Quantum Dot-Driven Stabilization of Liquid-Crystalline Blue Phases

Abstract

Liquid crystals hosting nanoparticles comprise a fascinating research field, ranging from fundamental aspects of phase transitions to applications in optics and photonics. Liquid-crystalline phases exhibit topological defects that can be used for assembly of nanoparticles in periodical arrays, and at the same time, the nanoparticles can increase the stability range of liquid-crystalline phases. This has been experimentally demonstrated over the past few years in the case of blue phases that are present in some strongly chiral liquid crystals. Experimental results in quantum dot-driven blue phase stabilization are presented here by means of high-resolution calorimetry and polarizing optical microscopy. It is demonstrated that quantum dots essentially stabilize the macroscopically amorphous blue phase III. There are discussed similarities and differences between the effects of spherical and anisotropic nanoparticles on blue phase stabilization; moreover, future prospects and trends in the field are addressed.

Experimental Advances in Nanoparticle-Driven Stabilization of Liquid-Crystalline Blue Phases and Twist-Grain Boundary Phases

“…An overview of the recent advances in NP-driven BP and TGB phase stabilization has been provided, focusing on experimental studies. Calorimetric and optical measurements, as well as the resulting phase diagrams, have been presented on BP and TGB stabilization by: (a) spherical CdSe, CdSSe, and Au NPs [17,56,57,59,[71][72][73], and (b) MoS 2 nanoplatelets, r-GO and CoPt-decorated r-GO nanosheets [74][75][76]. The simultaneous use of calorimetry and microscopy confirms the thermodynamic stability of these phases.…”

“…The temperature profiles of heat capacity and the optical textures have been obtained for several mixtures of CE8 + CdSSe and CE8 + Au NPs by ac calorimetry and polarizing optical microscopy, upon heating and cooling. In both cases, the spherical NPs induce a mild increase of the total BP range and a substantial increase of BPIII range, at the expense of BPII and BPI that gradually disappear [71,72]. In addition, both types of NPs induce the N L * and TGB A phases [59,71,73].…”

“…A substantially different picture is obtained for LCs exhibiting all three BPs, such as CE8 and CE6. Our systematic studies in mixtures of CE6 + CdSe (3.5 nm, OA and TOP coating) [57], CE8 + CdSe (3.5 nm, OA and TOP coating) [56], CE8 + CdSSe (3.4 nm, enhanced OA and reduced TOP coating) [72], and CE8 + Au (10 nm, OA coating) [73] yield phase diagrams resembling to some extent the ones of increased chirality [33,34]. BPIII is enhanced, BPII vanishes, whereas BPI is either mildly affected or gradually disappears under the presence of spherical NPs.…”

“…The temperature-concentration (T-χ) phase diagram for the CE8 + CdSSe system is presented upon cooling (g). A strong stabilization of BPIII is evident at higher temperatures, while the TGBA and NL* phases are induced at lower temperatures[59,72].…”

Low-voltage and fast-response polymer-stabilized blue-phase liquid crystals achieved using a new organosilicone monomer

“…[24][25][26][27] To reduce the driving voltage, device structures and nanocrystal-doped BPLC materials have been investigated extensively. 9,[28][29][30][31][32] However, limited research into monomers has been carried out for the synthesis of the polymers that can stabilize the blue phase. 33 From the viewpoint of BPLC materials, a large Kerr constant (K) is more helpful to reduce the driving voltage, 10 because the on-state voltage is inversely proportional to ffiffiffiffi K p .…”