Dissolution of spinel manganese oxides and the concomitant cathodic capacity losses were examined in 4 V Li/PC + DME + LiClO4/LiMn2O4 cells where PC is propylene carbonate and DME is dimethoxyethane. Dissolved Mn2 contents in the electrolytes were analyzed as a function of cathode potential and carbon contents in the composite cathodes. Characteristically, manganese dissolution was notably high at the charged state (at >4.1 V vs. Li/Lit), in which potential range an electrochemical oxidation of the solvent molecules was also prominent. From this and another observation whereby the Mn dissolution increased with increasing carbon content in the composite cathodes, it was proposed that, at the charged state of the cathode the solvent molecules are electrochemically oxidized on carbon surfaces and an as-generated species promotes the manganese dissolution. Results of an ac impedance study revealed that Mn dissolution brings about an increase in contact resistances at the Mn-depleted spinel/carbon interface, and also in the electrode reaction resistances for Li intercalation/deintercalation. Thus, the Mn dissolution causes capacity losses in two different pathways; material loss of the loaded spinel and polarization loss due to a cell resistance increment. The former prevailed when cathodes contained excess amounts of carbon, while the latter became more of a problem as the carbon contents decreased.

Contact angle goniometry is conducted for epitaxial graphene on SiC. Although only a single layer of epitaxial graphene exists on SiC, the contact angle drastically changes from 69 degrees on SiC substrates to 92 degrees on graphene. It is found that there is no thickness dependence of the contact angle from the measurements of single-, bi-, and multilayer graphene and highly ordered pyrolytic graphite (HOPG). After graphene is treated with oxygen plasma, the level of damage is investigated by Raman spectroscopy and the correlation between the level of disorder and wettability is reported. By using a low-power oxygen plasma treatment, the wettability of graphene is improved without additional damage, which can solve the adhesion issues involved in the fabrication of graphene devices.

Understanding magnetoresistance, the change in electrical resistance under an external magnetic field, at the atomic level is of great interest both fundamentally and technologically. Graphene and other two-dimensional layered materials provide an unprecedented opportunity to explore magnetoresistance at its nascent stage of structural formation. Here we report an extremely large local magnetoresistance of∼2,000% at 400 K and a non-local magnetoresistance of >90,000% in an applied magnetic field of 9 T at 300 K in few-layer graphene/boron–nitride heterostructures. The local magnetoresistance is understood to arise from large differential transport parameters, such as the carrier mobility, across various layers of few-layer graphene upon a normal magnetic field, whereas the non-local magnetoresistance is due to the magnetic field induced Ettingshausen–Nernst effect. Non-local magnetoresistance suggests the possibility of a graphene-based gate tunable thermal switch. In addition, our results demonstrate that graphene heterostructures may be promising for magnetic field sensing applications.

Tunability of the surface plasmon resonance wavelength is demonstrated by varying the thickness of Al 2 O 3 spacer layer inserted between the graphene and nanoparticles. By varying the spacer layer thickness from 0.3 to 1.8 nm, the resonance wavelength is shifted from 583 to 566 nm. The shift is due to a change in the electromagnetic field coupling strength between the localized surface plasmons excited in the gold nanoparticles and a single layer graphene film. In contrast, when the graphene film is absent from the system, no noticeable shift in the resonance wavelength is observed upon varying the spacer thickness. a)

To determine the friction coefficient of graphene, micro-scale scratch tests are conducted on exfoliated and epitaxial graphene at ambient conditions. The experimental results show that the monolayer, bilayer, and trilayer graphene all yield friction coefficients of approximately 0.03. The friction coefficient of pristine graphene is less than that of disordered graphene, which is treated by oxygen plasma. Ramping force scratch tests are performed on graphene with various numbers of layers to determine the normal load required for the probe to penetrate graphene. A very low friction coefficient and also its high pressure resistance make graphene a promising material for antiwear coatings.Graphene, a one-atom-thick planar sheet of carbon atoms, has been studied intensively in the last few years due to its unique characteristics. However, only a few studies investigate its mechanical properties [1, 2]. In particular, micro-scale friction coefficient of graphene has never been investigated despite its promising potential for low-friction antiwear coatings. In this report, scratch tests are conducted to determine the friction coefficient of mechanically exfoliated graphene on SiO 2 and epitaxial graphene on SiC under ambient conditions. Although the electrical properties of graphene are sensitive to the number of layers, no thickness dependence of friction coefficient is observed. The friction coefficient measurements on disordered graphene treated by oxygen plasma show that disorder in graphene increases the friction coefficient. Ramping force scratch tests are performed on graphene samples with different numbers of layers to determine the normal load required for the probe to penetrate through the graphene, inducing failure of the film. This load is referred to here the critical load. Single-, bi-, and tri-layer exfoliated graphene samples are identified by Raman spectra as shown in Fig (d) show error signal and topographical in-situ scanning probe microscopy (SPM) images after scratch tests, respectively. Although the magnitude of the error signal depends on the feedback parameters of the scan, the error signal image, the difference between the actual force and the set point at any given moment, is useful because it often shows more contrast than the accompanying topography image. Deformed parts of graphene after scratch tests are marked by red circles. . The difference from our data can be attributed to measurement environments [6]. First of all, our experiment is conducted at ambient conditions and their experiment is under ultra high vacuum conditions. It is well known that the existence of water can influence the friction coefficient, therefore it is reasonable to have a different 3 friction coefficient depending on the measurement conditions [6]. The different value could be also attributed to the difference in the size of probes; Filleter used an atomic force microscopy (AFM) based system, whereas we used a larger diamond probe with a 1 µm radius. This is in line with a previous study, where a lar...

