Reversible Nanoparticle Cubic Lattices in Blue Phase Liquid Crystals

Area of Science:

• Materials Science
• Condensed Matter Physics
• Crystallography

Background:

• Blue phases (BPs) are liquid crystals (LCs) with 3D periodic ordering.
• BPs have been theoretically explored as templates for tunable colloidal crystals.
• The self-assembly of nanoparticles within BPs remains an underexplored area.

Purpose of the Study:

• To investigate the spontaneous formation of nanoparticle assemblies in blue phases.
• To characterize the structure and thermal reversibility of these nanoparticle assemblies.
• To explore the potential of BP-nanoparticle composites for novel optical materials.

Main Methods:

• Dispersion of functionalized gold nanoparticles (NPs) in cyanobiphenyl-based BPs.
• Characterization using polarized optical microscopy.
• Analysis of NP assembly structure using synchrotron small-angle X-ray scattering (SAXS).

Main Results:

• Spontaneous formation of thermally reversible, cubic crystal nanoparticle assemblies.
• Nanoparticles selectively migrate to trapping sites within BP disclination lines.
• The NP lattice is commensurate with the BP matrix and reversibly switches between cubic structures at the BP I to BP II phase transition.

Conclusions:

• Demonstrated spontaneous, robust, and reversible cubic nanoparticle assembly in blue phases.
• The NP lattice symmetry is coupled to the BP phase.
• These findings open avenues for developing dynamic optical materials based on liquid crystal-nanoparticle composites.