Cholesteric liquid crystal-carbon nanotube hybrid architectures for gas detection

Chang, Chin Kai; Chiu, Shih-Wen; Kuo, Hui Lung; Tang, Kea Tiong

doi:10.1063/1.3679680

Cited by 34 publications

(19 citation statements)

References 13 publications

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“…It was reported that a hybrid material based on a cholesteric LC mixture and nanotubes could be used for detection of acetone vapors [240]. When the concentration of acetone (absorbed from air by the liquid crystal layer) is relatively low, the selective reflection maximum is shifted due to helical pitch variation.…”

Section: Smectic and Cholesteric Lcsmentioning

confidence: 99%

Carbon Nanotubes in Liquid Crystals: Fundamental Properties and Applications

Lisetski

Soskin

Lebovka

2015

Springer Proceedings in Physics

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The structure and properties of liquid crystalline suspensions filled by carbon nanotubes (CNTs) are critically reviewed. Special attention is paid to interactions between CNTs and molecules of the liquid crystals (LC), which lead to formation of ordered supramolecular structures. These structures, in turn, determine unique physical properties of LC + CNT suspensions, including electrical conductivity, dielectric permittivity, phase transitions, optical transmission, memory effects that can be used in electrooptic and optoelectronic devices, etc. Great variety of LC phases are considered as a host media, such as nematics, cholesterics, smectics of different types (including ferroelectrics), lyotropic, chromonic, ionic and hydrogen-bonded liquid crystals. Alongside multi-and single-walled carbon nanotubes, the suspensions can also contain the platelets of organoclays used for facilitation of CNT dispersing. Recent practical applications of LC + CNT suspensions and nanomaterials based thereon are also outlined.

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Section: Smectic and Cholesteric Lcsmentioning

confidence: 99%

Carbon Nanotubes in Liquid Crystals: Fundamental Properties and Applications

Lisetski

Soskin

Lebovka

2015

Springer Proceedings in Physics

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“…Whereas the commonly used nematic 5CB, other synthetic LCs and other phase (cholesteric) [69] or type (lyotropic) [70] of LCs offer a rich pool for exploration and provide more versatile properties. Taking advantage of emerging fabrication techniques, it is shown that low molecular weight LCs can be tailored to form a gel-like material with tunable mechanics [71], which promises a possibility of using LCs to culture mammalian cells (which are sensitive to substrate stiffness) [72] and reporting the interactions between cells and substrates.…”

Section: Discussionmentioning

confidence: 99%

Beyond displays: The recent progress of liquid crystals for bio/chemical detections

Dong

Yang

2013

Chin. Sci. Bull.

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Liquid crystals (LCs) are often known as electronic displays and have become ubiquitous in our daily life, apart from that, in the past 10 years, LCs have been investigated as exquisitely sensitive reporters for developing new molecular sensing and detection tools. The unique and primary advantage of this class of intriguing materials is the perturbation of the local ordering LCs at molecular scale by bio/chemical species can be communicated within LC molecules and extended over microns, allowing the observation of the optical signals by microscope or even the naked eye. Therefore, it provides a new platform for developing bio/chemical detection and potentially label-free sensing systems. In March 1888, a young botanist called Friedrich Reinitzer [1] first found that esters of cholesterol appeared to have two melting points between which the liquid showed iridescent colors and birefringence. Actually he discovered a new phase of matter: a liquid crystalline phase, distinguished from solids, liquids and gases that are already familiar to us [2]. Substances in this fourth state are called liquid crystals (LCs), flowing like a conventional liquid and exhibiting orientational order like a crystalline solid. In general, the molecules forming LCs are anisotropic, either rod-like or disc-like. There are two basic classes of LCs: thermotropic and lyotropic. In the thermotropic system, the liquid crystalline phase only exists within a particular temperature range, between a melting point, T m , and an upper transition temperature, T c (Figure 1). In the lyotropic system, LCs possess polar and non-polar parts within the same molecule. In a certain concentration range, molecules organize themselves into ordered structures showing LC properties. This review will not discuss lyotropes further and focus on thermotropic LCs, especially 4-cyano-4′-pentylbiphenyl (5CB), which exhibits liquid crystallinity in the nematic phase at room temperature, a simple and handy choice for constructing optical detectors performed at ambient condition. The key principle of employing LCs for molecular detection is illustrated in Figure 2. The local interruption of LC ordering at the molecular scale can be amplified to micron

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“…15 A hybrid CLC sensor containing CNTs (1.5%) was prepared and upon exposure to acetone a clear red-shi was observed up to a vapour concentration of 140 ppm. Acetone diffuses into the CLC lm, causing a swelling of the pitch and ultimately a total disruption of the liquid crystal assembly.…”

Section: Organic Vapour Sensorsmentioning

confidence: 99%

Chiral-nematic liquid crystals as one dimensional photonic materials in optical sensors

2014

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Current developments in the field of thermotropic chiral-nematic liquid crystals as sensors are discussed. These one dimensional photonic materials are based on low molecular weight liquid crystals and chiralnematic polymeric networks. For both low molecular weight LCs and polymer networks, real-time and time integrating sensors have been realized. The response mechanism is either based on a change of helical twisting power of the dopant upon exposure to an analyte, or due to physical swelling, with a change of order in the liquid crystalline phase upon uptake of the analyte, causing the pitch to change.Sensors that respond to organic and water vapour, amines, water CO 2 , O 2 , metal ions, pH, strain and temperature have been reported.

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Cholesteric liquid crystal-carbon nanotube hybrid architectures for gas detection

Cited by 34 publications

References 13 publications

Carbon Nanotubes in Liquid Crystals: Fundamental Properties and Applications

Carbon Nanotubes in Liquid Crystals: Fundamental Properties and Applications

Beyond displays: The recent progress of liquid crystals for bio/chemical detections

Chiral-nematic liquid crystals as one dimensional photonic materials in optical sensors

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