A clear gate voltage tunable weak antilocalization and a giant magnetoresistance of ~ 400 % are observed at 1.9 K in single layer graphene with an out-of-plane field. A large magnetoresistance value of 275% is obtained even at room temperature implying potential applications of graphene in magnetic sensors. Both the weak antilocalization and giant magnetoresistance persists far away from the charge neutrality point in contrast to previous reports, and both effects are originated from charged impurities. Interestingly, the signatures of Shubnikov-de Haas oscillations and the quantum Hall effect are also observed for the same sample.

This study shows that 6-[4-(1-cyclohexyl-1H-tetrazol-5-yl) butoxy]-3,4-dihydro-2(1H)-quinolinone (cilostazol) suppresses the atherosclerotic lesion formation in the low-density lipoprotein receptor (Ldlr)-null mice. Ldlr-null mice fed a high cholesterol diet showed multiple plaque lesions in the proximal ascending aorta including aortic sinus, accompanied by increased macrophage accumulation with increased expression of vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1). Supplementation of cilostazol (0.2% w/w) in diet significantly decreased the plaque lesions with reduced macrophage accumulation and suppression of VCAM-1 and MCP-1 in situ. Increased superoxide and tumor necrosis factor-␣ (TNF-␣) production were significantly lowered by cilostazol in situ as well as in cultured human umbilical vein endothelial cells (HUVECs). TNF-␣-induced increased inhibitory B␣ degradation in the cytoplasm and nuclear factor-B (NF-B) p65 activation in the nuclei of HUVECs were reversed by cilostazol (1 ϳ 100 M) as well as by (E)-3[(4-t-butylphenyl)sulfonyl]-2-propenenitrile (BAY 11-7085) (10 M), suggesting that cilostazol strongly inhibits NF-B activation and p65 translocation into the nuclei. Furthermore, in gel shift and DNA-binding assay, cilostazol inhibited NF-B/DNA complex and nuclear DNA-binding activity of the NF-B in the nuclear extracts of the RAW 264.7 cells. Taken together, it is suggested that the antiatherogenic effect of cilostazol in cholesterol-fed Ldlr-null mice is ascribed to its property to suppress superoxide and TNF-␣ formation, and thereby reducing NF-B activation/transcription, VCAM-1/MCP-1 expressions, and monocyte recruitments.Evidence accumulates that atherogenesis is closely related to the inflammatory and proliferative responses of the endothelium after injury (Ross, 1993). During early stages of the atherosclerosis, adhesion and chemoattractant molecules, including vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1), are secreted by the activated endothelial cells in the atherosclerotic lesions, by which the immune cells and monocytes are recruited and migrated into the intimal area of the vascular wall (Reape and Groot, 1999). Reactive oxygen species and TNF-␣ are critically implicated not only in the induction of endothelial apoptosis (Dimmeler et al., 1998) but also in the development and progression of atherosclerotic lesions in humans (Meyer et al., 1999).Inactive NF-B resides in the cytoplasm bound by its inhibitory subunit, IB␣ (Pahl, 1999). Inflammatory stimuli including TNF-␣ and endotoxin lead to degradation of IB␣ by its phosphorylation pathway (Chen et al., 1995), which allows translocation of active NF-B into the nucleus, where it regulates gene expression and binds to the promoter of the target genes such as VCAM-1 and MCP-1.The low-density lipoprotein receptor (Ldlr)-null mouse is an animal model of homozygous familial hypercholesterolemia characterized by an absence of functional LDL receptors. Th...

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