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Micrometer-sized oxidation patterns containing varying composition of functional groups including epoxy, ether, hydroxyl, carbonyl, carboxyl, were created in chemical vapor deposition grown graphene through scanning probe lithography and pulsed laser two-photon oxidation. The oxidized graphene films were then reduced by a focused x-ray beam. Through in-situ x-ray photoelectron spectroscopy measurement,...
To realize energy-efficient and cost-effective production of hydrogen by electrochemical water splitting, central to the research endeavors is the exploration of highly active and earth-abundant electrocatalysts for oxygen evolution reaction (OER). Promising non-noble candidates for OER are often based on transition metal oxides, while carbon-based electrocatalysts typically receive little attention...
A ternary composite of graphene oxide/carbon dots/polypyrrole (GO/CDs/PPy) used as electrode active material for supercapacitor has been synthesized via in situ polymerization of GO/CDs with pyrrole under a mild condition. The CDs sandwiched between GO film and PPy layer can promote electron transportation in the ternary composite and thus reduce the internal resistance and charge transfer resistance...
Chemical composition of two-photon oxidized single-layer graphene is studied by micrometer X-ray photoelectron spectroscopy (XPS). Oxidized areas with a size of 2 × 2 μm2 are patterned on graphene by tightly focused femtosecond pulsed irradiation under air atmosphere. The degree of oxidation is controlled by varying the irradiation time. The samples are characterized by four wave mixing (FWM) imaging...
In this work, boron and nitrogen co-doped hierarchical porous carbon (BN-HPC) with a relatively high contents of boron (3.97 wt%) and nitrogen (12.10 wt%) is synthesized by a method combined with template process and carbonization of hierarchical porous resin using melamine and boric acid as nitrogen and boron sources, respectively. The co-doping method achieves a high boron doping level (8 times...
In recent years, various doping methods for epitaxial graphene have been demonstrated through atom substitution and adsorption. Here we observe by angle-resolved photoemission spectroscopy (ARPES) a coupling-induced Dirac cone renormalization when depositing small amounts of Ti onto epitaxial graphene on SiC. We obtain a remarkably high doping efficiency and a readily tunable carrier velocity simply...
We have demonstrated a nonlinear behavior for the bandgap opening of doped graphene by controlling the concentration of B and N co-dopants. X-ray absorption and emission spectra reveal that the bandgap increases from 0 to 0.6 eV as the concentration of BN dopants is increased from 0 to 6%, while the bandgap closes when the doping concentration becomes 56%. This nonlinear behavior of bandgap opening...
We report semiconducting behavior of monolayer graphene enabled through plasma activation of substrate surfaces. The graphene devices are fabricated by mechanical exfoliation onto pre-processed SiO2/Si substrates. Contrary to pristine graphene, these graphene samples exhibit a transport gap as well as nonlinear transfer characteristics, a large on/off ratio of 600 at cryogenic temperatures, and an...
A simple and facile method for multiscale, in-plane patterning of graphene oxide and reduced graphene oxide (GO–rGO) was developed by region-specific reduction of graphene oxide (GO) under a mild irradiation. The UV-induced reduction of graphene oxide was monitored by various spectroscopic techniques, including optical absorption, X-ray photoelectron spectroscopy (XPS), Raman, and X-ray diffraction...
The defects created by scanning probe lithography (SPL) under ambient conditions in CVD grown graphene were investigated using atomic force microscopy, micro-Raman (μ-RS) and micro-X-ray photoelectron spectroscopy (μ-XPS). Topographically, both protrusion and depression structures with distinguishable tribological properties were produced simultaneously. However, the key aspects of the spectroscopy...
An amorphous carbon thin film, with through-pores of several tens of nanometers in size, has been synthesized by annealing magnetron sputtered nitrogen-doped carbon thin films at elevated temperature in an inert atmosphere. Based on this nanoporous carbon film, we first report forming-free resistive switching in a two terminal device containing ready-made metal nanofilaments. Such nanoporous carbon-based...
Fracture properties of both carbon nanotube (CNT) and carbon nanoscroll (CNS) reinforced silicon (Si) matrix composites under tension are investigated by molecular dynamics simulations. It is found that either a single-wall CNT or a multi-wall one (MWCNT) will be pulled out if the length of the CNT is short, while brittle fracture of CNT will happen for a relatively long one. It is interesting to...
Top-down process, comprising lithography and plasma etching is widely used in very-large-scale integration due to its scalability, has the greatest potential to fabricate graphene nanoribbon based nanoelectronic devices for large-scale intergraded circuits. However, conventional plasma etching inevitably introduces plenty of damage or defects to the etched materials, which drastically degrades the...
Activated carbon-supported copper, iron, or vanadium oxide catalysts were exposed to incineration flue gas to investigate the simultaneous catalytic oxidation of sulfur dioxide/hydrogen chloride and selective catalytic reduction of nitrogen oxide by carbon monoxide. The results show that AC-supported catalysts exhibit higher activities for SO 2 and HCl oxidation than traditional γ-Al 2...
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