Achiral Nanoparticle-Enhanced Chiral Twist and Thermal Stability of Blue Phase Liquid Crystals

Abstract

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.

When Quantum Dots Meet Blue Phase Liquid Crystal Elastomers: Visualized Full-Color and Mechanically-Switchable Circularly Polarized Luminescence

“…1a; QDs accumulate along the disclination lines and interact with LC molecules at the boundaries of disclinations. 71,72 The samples were then exposed to 365 nm UV light for curing at 28.0°C for 5 mins, with an intensity of 30 mW/cm 2 (Fig. 1b).…”

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

“…, the ODA molecules tethered to the QDs, tend to interact with the LC molecules near the disclination lines reducing the free energy of the defect cores leading to close packing of the DTCs and hence lattice contraction. 55,56 This in turn results in increased chirality and thus induction/stabilization of BPIII.…”

Optimizing Tunable LC Devices with Twisted Light

“…Other stabilization methods rely on using an assortment of different kinds of doping materials inserted into the disclination lines, which aid in expanding the temperature ranges where the BP phases are present: using properly functionalized gold nanoparticles, highly stable BPs with adjustable optical properties can be obtained [83].…”