Highly Polarized Fluorescent Illumination Using Liquid Crystal Phase

Gim, Min-Jun; Turlapati, Srikanth; Debnath, Somen; Rao, N. V. S.; Yoon, Dong Ki

doi:10.1021/acsami.5b10554

Cited by 34 publications

(27 citation statements)

References 41 publications

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“…One of the solutions avoiding steady‐state absorption is to use the ESIPT‐based materials with visible‐light emission from UV excitation, employing their large Stokes shift. Recently, several rod‐ and banana‐shaped fluorescent LCs have been used for polarized light emission . LC materials doped with AIEE dyes were also reported, aiming at the development of emissive LC displays or emergence of circularly polarized luminescence .…”

Section: Introductionmentioning

confidence: 99%

Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Zhang

Sakurai

Aotani

et al. 2018

Advanced Optical Materials

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solid-state emitters, electroluminescent devices, organic lasers, and so on. [1][2][3][4][5] Particularly, emission through excitedstate intramolecular proton transfer (ESIPT) mechanism with an extremely large Stokes shift [6][7][8][9] (anti-Kasha rule) suppresses excitation energy dissipation via self-absorption, providing attractive material platforms for optical device fabrication. [10,11] ESIPT is a photochemical process that produces a tautomer with a different electronic structure from the original excited form (Figure 1a). The requisite of chemical structures for ESIPT is the presence of an intramolecular hydrogen bond (H-bond) between the proton donor (OH and NH 2 ) and the proton acceptor (N and CO) groups close to one another in a single molecule. Recent notable reports on the ESIPT fluorophores include the polymorph-dependent emissive crystals, [12,13] double proton transfer process with an extra-large Stokes shift, [14] amplified spontaneous emission, [15][16][17] lasing system, [18][19][20] environment-sensitive multicolored materials, [21][22][23][24] and the use as emitters with electrically generated intramolecular proton transfers. [25] Most of ESIPT molecules show significant fluorescence in the solid states, not suffering from "concentration quenching" and thus serving as aggregation-induced emission enhancement (AIEE) materials. [26][27][28] The ESIPT process requires structural relaxations upon proton transfer, and thus a certain conformational freedom is allowed for the molecular structures. [29] The conformational freedom results in allowing the possible nonradiative pathways especially in solution (Figure 1b), giving AIEE characters to the ESIPT molecules. [30,31] The AIEE character is advantageous because light outputs from the systems are extremely high embedded into actual devices to avoid the concentration quenching. [32] However, most of the previous ESIPT as well as AIEE systems have been mostly reported in the rigid solid phase such as single crystals, polycrystals, or powders [11,12] -not in liquid crystals (LCs). Although columnar LCs with ESIPT-active cores were reported, [33,34] simple rod-shaped LC molecules embedded with ESIPT-active group have been limited. [35,36] In contrast to columnar and cubic liquid crystal phases with highly ordered structures, nematic as well as several smectic subphases can easily align macroscopically by rubbed surfaces, mechanical stimuli, and electric and magnetic fields. [37][38][39] Fluorescence via excited-state intramolecular proton transfer (ESIPT) provides strong light emission with a large Stokes shift and environment-sensitive unique spectral patterns. Particular systems including 2-(2-hydroxyphenyl) benzothiazole (HBT) serve as efficient solid-state emitters with the ESIPT mechanism and aggregation-induced emission enhancement (AIEE) property, but have not been used for liquid crystalline (LC) materials. Here, rod-shaped fluorescent LCs with ESIPT characters are newly developed based on the HBT motif. The design of the targeted mole...

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Section: Introductionmentioning

confidence: 99%

Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Zhang

Sakurai

Aotani

et al. 2018

Advanced Optical Materials

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“…To control these complex bent-core LC structures, more sophisticated methods should be used compared with the simple nematic phase, which is easily aligned using conventional LC alignment methods 9 . The problem of orientation control of the complex B phases could be solved using the topographic surface patterning method based on lithography 10 and the electric-field driven alignment method 11 , which has emerged as a new and powerful tool for producing single structural domains of LCs and other soft materials. This effort was extended to the organization of the complex HNF (B4) phase 12 13 14 15 .…”

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confidence: 99%

Airflow-aligned helical nanofilament (B4) phase in topographic confinement

Gim

Kim

Chen

et al. 2016

Sci Rep

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We investigated a controlled helical nanofilament (HNF: B4) phase under topographic confinement with airflow that can induce a shear force and temperature gradient on the sample. The resulting orientation and ordering of the B4 phase in this combinational effort was directly investigated using microscopy. The structural freedom of the complex B7 phase, which is a higher temperature phase than the B4 phase, can result in relatively complex microscopic arrangements of HNFs compared with the B4 phase generated from the simple layer structure of the B2 phase. This interesting chiral/polar nanofilament behaviour offers new opportunities for further exploration of the exotic physical properties of the B4 phase.

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“…Polarization-dependent liquid crystal (LC) films have been applied in broad fields, including in LC polarizers [1][2][3][4][5], photo-luminescence films [6][7][8], and photonic crystals [9][10][11]. Among these, dye-doped LC films composed of coaligned LC polymer networks and dichroic dyes attract interest among researchers due to their novel optical property and efficient fabrication process [1][2][3][4][5][6][7][12][13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Security use of bilayer dichroic films made of liquid crystal polymer networks

Park

Yoon

2021

Journal of Information Display

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We report on bilayer dichroic dye-doped liquid crystal (BDLC) films for patternable color codes, which can be used in anti-counterfeiting applications such as security codes and, unlike the conventional single-layer LC color films, show unique color changes depending on the direction of the polarization of the incident light that passes through them. This is a facile way to enhance the security level of security codes. BDLC films are fabricated by laminating two single-layer LC polymer network films with crossed optical axes. We believe that BDLC films can be used as a new platform for a securityenhanced anti-counterfeiting code that can replace complex chiral materials or expensive plasmonic particles.

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Highly Polarized Fluorescent Illumination Using Liquid Crystal Phase

Cited by 34 publications

References 41 publications

Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Airflow-aligned helical nanofilament (B4) phase in topographic confinement

Security use of bilayer dichroic films made of liquid crystal polymer networks

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