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(a) Typical TEM image of PbS NPs. Scale bar: 20 nm; POM optical image of sample with concentration of E7 (70.7 wt%): CB15 (22.6 wt%): R1011 (5.7 wt%) by doping of 0.15 wt% PbS NPs, the image was measured during the BP appearing process at (b) 39.1°C and (c) 38.1°C.
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A kind of blue phase liquid crystal (BPLC), consisting of nematic liquid crystal, E7, and chiral dopants, CB15 and R1011, was investigated by doping PbS nanoparticles. The blue phase temperature range was extended from 3oC to 4.6°C by doping PbS nanoparticles with diameters around 9.6 nm. A kind of porous texture was observed both in the forming pr...
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... size of the PbS NPs was measured using a trans- mission electron microscope (TEM, Tecnai G2 20S-TWIN), by taking a small amount (2 μL) of the sample on a carbon-coated copper grid in the isotropic phase, and rinsing the sample in acetone. Figure 3(a) shows a TEM image of the fabricated particles along with statistical data. The mean dia- meter was 9.6 nm, which was calculated by the aver- age diameter of sum of 200 NPs. ...
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... sample was cooled down from the isotropic phase 55°C decreasing to 38.1°C, at rate of 0.1°C /min which has stayed at 38.1°C for 15 minutes. Figure 3(b) and 3(c) show the optical image of BPLC sample measured under POM at 39.1°C and 38.1°C, respectively. It is noticed that a porous texture is found here, as shown in Figure 3(b), which was not found in corresponding BPLC sample without doping PbS NPs. ...
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... 3(b) and 3(c) show the optical image of BPLC sample measured under POM at 39.1°C and 38.1°C, respectively. It is noticed that a porous texture is found here, as shown in Figure 3(b), which was not found in corresponding BPLC sample without doping PbS NPs. ...
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... is worth noticing that, an interesting phenom- enon is that we observe a porous morphology here again, as shown in Figure 5(b) and Figure 5(e), which is similar to the textures found in Figure 3(b) during the PbS NPs doped BPLC formation process. As is known, the molecular orientation change occurred during the electric field assisting BPLCs. ...
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Citations
... After that experimentally the impact of CdSe and aerosil NPs of different concentrations on BP phases in CE8 LC were investigated using high resolution calorimetry and polarising microscopy. For the time being, various nanoparticles like graphene oxide [64], PbS [66], 3 4 [65], Ni [68], nickel zinc ferrite [67] and perovskite quantum dots [69] were dispersed in BPLCs to improve the thermal stability and the electro-optical properties of BPLC. ...
This paper presents a review of the literature that deals with Blue phase liquid crystal and focus on the recent progress in developing high performance applications. Blue phase liquid crystal show unique property of selective reflection of incident light and has potential to be used in fast light modulators or tunable photonic crystals. An extensive research is going on these materials to make them suitable for commercial displays and photonic technology. The presents work is an attempt to review the research carried out on Blue Phase Liquid Crystal materials and Devices. Starting from the brief history of Blue Phase Liquid Crystals, it mainly focuses on the recent advancement in development of highly efficient Blue Phase Liquid Crystal Devices for practical applications. The problems encountered in commercialization of Blue Phase Devices and the ways to overcome the issues is outlined. These Blue Phase Liquid Crystals are observed to show enhancement in their properties like high efficiency, wide viewing angle and excellent dark state without any damage to films, low operating voltage, high contrast ratio, high transmittance when doped with materials like polymers and nanoparticles and discussed in details. These promising results indicate that the Blue Phase Liquid Crystals materials with doping will play a vital role in development of devices for future applications.
... The expansion and stabilization of BP-I, BP-II phases by doping with spherical shape Au (∼10 nm) [29,30] and CdSe (3.5 nm) quantum dots [31,32] NPs were successfully achieved. Zhang et al. [33] dispersed PbS NPs (size < 10 nm) into BP material and observed a stabilization from 3°C to 4.6°C wide. Whang et al. [34] used ZnS NPs (size ∼ 33 nm) for BP stabilization and demonstrated a hysteresis-fee BPLC device. ...
