Doping with Graphitic Nitrogen Triggers Ferromagnetism in Graphene

Nitrogen doping opens possibilities for tailoring the electronic properties and band gap of graphene toward its applications, e.g., in spintronics and optoelectronics. One major obstacle is development of magnetically active N-doped graphene with spin-polarized conductive behavior. However, the effect of nitrogen on the magnetic properties of graphene has so far only been addressed theoretically, and triggering of magnetism through N-doping has not yet been proved experimentally, except for systems containing a high amount of oxygen and thus decreased conductivity. Here, we report the first example of ferromagnetic graphene achieved by controlled doping with graphitic, pyridinic, and chemisorbed nitrogen. The magnetic properties were found to depend strongly on both the nitrogen concentration and type of structural N-motifs generated in the host lattice. Graphenes doped below 5 at. % of nitrogen were nonmagnetic; however, once doped at 5.1 at. % of nitrogen, N-doped graphene exhibited transition to a ferromagnetic state at ∼69 K and displayed a saturation magnetization reaching 1.09 emu/g. Theoretical calculations were used to elucidate the effects of individual chemical forms of nitrogen on magnetic properties. Results showed that magnetic effects were triggered by graphitic nitrogen, whereas pyridinic and chemisorbed nitrogen contributed much less to the overall ferromagnetic ground state. Calculations further proved the existence of exchange coupling among the paramagnetic centers mediated by the conduction electrons

Zero-Valent Iron Nanoparticles with Unique Spherical 3D Architectures Encode Superior Efficiency in Copper Entrapment

The large-scale preparation of spherical condensed-type superstructures of zero-valent iron (nZVI), obtained by controlled solid-state reaction through a morphologically conserved transformation of a magnetite precursor, is herein reported. The formed 3D nanoarchitectures (S-nZVI) exhibit enhanced entrapment efficiency of heavy metal pollutants, such as copper, compared to all previously tested materials reported in the literature, thus unveiling the relevance in the material’s design of the morphological variable. The superior removal efficiency of these mesoporous S-nZVI superstructures is linked to their extraordinary ability to couple effectively processes such as reduction and sorption of the metal pollutant

Reactivity of Fluorographene: A Facile Way toward Graphene Derivatives

Fluorographene (FG) is a two-dimensional graphene derivative with promising application potential; however, its reactivity is not understood. We have systematically explored its reactivity in vacuum and polar environments. The C–F bond dissociation energies for homo- and heterolytic cleavage are above 100 kcal/mol, but the barrier of S_N2 substitution is significantly lower. For example, the experimentally determined activation barrier of the FG reaction with NaOH in acetone equals 14 ± 5 kcal/mol. The considerable reactivity of FG indicates that it is a viable precursor for the synthesis of graphene derivatives and cannot be regarded as a chemical counterpart of Teflon

In Situ Generation of Pd–Pt Core–Shell Nanoparticles on Reduced Graphene Oxide (Pd@Pt/rGO) Using Microwaves: Applications in Dehalogenation Reactions and Reduction of Olefins

Core–shell nanocatalysts are a distinctive class of nanomaterials with varied potential applications in view of their unique structure, composition-dependent physicochemical properties, and promising synergism among the individual components. A one-pot microwave (MW)-assisted approach is described to prepare the reduced graphene oxide (rGO)-supported Pd–Pt core–shell nanoparticles, (Pd@Pt/rGO); spherical core–shell nanomaterials (∼95 nm) with Pd core (∼80 nm) and 15 nm Pt shell were nicely distributed on the rGO matrix in view of the choice of reductant and reaction conditions. The well-characterized composite nanomaterials, endowed with synergism among its components and rGO support, served as catalysts in aromatic dehalogenation reactions and for the reduction of olefins with high yield (>98%), excellent selectivity (>98%) and recyclability (up to 5 times); both Pt/rGO and Pd/rGO and even their physical mixtures showed considerably lower conversions (20 and 57%) in dehalogenation of 3-bromoaniline. Similarly, in the reduction of styrene to ethylbenzene, Pd@Pt core–shell nanoparticles (without rGO support) possess considerably lower conversion (60%) compared to Pd@Pt/rGO. The mechanism of dehalogenation reactions with Pd@Pt/rGO catalyst is discussed with the explicit premise that rGO matrix facilitates the adsorption of the reducing agent, thus enhancing its local concentration and expediting the hydrazine decomposition rate. The versatility of the catalyst has been validated via diverse substrate scope for both reduction and dehalogenation reactions