Liming Dai,*,†,‡ Yuhua Xue,†,‡ Liangti Qu,* Hyun-Jung Choi, and Jong-Beom Baek* †Center of Advanced Science and Engineering for Carbon (Case4Carbon), Department of Macromolecular Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States Key Laboratory of Cluster Science, Ministry of Education of China, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, Department of Chemistry, School of Science, Beijing Institute of Technology, Beijing 100081, People’s Republic of China School of Energy and Chemical Engineering/Center for Dimension-Controllable Covalent Organic Frameworks, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon, Ulsan, 689-798, South Korea

Metal-free catalysts for oxygen reduction reaction.

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Electrochromics for smart windows: Oxide-based thin films and devices

An apparatus including a plurality of adjacent repeated base units, each base unit formed from an active electrode of first, second and third touch sensor arrays, the first, second and third touch sensor arrays each including a plurality of active electrodes connected to a respective common terminal of the touch sensor array, wherein each base unit includes an active electrode of the second touch sensor array interlaced between an active electrode of the first touch sensor array and an active electrode of the third touch sensor array such that a swipe touch gesture applied to two or more adjacent active electrodes of the apparatus generates signalling at the respective common terminals of the corresponding touch sensor arrays which allows the direction of the swipe touch gesture to be determined.

Apparatus and associated methods

We report a facile nitrogenation/exfoliation process to prepare hybrid Ni–C–N nanosheets. These nanosheets are <2 nm thin, chemically stable, and metallically conductive. They serve as a robust catalyst for the hydrogen evolution reaction in 0.5 M H2SO4, or 1.0 M KOH or 1.0 M PBS (pH = 7). For example, they catalyze the hydrogen evolution reaction in 0.5 M H2SO4 at an onset potential of 34.7 mV, an overpotential of 60.9 mV (at j = 10 mA cm–2) and with remarkable long-term stability (∼10% current drop after 70 h testing period). They are promising as a non-Pt catalyst for practical hydrogen evolution reaction.

Ni–C–N Nanosheets as Catalyst for Hydrogen Evolution Reaction

Graphene forms an important two-dimensional (2D) material class that displays both a high electronic conductivity and optical transparency when doped. Yet, the microscopic origin of the doping mechanism in single sheet or bulk intercalated systems remains unclear. Using large-scale ab initio simulations, we show the graphene surface acts as a catalytic reducing/oxidizing agent, driving the chemical disproportionation of adsorbed dopant layers into charge-transfer complexes which inject majority carriers into the 2D carbon lattice. As pertinent examples, we focus on the molecular SbCl5 and HNO3 intercalates, and the solid compound AlCl3. Identifying the microscopic mechanism for the catalytic action of graphene is important, given the availability of large area graphene sheets, to spur research into new redox reactions for use in science and technology.

The role of chemistry in graphene doping for carbon-based electronics.

The performance of novel graphene-based devices often strongly depends on the electrical quality of the supporting oxide. To elucidate the general governing principles underlying this behavior, we use first-principles simulations to generate representative classes of experimentally known defect centers in passivated silicon dioxide substrates and study their charge transfer with adsorbed graphene. We find that many of the open-shell structural perturbations generated near the interface self-passivate during annealing, leading to occupied-unoccupied pairs of midgap states in the silicon dioxide band structure, but no doping of the graphene occurs. However, dangling bonds or paramagnetic defect centers stable to thermal annealing do lead to partially occupied midgap energy states that are energetically misaligned with the Dirac point of graphene allowing charge to flow to or from the carbon layer. In particular, dangling oxygen bonds in the oxide strongly $p$ dope the graphene. We also study doping from charge donating impurities within the substrate lattice as these also act to limit the performance of graphene-based devices.

Doping of adsorbed graphene from defects and impurities in SiO 2 substrates

Graphene nanomeshes (GNMs) formed by the creation of pore superlattices in graphene are a possible route to graphene-based electronics due to their semiconducting properties, including the emergence of fractional electronvolt band gaps. The utility of GNMs would be markedly increased if a scheme to stably and controllably dope them was developed. In this work, a chemically motivated approach to GNM doping based on selective pore-perimeter passivation and subsequent ion chelation is proposed. It is shown by first-principles calculations that ion chelation leads to stable doping of the passivated GNMs-both n- and p-doping are achieved within a rigid-band picture. Such chelated or "crown" GNM structures are stable, high mobility semiconducting materials possessing intrinsic doping-concentration control; these can serve as building blocks for edge-free graphene nanoelectronics including GNM-based complementary metal oxide semiconductor (CMOS)-type logic switches.

Crown Graphene Nanomeshes: Highly Stable Chelation-Doped Semiconducting Materials

Graphene nanomeshes (GNM's) formed by the creation of pore superlattices in graphene, are a possible route to graphene-based electronics due to their semiconducting properties, including the emergence of fractional eV band gaps. The utility of GNM's would be markedly increased if a scheme to stably and controllably dope them was developed. In this work, a chemically-motivated approach to GNM doping based on selective pore-perimeter passivation and subsequent ion chelation is proposed. It is shown by first-principles calculations that ion chelation leads to stable doping of the passivated GNM's -- both {\it n}- and {\it p}-doping are achieved within a rigid-band picture. Such chelated or ``crown'' GNM structures are stable, high mobility semiconducting materials possessing intrinsic doping-concentration control; these can serve as building blocks for edge-free graphene nanoelectronics including GNM-based complementary metal oxide semiconductor (CMOS)-type logic switches.

Razvan A. Nistor

Papers

The role of chemistry in graphene doping for carbon-based electronics.

Doping of adsorbed graphene from defects and impurities in SiO 2 substrates

Crown Graphene Nanomeshes: Highly Stable Chelation-Doped Semiconducting Materials

Crown Graphene Nanomeshes: Highly Stable Chelation-Doped Semiconducting Materials

High performance metal microstructure for carbon-based transparent conducting electrodes