerical simulations are also carried out. Copyright © 2014 John Wiley & Sons, Ltd.     

Stability and Hopf bifurcation of a diffusive predator–prey model with predator saturation and competition

This article discusses a predator–prey system with predator saturation and competition functional response. The local stability, existence of a Hopf bifurcation at the coexistence equilibrium and stability of bifurcating periodic solutions are obtained in the absence of diffusion. Further, we discuss the diffusion-driven instability, Hopf bifurcation for corresponding diffusion system with zero flux boundary condition and Turing instability region regarding the parameters are established. Finally, numerical simulations supporting the theoretical analysis are also included.