Orientation Control of Helical Nanofilament Phase and Its Chiroptical Applications

Park, Wongi; Yoon, Dong Ki

doi:10.3390/cryst10080675

Cited by 18 publications

(15 citation statements)

References 106 publications

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“…[ 49 ] To unequivocally determine the mesoscopic morphology of the dark conglomerate phase, transmission electron microscopy (TEM) was used. TEM images of a dropcasted and heat‐annealed (i.e., heated above the isotropization point and then cooled down back to room temperature at 20 K min −1 ) material revealed helical nanofibers with dimensions characteristic of LC HNFs: [ 50–53 ] Pitch p ≈ 230 nm, width w ≈ 45 nm, thickness z ≈ 15 nm (Figure 1c). OIM nanofibers formed dendritic domains, suggesting that fibers in a single domain grow from a single nucleation point upon freezing.…”

Section: Resultsmentioning

confidence: 99%

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Liquid Crystal Templated Chiral Plasmonic Films with Dynamic Tunability and Moldability

Grzelak

Tupikowska

Vila‐Liarte

et al. 2022

Adv Funct Materials

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Thin films sustaining plasmonic circular dichroism (PCD) have acquired high scientific relevance and a great potential for applications. While most efforts in PCD thin film structures focus on lithographically fabricated static metasurfaces, the bottom-up fabrication of active chiral plasmonic films constitutes an alternative approach. Herein, the preparation of PCD thin films by melting and freezing a mixture of liquid crystal (LC), a chiral dopant, and gold nanoparticles (Au NPs), serving as helical matrix, symmetry breaking inducer, and plasmonic component, respectively is reported. UV-vis and circular dichroism spectroscopies, as well as theoretical modeling are used to disclose the interactions among thin film components, toward maximizing the PCD dissymmetry factor (g-factor). Variation of substrate temperature affords reversible off/on switching of the chiroptical response. The soft nature of LC matrix enables patterning of the films via a thermal nanoimprinting method, using a poly dimethylsiloxane mold for transfer-printing onto a flexible substrate, leading to stretchable PCD films. The PCD wavelengths can be readily tuned by varying the geometry of the Au NPs. This work provides an efficient technique to produce PCD thin films with active plasmonic properties and mechanical tunability.

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Section: Resultsmentioning

confidence: 99%

“…In the context of achieving higher g‐values in the visible range, the performed optical modelling directs our attention toward optimizing the characteristic of constituents to increase length of the helical assemblies (Figure 4g) and achieving directional control over HNF growth [ 77 ] (Figures S37 and S38, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Liquid Crystal Templated Chiral Plasmonic Films with Dynamic Tunability and Moldability

Grzelak

Tupikowska

Vila‐Liarte

et al. 2022

Adv Funct Materials

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“…An HNF is formed by twisted smectic layers composed of BLC molecules (Figure 1). [15, 26, 27] Here, a dimeric molecule having aromatic groups on both sides of a central alkyl linkage with an odd number of C atoms (Figure 1 a) was used as BLC [19, 28, 29] . In particular, it was reported that D–n dimers with photoresponsive azobenzene moieties in their arm parts could be uniaxially oriented when irradiated with unpolarized UV light due to the Weigert effect [19] .…”

Section: Resultsmentioning

confidence: 99%

Directing Polymorphism in the Helical Nanofilament Phase

Park

Yang

Park

et al. 2021

Chemistry A European J

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Herein, it is reported that the polymorphismin the helical nanofilament (HNF,B 4 )l iquid-crystallinep hase depends on the fabrication methods, that is, UV-driven formation andt emplate-assisted self-assembly in the nanoconfined geometry. As aresult, uniaxially oriented HNFs with different helical structures wereo btained, in which generation of the twisted-ribbon and cylindrical-ribbonp olymorphs showed that even the molecular lattice has ad ifferent orientation.T he detailed structures were directly observed by SEM and grazing-incidence X-ray diffractionw ith synchrotron radiation. Ther esultant polymorphs could be used in chiro-optical applicationsd ue to the capability for fine control of the helical structures.

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“…The absence of residual solvent in the sample was examined via phase-transition temperature measurement using polarized optical microscopy (POM). In the mixture system, unique phases found in the BC molecule, such as B2 and B7, readily disappeared upon mixing of the rod-like mesogen [8,13,14]. Instead, the aforementioned nano-sized separation phases, such as <HNF/N>, <HNF/SmA>, and <HNF/Iso> were observed.…”

Section: Methodsmentioning

confidence: 98%

“…A mixed system, consisting of an achiral bent-core (BC) molecule and rod-like nematogen, has been reported as a promising chiroptic material [4][5][6][7][8]. In this system, nano-sized phase separation-between helical nanofilaments (HNF) originating from the BC molecule and the calamitic liquid-crystalline (LC) nematic (N) phase originating from rod-like nematogen-shows high chiropticity, such as optical rotatory power or circular dichroism [5,9,10].…”

Section: Introductionmentioning

confidence: 99%

Enhancement of Luminescence Dissymmetry Factor in Nano-Segregated Phase Generated by Phase Separation between Helical Nanofilaments and Liquid-Crystalline Smectic A Phase

Lee

Choi

2020

Crystals

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Although several methods exist for the synthesis of circularly polarized luminescent (CPL) materials, the methods are extremely complex and tedious. In recent years, the chiral host-achiral luminescent guest method and the achiral host-achiral luminescent guest method have been employed to fabricate CPL materials; however, the main disadvantage of the latter is the small luminescence dissymmetry factor (glum) that limits the practical applications of the method. Therefore, this study reports on the enhancement of glum in a nano-segregated phase system, generated by the phase separation between helical nanofilaments (HNFs; originating from an achiral bent-core molecule) and a liquid-crystalline (LC) smectic A (SmA) phase (originating from an achiral rod-like mesogen). The observed glum value in the nano-segregated phase between the HNFs and LC SmA phase was larger than that in the nano-segregated phase between the HNFs and LC nematic (N) phase. The enhancement of the glum value was attributed to the order parameter (S) of the dye molecules in the SmA phase being larger than that in the N phase. Therefore, we concluded that the S value of the fluorescent dye molecules, doped into the embedded LC phase between the HNFs, strongly influenced the glum value.

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Orientation Control of Helical Nanofilament Phase and Its Chiroptical Applications

Cited by 18 publications

References 106 publications

Liquid Crystal Templated Chiral Plasmonic Films with Dynamic Tunability and Moldability

Liquid Crystal Templated Chiral Plasmonic Films with Dynamic Tunability and Moldability

Directing Polymorphism in the Helical Nanofilament Phase

Enhancement of Luminescence Dissymmetry Factor in Nano-Segregated Phase Generated by Phase Separation between Helical Nanofilaments and Liquid-Crystalline Smectic A Phase

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