Topological defects stabilized by a soft twist-bend dimer and quantum dots lead to a wide thermal range and ultra-fast electro-optic response in a liquid crystalline amorphous blue phase

Khatun, Nurjahan; Vimala, S.; Fodor‐Csorba, Katalin; Nair, Geetha G.

doi:10.1039/d3tc00861d

Cited by 3 publications

(8 citation statements)

References 61 publications

(114 reference statements)

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“…The NPs of such dimensions, when doped in the BP, are known to get trapped inside the cores of disclination lines. 41–44 Therefore, for the Se–BP ( i.e. , the nanoparticle-doped BPI), the n DTC and n Disclination are considered to be 1.6 and 3.07, respectively.…”

Section: Resultsmentioning

confidence: 99%

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Towards complete photonic band gap in a high refractive index nanoparticle-doped blue phase liquid crystal

Khatun,

Sridurai,

Nair

2023

Nanoscale

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Section: Resultsmentioning

confidence: 99%

“…The disclination cores of BP are known to act as trapping sites for dopants such as nanoparticles, polymers, etc . 41–44 Therefore the as-synthesized Se NPs (∼5 nm dia) can be confined efficiently inside the disclination cores of BPI, forming a stable cubic lattice.…”

Section: Resultsmentioning

confidence: 99%

Towards complete photonic band gap in a high refractive index nanoparticle-doped blue phase liquid crystal

Khatun,

Sridurai,

Nair

2023

Nanoscale

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“…The chiral dopant is added to induce chirality to the medium and hence the BPI. The LC dimer, which exhibits the twist bend nematic phase (NTB) with ultralow bend elastic constant and saddle-splay deformation, is added to increase the thermal range of BPI. , Rhodamine B (from TCI Chemicals ), which possesses a high quantum yield of 90% and exhibits an emission wavelength (570 nm) in the vicinity of the PBG of BP, is chosen as the dye material for the PL study. Se NPs (diameter ∼5 nm), the high-index particles of choice, capped with polyvinylpyrrolidone (PVP) (to facilitate uniform dispersion of NPs in the BPLC medium), are synthesized in the laboratory using the modified chemical reduction method, as reported in our previous publication .…”

Section: Methodsmentioning

confidence: 99%

Effect of High-Index Nanoparticles on the Emission Properties of a Dye-Doped Blue Phase Liquid Crystal

Khatun,

Nair

2024

Chem. Mater.

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This study demonstrates a significant advancement in enhancing photoluminescence (PL) intensity by the inclusion of high-index dielectric nanoparticles into a dye-doped blue phase liquid crystal (BPLC). The blue phase I (BPI), the cubic subphase of the blue phase exhibited by highly chiral liquid crystals, is inherently an incomplete photonic band gap (PBG) system due to the low refractive index contrast Δn (<0.1). The Δn is given by the difference between the refractive indices corresponding to the double twisted cylinders and disclination lines that constitute the blue phases. Being an incomplete PBG system, BPI exhibits a narrow PBG width (2 to 3%), affecting the extent of enhancement in PL intensity in the dye-doped BPLC. An elegant pathway of confining highrefractive index selenium nanoparticles (n = 3.07 at optical frequencies) inside the core of disclination lines effectively increases the Δn (1.4) and thus the PBG width (6%), driving BPI toward a complete PBG. This, in turn, enhances the PL intensity by a factor of 3 when compared to the pristine BPLC, as demonstrated by finite element method simulations and reflection spectroscopy experiments. The simulations reveal that the efficient confinement of electromagnetic waves by the high-index nanoparticles leads to increased density of states (DOS) at the band edges, and hence, the enhanced emission. However, the emission gets suppressed at PBG as the DOS is nearly zero at the band gap. The in situ modulation in PL intensity is experimentally established utilizing thermally induced PBG tunability. Simulations also suggest that the enhancement in PL intensity strongly depends on the orientation and position of the dipole (dye) within the photonic cavity. Thus, incorporating high-index nanoparticles in the dyedoped BPLC enhances PL intensity, rendering the system more conducive for various optoelectronic applications such as lightemitting diodes and light-emissive displays.

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“…Recently, Cordoyiannis et al demonstrated that quantum dots essentially stabilize BPIII [ 67 ]. Khatun and Nari et al reported stabilizing BPIII by using a twist–bend nematic LC and surface-functionalized quantum dots (QDs: CdSe (core)/ZnS (shell) tethered with octadecylamine) [ 68 ]. Adding a twist–bend nematic dimer N TB LC ( Figure 22 ) to a mixture comprising a nematic liquid crystal mixture and a chiral dopant S-811 stabilizes the cubic BPI, as shown in Figure 23 a.…”

Section: Materials Stabilizing Bpiiimentioning

confidence: 99%

“…Electro-optical switching in BPIII by using polymer-stabilized materials [ 14 , 49 , 75 , 76 ] or a low-molecular-mass system [ 68 , 77 ] has been reported. Gandhi and Chien et al reported that a polymer network based on BPIII can memorize the 3D structure on the original PS-BPIII from which they are nanoengineered, and can transfer this structural information to achiral nematic LCs [ 49 ].…”

Section: Physical Properties In Bpiiimentioning

confidence: 99%

Amorphous Blue Phase III: Structure, Materials, and Properties

Yoshizawa

2024

Materials

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Blue phases (BPs) have a frustrated structure stabilized by chirality-dependent defects. They are classified into three categories: blue phase I (BPI), blue phase II (BPII), and blue phase III (BPIII). Among them, BPIII has recently attracted much attention due to its elusive amorphous structure and high-contrast electro-optical response. However, its structure has remained unelucidated, and the molecular design for stabilizing BPIII is still unclear. We present the following findings in this review. (1) BPIII is a spaghetti-like tangled arrangement of double-twist cylinders with characteristic dynamics. (2) Molecular biaxiality and flexibility contribute to stabilize BPIII. (3) BPIII exhibits submillisecond response, high contrast, and wide-viewing angle at room temperature without surface treatment or an optical compensation film. It was free from both hysteresis and residual transmittance. The electro-optical effects are explained in relation to the revealed structure of BPIII. Finally, we discuss the memory effect of a polymer network derived from the defects of BPIII.

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Topological defects stabilized by a soft twist-bend dimer and quantum dots lead to a wide thermal range and ultra-fast electro-optic response in a liquid crystalline amorphous blue phase

Abstract: Amorphous Blue phase, or BPIII, a mesophase exhibited by highly chiral liquid crystals, is increasingly being investigated for next-generation displays due to its attractive electro-optical properties such as sub-millisecond response...

Cited by 3 publications

References 61 publications

Towards complete photonic band gap in a high refractive index nanoparticle-doped blue phase liquid crystal

Towards complete photonic band gap in a high refractive index nanoparticle-doped blue phase liquid crystal

Effect of High-Index Nanoparticles on the Emission Properties of a Dye-Doped Blue Phase Liquid Crystal

Amorphous Blue Phase III: Structure, Materials, and Properties

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