Graphene and chiral nematic liquid crystals: A focus on lasing

© The Royal Society of Chemistry 2015. This work presents the interaction of self-assembled liquid crystalline (LC) unidimensional photonic structures on the surface of polycrystalline graphene. Further, this surface effect is studied through different substrate geometries in the test devices. Primarily, these devices are characterised through polarizing optical microscopy (POM) and their laser emission features in the dye-doped chiral systems. Then the conductive nature of graphene is utilized to apply external electric fields to the photonic medium and its effect is envisaged. These graphene-based devices demonstrate a unique result in polarizing optical micrographs and electro-optic responses which indicates the presence of multidirectional domain formations. Additionally, the LC band-edge lasing from graphene cells is found to be anisotropic and depends on the directionality of the optical pump. This work attempts to lay the foundation for the implementation of a new class of defused chiral nematic liquid crystal based devices e.g. optical filters, notch filters, colour reflectors, and light shutters and may add toward the knowledge base necessary in the substitution of Indium Tin Oxide (ITO) with graphene in traditional LC based display devices.This work was carried out under the GRAPHTED project which is funded by the Engineering and Physical Sciences Research Council UK (project ref. EP/K016636/1, Grant No. EP/H047565/ 1). A. A. K. would like to thank the Higher Education of Pakistan (HEC), P. R. K. acknowledges Lindemann Trust Fellowship. A. A. K. and P. R. K. acknowledge the Cambridge Commonwealth, European and International Trust and for the nancial suppo

Hybrid graphene nematic liquid crystal light scattering device.

A hybrid graphene nematic liquid crystal (LC) light scattering device is presented. This device exploits the inherent poly-crystallinity of chemical vapour deposited (CVD) graphene films to induce directional anchoring and formation of LC multi-domains. This thereby enables efficient light scattering without the need for crossed polarisers or separate alignment layers/additives. The hybrid LC device exhibits switching thresholds at very low electric fields (< 1 V μm(-1)) and repeatable, hysteresis free characteristics. This exploitation of LC alignment effects on CVD graphene films enables a new generation of highly efficient nematic LC scattering displays as well as many other possible applications.Funding from the EPSRC (Grant No. EP/K016636/1, GRAPHTED) is acknowledged. P.R.K. acknowledges funding from Cambridge Commonwealth Trust (CCT) and the Lindemann Trust Fellowship. A.A.K would like to thank the Higher Education of Pakistan (HEC) and the CCT for financial support. A.C.V. acknowledges funding from the Cambridge Conacyt Scholarship and the Roberto Rocca Fellowship. A.K. would like to thank the Luys Educational Foundation and Hovnanian Foundation for scholarships.This is the author accepted manuscript. The final version is available from the Royal Society of Chemistry via http://dx.doi.org/10.1039/c5nr04094

ART DEMONSTRATES THAT FOOTBALL IS METASTASIZED, AND GIVES IT REFUGE

U ovom se radu problemski analiziraju obilježja nogometa u hit-romanu Alena Bovića Metastaze (2006) te u dvjema kasnijim obradama tog književnog djela – u kazališnoj predstavi Metastaze i istoimenom igranom filmu. Otuda ideja da se ondje zatečen, devijantnim pojavama obilježen nogomet, koji više baš i nema puno dodirnih točaka s igrom koja mu leži u korijenima, nazove metastaziralim. Umjetnička se stvarnost pritom promatra kao korespondentna društvenoj stvarnosti pa se za takvo etiketiranje nogometa prepoznaju razlozi na objema razinama. Na temelju takvog pristupa Metastazama, ali i na osnovi prethodno ponuđenog komparativnog uvida u nogometnu tematiku u nekim drugim književnim, kazališnim i filmskim ostvarenjima u Hrvatskoj i izvan nje, postavlja se teza o umjetnosti kao dokazu metastaziralog nogometa. No, još je izazovnije utvrditi može li umjetnost istodobno poslužiti i kao utočište metastaziralom nogometu tako da se njome revitalizira ponajprije estetska, ali istodobno i etička dimenzija tog sporta. Iz tih pobuda argumentacija u ovome radu uključuje tekstove i autore u širokom rasponu od književne kritike, antropologije igara i sociologije sporta do semiotike, kulturalnih studija i estetike. U ovom se radu problemski analiziraju obilježja nogometa u hit-romanu Alena Bovića Metastaze (2006) te u dvjema kasnijim obradama tog književnog djela – u kazališnoj predstavi Metastaze i istoimenom igranom filmu. Otuda ideja da se ondje zatečen, devijantnim pojavama obilježen nogomet, koji više baš i nema puno dodirnih točaka s igrom koja mu leži u korijenima, nazove metastaziralim. Umjetnička se stvarnost pritom promatra kao korespondentna društvenoj stvarnosti pa se za takvo etiketiranje nogometa prepoznaju razlozi na objema razinama. Na temelju takvog pristupa Metastazama, ali i na osnovi prethodno ponuđenog komparativnog uvida u nogometnu tematiku u nekim drugim književnim, kazališnim i filmskim ostvarenjima u Hrvatskoj i izvan nje, postavlja se teza o umjetnosti kao dokazu metastaziralog nogometa. No, još je izazovnije utvrditi može li umjetnost istodobno poslužiti i kao utočište metastaziralom nogometu tako da se njome revitalizira ponajprije estetska, ali istodobno i etička dimenzija tog sporta. Iz tih pobuda argumentacija u ovome radu uključuje tekstove i autore u širokom rasponu od književne kritike, antropologije igara i sociologije sporta do semiotike, kulturalnih studija i estetike.This article presents an analysis of the characteristics of football as depicted in the bestselling novel Metastaze (Metastases) (2006) by Alen Bović and in its two subsequent adaptations – the play Metastaze (Metastases) directed by Boris Svrtan and the film Metastaze (Metastases) directed by Branko Schmidt. Football as it appears in these three pieces is metastasized: it is deviant and in fact undergoes so many significant changes that it no longer has much in common with the original game. Artistic reality is seen as corresponding to social reality, and reasons for the metastasized nature of football are found on both levels. Based on the proposed analysis of Metastaze and a comparative analysis of descriptions of football in other books, plays and films in Croatia and abroad a hypothesis is put forward whereby art offers evidence as to the metastasized nature of football. A greater challenge still is to establish whether art might, at the same time, provide refuge to the metastasized football, revitalizing its aesthetic and ethical dimension. Given the scope of these claims, the arguments in the article are based on a wide array of texts and authors ranging from literary criticism, anthropology of games and sociology of sport to semiotics, cultural studies and aesthetics

