Role Of Metal Centers Research Articles

In-situ growth of metal-organophosphorus nanosheet/nanorod on graphene for enhancing flame retardancy and mechanical properties of epoxy resin

Metal phenylphosphonate (MPhP)/piperazine-reduced graphene oxide (PGO) nanomaterials with different metal centers (M = Ce, Al, Co, Zn) were facilely synthesized. We found that the morphology of metal-organophosphorus was controlled by the coordinated metal centers, trivalent metal-organophosphorus exhibited nanosheet morphology, while divalent metal-organophosphorus displayed nanorod morphology. In addition, the role of metal centers on the flame safety and mechanical performance of epoxy resin (EP) were studied. The limiting oxygen index values of EP composites with only 3 wt% of additive were increased in different levels (the CePhP-PGO/EP was increased most, up from 24.5% to 34.5%), and the MPhP-PGO/EP composites all pass UL-94 V-0 rating, which was owing to the multi-coordinating effect (physical shield of GO, the catalytic of metal and gas-phase effect of P-containing radicals). Specifically, we verified that P element of MPhP-PGO (M = Ce, Al) could act on both condensed and gas phase, while MPhP-PGO (M = Co, Zn) only acted in the condensed-phase, thus MPhP-PGO/EP (M = Ce, Al) showed better enhancing effect on flame retardancy of EP. Beyond that, MPhP-PGO/EP (M = Co, Zn) displayed more excellent mechanical properties, is due to MPhP (M = Co, Zn) (nanorod) which had good reinforcement effect to EP matrix.

Trimetallic nanocatalysts to enhanced hydrogen production from hydrous hydrazine: The role of metal centers

A simple low-cost cetyltrimethylammonium bromide (CTAB) assisted step-wise metal displacement plating method was used to prepare noble-and noble-metal free Ni/Fe/Pd, Ni/Fe/Ag and Ni/Fe/Cu nickel based nanocatalysts for the hydrogen production from complete hydrazine decomposition in basic solution at mild temperature. Pd/Ag/Ni was prepared by seedless method. Compared to the mono-metallic (Ag0, Pd0, Fe0, Ni0 and Cu0) and bi-metallic (Pd/Ag, Ag/Ni and Ni/Fe), the tri-metallic catalyst exhibits higher catalytic performance towards hydrazine decomposition. The nessler's reagent was used to detect the formation of ammonia during hydrazine dehydrogenation. The effect of [catalyst], [hydrazine], [NaOH] and temperature were determined on hydrogen generation by using Ni/Fe/Pd. The generation of hydrogen follows excellent first-order kinetics with [hydrazine]. The activation energies were determined to be 32.1, 42.3, 44.6 and 75.9 kJ/mol for Ni/Fe/Pd, Ni/Fe/Ag, Ni/Fe/Cu and Pd/Ag/Ni, respectively. Noble-metal nickel based Ni/Fe/Pd nanocatalyst shows better catalytic efficiency and hydrogen selectivity. The durability of Ni/Fe/Pd provides evidence to excellent catalytic degree for five kinetic runs. The morphology of Ni/Fe/Pd was determined by using FESEM, EDX, TEM, XRD and UV–visible spectroscope. Hydrazine dehydrogenation mechanism proposed, which follows the following rate-law:−d[hydrazine]dt=k1KadOH−]Ni@Fe@Pd][NH2−NH2]T1+Kb[OH−]+Kad[NH2−NH2]T

Role of Metal Centers in Tuning the Electronic Properties of Graphene-Based Conductive Interfaces

Role of Metal Centers in Tuning the Electronic Properties of Graphene-Based Conductive Interfaces

Metal-organic frameworks for electrochemical reduction of carbon dioxide: The role of metal centers

Abstract Direct electrochemical reduction of CO2 into valuable chemicals and fuel is one of the most promising approaches to address the current energy crisis and lower CO2 emission. Recently, numerous metal-organic framework (MOF) and their derived materials have extensively been developed as electrocatalysts for CO2 reduction owing to their unique structure including porosity, large specific surface area, and tunable chemical structures. In this review, the recent progress of MOF-based electrocatalysts for CO2 reduction was summarized and discussed. Detailed discussions mainly focus on the synthesis and mechanism of pristine MOFs and MOF-derived materials for electrocatalytic CO2 reduction. These examples are expected to provide clues to rational design and synthesis of stable and high-performance MOFs-based electrocatalysts for CO2 reduction.

Role of Metal Centers in Tuning the Electronic Properties of Graphene-Based Conductive Interfaces

A major bottleneck in the fabrication of efficient bio-organic nanoelectronic devices resides in the strong charge recombination that is present at the different interfaces forming the complex system. An efficient way to overcome this bottleneck is to add a self-assembled monolayer (SAM) of molecules between the biological material and the electrode that promotes an efficient direct electron transfer whilst minimising wasteful processes of charge recombination. In this work, the presence of a pyrene-nitrilotriacetic acid layer carrying different metal centers as SAM physisorbed on graphene is fully described by mean of electrochemical analysis, field emission scanning electron microscopy, photoelectrochemical characterisation and theoretical calculations. Our multidisciplinary study reveals that the metal center holds the key role for the efficient electron transfer at the interface. While Ni2+ is responsible for an electron transfer from SAM to graphene, Co2+ and Cu2+ force an opposite transfer, from graphene to SAM. Moreover, since Cu2+ inhibits the electron transfer due to a strong charge recombination, Co2+ seems the transition metal of choice for the efficient electron transfer.

ChemInform Abstract: The Role of Metal Centers in Reduction and Carboxylation Reactions Utilizing Carbon Dioxide

ChemInform Abstract: The Role of Metal Centers in Reduction and Carboxylation Reactions Utilizing Carbon Dioxide

Electronic structure and optical properties of germanium-bridged platinum(II)-containing diethynylfluorene monomer and oligomers: A theoretical investigation

We apply quantum-chemical techniques to investigate the structural, electronic, and optical properties of some platinum-containing fluorenyleneethynylenegermylene-derived monomers and oligomers. The aim of our quantum-chemical calculations is to investigate the role of the transition metal centers in the organometallic system in terms of electronic structure and to estimate the influence of metal on the optical properties of the monomer and oligomers. The results indicate that there is a weak electronic interaction between the metal-based fragment and the π-conjugated organic segments, and consequently the photophysical properties are mainly based on the fluorenyleneethynylene (TFT) π-conjugated fragment with little contribution from the metal center. The role of metal center can be described as weak delocalization coupled with strong localization characteristic along the organometallic backbone. The introduction of platinum ions into the π-conjugated structure leads to bathochromic shifts in the absorption features as compared to those for the free ligands.

Theoretical Study on the Electronic Structure and Optical Properties of Mercury-Containing Diethynylfluorene Monomer, Oligomer, and Polymer

We present a first-principles study of the structural, electronic, and optical properties on mercury-containing diethynylfluorene monomer, oligomer, and polymer. The aim of our quantum-chemical calculations is to shed light on the role of the transition metal centers in the organometallic system in terms of electronic structure and to estimate the influence of metal on the optical properties of the mercury polyyne polymer as well as the nature of luminescence in the polymer. The results indicate that there is a weak electronic interaction between the metal-based fragment and the π-conjugated organic segments, and consequently the photophysical properties are mainly based on the diethynylfluorene π-conjugated fragment (TFT) with little contribution from the metal center. The role of the metal center can be described as weak delocalization coupled with strong localization characteristics along the organometallic polymer backbone. The lowest singlet and triplet excited state have been studied by the singles ...