Self-organisation processes and phase-structural states in hybrid metal-mesogenic nanosystems

ABSTRACT

Hybrid nanosystems including silver and copper and long-chain mesogenic derivatives of alkylcyanobiphenyls have been obtained by low temperature vacuum co-condensation of reagent vapors on cooled surfaces of quartz, KBr, CaF₂ or polished copper under molecular beam conditions. Controlled thermal treatment of the samples allowed the directed formation of metal nanoparticles of definite size from 2 up to 100 nm. It was shown that manner of temperature treatment and molecular self-organisation of different liquid crystalline phases controlling of the size and morphology of nanoparticles and their aggregates formed in the system. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) data of the samples show the formation of orientationally ordered structures in nematic mesophases. Formation of flat 2D-aggregates has been found in layered smectic mesophases Optical absorbance spectra of silver/4-pentyl-4-cyanobiphenyl (Ag/5СВ) and copper/4-pentyl-4-cyanobiphenyl (Cu/5CB) samples encapsulated in polymer poly-para-xylylene at 300 K contain characteristic bands of plasmonic absorbance of metal nanoparticles at 420–440 nm and 560–600 nm. Rising of metal concentration in the sample led to the performable growth of rod-like metal particles with anisometric ratio l/d>20 and intensive absorbance at higher wavelengths (λ ≥ 650 nm)

KEYWORDS:

• hybrid metal-mesogenic nanosystems
• metal nanoparticles
• low temperature deposition
• optical properties

Acknowledgments

The authors thank the collaborators from Moscow State University Dr. S. Abramchuk for TEM measurements and Dr. A. Tikhomirov from NT-MDT company for AFM measurements. The work is financially supported by RFBR grant 13–03–00792-a.