Effects of functionalized metal and semiconductor nanoparticles in nematic liquid crystal phases

Qi, Hao; Kinkead, Brandy; Hegmann, Torsten

doi:10.1117/12.759473

Cited by 48 publications

(34 citation statements)

References 23 publications

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“…convection rolls or Kapustin-Williams domains), 26,28,29 we here present new, detailed data from optical (textures and defects), electro-optic as well as alignment studies using magic-sized QDs with very low polydispersity index as dopants in the N-LC host LC1 (frequently used in earlier studies). To demonstrate effects of small changes in QD surface disorder or the QD surface composition on the optical, electro-optic and alignment properties of LC1, we selected three CdSe QDs with QD1 30 and QD2…”

Section: 25-27mentioning

confidence: 99%

Nanocomposites of a nematic liquid crystal doped with magic-sized CdSe quantum dots

Mirzaei

Urbanski

et al. 2011

J. Mater. Chem.

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We here report on the optical, alignment and electro-optic properties of a nematic liquid crystal affected by the presence of semiconductor CdSe magic-sized nanocrystals (MSNCs). Three single-sized CdSe samples were tested, exhibiting bright bandgap photoluminescence (PL) with l max z 463 nm and $10 nm full width at half-maximum (fwhm). The three quantum dot (QD) samples were passivated with a monolayer of myristic acid. Two of them (QD1 and QD2) only vary in the amount of defects as indicated by different bandgap and deep trap PL. The third MSNC sample (QD3) is compositionally different, doped with Zn. These MSNCs with almost identical sizes were doped at different concentrations (1-5 wt%) into the nematic phase of 5-n-heptyl-2-(4-n-octyloxyphenyl)-pyrimidine (LC1). Only QD3 showed the formation of birefringent stripes surrounded by areas of homeotropic alignment between plain glass slides at all concentrations as observed for many other nanoparticledoped nematic liquid crystals reported earlier by our group. In polyimide-coated glass slides favouring planar orientation of the nematic director, planar alignment was observed. Surprisingly, only the Zndoped magic-sized QD3 quantum dots (CdSe@Zn) significantly lower the dielectric anisotropy as well as the splay elastic constant of the nematic host, despite identical size and surface functionality, which highlights the tremendous effect of the nanocrystal core composition on the electro-optic properties of the nematic host. In addition, fluorescence confocal (polarizing) microscopy studies show the director field within and around the birefringent stripes and confirm locally elevated concentrations or aggregates of the MCNC that are otherwise randomly distributed in the nematic host.

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Section: 25-27mentioning

confidence: 99%

Nanocomposites of a nematic liquid crystal doped with magic-sized CdSe quantum dots

Mirzaei

Urbanski

et al. 2011

J. Mater. Chem.

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“…In 2008, we reported that mixtures of two types of CdTe QDs of two different sizes (3.5 and 4.1 nm) capped with a mixed monolayer consisting of thioglycolic acid and hexane or dodecane thiolate, respectively, in nematic 5-n-heptyl-2-(4-noctyloxyphenyl)-pyrimidine (Felix-2900-03) and 4-octyl-4 0 -cyanobiphenyl (8CB) showed lower threshold voltages, V th , and altered dielectric permittivities (3 || and 3 t ). 126 The results obtained from electro-optic measurements using these two CdTe QDs as additives indicated that the QDs with shorter alkyl chain length in the capping layer induced more pronounced effects regarding the electro-optic parameters of the N-LC used in comparison to other QDs and even gold NPs at the same size-regime.…”

Section: -3mentioning

confidence: 96%

Quantum dots as liquid crystal dopants

2012

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Liquid crystal nanoscience, a field exploring the mutually beneficial combination of the unique properties of nanoscale materials and fluid, yet ordered liquid crystalline phases, is increasingly focusing on semiconductor quantum dots. In one major research thrust, the anisotropic properties of the liquid crystal host are sought to facilitate the assembly of quantum dots into arrays, in another, both size-and shape-dependent optical and electronic properties of quantum dots are used to manipulate optical, electro-optical and alignment properties of liquid crystalline materials. This feature article reviews recent accomplishments and new insights in this fascinating area of soft matter nanocomposites including work from our laboratory on a series of CdSe and CdTe quantum dots as additives in nematic liquid crystal hosts.

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“…For example, switching voltages and times of nematic liquid crystal cells can be reduced by adding only a few volume percent of metal NPs (see, for example, Refs. [2][3][4][5][6]). Doping of nematics with strongly polar ferroelectric NPs also leads to an increase of their dielectric constant and enhances the electro-optic response [7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Phase behavior and orientational ordering in block copolymers doped with anisotropic nanoparticles

et al. 2018

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This version is available at https://strathprints.strath.ac.uk/64399/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output.Phase behaviour and orientational ordering in block copolymers doped with anisotropic nanoparticles. A molecular field theory and coarse grained computer simulations with dissipative particle dynamics have been used to study the spontaneous orientational ordering of anisotropic nanoparticles in the lamellae and hexagonal phases of diblock copolymers and the effect of nanoparticles on the phase behaviour of these systems. Both a molecular theory and computer simulations indicate that strongly anisotropic nanoparticles are ordered orientationally mainly in the boundary region between the domains, and the nematic order parameter possesses opposite signs in adjacent domains. The orientational order is induced by the boundary and by the interaction between nanoparticles and the monomer units in different domains. In simulations, sufficiently long and strongly selective nanoparticles order also inside the domains. Nematic order parameter and local concentration profiles of nanoparticles have been calculated numerically using the model of a nanoparticle with two interaction centres and also determined using the results of computer simulations. A number of phase diagrams have been obtained which illustrate the effect of nanoparticle selectivity and molar fraction of the stability ranges of various phases. Different morphologies have been identified by analysing the static structure factor and a phase diagram has been constructed in coordinates nanoparticle concentration -copolymer composition. Orientational ordering of even a small fraction of nanoparticles may result in a significant increase of the dielectric anisotropy of a polymer nanocomposite which is important for various applications.

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Effects of functionalized metal and semiconductor nanoparticles in nematic liquid crystal phases

Cited by 48 publications

References 23 publications

Nanocomposites of a nematic liquid crystal doped with magic-sized CdSe quantum dots

Nanocomposites of a nematic liquid crystal doped with magic-sized CdSe quantum dots

Quantum dots as liquid crystal dopants

Phase behavior and orientational ordering in block copolymers doped with anisotropic nanoparticles

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