Identifying signatures of thermal and non-thermal reaction pathways in plasmon induced H2 + D2 exchange reaction

In this work we demonstrate a strategy for identifying experimental signatures of thermal and non-thermal effects in plasmon mediated heterogeneous catalytic chemistry, a topic widely debated and discussed in the literature. Our method is based on monitoring the progress of plasmon-induced (or thermally-driven) reaction, carried out in a closed system, all the way to equilibrium. Initial part of evolution of the reaction provides information about kinetics, whereas at later times the equilibrium concentrations provide information about effective temperature at the reaction sites. Combining these two pieces of information we estimate the activation energies. Using this strategy on H 2 (g) + D 2 (g) <-->2 HD(g) isotope exchange reaction, catalyzed by Au nanoparticles under thermally-driven and light-induced conditions, we estimate the activation energies to be 0.75 ± 0.02 eV and 0.21 ± 0.02 eV, respectively. These vastly different activation energies observed are interpreted as a signature of different reaction pathways followed by the system under thermally-driven and light-induced conditions.

Identifying signatures of thermal and non-thermal reaction pathways in plasmon induced H2 + D2 exchange reaction

In this work we demonstrate a strategy for identifying experimental signatures of thermal and non-thermal effects in plasmon mediated heterogeneous catalytic chemistry, a topic widely debated and discussed in the literature. Our method is based on monitoring the progress of plasmon induced (or thermally driven) reaction, carried out in a closed system, all the way to equilibrium. Initial part of evolution of the reaction provides information about kinetics, where as at later times the equilibrium concentrations provide information about effective temperature at the reaction sites. Combining these two pieces of information we estimate the activation energies. Using this strategy on H2 (g) + D2 (g) <--> 2 HD(g) isotope exchange reaction, catalyzed by Au nanoparticles under thermally driven and light induced conditions, we estimate the activation energies to be 0.75 ± 0.02 and 0.21 ± 0.02, respectively. These vastly different activation energies observed are interpreted as signatures of different reaction pathways followed by the system under thermally driven and light induced conditions.

Microkinetic Modeling of CO2 and H2O Electrolysis on Ni in a Solid Oxide Electrolysis Cell: A Critical Evaluation

Solid oxide cells (SOC) are ideal candidates for the electrochemical conversion of H2O and CO2 into H2 and CO using renewable sources. This work develops different electrochemical models for the reduction of H2O and CO2 based on elementary step kinetics and discriminates them based on their ability to predict experimentally measured cell performances. The thermo-catalytic chemistry is represented using a micro kinetic model, which is coupled to the electrochemical model through the surface coverage terms. A one dimensional representation of SOC resolving the cell across the thickness of the electrodes is used for simulations. The source terms for the species transport equations are calculated using the micro kinetic model by applying mean field approximation. The discussion in the paper covers aspects related to parameter fitting, model development, solution methodology, model discrimination and identification of rate limiting step.

Asymmetric biomimetic transamination of α-keto amides to peptides

Peptides are important compounds with broad applications in many areas. Asymmetric transamination of α-keto amides can provide an efficient strategy to synthesize peptides, however, the process has not been well developed yet and still remains a great challenge in both enzymatic and catalytic chemistry. For biological transamination, the high activity is attributed to manifold structural and electronic factors of transaminases. Based on the concept of multiple imitation of transaminases, here we report N-quaternized axially chiral pyridoxamines 1 for enantioselective transamination of α-keto amides, to produce various peptides in good yields with excellent enantio- and diastereoselectivities. The reaction is especially attractive for the synthesis of peptides made of unnatural amino acids since it doesn’t need great efforts to make chiral unnatural amino acids before amide bond formation.

Future directions of catalytic chemistry

The philosophy of sustainable development is prevailing worldwide, and will probably bring about a society revolution trend in the future. Catalytic chemistry will play a crucial role in sustainable economic development since at least a catalytic process is involved in almost all-important areas of chemical industry, such as synthesis of chemicals and materials, energy production and conversion as well as pollution abatement and environmental protection. In this paper, we attempt to summarize three common critical directions for catalysis research, in order to meet future needs for sustainable economic development. (i) The discovery of high-performance catalysts will evolve from trial-and-error to rational design. This is due to the maturing theory-experiment joint research schemes and the increasing abilities to explore dynamic nature of catalysts under reaction conditions. (ii) The catalysis for the transition of energy and chemicals generation from oil and coal to more renewable sources will be highly pursued. (iii) The catalysis for cleaner chemical processes will be another active research direction. In Sections “Sustainable catalysis for renewable fuels and chemicals” and “Ecologically clean catalytic process”, some important examples are discussed especially.

