- 标题
- 摘要
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- 实验方案
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Dielectric and electro-optic properties of two biphenylyl benzoate-based ferroelectric mesogens with tilted hexagonal phases
摘要： Two partially fluorinated ferroelectric liquid crystals (2F3R, 3F3R) with biphenylyl benzoate core have been investigated by frequency domain dielectric spectroscopy and electro-optic method. Both the compounds exhibit SmC* phase over a wide range of temperature along with tilted hexatic phase SmF* and soft crystal phases SmJ* (in 2F3R) and SmG* (in 3F3R) and one coexistence phase of (SmF*+SmC*). Both BOO phason and tilt phason relaxations are observed in SmF* phase and cooperative relaxation behaviour is also observed in crystal-like smectic phases. Goldstone mode relaxation is observed in SmC* phase and Maxwell Wagner mode is observed in all the phases. In 2F3R soft mode is detected in both SmC* and SmA* phases but not in 3F3R which melts directly to isotropic phase from SmC* phase. Compounds possess moderate values of spontaneous polarisation and exhibit quite sharp electrical response especially in 2F3R. Rotational viscosities, pitch and elastic constant are also measured. Effect of chain length and fluorination on various physical parameters has been discussed.
关键词： soft mode,tilted hexagonal phase,BOO and tilt phason mode,spontaneous polarisation,Ferroelectric liquid crystal,response time
更新于2025-09-12 10:27:22
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Investigation of dielectric and electro-optical parameters of high birefringent nematic liquid crystal doped with TiO <sub/>2</sub> nanoparticles and its applicability toward liquid crystal displays
摘要： In the present study, anatase TiO2 nanoparticles (NPs) have been doped in three different concentrations into nematic liquid crystal (NLC) 2020 (fluorinated 4’-alkylphenyl-4-isothiocyanatotolanes). The ratio has decreased and increased, response time and contrast respectively for the NLC-NPs composite system. Polarizing optical microscope images reveal that alignment has been improved after the doping of TiO2 NPs. Dielectric measurement study shows that the tan d has been decreased and relaxation frequency shifted toward the lower frequency region for the doped system. The outcome of the present investigation may be very useful in the improvement of electro-optical features of liquid crystal displays.
关键词： Nematic liquid crystal,response time,Contrast ratio,TiO2 nanoparticles
更新于2025-09-12 10:27:22
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Detection of IL-8 in human serum using surface-enhanced Raman scattering coupled with highly-branched gold nanoparticles and gold nanocages
摘要： Mesoporous materials are ideal carriers for guest molecules and they have been widely used in analytical science. The unique mesoporous structure provides special properties including large specific surface area, tunable pore size, and excellent pore connectivity. The structural properties of mesoporous materials have been largely made use of to improve the performance of analytical methods. For instance, the large specific surface area of mesoporous materials can provide abundant active sites and increase the probability of contact between analytes and active sites to produce stronger signals, thus leading to the improvement of detection sensitivity. The connections between analytical performances and the structural properties of mesoporous materials have not been discussed previously. Understanding the "structure–performance relationship" is highly important for the development of analytical methods with excellent performance based on mesoporous materials. In this review, we discuss the structural properties of mesoporous materials that can be optimized to improve the analytical performance. The discussion is divided into five sections according to the analytical performances: (i) selectivity-related structural properties, (ii) sensitivity-related structural properties, (iii) response time-related structural properties, (iv) stability-related structural properties, and (v) recovery time-related structural properties.
关键词： analytical science,stability,recovery time,response time,structure–performance relationships,selectivity,sensitivity,mesoporous materials
更新于2025-09-11 14:15:04
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37.5: Hybrid Backlight System based on Blue, Red LEDs and Perovskite Quantum Dots for Liquid Crystal Display Application
摘要： This paper reports a novel backlight system for liquid crystal display by combining blue and red emissive LEDs and perovskite quantum dots embedded composite films as color converters. The backlights can realize 95% BT.2020 color gamut with a brightness of 90% relative to the backlight using blue LEDs and YAG. In comparison to the backlights using blue LEDs, perovskite quantum dots and K2SiF6:Mn4+ phos- phors, this backlight system suppresses the tailing problem for dynamic dimming from red emissive K2SiF6:Mn4+ phosphors.