... These porous type textures may be appeared due to the reorientation of LC molecules with the change in temperature. These types of textures were also reported by Zhang et al. [33] and gave the possible reasons for this reorientation of LC molecules due to electric field or diffusion of nanoparticles. On further reducing the temperature of the sample from Iso phase, growth of BP-II starts at 66.9°C (Figure 3(b)). ...
Blue phases (BPs) in chiral nematic liquid crystals (LC) remained a field of ample research interest due to their exotic optical properties. In the present work, we report the doping effect of dimensionality varying NPs (alumina nanowires [ANWs] and citrate buffer stabilized gold nanoparticles [GNPs]) on the phase transition temperatures and stability of the BP temperature range using polarizing optical microscopy. An increase in the BP thermal stability after the dispersion of NP is observed than an undoped sample. Doping of GNPs and ANWs could expand the BP temperature range of ∼8.0°C and ∼4.5°C respectively at an optimum concentration of dopants. A decrease in BP temperature range is noticed beyond a critical concentration of doped NPs. A platelet type texture, which corresponds to BP-I/BP-II is clearly seen.
... The combination of nanoparticles (NPs) and liquid crystals (LCs) has drawn widespread attention in the scientific field [1][2][3]. In the LC/NP composite systems, because of good compatibility of LCs and excellent properties of NPs, the NPs can improve the electro-optical properties of LCs [4][5][6][7][8][9][10][11][12][13][14], regulate LC alignment [15][16][17][18][19], and stabilise LC phases [20,21]. The E-O properties of chiral nematic LCs (N*LCs) are obviously improved by Cu 2 O with different crystal planes due to the exposure of different properties [8]. ...
Doping nanoparticles into liquid crystal (LC) systems can effectively improve the electro-optical (E-O) properties of LCs. The authors introduced three types of (cubic, octahedral, and rhombic dodecahedral) Au nanocrystals (NCs) into a nematic LC 4-cyano-4?npentylbiphenyl (5CB) and investigated the facet-dependent Au NCs in improving the E-O properties of 5CB. The surface energies of Au facets decreased in the order {110}>{100}>{111}. The improvement in the E-O properties of LC is related to the interaction between LC and different exposed crystal planes of dopants. Dodecahedral Au NCs, exposing {110} facets, are the most effective in improving the E-O properties because of their highest surface energy, resulting in a 30.15% reduction of the threshold voltage (Vth) and a 29.08% of the saturation voltage (Vsat) at a doping concentration of 0.4 wt%. The Au NCs trapped impurity particles. The screening effect could be suppressed, and the electric field could be strengthened, resulting in outstanding E-O properties. This work provides a novel way to enhance the E-O properties of LC molecules by doping with noble metal nanomaterials, thus improving their potential applications in energy-saving LC displays.
... Here it was observed that isotropic temperature of the BL036 (~95 C) reduced to very low value i.e. 40 C for BPLC material. This large decrement in isotropic temperature is attributed to the addition of CB15 having low melting point of~4 C. The similar observations were also reported by others [32,40]. ...
Graphene oxide (GO) in various concentrations (0.04 wt.%, 0.1 wt.% and 0.3 wt.%) was dispersed into nematic liquid crystal (LC) 5CB and studied for electro-optical, dielectric and optical responses. The textural and phase transition studies were investigated by optical polarising microscopy in the nematic phase. The effect of GO concentration on the micro-texture, phase transition temperatures, birefringence, threshold voltage, contrast ratio, dielectric permittivity, dielectric loss and conductivity was also investigated. The nematic–isotropic transition temperature slight increases (~3%) in the 0.04 wt.% and 0.1 wt.% GO dispersed 5CB composites as compared to 5CB. Threshold voltage decreases in the GO–5CB composites with the increase of GO concentration. Additionally, the effect of GO concentration on the optical absorbance of UV–visible light and energy bandgap is also considered.
... Here it was observed that isotropic temperature of the BL036 (~95 C) reduced to very low value i.e. 40 C for BPLC material. This large decrement in isotropic temperature is attributed to the addition of CB15 having low melting point of~4 C. The similar observations were also reported by others [32,40]. ...
