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Anomalously large reactivity of single graphene layers and edges toward electron transfer chemistries.

ABSTRACT: The reactivity of graphene and its various multilayers toward electron transfer chemistries with 4-nitrobenzene diazonium tetrafluoroborate is probed by Raman spectroscopy after reaction on-chip. Single graphene sheets are found to be almost 10 times more reactive than bi- or multilayers of graphene according to the relative disorder (D) peak in the Raman spectrum examined before and after chemical reaction in water. A model whereby electron puddles that shift the Dirac point locally to values below the Fermi level is consistent with the reactivity difference. Because the chemistry at the graphene edge is important for controlling its electronic properties, particularly in ribbon form, we have developed a spectroscopic test to examine the relative reactivity of graphene edges versus the bulk. We show, for the first time, that the reactivity of edges is at least two times higher than the reactivity of the bulk single graphene sheet, as supported by electron transfer theory. These differences in electron transfer rates may be important for selecting and manipulating graphitic materials on-chip.

SUBMITTER: Sharma R

PROVIDER: S-EPMC6396976 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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Anomalously large reactivity of single graphene layers and edges toward electron transfer chemistries.

Sharma Richa R Baik Joon Hyun JH Perera Chrisantha J CJ Strano Michael S MS

Nano letters 20100201 2

The reactivity of graphene and its various multilayers toward electron transfer chemistries with 4-nitrobenzene diazonium tetrafluoroborate is probed by Raman spectroscopy after reaction on-chip. Single graphene sheets are found to be almost 10 times more reactive than bi- or multilayers of graphene according to the relative disorder (D) peak in the Raman spectrum examined before and after chemical reaction in water. A model whereby electron puddles that shift the Dirac point locally to values b ...[more]

PMID: 20055430

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Project description:Conductive materials are known to promote direct interspecies electron transfer (DIET) by electrically bridging microbial cells. Previous studies have suggested that supplementation of graphene oxide (GO) based materials, including GO, and reduced GO (rGO), to anaerobic microbial communities, can promote DIET. This promotion mechanism is thought to be involved in electron transfer via rGO or biologically formed rGO. However, concrete evidence that rGO directly promotes DIET is still lacking. Furthermore, the effects of the physicochemical properties of GO-based materials on DIET efficiency have not been elucidated. In the current work, we investigated whether chemically and biologically reduced GO compounds can promote DIET in a defined model coculture system, and also examined the effects of surface properties on DIET-promoting efficiency. Supplementation of GO to a defined DIET coculture composed of an ethanol-oxidizing electron producer Geobacter metallireducens and a methane-producing electron consumer Methanosarcina barkeri promoted methane production from ethanol. X-ray photoelectron spectroscopy revealed that GO was reduced to rGO during cultivation by G. metallireducens activity. The stoichiometry of methane production from ethanol and the isotope labeling experiments clearly showed that biologically reduced GO induced DIET-mediated syntrophic methanogenesis. We also assessed the DIET-promoting efficiency of chemically reduced GO and its derivatives, including hydrophilic amine-functionalized rGO (rGO-NH2) and hydrophobic octadecylamine-functionalized rGO (rGO-ODA). While all tested rGO derivatives induced DIET, the rGO derivatives with higher hydrophilicity showed higher DIET-promoting efficiency. Optical microscope observation revealed that microbial cells, in particular, G. metallireducens, more quickly adhered to more hydrophilic GO-based materials. The superior ability to recruit microbial cells is a critical feature of the higher DIET-promoting efficiency of the hydrophilic materials. This study demonstrates that biologically and chemically reduced GO can promote DIET-mediated syntrophic methanogenesis. Our results also suggested that the surface hydrophilicity (i.e., affinity toward microbial cells) is one of the important determinants of the DIET-promoting efficiencies. These observations will provide useful guidance for the selection of conductive particles for the improvement of methanogenesis in anaerobic digesters.

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Anomalously large reactivity of single graphene layers and edges toward electron transfer chemistries.

Publications

Anomalously large reactivity of single graphene layers and edges toward electron transfer chemistries.

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