Effect of inorganic 1D nanoparticles on electrooptic properties of 5CB liquid crystal

Abstract

Electrooptic properties of mixtures of 4-cyano-40 -pentylbiphenyl (5CB) thermotropic liquid crystal with four different inorganic dopants: (i) MoSI nanowires, (ii) MnO 2 nanorods, (iii) Ag nanowires, and (iv) WS 2 nanotubes were investigated by a conventional optical measurement technique. The dopant concentrations were in the range from 0.1 to 0.5 wt%. In all mixtures aggregation of the 1D nanoparticle (1D-NP) material was observed, therefore electrooptic response was probed in the regions in-between the aggregates. All four 1D-NP dopants produce a decrease of the threshold voltage for electrooptic switching and also a decrease of the corresponding switching times. The most profound effects are observed for MnO 2 /5CB system, which exhibits a reduction of the threshold voltage by a factor of 1.7 and a reduction of the total switching time by a factor of 1.5. The effect is associated with an increase of the dielectric anisotropy of the mixture. The specific behaviour of the MnO 2 nanorods is attributed to their relatively low aspect ratio that provides most suitable conditions for good alignment in the liquid crystal host. , are naturally suited for hosting 1D nanoparticles (1D-NPs), such as nanowires, nanotubes and nanorods. This is, because dispersions of rod-shaped objects in isotropic fluids commonly exhibit spontaneous formation of orienationally ordered phases by themselves [2-5], therefore introducing them into an LC host is expected to result in a synergetic orientational ordering process. However, in reality, the mixing behaviour is quite complex and addition of a relatively small amount ( 1 wt%) of 1D-NPs to the nematic LC host can cause both: increase or decrease of the orientational order of the host medium [6,7]. The effect depends on the size of the dispersed 1D-NPs with respect to the size of the LC molecules, on the interaction between the NPs and on the interfacial interaction between the NPs and the LC

Properties of a Thermotropic Nematic Liquid Crystal Doped with Graphene Oxide

“…[ 11 ] Rajh et al compared the effects of nanowires, nanorods, and nanotubes; they concluded that, due to the small aspect ratio, the nanorods showed more compatibility than the other nanomaterials. [ 12 ] In addition, 2D graphene fl akes doped in NLCs have improved electrooptic switching and dielectric anisotropy. [ 13,14 ] An investigation, like the one presented in this paper, combining two modern functional materials, liquid crystals and graphene oxide (GO), is not only of fundamental interest but also of applicational relevance.…”

“…[ 1,2 ] The incorporation of various nanomaterials into liquid crystals (LCs), and the complexity of their interaction, have recently attracted much interest. [3][4][5][6][7][8][9][10][11][12] The addition of nanoparticles (NPs) to liquid crystals produces composite materials with additional functionality, and tunable optic, electric, magnetic, or electrooptic properties. Both molecular and macroscopic bulk properties are modifi ed.…”

Composites of Inorganic Nanotubes and Polymers

“…Rajh and co-workers report electro-optic properties of mixtures of 4-cyano-4'-pentylbiphenyl (5CB) thermotropic liquid crystal with four different 1D inorganic nanoparticles [11]. The most profound effect was obtained for MnO 2 /5CB: a reduction of the threshold voltage by a factor of 1.7 and of the total switching time by a factor of 1.5.…”

Incorporation of luminescent semiconductor nanoparticles into liquid crystal matrix

“…Solubility of the nanoparticles in liquid crystal matrix is limited [4][5][6]. Authors of article [4] dissolved 0.3% of ferroelectric Sn 2 P 2 S 6 nanoparticles capped with oleic acid in liquid crystal and claimed no aggregation effect, however no photos of the mixtures were provided.…”

“…Authors of article [4] dissolved 0.3% of ferroelectric Sn 2 P 2 S 6 nanoparticles capped with oleic acid in liquid crystal and claimed no aggregation effect, however no photos of the mixtures were provided. Elongated particles of diameter from tens to hundreds of nanometers: MoSI and Ag nanowires, MnO 2 nanorods, WS 2 nanotubes, synthesized and used without surrounding ligands, added to liquid crystal at weight fraction in range 0.1-0.5%, caused aggregation effect and formation of two phase composition [5]. Usage of ligands with enhanced compatibility with liquid crystal molecules for gold nanoparticles made possible to dissolve maximum 0.2% of the nanoparticles in liquid crystal matrix [6].…”