Graphene-Based Liquid Crystal Device

School of Computer Science, University of Manchester, Manchester, UK.
Nano Letters (Impact Factor: 13.59). 07/2008; 8(6):1704-8. DOI: 10.1021/nl080649i
Source: PubMed

ABSTRACT Graphene is only one atom thick, optically transparent, chemically inert, and an excellent conductor. These properties seem to make this material an excellent candidate for applications in various photonic devices that require conducting but transparent thin films. In this letter, we demonstrate liquid crystal devices with electrodes made of graphene that show excellent performance with a high contrast ratio. We also discuss the advantages of graphene compared to conventionally used metal oxides in terms of low resistivity, high transparency and chemical stability.

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    • "They obtained »1.5 nm-thick films over centimeter sized areas. However, Blake et al. (2008) did not report the spray-deposition parameters and conditions, i.e., deposition area, deposition time, suspension concentration, liquid feeding rate. Jang et al. (2012) electrosprayed suspensions of graphene nanosheets (0.16 mg/mL in deionized (DI) water/ethanol 6/4 v/v) onto a transparent conductive oxide (TCO)-coated glass to prepare cathodes for dye-sensitized solar cells (DSCs). "
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    ABSTRACT: Graphene, a two-dimensional carbon allotrope, exhibits excellent optoelectronic properties. The assembly of graphene into films provides a platform to deepen the study of its interaction with varying surfaces, to engineer devices, and to develop functional materials. A general approach to produce graphene films consists of preparing a dispersion and laying it on a substrate of choice, followed by solvent evaporation. Here we report the preparation of stable suspensions of new types of graphene nanomaterials namely, graphene nanoflowers (GNFs) and multi-layer graphene (MLG) flakes, in ethanol, N,N Dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP). Sprayable suspensions of both GNFs and MLG were prepared in DMF/ethanol, which showed high stability, without addition of any surfactant. The stable suspensions were used to deposit MLG/GNF films on glass substrates. Calculations of the initial droplet size and of the timescale of droplet evaporation are performed and possible thermophoretic effects on droplet deposition discussed as well. Coating glass substrates with a methacrylic acid - methyl methacrylate (MA) copolymer prior to the deposition significantly improved the adhesion of the nanomaterials to the substrate. With the MA coating, a substrate coverage of nearly 100 % was achieved at 14-min spraying time for 0.05 wt % GNF and 0.1 wt % MLG suspensions. Raman spectra of the GNF and MLG films reveal that the films were made of MLG in which the individual graphene layers rotated from each other as in turbostratic graphene. This work provides a general approach to prepare graphene nanomaterial suspensions and to create films for a variety of applications. The spraying process applied in the current work is highly scalable and allows control of film characteristics through process parameters.
    Aerosol Science and Technology 01/2015; 49:45-56. DOI:10.1080/02786826.2014.991438 · 2.41 Impact Factor
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    • "By employing a controlled polymerization technique, the imprinting structure can be defined and the MIPs can be directly deposited onto the GO without any additional procedure such as stamping. Several methods to functionalize graphene have been developed, however it is challenging to control the density and thickness of materials grafted onto the surface [15] [16]. A MIP-graphene hybrid has been prepared by Mao et al. [17]. "
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    ABSTRACT: Graphene oxide (GO), with its small dimension and high surface-to-volume ratio, can enhance the binding capacity and sensitivity of molecularly imprinted polymers (MIPs). Therefore, a straightforward and fast method was developed to graft MIPs onto GO by reversible addition–fragmentation chain transfer (RAFT) polymerization. First, the initiator was linked to the GO in a simple two-step process which was verified via UV–vis spectroscopy. Subsequently, a MIP layer for histamine was grown onto the functionalized surface by RAFT crosslinking polymerization, enabling control over the imprint structure. The formation of a hybrid GO–MIP structure, particles surrounded with a polymer network of ∼2.4 nm thick, was verified by atomic force microscopy (AFM). Classical batch rebinding experiments demonstrated the specificity of the MIP towards its original template histamine. Next, the heat-transfer method (HTM) was applied, a novel sensing technique requiring only two thermocouples and an adjustable heat source. This method has been employed for the detection of small organic molecules with bulk MIPs, but never with a GO-hybrid structure. For proof-of-principle purposes, silicon substrates were functionalized with the GO–MIPs and sensing was performed on histamine in buffer solutions. The designed sensor platform could detect histamine in the nanomolar regime, similar to conventional techniques. In summary, we have developed a fast and straightforward method to prepare MIP–GO hybrids which were able to measure histamine in buffer solutions by thermal detection. Since GO exhibits excellent thermal properties, this opens the window to sensing of small organic molecules in relevant biological samples.
    Sensors and Actuators B Chemical 07/2014; 203:527-535. DOI:10.1016/j.snb.2014.07.013 · 4.10 Impact Factor
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    • "Graphene, one of the most attractive research topics in modern science owing to its fascinating electrical properties, has been attracted much attention123. Its unique structure, two-dimensional honeycomb carbon lattice, enables high conductivity and transparency1234. This material is thus potentially expected to become a transparent conductive layer5 in optoelectrical applications6789 and thus stimulates a lot of studies on the synthetic growth methods to requisitely develop high uniformity with high quality and simple process for industrial manufactory3. "
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    ABSTRACT: A directly self-crystallized graphene layer with transfer-free process on arbitrary insulator by Ni vapor-assisted growth at growth temperatures between 950 to 1100°C via conventional chemical vapor deposition (CVD) system was developed and demonstrated. Domain sizes of graphene were confirmed by Raman spectra from ~12 nm at growth temperature of 1000°C to ~32 nm at growth temperature of 1100°C, respectively. Furthermore, the thickness of the graphene is controllable, depending on deposition time and growth temperature. By increasing growth pressure, the growth of graphite nano-balls was preferred rather than graphene growth. The detailed formation mechanisms of graphene and graphite nanoballs were proposed and investigated in detail. Optical and electrical properties of graphene layer were measured. The direct growth of the carbon-based materials with free of the transfer process provides a promising application at nanoelectronics.
    Scientific Reports 05/2014; 4:4739. DOI:10.1038/srep04739 · 5.58 Impact Factor
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