ORCID Profile
0000-0001-8278-1995
Current Organisation
Institute for Basic Science
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Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8MH01507D
Abstract: We report the effect of single crystal graphene on carbonization and graphitization of thin film polymers.
Publisher: American Chemical Society (ACS)
Date: 20-02-2017
DOI: 10.1021/ACS.NANOLETT.6B04459
Abstract: Folded graphene in which two layers are stacked with a twist angle between them has been predicted to exhibit unique electronic, thermal, and magnetic properties. We report the folding of a single crystal monolayer graphene film grown on a Cu(111) substrate by using a tailored substrate having a hydrophobic region and a hydrophilic region. Controlled film delamination from the hydrophilic region was used to prepare macroscopic folded graphene with good uniformity on the millimeter scale. This process was used to create many folded sheets each with a defined twist angle between the two sheets. By identifying the original lattice orientation of the monolayer graphene on Cu foil, or establishing the relation between the fold angle and twist angle, this folding technique allows for the preparation of twisted bilayer graphene films with defined stacking orientations and may also be extended to create folded structures of other two-dimensional nanomaterials.
Publisher: AIP Publishing
Date: 19-10-2010
DOI: 10.1063/1.3486196
Abstract: The Kawasaki identity (KI) and the Jarzynski equality (JE) are important nonequilibrium relations. Both of these relations take the form of an ensemble average of an exponential function and can exhibit convergence problems when the average of the exponent differs greatly from the log of the average of the exponential function. In this work, we re-express these relations so that only selected regions need to be evaluated in an attempt to avoid these convergence issues. In the context of measuring free energies, we compare our method to the JE and the literature standard approach, the maximum likelihood estimator (MLE), and show that in a system with asymmetric work distributions it can perform as well as the MLE. For the KI, we derive an analog to the MLE to compare with our relation and show that these two new relations improve on the KI and are complimentary to each other.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 18-10-2018
Abstract: Single-crystal metals have distinctive properties owing to the absence of grain boundaries and strong anisotropy. Commercial single-crystal metals are usually synthesized by bulk crystal growth or by deposition of thin films onto substrates, and they are expensive and small. We prepared extremely large single-crystal metal foils by “contact-free annealing” from commercial polycrystalline foils. The colossal grain growth (up to 32 square centimeters) is achieved by minimizing contact stresses, resulting in a preferred in-plane and out-of-plane crystal orientation, and is driven by surface energy minimization during the rotation of the crystal lattice followed by “consumption” of neighboring grains. Industrial-scale production of single-crystal metal foils is possible as a result of this discovery.
Publisher: Springer Science and Business Media LLC
Date: 05-02-2015
DOI: 10.1557/JMR.2015.3
Publisher: Elsevier BV
Date: 02-2011
Publisher: IOP Publishing
Date: 23-07-2014
DOI: 10.1088/0957-4484/25/32/325301
Abstract: Currently proven methods that are used to obtain devices with high-quality graphene on silicon wafers involve the transfer of graphene flakes from a growth substrate, resulting in fundamental limitations for large-scale device fabrication. Moreover, the complex three-dimensional structures of interest for microelectromechanical and nanoelectromechanical systems are hardly compatible with such transfer processes. Here, we introduce a methodology for obtaining thousands of microbeams, made of graphitized silicon carbide on silicon, through a site-selective and wafer-scale approach. A Ni-Cu alloy catalyst mediates a self-aligned graphitization on prepatterned SiC microstructures at a temperature that is compatible with silicon technologies. The graphene nanocoating leads to a dramatically enhanced electrical conductivity, which elevates this approach to an ideal method for the replacement of conductive metal films in silicon carbide-based MEMS and NEMS devices.
Publisher: Elsevier BV
Date: 04-2014
Publisher: Wiley
Date: 11-07-2018
Abstract: A folding technique is reported to incorporate large-area monolayer graphene films in polymer composites for mechanical reinforcement. Compared with the classic stacking method, the folding strategy results in further stiffening, strengthening, and toughening of the composite. By using a water-air-interface-facilitated procedure, an A5-size 400 nm thin polycarbonate (PC) film is folded in half 10 times to a ≈0.4 mm thick material (1024 layers). A large PC/graphene film is also folded by the same process, resulting in a composite with graphene distributed uniformly. A three-point bending test is performed to study the mechanical performance of the composites. With a low volume fraction of graphene (0.085%), the Young's modulus, strength, and toughness modulus are enhanced in the folded composite by an average of 73.5%, 73.2%, and 59.1%, respectively, versus the pristine stacked polymer films, or 40.2%, 38.5%, and 37.3% versus the folded polymer film, proving a remarkable mechanical reinforcement from the combined folding and reinforcement of graphene. These results are rationalized with combined theoretical and computational analyses, which also allow the synergistic behavior between the reinforcement and folding to be quantified. The folding approach could be extended/applied to other 2D nanomaterials to design and make macroscale laminated composites with enhanced mechanical properties.
