Preparation of uncurled and planar multilayered graphene using polythiophene derivatives via liquid-phase exfoliation of graphite

We have investigated the effects of the preparation conditions of polythiophene/graphene complexes on their dispersion in organic solvents, and on the in-solution morphology of the multilayered graphene. Among four different regioregular polythiophene derivatives synthesized, poly(3-hexylthiophene) (P3HT) with a low molecular weight (Mn 6000) was the most effective derivative for exfoliating graphite and for dispersing the multilayered graphene in toluene. Spectroscopic analysis revealed that P3HT interacted strongly with graphene to form a P3HT/graphene complex. We investigated the in situ morphology of multilayered graphene in organic solvents, using a flow particle image analyzer (FPIA) and revealed that the presence of polythiophenes produced larger P3HT/graphene complexes than that prepared in N-methylpyrrolidone (NMP). Microscopy analysis demonstrated that graphite flakes and multilayered graphene shrunk in the absence of P3HT when drying in organic solvents. The presence of P3HT immobilized the extended morphology of the multilayered graphene by forming the complex. This prevented shrinkage of the multilayered graphene when drying in toluene. Transmission electron, atomic force and field-emission scanning electron microscopy observations revealed that the P3HT/graphene complex consisted of relatively flat and ultrathin multilayered graphene of approximately <10 nm in thickness. The polythiophene/graphene complexes had high electrical conductivity, which depended on the kinds of polythiophenes. These findings further our understanding of the morphology of multilayered graphene, and will promote the development of uncurled multilayered graphene

Potential of Aerobic Denitrification by Pseudomonas stutzeri TR2 To Reduce Nitrous Oxide Emissions from Wastewater Treatment Plants▿ †

In contrast to most denitrifiers studied so far, Pseudomonas stutzeri TR2 produces low levels of nitrous oxide (N2O) even under aerobic conditions. We compared the denitrification activity of strain TR2 with those of various denitrifiers in an artificial medium that was derived from piggery wastewater. Strain TR2 exhibited strong denitrification activity and produced little N2O under all conditions tested. Its growth rate under denitrifying conditions was near comparable to that under aerobic conditions, showing a sharp contrast to the lower growth rates of other denitrifiers under denitrifying conditions. Strain TR2 was tolerant to toxic nitrite, even utilizing it as a good denitrification substrate. When both nitrite and N2O were present, strain TR2 reduced N2O in preference to nitrite as the denitrification substrate. This bacterial strain was readily able to adapt to denitrifying conditions by expressing the denitrification genes for cytochrome cd1 nitrite reductase (NiR) (nirS) and nitrous oxide reductase (NoS) (nosZ). Interestingly, nosZ was constitutively expressed even under nondenitrifying, aerobic conditions, consistent with our finding that strain TR2 preferred N2O to nitrite. These properties of strain TR2 concerning denitrification are in sharp contrast to those of well-characterized denitrifiers. These results demonstrate that some bacterial species, such as strain TR2, have adopted a strategy for survival by preferring denitrification to oxygen respiration. The bacterium was also shown to contain the potential to reduce N2O emissions when applied to sewage disposal fields