We investigated thermal conductivity of free-standing reduced graphene oxide films subjected to a high-temperature treatment of up to 1000°C. It was found that the hightemperature annealing dramatically increased the in-plane thermal conductivity, K, of the films from ~3 W/mK to ~61 W/mK at room temperature. The cross-plane thermal conductivity, K  , revealed an interesting opposite trend of decreasing to a very small value of ~0.09 W/mK in the reduced graphene oxide films annealed at 1000 o C. The obtained films demonstrated an exceptionally strong anisotropy of the thermal conductivity, K/K  ~ 675, which is substantially larger even than in the high-quality graphite. The electrical resistivity of the annealed films reduced to 1 / -19 /. The observed modifications of the in-plane and cross-plane thermal conductivity components resulting in an unusual K/K  anisotropy were explained theoretically. The theoretical analysis suggests that K can reach as high as ~500 W/mK with the increase in the sp 2 domain size and further reduction of the oxygen content. The strongly anisotropic heat conduction properties of these films can be useful for applications in thermal management.  Corresponding author (AAB): balandin@ee.ucr.edu ; web: http://ndl.ee.ucr.edu/ University of California -Riverside and Graphenea Inc. (2015) 2 | P a g e

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We investigated toxicity of 2–3 layered >1 μm sized graphene oxide (GO) and reduced graphene oxide (rGO) in mice following single intratracheal exposure with respect to pulmonary inflammation, acute phase response (biomarker for risk of cardiovascular disease) and genotoxicity. In addition, we assessed exposure levels of particulate matter emitted during production of graphene in a clean room and in a normal industrial environment using chemical vapour deposition. Toxicity was evaluated at day 1, 3, 28 and 90 days (18, 54 and 162 μg/mouse), except for GO exposed mice at day 28 and 90 where only the lowest dose was evaluated. GO induced a strong acute inflammatory response together with a pulmonary (Serum-Amyloid A, Saa3) and hepatic (Saa1) acute phase response. rGO induced less acute, but a constant and prolonged inflammation up to day 90. Lung histopathology showed particle agglomerates at day 90 without signs of fibrosis. In addition, DNA damage in BAL cells was observed across time points and doses for both GO and rGO. In conclusion, pulmonary exposure to GO and rGO induced inflammation, acute phase response and genotoxicity but no fibrosis.

Graphene and graphene oxide receive much attention these years, because they add attractive properties to a wide range of applications and products. Several studies have shown toxicological effects of other carbon‐based nanomaterials such as carbon black nanoparticles and carbon nanotubes in vitro and in vivo. Here, we report in‐depth physicochemical characterization of three commercial graphene materials, one graphene oxide (GO) and two reduced graphene oxides (rGO) and assess cytotoxicity and genotoxicity in the murine lung epithelial cell line FE1. The studied GO and rGO mainly consisted of 2–3 graphene layers with lateral sizes of 1–2 µm. GO had almost equimolar content of C, O, and H while the two rGO materials had lower contents of oxygen with C/O and C/H ratios of 8 and 12.8, respectively. All materials had low levels of endotoxin and low levels of inorganic impurities, which were mainly sulphur, manganese, and silicon. GO generated more ROS than the two rGO materials, but none of the graphene materials influenced cytotoxicity in terms of cell viability and cell proliferation after 24 hr. Furthermore, no genotoxicity was observed using the alkaline comet assay following 3 or 24 hr of exposure. We demonstrate that chemically pure, few‐layered GO and rGO with comparable lateral size (> 1 µm) do not induce significant cytotoxicity or genotoxicity in FE1 cells at relatively high doses (5–200 µg/ml). Environ. Mol. Mutagen. 57:469–482, 2016. © 2016 The Authors. Environmental and Molecular Mutagenesis Published by Wiley Periodicals, Inc.

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The energy and power requirements of portable electronic devices and electric vehicles are ever increasing, driving research into novel battery structures with increased volumetric energy and power densities.Existing energy storage technologies cannot satisfy both of these requirements. There are many reports on the application of graphene in batteries and supercapacitors with enhanced power and energy densities; however, few results were shown on the performance of an electrochemical energy storage device made of monolayer graphene. The energy storage capability of monolayer graphene is investigated in this paper and it can contribute an understanding of the application of graphene materials in high energy and power density batteries. In parallel, flexible solid-state batteries will relax design constraints, giving the freedom to create new device form factors. A mechanically flexible allsolid state battery can be made of monolayer graphene grown by chemical vapour deposition (CVD) directly onto copper (Cu) foil. The total thickness of the resulting battery was $50 mm. Such an ultrathin battery showed the highest energy density of 10 W h L À1 and the highest power density of 300 W L À1 .It also shows excellent cyclic stability and sustains a discharge current density of 100 mA cm À2 over 100 cycles, maintaining energy capacity over 0.02 mA h cm À2 .

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Graphene related materials, if prepared with non-irritant exfoliation agents, do not induce skin irritation on a 3D model of human epidermis, following the OECD guideline 439.