Characterizations of a graphene-polyimide hybrid electro-optical liquid crystal device

Basu, Rajratan; Atwood, Lukas J.

doi:10.1364/osac.2.000083

Cited by 10 publications

(2 citation statements)

References 40 publications

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“…This interaction is further characterized by the π-π electron stacking interaction with a binding energy ranging from 0.74 to 0.88 eV/molecule [31], which is attributed to a significant amount of charge transfer from the NLC molecule to the honeycomb pattern of the carbon atoms. Supporting this, the previous findings of Basu et al [27,32,33] demonstrated that graphene can serve as the planar-alignment agent for an NLC due to this specific graphene-NLC interaction.…”

Section: Introductionsupporting

confidence: 65%

Alignment of Nematic Liquid Crystal 5CB Using Graphene Oxide

Politano,

Filice,

Versace

2023

Crystals

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In this article, we employed the saturation voltage method (SVM) to investigate the interaction between a nematic liquid crystal (NLC) and a graphene oxide (GO) substrate. The SVM approach involved applying a potential difference (ΔV) to the cell containing the NLC (specifically, 5CB) to reorient the nematic director (n) from a parallel to a perpendicular configuration with respect to the cell’s surface. By utilizing sandwich cells with indium–tin oxide semi-transparent electrodes covered by GO, we measured the anchoring energy between the NLC and the thin GO film. To evaluate the strength of this anchoring energy, we compared the results with two other cells: one exhibiting strong anchoring energy (polyimide cell) and the other demonstrating weak anchoring energy (formvar cell). The influence of GO thin films on the alignment of nematic 5CB was distinctly observed.

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Section: Introductionsupporting

confidence: 65%

Alignment of Nematic Liquid Crystal 5CB Using Graphene Oxide

Politano,

Filice,

Versace

2023

Crystals

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“…Therefore, this nano-architectural symmetry between the hexagons in both these species leads to an epitaxial interaction between them, and the benzene rings of the LC coherently align on the hexagonal lattice of h-BN [46]. This type of epitaxial interaction also exists between the nematic LC and the hexagonal lattice of other different nanomaterials, such as graphene [47][48][49][50][51][52][53][54][55] and carbon nanotube [56,57]. This spontaneous alignment mechanism of the LC on the hexagonal lattice is the fundamental principle behind designing the LC cell employing the 2D h-BN as a planar-alignment agent.…”

Section: Fabrication Of the 2d H-bn Based Lc Devicementioning

confidence: 99%

Reduced ionic effect and accelerated electro-optic response in a 2D hexagonal boron nitride planar-alignment agent based liquid crystal device

Basu

Atwood

2019

Opt. Mater. Express

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The presence of excess free-ion impurities in liquid crystals (LCs) gives rise to a number of problems in the electro-optical liquid crystal displays (LCDs), e.g., slow electro-optical responses and image sticking effects. Here we experimentally present that the two-dimensional (2D) hexagonal boron nitride (h-BN) nanosheet can serve as a planar-alignment agent and as an ion-capturing agent at the same time in an electro-optic LC device. The 2D h-BN nanosheet is employed as a planar-alignment agent on one side of an LC cell, where the standard planaraligning polyimide (PI) layer is used on the other side of the cell. The LC exhibits uniform planar-alignment in this h-BN/PI hybrid device. It is found that the free-ion impurities in the LC are significantly suppressed in this h-BN/PI hybrid cell compared to that in a standard PI/PI LC cell. The free-ion density is reduced in the hybrid cell due to the 2D h-BN nanosheet's ion-capturing process. The reduction of ionic impurities results in an accelerated electro-optic response of the LC in the h-BN based hybrid cell-which may have potential application for faster electro-optic devices.

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Utilizing 2D materials in liquid crystal–based electro-optic devices: A perspective

Basu

2023

Applied Physics Letters

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The alignment agent plays a crucial role in the electro-optical characteristics of an electro-optic liquid crystal (LC) device. Conventionally, rubbed polyimide (PI) layers have been utilized as alignment agents in LC devices. However, these organic PI layers are sensitive to UV rays and high temperatures. The rubbing procedure involved in preparing PI layers also introduces drawbacks, including non-uniform brightness due to uneven rubbing mechanisms and the presence of residual fiber dust. In our recent research, we demonstrated that various hexagonal 2D (inorganic) materials, such as monolayer graphene, monolayer tungsten diselenide (WSe2), and monolayer hexagonal boron nitride (h-BN) nanosheets, can effectively serve as planar-alignment agents in electro-optic LC devices. In this Perspective, we review the rubbing-free LC alignment process, which relies on the coherent overlay of the benzene rings of LC molecules on the hexagonal lattice structure of 2D materials. We review our recent results on LC devices utilizing 2D materials as alignment agents, highlighting their potential advantages. Furthermore, we discuss the challenges associated with this research field. Finally, we provide our perspectives on the future directions and opportunities for advancing this area of study, aiming to overcome challenges and extend the benefits of employing 2D materials as planar-alignment agents in electro-optic LC devices.

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Characterizations of a graphene-polyimide hybrid electro-optical liquid crystal device

Cited by 10 publications

References 40 publications

Alignment of Nematic Liquid Crystal 5CB Using Graphene Oxide

Alignment of Nematic Liquid Crystal 5CB Using Graphene Oxide

Reduced ionic effect and accelerated electro-optic response in a 2D hexagonal boron nitride planar-alignment agent based liquid crystal device

Utilizing 2D materials in liquid crystal–based electro-optic devices: A perspective

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