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Graphene-based humidity sensors: the origin of alternating resistance change

2017-07-26T10:29:10+00:00 July 26th, 2017|Categories: Publications|Tags: |

By V I Popov, D V Nikolaev, V B Timofeev, S A Smagulova and I V Antonova

The response of a graphene-based humidity sensor is considered as a function of film structures. Analysis of the resistance changes due to water molecule adsorption on the graphene or multi-layer graphene (MLG) surface is performed for films with different structures and resistivities from hundreds of ohms/sq to hundreds of kilo-ohms/sq. The results revealed possible increase, decrease and non-monotonous behavior of resistance with changes in film structure. Adsorption of water molecules at grain boundary defects is assumed to lead to an increase in film resistivity due to the donor property of water and the p-type conductivity of graphene. Another type of conductive center with a higher capture cross-section is realized in the case of water molecule adsorption at edge defects in MLG films (the formation of conductive chains with ionic conductivity). If these chains form a continuous network the film resistivity decreases. The result of the competition between the opposite effec…

Published in: "Nanotechnology".

Real time polymer nanocomposites-based physical nanosensors: theory and modeling

2017-07-26T10:29:09+00:00 July 26th, 2017|Categories: Publications|Tags: |

By Stefano Bellucci, Yuri Shunin, Victor Gopeyenko, Tamara Lobanova-Shunina, Nataly Burlutskaya and Yuri Zhukovskii

Functionalized carbon nanotubes and graphene nanoribbons nanostructures, serving as the basis for the creation of physical pressure and temperature nanosensors, are considered as tools for ecological monitoring and medical applications. Fragments of nanocarbon inclusions with different morphologies, presenting a disordered system, are regarded as models for nanocomposite materials based on carbon nanoсluster suspension in dielectric polymer environments (e.g., epoxy resins). We have formulated the approach of conductivity calculations for carbon-based polymer nanocomposites using the effective media cluster approach, disordered systems theory and conductivity mechanisms analysis, and obtained the calibration dependences. Providing a proper description of electric responses in nanosensoring systems, we demonstrate the implementation of advanced simulation models suitable for real time control nanosystems. We also consider the prospects and prototypes of the proposed physical nano…

Published in: "Nanotechnology".

Large single-crystal graphene is possible

2017-07-26T10:28:56+00:00 July 26th, 2017|Categories: News|Tags: |

Thanks to its conductivity, strength and flexibility, graphene is considered as one of the most likely substitutes for silicon and other materials. However, it has not yet resulted in industrial applications. High-quality single-crystal graphene can only be produced in quantities a couple of millimeters to mere centimeters in size. Recently, a team led by Prof. Feng Ding and Prof. Rodney Ruoff with the Institute for Basic Science (IBS), Prof. Kaihui Liu at Peking University, and their collaborators reported the synthesis of a large sheet of monolayer single-crystal graphene. This result allows a leap forward in graphene production to an optimized method of fabricating an almost-perfect (> 99.9 % aligned) 5 × 50 cm2 single-crystal graphene in just 20 minutes. Moreover, the low production costs, comparable to commercially available lower-quality polycrystalline graphene films, could expand its usability. Detailed in Science Bulletin, the method is expected to stimulate further fundamental work on graphene and related materials, including large-scale folding of graphene sheets, similar to paper, creating origami-like or kirigami-like shapes that could be applied to future flexible circuits.

Published in: "Phys.org".

Organic dispersions of graphene oxide with arbitrary concentrations and improved chemical stability

2017-07-26T10:28:45+00:00 July 26th, 2017|Categories: Publications|Tags: , |

Chem. Commun., 2017, Accepted ManuscriptDOI: 10.1039/C7CC04584K, CommunicationWencheng Du, Mingmao Wu, Miao Zhang, Guochuang Xu, Tiantian Gao, Qian Liu, Xiaowen Yu, Fengyao Chi, Chun Li, Gaoquan ShiWe report a simple method that can dissolve graphene oxide (GO) in pure organic solvent (e.g., propylene carbonate) as readily as in pure water to form stable dispersions of single…The content of this RSS Feed (c) The Royal Society of Chemistry

Published in: "Chemical Communications".

