Bandgap Oscillation in Polyphenanthrenes

Yoshizawa, Kazunari; Yahara, Kazuyuki; Tanaka, Kazuyoshi; Yamabe, Tokio

doi:10.1021/jp972799f

Cited by 81 publications

(92 citation statements)

References 76 publications

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“…[35,36] 1D band structure calculations at various approximations have already done to show that infinitely long M-type tracks have nearly zero gaps, [35][36][37][38] whereas K-type tracks show bandgap oscillations which decrease slowly with width. [35][36][37][38] Our calculations here show that across similar size graphenites (i.e. with similar number of carbon atoms), the energy gap varies as hexagonal dots ) K-tracks > M-tracks.…”

Section: à2mentioning

confidence: 99%

Band‐like Transport in Surface‐Functionalized Highly Solution‐Processable Graphene Nanosheets

et al. 2008

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Graphenes are attracting renewed interests owing to recent advances in micromechanical exfoliation and epitaxial growth methods that make macroscopic 2D sheets of sp 2 -carbon atoms available.[1] A variety of simple yet elegant physics relating to its zero-gap semiconductor character has thus been demonstrated. [2][3][4][5] It would be very desirable to make these materials solution (or more accurately, dispersion) processable by coating or printing, which will open applications for large and/or flexible substrates. Graphite oxide (GO) is a possible candidate for this because it is a precursor to graphene through deoxidation either thermally or by chemical reduction. [6][7][8] Although GO itself has been studied for over a century, [9] its structure and properties remain elusive, and progress has been made only recently to give materials with limited dispersability and electronic quality. [10][11][12][13][14] Here we show that substoichiometric GO nanosheets can be surface-functionalised and purified to show excellent dispersability at the single-sheet level, >15 mg mL À1 in organic solvents, sufficient for spincoating and printing onto a variety of substrates. The films could then be deoxidised to graphene (ca. 80% completion at 300 8C) to give a network of low-dimensional ''graphenite'' tracks and dots on the nanosheets. Though imperfect and disordered, these show well-behaved and trap-free field-effect transistor charge-carrier mobilities for both electrons and holes of the order of 10 cm 2 V À1 s À1 , limited presently by the density of this graphenite network. Devices can be operated continuously in air for both p-and n-channels. The transport activation energies are in the meV region at low temperatures which together with the delocalisation of carriers indicate bandlike transport. The density-of-states at the Fermi level deduced by electrical measurements is higher than in graphite. MNDO-PM3 semiempirical electronic structure calculations relate this to defects in the 1D graphenite network. The fact that charge carriers can still be sufficiently delocalised in such disordered graphenites opens new opportunities for graphenes. It is well-known that chemical oxidation of graphite crystals gives GO which can be exfoliated by rapid-thermal-anneal >1000 8C, [15] or in solvents to give few-layer stacks that aggregate over time. [16,17] Recent work has shown that chemical functionalisation of GO can improve dispersability, particularly in the presence of stabilising polyelectrolytes. [10][11][12][13] However it is crucial to achieve more stable and concentrated dispersions without the added polyelectrolytes or ions, for electronic applications. We show here that substoichiometric (i.e. under-oxidised) GO can be obtained by a modified Staudenmaier oxidation of graphite with potassium chlorate [15] in a concentrated sulphuric-nitric acid mixture to give a material with an empirical formula containing less oxygen than the fully oxidised GO (C 2.0 O 1.0 H x ), [8,9,18] for example, C 2.0 O 0.77 H 0.75 . This material...

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Section: à2mentioning

confidence: 99%

Band‐like Transport in Surface‐Functionalized Highly Solution‐Processable Graphene Nanosheets

et al. 2008

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“…On the other hand, graphene is used to produce high-performance electronic devices due to its high carrier mobility and large mean free path. Graphene strips, nanographene ribbons, are promising material for future electronic applications because of their fascinating structural and electronic properties [7][8][9][10][11][12][13][14][15][16]. This one-dimensional material is fabricated by lithographic [17,18], chemical [19][20][21], and synthetic [22] methods.…”

Section: Introductionmentioning

confidence: 99%

Destruction of quasi-Landau levels in nanographene ribbons by the external electric fields

Chen

Chiu

Chang

et al. 2010

Chemical Physics Letters

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“…[7][8][9]). Polyacene (trans-polyene-edge) and polyphenanthrene (cis-polyene-edge) are among the most studied prototypes for such systems.…”

Section: Introductionmentioning

confidence: 99%

Optical properties of one‐dimensional graphene polymers: the case of polyphenanthrene

Prezzi

Varsano²,

Ruini

et al. 2007

Physica Status Solidi (b)

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We investigate from first principles the effect of many-body corrections on the optoelectronic properties of polyphenanthrene (PPh), a prototype system for carbon-based ladder polymers and I D nanographenes with cis-polyene edges. We show that the inclusion of many-body effects is essential to correctly describe both quasiparticle bandstructure and optical response. Consistently with the reduced dimensionality of the system, the inclusion of electron-hole interaction leads to strongly bound excitons which dominate the spectra. A complete characterization of the low-energy excitonic states is carried out, together with their optical activity. In particular, we find a dark exciton below the first optically active one, which is expected to crucially affect the luminescence efficiency. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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Bandgap Oscillation in Polyphenanthrenes

Cited by 81 publications

References 76 publications

Band‐like Transport in Surface‐Functionalized Highly Solution‐Processable Graphene Nanosheets

Band‐like Transport in Surface‐Functionalized Highly Solution‐Processable Graphene Nanosheets

Destruction of quasi-Landau levels in nanographene ribbons by the external electric fields

Optical properties of one‐dimensional graphene polymers: the case of polyphenanthrene

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