Fabrication of Liquid Crystal Sol Containing Capped Ag−Pd Bimetallic Nanoparticles and Their Electro-Optic Properties

Abstract

Liquid crystal molecule-capped Ag−Pd bimetallic nanoparticles (atomic ratio = 1/9, 1/4, 1/1, 4/1, and 9/1) were prepared by photoirradiation of the tetrahydrofuran solution of silver perchlorate and palladium(II) acetate in the presence of liquid crystal molecule, 4′-pentylbiphenyl-4-carbonitrile. (5CB is often used for this compound based on conventional nomenclature 4′-pentyl-4-cyanobipenyl. Thus, 5CB is used in this paper.) The prepared bimetallic nanoparticles had an average diameter of 1.8−3.6 nm. Infrared spectra of carbon monoxide adsorbed on the bimetallic nanoparticles suggested that bimetallic nanoparticles had a random alloy structure. The nanoparticles were dispersed in liquid crystal 5CB to construct novel twisted nematic liquid crystal devices (TN-LCDs). The TN-LCDs containing Ag−Pd bimetallic nanoparticles revealed the electro-optic properties depending on the composition of nanoparticles, especially surface composition of nanoparticles, which was shown to be of importance to control not only the properties but also the stability of nanoparticle-doped LCDs by bimetallization.