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


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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    • "Transparent conducting electrodes (TCEs) are a crucial and basic component in a variety of optoelectronic devices, such as thin-film solar cells [1] [2] [3], organic light emitting diodes (OLEDs) [4] [5], and flat panel displays [6] [7], touches screens [8] [9] [10]. Recently , carbon nanotubes (CNT) [11] [12], graphenes [3] [13], metal grid or metal nanowires [14] [15] [16], conducting polymers [17] [18] with attractive mechanical, electrical and optical properties have been extensively studied. "
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    ABSTRACT: We report a facile transfer fabrication of tin-doped indium oxide (In2O3:Sn) nanowires array (ITO NWs) electrode with high transparency and bending stability via selective wet-etching of a sacrificial ZnO layer. The ITO NWs are grown on ZnO (200 nm)/Si substrate by using a vapor-liquid-solid (VLS) method and then subsequently it is soaked in basic solution (1 M NaOH) to dissolve ZnO under-layer selectively, which enables to detach the ITO NWs electrode from the substrate without damage. We found that open-structure and porous nature of the ITO NWs with ITO nanoparticles support facilitate the NaOH solution penetration into the ZnO layer, thus enabling rapid peeling off the ITO NWs, even for a large sized substrate. The fabricated ITO NWs electrode on the PET substrate showed good transparency, conductivity and flexibility, eventually enabling to fabricate a flexible solid-state dye-sensitized solar cell with a satisfactory performance.
    Full-text · Article · Nov 2015 · Materials Letters
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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.
    Full-text · Article · Jan 2015 · Aerosol Science and Technology
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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.
    Full-text · Article · Jul 2014 · Sensors and Actuators B Chemical
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