Synthesis of Graphene-like Materials from Acetylene Black, Activated Carbon, and Ketjenblack via Separated Microwave Electric and Magnetic Field Heating.

Acetylene black, activated carbon, and Ketjenblack were subjected to microwave heating up to 1000 °C under N2 atmosphere to rapidly convert them into graphene-like materials. Few carbon materials exhibit a favorable increase in the intensity of the G' band with increasing temperature. Upon electric field heating of acetylene black to 1000 °C, the observed relative intensity ratios of D and G bands (or G' and G band) were equivalent to those of reduced graphene oxide heated under identical conditions. In addition, microwave irradiation under different conditions, i.e., electric field or magnetic field heating, produced graphene of qualities different from those of the same carbon material conventionally treated at the same temperature. We propose that this difference arises from the different mesoscale temperature gradients. The conversion of inexpensive acetylene black and Ketjenblack into graphene-like materials within 2 min of microwave heating is a major achievement toward low-cost mass synthesis of graphene.

Water-resistant antibacterial properties of a graphene oxide/cetylpyridinium chloride complex formed on medical gauze fibers.

OBJECTIVES: Graphene oxide (GO) is a nanocarbon material with a high aspect ratio (width:thickness) and abundant anionic functional groups on its surface. In this study, we attached GO to the surface of medical gauze fibers, constructed a complex with a cationic surface active agent (CSAA), and demonstrated that the treated gauze exhibits antibacterial activity even after rinsing with water. METHODS: Medical gauze was immersed in GO dispersion (0.001%, 0.01%, and 0.1%), rinsed with water, dried, and subjected to the Raman spectroscopy analysis. Subsequently, the gauze treated with 0.001% GO dispersion was immersed in 0.1% cetylpyridinium chloride (CPC) solution, immediately rinsed with water, and dried. Untreated, GO-only, and CPC-only gauzes were prepared for comparison. Each gauze was placed in a culture well, seeded with Escherichia coli or Actinomyces naeslundii, and turbidity was measured after 24 h of incubation. RESULTS: The Raman spectroscopy analysis of the gauze after immersion and rinsing showed a G band peak, indicating that GO remained on the surface of the gauze. The turbidity measurements indicated that GO/CPC-treated gauze (GO-treated and rinsed, followed by CPC-treatment and rinsing) significantly decreased turbidity compared to the other gauzes (P < 0.05), suggesting that the GO/CPC complex remained on the gauze fibers even after water rinsing and showed antibacterial activity. CONCLUSIONS: The GO/CPC complex imparts water-resistant antibacterial properties to gauze and has the potential to be widely used for the antimicrobial treatment of clothes.

Sustained antibacterial coating with graphene oxide ultrathin film combined with cationic surface-active agents in a wet environment.

Antimicrobial surfactants contained in mouthrinse have excellent efficacy, but are not retained on the tooth surface (are rinsed away) due to their low water resistance and thus do not exhibit sustained antibacterial activity. We have developed a new coating method using graphene oxide (GO) that retains the surfactant on the tooth surface even after rinsing with water, thus providing a sustained antibacterial effect. Ultra-thin films of GO and an antimicrobial agent were prepared by (1) applying GO to the substrate surface, drying, and thoroughly rinsing with water to remove excess GO to form an ultrathin film (almost a monolayer, transparent) on the substrate surface, then (2) applying antimicrobial cationic surface active agents (CSAAs) on the GO film to form a composite coating film (GO/CSAA). GO/CSAA formation was verified by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and ζ-potential and contact angle measurements. GO/CSAA was effective at inhibiting the growth of oral pathogens for up to 7 days of storage in water, and antibacterial activity was recovered by reapplication of the CSAA. Antibacterial GO/CSAA films were also formed on a tooth substrate. The results suggest that GO/CSAA coatings are effective in preventing oral infections.

A new sealed lithium-peroxide battery with a co-doped Li2O cathode in a superconcentrated lithium bis(fluorosulfonyl)amide electrolyte.

We propose a new sealed battery operating on a redox reaction between an oxide (O(2-)) and a peroxide (O2(2-)) with its theoretical specific energy of 2570 Wh kg(-1) (897 mAh g(-1), 2.87 V) and demonstrate that a Co-doped Li2O cathode exhibits a reversible capacity over 190 mAh g(-1), a high rate capability, and a good cyclability with a superconcentrated lithium bis(fluorosulfonyl)amide electrolyte in acetonitrile. The reversible capacity is largely dominated by the O(2-)/O2(2-) redox reaction between oxide and peroxide with some contribution of the Co(2+)/Co(3+) redox reaction.