Preparation of ferroelectric nanoparticles for their use in liquid crystalline colloids

Atkuri, Hari M.; Cook, Gary; Evans, Dean R.; Cheon, Chae Il; Glushchenko, Anatoliy; Reshetnyak, Victor; Reznikov, Yuriy; West, John L.; Zhang, K.

doi:10.1088/1464-4258/11/2/024006

Cited by 67 publications

(60 citation statements)

References 19 publications

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“…The particle size, measured with dynamic light scattering, was always greater than reported in recent studies [1,3,5]. Dynamic light scattering measures the hydrodynamic radius of the particles when in dilute suspension.…”

Section: (Iv) Suspensionsmentioning

confidence: 67%

“…We tried to mill under equivalent conditions as described in Atkuri et al [5], but failed to generate samples that showed any characteristic indicative of ferroelectricity. The particle suspensions tested showed no shift in the Frederiks transition whether BaTiO 3 or silica nanoparticles were used.…”

Section: Discussionmentioning

confidence: 99%

“…for 510 min. This speed was adapted to the different disc radius of the Pulverisette 7 and the 510 min is a pure milling time, excluding cooling cycles which are necessary to keep the temperature inside the pots below 50 • C. The ratio of BaTiO 3 to milling beads by weight was 1 : 10 as recommended in Atkuri et al [5]. The hydrodynamic radius of the sample in heptane was determined as 315 ± 9 nm by light scattering, indicating substantial aggregation.…”

Section: (I) Ferroelectric Barium Titanatementioning

confidence: 99%

“…The technique is, therefore, only useful for assessing primary particle size for well-dispersed (non-aggregated) suspensions. Atkuri et al [5] determined the particle size by transmission electron microscopy (TEM). AFM was used here to attempt comparable measurements.…”

Section: (Iv) Suspensionsmentioning

confidence: 99%

“…While these improved properties are of great interest for display manufacturing, they appear to be dependent on the nematic host used and on the particle preparation and dispersion methods [4,5]. In this paper, we have prepared and carefully characterized particle systems in various ways and assessed their behaviour in both the ubiquitous nematic liquid crystal 4-cyano-4 -n-pentylbiphenyl (5CB) and the commercially important ZLI2293-a Merck nematic blend.…”

Section: Introductionmentioning

confidence: 99%

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The influence of suspended nanoparticles on the Frederiks threshold of the nematic host

Klein

Richardson

Greasty

et al. 2013

Phil. Trans. R. Soc. A.

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In recent years, several papers reported an enhanced dielectric anisotropy when ferroelectric particles were suspended in a liquid crystal. These results seem to be sensitive to the liquid crystal used and the preparation method of the ferroelectric particles. In this paper, we compare different preparation methods of suspended barium titanate in two different liquid crystal hosts. As a control experiment, we followed similar preparation steps with non-ferroelectric silica particles. In all cases, we found a broadening of the optical Frederiks transition but no change in the dielectric anisotropy. Raman spectroscopy has been used to investigate the loss of tetragonal structure in the barium titanate as a function of milling time and particle size. As reported in the earlier literature, barium titanate does not exhibit a welldefined tetragonal crystal structure below a certain particle size and loses its ferroelectric features. This provides a simple rationalization for the absence of any dielectric enhancement.

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Section: (Iv) Suspensionsmentioning

confidence: 67%

Section: Discussionmentioning

confidence: 99%

Section: (I) Ferroelectric Barium Titanatementioning

confidence: 99%

Section: (Iv) Suspensionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The influence of suspended nanoparticles on the Frederiks threshold of the nematic host

Klein

Richardson

Greasty

et al. 2013

Phil. Trans. R. Soc. A.

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Ferroelectric Colloids in Liquid Crystals

Reznikov

2012

Liquid Crystals Beyond Displays

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INTRODUCTIONFor many years the science of liquid crystals mostly served the needs of liquid crystal display (LCD) industry; vast majority of funds and human resources were directed to development of numerous LCD modes in nematic liquid crystals (LCs). It was the needs of LCD industry that initiated rapid development of surface LC science, deep studies of correlation between the molecular structures and macroscopic properties of nematic LCs. Studies of more complicated LCs phases and composite LC materials to a large extent have also been initiated by numerous attempts to propose competitive alternative to the traditional nematic LCDs (e.g. PDLCs, bistable LCDs, ferroelectric LCDs). By the beginning of the last decade, the LCD industry has reached such a high level that its further progress has become determined mainly by development of the technology of non-LC components (for example, by fabrication of gigantic highquality glass substrates for the last generation LCDs). This initiated some kind of rebooting of the scientific and mercantile interests of the LC scientific community. There are many sectors of hi-tech industry where LCs have great potentials, such as biotech, telecommunication, and optical processing. The new applications require new materials, sometimes with rather exotic properties, and new technologies. For example, LC materials for telecommunications usually require LCs with strong birefringence but low refractive index, adaptive LC optics needs materials with huge birefringence and low viscosity. Many promising applications of LC for terahertz region are suppressed by a strong absorption of LCs in this region; biotech needs replacement of thermotropic LCs to water-based lyotropic LCs. Tiny and precise patterning of LC alignment over the boundary surfaces becomes crucial for developing new optical elements. All of these new industry needs changed the priority points of LCs science; a number of LCD-related publications steadily decrease in expense of publications on application of LCs in photonics, optical processing, biosensors, and magneto-optics.One of the directions of the development of the modern LCs science is design and study of numerous LC composite materials. Long-distance orientation interaction in mesophase leads to extremely strong influence of a dispersed material on the mesogenic properties of the LC and vice versa; the LC matrix can effectively arrange the positional and translational ordering of the inclusions in the matrix. Therefore, combination of the orientational ordering and relative translation freedom in LCs with properties of the dispersed materials allows scientists to give unique properties to the composite, which are not inherent to its components. In order to obtain synergetic properties, part of the dispersion material in a LC matrix should not be high. Apparently, Brochard and de Gennes [1] first suggested that doping of a nematic LC with elongated submicron ferromagnetic particles in very low volume fraction (f n 10 À3 ) should result in drastic increase of the LC ...

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