Recent advancements, key challenges and solutions in non-enzymatic electrochemical glucose sensors based on graphene platforms

2017-07-26T10:28:38+00:00 July 26th, 2017|Categories: Publications|Tags: |

RSC Adv., 2017, 7,36949-36976DOI: 10.1039/C7RA02845H, Review Article Open Access &nbsp This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.G. Gnana kumar, G. Amala, S. M. GowthamThis review elucidates the recent advances in graphene platforms in electrochemical non-enzymatic glucose sensors and

Published in: "RSC Advances".

Chemically Bonded NaTi2(PO4)3/rGO Microsphere Composite as High-Rate Insertion Anode for Sodium-Ion Capacitor

2017-07-26T09:17:57+00:00 July 26th, 2017|Categories: Publications|Tags: |

J. Mater. Chem. A, 2017, Accepted ManuscriptDOI: 10.1039/C7TA05252A, PaperHa-Kyung Roh, Myeong Seong Kim, Kyung Yoon Chung, Ulaganathan Mani, Vanchiappan Aravindan, Madhavi Srinivasan, Kwang Chul Roh, Kwang Bum KimWe report on the synthesis of high rate NaTi2(PO4)3/graphene composite for use as an anode material

Published in: "Journal of Materials Chemistry A".

A Doubly Boron-Doped Perylene by N-Heterocylic Carbene-Borenium Hydroboration—C-H Borylation—Dehydrogenation

2017-07-25T20:25:47+00:00 July 25th, 2017|Categories: Publications|Tags: |

By Jeffrey M Farrell, David Schmidt, Vincenzo Grande, Frank Würthner

Reaction of an N-heterocyclic carbene (NHC)-borenium ion with 9,10-distyrylanthracene forms four B-C bonds through two selective, tandem hydroboration—electrophilic C-H borylations to yield an isolable, crystallographically characterizable polycyclic diborenium ion as its [NTf2]- salt (1). Dehydrogenation of 1 with TEMPO radical followed by acidic workup yields a 3,9-diboraperylene as its corresponding borinic acid (2). This sequence can be performed in one pot to allow the facile, metal-free conversion of an alkene to a small molecule containing a boron-doped graphene substructure. Doubly boron-doped perylene 2 exhibits visible range absorbance and fluorescence in chloroform solution (Φ = 0.63) and undergoes two reversible one electron reductions at moderate potentials of -1.30 and -1.64 eV vs. ferrocenium/ferrocene in DMSO. Despite sterically accessible boron centers and facile electrochemical reductions, compound 2 is air-, moisture- and silica gel-stable.

Published in: "Angewandte Chemie International Edition".

Two-dimensional InSe as a potential thermoelectric material. (arXiv:1705.06688v3 [cond-mat.mtrl-sci] UPDATED)

2017-07-25T19:59:02+00:00 July 25th, 2017|Categories: Publications|Tags: , , |

By Nguyen T. Hung, Ahmad R. T. Nugraha, R. Saito

Thermoelectric properties of monolayer indium selenide (InSe) are investigated by using Boltzman transport theory and first-principles calculations as a function of Fermi energy and crystal orientation. We find that the maximum power factor of p-type (n-type) monolayer InSe can be as large as 0.049 (0.043) W/K$^2$m at 300 K in the armchair direction. The excellent thermoelectric performance of monolayer InSe is attributed to both of its Seebeck coefficient and electrical conductivity. The large Seebeck coefficient originates from the moderate (about 2 eV) band gap of monolayer InSe as an indirect gap semiconductor, while its large electrical conductivity is due to its unique two-dimensional density of states (DOS), which consists of an almost constant DOS near the conduction band bottom and a sharp peak near the valence band top.

Published in: "arXiv Material Science".