Blue phase liquid crystal (BPLC) material was prepared using nematic liquid crystal (BL036) and a chiral dopant (CB15) in equal wt./wt. ratio. Polymer-stabilized blue phase liquid crystals (PSBPLCs) material was also prepared by polymer stabilization in BPLC material. The phase transition temperatures (Isotropic-BP, BP-N*) and electro-optic behaviour of PSBPLC material was investigated in thin cell. A platelet type texture clearly specifies the appearance of BP in the narrow range of 3.7 °C and increases up to 10.7 °C after polymer stabilization. This increment in BP range is attributed to the localization of the polymer at the disclinations lines and hence improve the thermal stability. The electro-optic parameters, such as On state voltage and Kerr constant were found 70 V and 1.04 nm/V2 respectively.
... Other techniques for BP stabilisation involve T-shaped molecules, [20] binaphthyl derivatives, [21,22] bent-shaped molecules, [23] hydrogen-bonded selfassembled complexes [24] and nanoparticles. [25][26][27][28][29][30][31] Coles and co-workers reported a dimeric LC having large flexo-electric coefficient and extended the BP range to 44 K. [32] PS-BPLC seems to be most promising but high onstate voltage (V on ), hysteresis, residual transmittance and long-term stability are a few remaining challenges yet to be resolved. The practical applications of BPs are limited due to hysteresis effect and many groups are actively engaged to meet this challenge. ...
In the present work, polymer-stabilised blue phase liquid crystal ***(PS-BPLC) that exhibit the blue phase (BP) in a temperature range of 312.15 K to 298.15 K has been prepared. The textural and electro-optic studies were performed in the BP range using an in-plane switching (IPS) cell. Platelet-type textures of cubic BP having an average domain size of ~12 µm were observed. The on-state voltage increased with increasing the temperature due to reduced value of the Kerr constant. Further, the hysteresis was found to be reduced from 19.2% to 5.1% by operating the PS-BPLC sample cell at an elevated temperature.
Blue phase liquid crystals (BPLCs) are chiral mesophases with 3D order, which makes them a promising template for doping nanoparticles (NPs), yielding tunable nanomaterials attractive for microlasers and numerous microsensor applications. However, doping NPs to BPLCs causes BP lattice extension, which translates to elongation of operating wavelengths of light reflection. Here, it is demonstrated that small (2.4 nm diameter) achiral gold (Au) NPs decorated with designed LC-like ligands can enhance the chiral twist of BPLCs (i.e., reduce cell size of the single BP unit up to ∼14% and ∼7% for BPI and BPII, respectively), translating to a blue-shift of Bragg reflection. Doping NPs also significantly increases the thermal stability of BPs from 5.5 °C (for undoped BPLC) up to 22.8 °C (for doped BPLC). In line with our expectations, both effects are saturated, and their magnitude depends on the concentration of investigated nanodopants as well the BP phase type. Our research highlights the critical role of functionalization of Au NPs on the phase sequence of BPLCs. We show that inappropriate selection of surface ligands can destabilize BPs. Our BPLC and Au NPs are photochemically stable and exhibit great miscibility, preventing NP aggregation in the BPLC matrix over the long term. We believe that our findings will improve the fabrication of advanced nanomaterials into 3D periodic soft photonic structures.
Blue phase liquid crystal material having a wide blue phase range of 7 °C was prepared in a binary mixture of nematic and chiral nematic liquid crystals with optimization of chiral dopant concentration. Magnetic nanoparticles of size 20 nm, 40 nm in varying concentrations (<0.5 wt %) could successfully stabilize the blue phase temperature range. Interestingly, the BP stability increases approximately 7.8 °C with an increase in nanoparticles concentration up to a critical concentration (0.1 wt %) and then gradually decreases at higher concentrations of nickel nanoparticles. A detailed comparative electro-optical study of pure blue phase liquid crystal and size dependent nickel nanoparticles doped blue phase liquid crystals is accomplished. The transmission of light increases up to 42–45% for nickel nanoparticles doped blue phase liquid crystal samples than pure blue phase liquid crystal with negligible residual birefringence. An increase in isotropic temperature was noticed in 40 nm nickel nanoparticles doped sample. Also an improvement in threshold voltage, induced birefringence, contrast ratio and Kerr constant with doping of nickel nanoparticles was observed. The present study is a synergistic correlation of size and concentration of nickel nanoparticles with blue phase liquid crystals and sufficiently productive for developing nanoparticles doped blue phase liquid crystal optical devices in future.