A Computational Study of the Properties of Pd, Cu and Zn Surfaces

<p>We report a detailed Density Functional Theory (DFT) based investigation of the structure and stability of bulk and surface structures for the Group 10-12 elements Pd, Cu and Zn, considering the effect of the choice of exchange-correlation density functionals and computation parameters. For the initial bulk structures, the lattice parameter and cohesive energy are calculated, which are then augmented by calculation of surface energies and work functions for the lower-index surfaces. Of the 22 density functionals considered, we highlight the mBEEF density functional as providing the best overall agreement with experimental data. The optimal density functional choice is applied to the study of higher index surfaces for the three metals, and Wulff constructions performed for nanoparticles with a radius of 11nm, commensurate with nanoparticle sizes commonly employed in catalytic chemistry. For Pd and Cu, the low-index (111) facet is dominant in the constructed nanoparticles, covering ~50% of the surface, with (100) facets covering a further 10 to 25%; however, non-negligible coverage from higher index (332), (332) and (210) facets are also observed for Pd, and (322), (221) and (210) surfaces are observed for Cu. In contrast, only the (0001) and (10-10) facets are observed for Zn. Overall, our results highlight the need for carefully validation of computational settings before performing extensive density functional theory investigations of surface properties and nanoparticle structures of metals.</p>

A Computational Study of the Properties of Pd, Cu and Zn Surfaces

<p>We report a detailed Density Functional Theory (DFT) based investigation of the structure and stability of bulk and surface structures for the Group 10-12 elements Pd, Cu and Zn, considering the effect of the choice of exchange-correlation density functionals and computation parameters. For the initial bulk structures, the lattice parameter and cohesive energy are calculated, which are then augmented by calculation of surface energies and work functions for the lower-index surfaces. Of the 22 density functionals considered, we highlight the mBEEF density functional as providing the best overall agreement with experimental data. The optimal density functional choice is applied to the study of higher index surfaces for the three metals, and Wulff constructions performed for nanoparticles with a radius of 11nm, commensurate with nanoparticle sizes commonly employed in catalytic chemistry. For Pd and Cu, the low-index (111) facet is dominant in the constructed nanoparticles, covering ~50% of the surface, with (100) facets covering a further 10 to 25%; however, non-negligible coverage from higher index (332), (332) and (210) facets are also observed for Pd, and (322), (221) and (210) surfaces are observed for Cu. In contrast, only the (0001) and (10-10) facets are observed for Zn. Overall, our results highlight the need for carefully validation of computational settings before performing extensive density functional theory investigations of surface properties and nanoparticle structures of metals.</p>

A Computational Study of the Properties of Pd, Cu and Zn Surface

<p>We report a detailed Density Functional Theory (DFT) based investigation of the structure and stability of bulk and surface structures for the Group 10-12 elements Pd, Cu and Zn, considering the effect of the choice of exchange-correlation density functionals and computation parameters. For the initial bulk structures, the lattice parameter and cohesive energy are calculated, which are then augmented by calculation of surface energies and work functions for the lower-index surfaces. Of the 22 density functionals considered, we highlight the mBEEF density functional as providing the best overall agreement with experimental data. The optimal density functional choice is applied to the study of higher index surfaces for the three metals, and Wulff constructions performed for nanoparticles with a radius of 11nm, commensurate with nanoparticle sizes commonly employed in catalytic chemistry. For Pd and Cu, the low-index (111) facet is dominant in the constructed nanoparticles, covering ~50% of the surface, with (100) facets covering a further 10 to 25%; however, non-negligible coverage from higher index (332), (332) and (210) facets are also observed for Pd, and (322), (221) and (210) surfaces are observed for Cu. In contrast, only the (0001) and (10-10) facets are observed for Zn. Overall, our results highlight the need for carefully validation of computational settings before performing extensive density functional theory investigations of surface properties and nanoparticle structures of metals.</p>

Silver (I) N-Heterocyclic Carbene Complexes: A Winning and Broad Spectrum of Antimicrobial Properties

The evolution of antibacterial resistance has arisen as the main downside in fighting bacterial infections pushing researchers to develop novel, more potent and multimodal alternative drugs.Silver and its complexes have long been used as antimicrobial agents in medicine due to the lack of silver resistance and the effectiveness at low concentration as well as to their low toxicities compared to the most commonly used antibiotics. N-Heterocyclic Carbenes (NHCs) have been extensively employed to coordinate transition metals mainly for catalytic chemistry. However, more recently, NHC ligands have been applied as carrier molecules for metals in anticancer applications. In the present study we selected from literature two NHC-carbene based on acridinescaffoldand detailed nonclassicalpyrazole derived mono NHC-Ag neutral and bis NHC-Ag cationic complexes. Their inhibitor effect on bacterial strains Gram-negative and positivewas evaluated. Imidazolium NHC silver complex containing the acridine chromophore showed effectiveness at extremely low MIC values. Although pyrazole NHC silver complexes are less active than the acridine NHC-silver, they represent the first example of this class of compounds with antimicrobial properties. Moreover all complexesare not toxic and they show not significant activity againstmammalian cells (Hek lines) after 4 and 24 h. Based on our experimental evidence, we are confident that this promising class of complexes could represent a valuable starting point for developing candidates for the treatment of bacterial infections, delivering great effectiveness and avoiding the development of resistance mechanisms.