Graphene and chiral nematic liquid crystals: A focus on lasing

© The Royal Society of Chemistry 2015. This work presents the interaction of self-assembled liquid crystalline (LC) unidimensional photonic structures on the surface of polycrystalline graphene. Further, this surface effect is studied through different substrate geometries in the test devices. Primarily, these devices are characterised through polarizing optical microscopy (POM) and their laser emission features in the dye-doped chiral systems. Then the conductive nature of graphene is utilized to apply external electric fields to the photonic medium and its effect is envisaged. These graphene-based devices demonstrate a unique result in polarizing optical micrographs and electro-optic responses which indicates the presence of multidirectional domain formations. Additionally, the LC band-edge lasing from graphene cells is found to be anisotropic and depends on the directionality of the optical pump. This work attempts to lay the foundation for the implementation of a new class of defused chiral nematic liquid crystal based devices e.g. optical filters, notch filters, colour reflectors, and light shutters and may add toward the knowledge base necessary in the substitution of Indium Tin Oxide (ITO) with graphene in traditional LC based display devices

Visible diffraction from graphene and its application in holograms

A fundamental study of visible diffraction effects from patterned graphene layers is presented. By patterning graphene into optical gratings, visible diffraction from graphene is experimentally measured as a function of the number of layers and visible wavelengths. A practical application of these effects is also presented, by demonstrating an optical hologram based on graphene. A high resolution (pixel size 400 nm) intensity hologram is fabricated which, in response to incident laser light, generates a visible image. These findings suggest that visible diffraction in graphene can find practical application in holograms and should also be considered during the design and characterisation of graphene-based optical applications. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Successful implementation of Lynch syndrome screening in a safety net institution

Lynch syndrome (LS) is the most common cause of hereditary colorectal cancer (CRC), and national guidelines recommend screening patients with CRC for LS. However, there is a paucity of data related to Lynch syndrome in the underserved population, in which unique issues of access, cultural beliefs regarding cancer, language barriers, immigration status, and financial restraints exist. We performed a descriptive, retrospective review of a selective LS screening protocol at an urban safety net hospital between 2009 and 2014 with the aim of describing the detected prevalence of LS as well as reporting the high quality and suboptimal screening rates. A total of 154 cases of CRC were identified over the 5-year period, of which 57 met selective LS screening criteria. Eleven patients had a positive screen, and three patients were diagnosed with LS, leading to an overall detected LS prevalence of 1.9 %. The rate of high quality screen was greater than 90 %, consistent with prior studies. Thus, we show that screening for LS in a safety net hospital can be successful in achieving high quality screening and provide an example for other public hospitals considering implementation of hereditary cancer screening

Hybrid graphene nematic liquid crystal light scattering device

A hybrid graphene nematic liquid crystal (LC) light scattering device is presented. This device exploits the inherent poly-crystallinity of chemical vapour deposited (CVD) graphene films to induce directional anchoring and formation of LC multi-domains. This thereby enables efficient light scattering without the need for crossed polarisers or separate alignment layers/additives. The hybrid LC device exhibits switching thresholds at very low electric fields (-1) and repeatable, hysteresis free characteristics. This exploitation of LC alignment effects on CVD graphene films enables a new generation of highly efficient nematic LC scattering displays as well as many other possible applications

Engineering high charge transfer n-doping of graphene electrodes and its application to organic electronics

Using thermally evaporated cesium carbonate (Cs2CO3) in an organic matrix, we present a novel strategy for efficient n-doping of monolayer graphene and a ∼90% reduction in its sheet resistance to ∼250 Ohm sq-1. Photoemission spectroscopy confirms the presence of a large interface dipole of ∼0.9 eV between graphene and the Cs2CO3/organic matrix. This leads to a strong charge transfer based doping of graphene with a Fermi level shift of ∼1.0 eV. Using this approach we demonstrate efficient, standard industrial manufacturing process compatible graphene-based inverted organic light emitting diodes on glass and flexible substrates with efficiencies comparable to those of state-of-the-art ITO based devices

Graphene-based ultrathin flat lenses

Flat lenses when compared to curved surface lenses have the advantages of being aberration free, and they offer a compact design necessary for a myriad of electro-optical applications. In this paper we present flat and ultrathin lenses based on graphene, the worlds thinnest known material. Monolayers and multilayers of graphene were fabricated into Fresnel zones to produce Fresnel zone plates, which utilize the reflection and transmission properties of graphene for their operation. The working of the lenses and their performance in the visible and terahertz regimes were analyzed computationally. Experimental measurements were also performed to characterize the lens in the visible regime, and a good agreement was obtained with the simulations. This work demonstrates the principle of atom-thick graphene-based lenses, with perspectives for ultracompact integration