关键词： color gamut,perovskite quantum dots,delayed response time,hybrid backlight,dual LEDs
更新于2025-09-11 14:15:04
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The static and dynamic analysis of GaN-based blue light-emitting diodes used in visible light communication
摘要： The static and dynamic electrical characteristics of GaN-based blue light-emitting diodes with different numbers of quantum wells were investigated by software Silvaco technology computer-aided design numerically, which were essential for visible light communication study. As a factor impacts on the response time of light-emitting diodes, the capacitance, varying with applied bias, with modulation frequency, and with the numbers of quantum wells, was analyzed detailedly. Besides that, the response time of light-emitting diodes, including the optical rise time and fall time, was also ?rstly simulated in Silvaco, and then, based on these, the pure - 3 dB bandwidth of the light-emitting diodes without building-out circuit could be calculated, so as to self-design semiconductor devices like light-emitting diodes mentioned in this study with the optimum bandwidth used for visible light communication.
关键词： Silvaco,Visible light communication,Response time,Bandwidth,GaN-based LED
更新于2025-09-11 14:15:04
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Fast-Tunable Terahertz Metamaterial Absorber Based on Polymer Network Liquid Crystal
摘要： This paper introduces a tunable metamaterial absorber (MA) based on polymer network liquid crystal (PNLC) in the terahertz (THz) frequency band. Under the optimal polymerization condition, through electrical control of the orientation of the PNLC embedded in the frequency selective surface, the resonant frequency of the absorber can be tuned from 416.5 to 405.0 GHz, corresponding to fractional frequency bandwidth of 2.8%. The experimental results show that the proposed MA based on the PNLC offers an adjustment time of 10 ms and recovery time of 85 ms, which is significantly faster than the tunable metamaterial devices based on conventional nematic liquid crystal (LC).
关键词： liquid crystal,response time,absorber,terahertz,polymer network
更新于2025-09-09 09:28:46
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28.3: Development of High Performance TFT-LCD Module for Vehicle Display
摘要： The methods to achieve high performance vehicle displays are introduced. In order to achieve high contrast of wide viewing angle, the improvements include: a) the special function polarizer (POL), b) optical alignment process (OA), c) the optimal design of cell gap and d) a specific back light unit (BLU) film structure. Wide color gamut with high saturation is achieved by using the specially formulated light emitting diode (LED) with the specific color filter (CF). A special liquid crystal (LC) can help to come up to quick response time in wide temperature range.
关键词： wide color gamut with high saturation,vehicle display,quick response time in wide temperature range,high contrast of wide viewing angle
更新于2025-09-09 09:28:46
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Improvement of response time in GAGG:Ce scintillation crystals by magnesium codoping
摘要： Dynamics of the population of the excited Ce states responsible for the luminescence response time in Gd3Al2Ga3O12:Ce scintillating crystals is studied by revealing the dynamics of nonequilibrium carriers in the picosecond domain. Optical pump and probe technique exploiting selective excitation of structural units of the crystal and probing the induced absorption as a function of time and spectral position is exploited. A fast response within a few picoseconds due to the absorption by holes at Gd ions and by electrons occupying the first excited state of Ce ions with the intracenter relaxation time of 500 fs are identified. Trapping of nonequilibrium electrons during their migration through the matrix to the emitting Ce ions are shown to be responsible for the slow component in the population of the excited Ce state. Elimination of the slow component is evidenced even at Mg codoping as low as 10 ppm. The elimination correlates with the acceleration of the response in coincidence time resolution experiments showing potential of GAGG:Ce, Mg in medical and high-energy physics applications.
关键词： response time,nonequilibrium carriers,optical pump and probe technique,magnesium codoping,scintillation crystals,GAGG:Ce,coincidence time resolution
更新于2025-09-04 15:30:14