Publisher: Wiley
Date: 21-10-2018
Abstract: N-doped carbon nanomaterials have rapidly grown as the most important metal-free catalysts in a wide range of chemical and electrochemical reactions. This current report summarizes the latest advances in N-doped carbon electrocatalysts prepared by N mono-doping and co-doping with other heteroatoms. The structure-performance relationship of these materials is subsequently rationalized and perspectives on developing more efficient and sustainable electrocatalysts from carbon nanomaterials are also suggested.
Publisher: AIP Publishing
Date: 26-12-2011
DOI: 10.1063/1.3672418
Abstract: Saturable absorbers are a key component for mode-locking femtosecond lasers. Polymer films containing graphene flakes have recently been used in transmission as laser mode-lockers but suffer from high nonsaturable loss, limiting their application in low-gain lasers. Here, we present a saturable absorber mirror based on a film of pure graphene flakes. The device is used to mode lock an erbium-doped fiber laser, generating pulses with state-of-the-art, sub-200-fs duration. The laser characteristic indicates that the film exhibits low nonsaturable loss (13% per pass) and large absorption modulation depth (45% of low-power absorption).
Publisher: IEEE
Date: 2006
Publisher: AIP Publishing
Date: 05-05-2014
DOI: 10.1063/1.4875580
Abstract: We examine the ultrafast carrier phonon dynamics in graphene flakes with different lateral sizes. By using a size-selective centrifugation technique, we create graphene films with graphene flake sizes in the region of 120–450 nm. The transient transmission exhibits two-step relaxation, which are attributed to carrier thermalization followed by hot phonon cooling. We find that the cooling of the hot phonons proceeds faster, by a factor of three, for the smallest graphene flakes.
Publisher: Elsevier BV
Date: 12-2019
Publisher: Wiley
Date: 17-11-2011
Abstract: A structurally erse range of lipophilic, cationic η(6)-arene η(5)-cyclopentadienyl (η(5)-Cp*) full-sandwich complexes of ruthenium(II) have been prepared and structurally characterized by Fourier-transform IR and NMR spectroscopy, electrospray mass spectrometry, and elemental microanalyses. Computational experiments incorporating the Hartree-Fock theory and the second-order Møller-Plesset perturbation theory predict each complex to possess a uniform δ+ electrostatic potential, with the cationic charge of the [RuCp*](+) moiety completely delocalizing throughout the molecular structure of each metallocene. In vitro cytotoxicity studies demonstrate these delocalized lipophilic cations to be potent growth inhibitors of eleven unique tumorigenic cell lines, while exhibiting significantly lower levels of toxicity towards both a normal human fibroblast and a mouse macrophage cell line. Single-crystal X-ray structural determinations are additionally reported for five complexes, [Ru(η(6)-C(6)H(5)(CH(2))(2)CH(3))(η(5)-C(5)(CH(3))(5))]BPh(4), [Ru(η(6)-C(6)H(5)CO(2)CH(2)CH(3))(η(5)-C(5)(CH(3))(5))]BF(4), [Ru(η(6)-C(10)H(8))(η(5)-(5) (CH(3))(5))]BPh(4), [Ru(η(6)-C(14)H(10))(η(5)-C(5)(CH(3))(5))]BPh(4), and [Ru(η(6)-C(16)H(10))(η(5)-C(5)(CH(3))(5))]BPh(4).
Publisher: Wiley
Date: 03-06-2019
Abstract: A macroscopic film (2.5 cm × 2.5 cm) made by layer-by-layer assembly of 100 single-layer polycrystalline graphene films is reported. The graphene layers are transferred and stacked one by one using a wet process that leads to layer defects and interstitial contamination. Heat-treatment of the s le up to 2800 °C results in the removal of interstitial contaminants and the healing of graphene layer defects. The resulting stacked graphene s le is a freestanding film with near-perfect in-plane crystallinity but a mixed stacking order through the thickness, which separates it from all existing carbon materials. Macroscale tensile tests yields maximum values of 62 GPa for the Young's modulus and 0.70 GPa for the fracture strength, significantly higher than has been reported for any other macroscale carbon films microscale tensile tests yield maximum values of 290 GPa for the Young's modulus and 5.8 GPa for the fracture strength. The measured in-plane thermal conductivity is exceptionally high, 2292 ± 159 W m
No related grants have been discovered for Benjamin Cunning.