Low-frequency relaxation modes in ferroelectric liquid crystal/gold nanoparticle dispersion: impact of nanoparticle shape

ABSTRACT

Low-frequency (1 mHz–100 Hz) dielectric relaxation modes were experimentally studied in ferroelectric liquid crystal (FLC)/gold nanoparticles (nanospheres and nanorods) dispersion. It was demonstrated that the dielectric spectra of nanodispersion are strongly influenced by the shape of nanoparticles. Using different formalisms of the impedance spectroscopy, three possible low-frequency relaxation processes were found in the dispersions and the pure FLC. Due to the electrical double layers (EDLs) near nanoparticles and the alignment layers, one can observe the relaxation of the EDL polarisation around the nanoparticles (Schwarz’s relaxation) and near the driving indium tin oxide (ITO) electrodes (electrode polarisation). The other possible relaxation process is interfacial polarisation (Maxwell–Wagner mode) in which the frequency is unaffected by the nanoparticles. It was shown that Schwarz’s relaxation frequency strongly depended on the shape and size of the nanoparticles. Moreover, dispersion of nanoparticles significantly reduced direct current conductivity of the FLC mixture.

GRAPHICAL ABSTRACT

KEYWORDS:

• Ferroelectric liquid crystals
• gold nanoparticles
• relaxation modes
• dielectric spectroscopy
• electric double layers

Acknowledgements

The authors are thankful to I. Chernyaev for preparation of the FLC mixture.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors acknowledge financial support from the International Bureau of the German Federal Ministry for Education and Research (BMBF, Project BMBF/DLR 08/10), the German Science Foundation (DFG, Project Ha 782/98-1) and South Ural State University (National Research University) within the framework of Perspective Direction of Development № 2 and Physics Programs.