胶囊化胆甾液晶薄膜在不同基板下的光电性能

采用紫外光聚合诱导相分离法制备了胶囊化胆甾液晶薄膜,系统研究了玻璃和塑料基板对于驱动电压、反射率及对比度等显示性能的影响。研究表明:不论是玻璃或塑料基板,液晶胶囊化均有助于显示对比度的提升,同时相应的驱动电压也有所增加。相较于刚性的玻璃基板,在柔性基板下液晶胶囊化前后的驱动电压由70V增加到200V,显示对比度达到6.2∶1。总体而言,初步实现了胆甾液晶的柔性显示。     

带宽可调型光学滤波器的研究

为了研究带宽可调型光学滤波器,采用对手性液晶膜施加电压的方法,对手性液晶布喇格反射带宽随外加电场的变化规律进行了分析和测量.实验结果表明,在外加电场到达一定的阈值后,液晶分子要旋转一定的角度;在外加电场和液晶盒边界条件的共同限制下,手性液晶的螺距在螺旋轴方向上形成了梯度变化,造成了手型液晶布喇格反射带宽的加宽,且反射带宽随外加电压的增加而增加,以此可制成带宽可调型光学滤光片.     

Alcohol‐Responsive,Hydrogen‐Bonded,Cholesteric Liquid‐Crystal Networks

Hydrogen‐bridged, cholesteric liquid‐crystal (CLC) polymer networks are adopted as an optical sensor material to distinguish between ethanol and methanol. Fast uptake of the alcohols is facilitated by an incorporated porosity created by breaking the hydrogen bridges and by a previously removed non‐reactive liquid‐crystal agent. The discrimination between the alcohols is based on the diversity in molecular affinity of ethanol and methanol with the hydrogen‐bridged CLC polymer networks. The CLC networks are molecular‐helix‐based, one‐dimensional bandgap materials with a discrete reflection band in the visible part of the spectrum that depends on the pitch of the molecular helix. The changes in positions of the reflection bands of the CLC network accurately discriminate between the alcohol types and provide information on their ratio in case they are blended.     

Controlling Surface Plasmon Optical Transmission with an Electrochemical Switch Using Conducting Polymer Thin Films

Surface plasmon resonance (SPR)‐enhanced optical transmission is actively controlled by an electrochromism of conducting polymer thin films. Polyaniline and poly(3,4‐ethylenedioxythiophene) thin films are deposited on a thin gold grating surface. SPR‐enhanced optical transmission is demonstrated by irradiating white light on the conducting polymer thin film–gold grating surface and detecting the transmitted light from the back side. The transmission SPR system is combined with an electrochemical setup to manipulate the resonance. The wavelength of the sharp peak in the transmission light spectra is tuned by electrochemical doping/dedoping of the conducting polymer thin films. The present study of controllable SPR‐enhanced optical transmission should provide novel active plasmonic devices such as active bandpass filters or biosensors.     

An Optical Sensor Based on a Photonic Polymer Film to Detect Calcium in Serum

An optical calcium sensor is fabricated based on a cholesteric liquid crystalline (CLC) polymer containing benzoic acid metal binding sites. A chiral imprinted CLC polymer is made which is subsequently treated with KOH to yield a responsive green reflecting film. On investigation of various metal ions, the polymer film shows a high optical response, and selectivity for calcium ions, which is related to the preorganized binding sites in the ordered liquid crystalline phase, leading to a blue reflecting film. The photonic polymer film is sensitive to Ca²⁺ within the physiologically relevant concentration range of 10^?4 to 10^?2 m . Measurement of total calcium concentration in serum is also investigated using the film. The optical responses of normal serum and samples mimicking hypocalcemia and hypercalcemia can be clearly distinguished, providing a cheap, battery‐free, and easy‐to‐use alternative for calcium determination in clinical diagnostics.     

环己烷类聚硅氧烷侧链液晶的合成与液晶行为研究

选用环己烷类液晶基元反式-4-乙烯基-反式-4’-丙基双环己烷(MA)和反式-4-丁烯基-反式-4’-丙基双环己烷(MB),通过硅氢加成反应将其接枝到柔性的聚硅氧烷主链上,合成了含有2种环己烷结构的聚硅氧烷侧链液晶P_(AB),产率为80.3%。采用傅立叶变换红外光谱法(FTIR)和氢核磁共振谱法(~1H-NMR)对其分子结构进行表征,说明其分子结构符合预期;采用热台偏光显微镜法(POM)和X射线衍射法(XRD)对其液晶相类型和液晶行为进行观察和分析,发现在升降温过程中所呈现出胆甾相油状条纹织构和小板块织构,揭示出因有序度不同所导致的不同织构特征;采用差示扫描量热法(DSC)和综合热分析法(TGA)对其热性能进行分析,确定其液晶区间为28.68K,T_(d(5wt%))为405.25℃,均高于液晶基元的液晶区间和热稳定性。     

A Ca-Ion Electrochromic Battery via a Water-in-Salt Electrolyte

Multivalent-ion batteries with electrochromic functionality are an emerging green technology for development of low-carbon society. Compared to Mg²⁺, Zn²⁺ and Al³⁺, Ca²⁺ has a low polarization strength similar to that of Li⁺, therefore Ca²⁺ for electrochromism and battery can avoid kinetic issues caused by other multivalent-ions with high polarization strength. Here, by exploiting Ca-ion carriers for electrochromism and a water-in-salt (WIS) Ca(OTF)₂ electrolyte for the first time, a new and safe aqueous Ca-ion electrochromic battery (CIEB) has been demonstrated. The WIS Ca(OTF)₂ electrolyte demonstrates enhanced anion-cation interactions and decreased water activity. Vanadium oxide (VO_x) and indium hexacyanoferrate (InHCF) films are respectively developed as anode and cathode because of their stable and high-rate Ca²⁺ insertion/extraction, as well as matched electrochromism. The CIEB demonstrates a stable and high-rate capability, a high energy density of 51.4 mWh m⁻² at a power density of 1737.3 mW m⁻², and a greenish yellow-to-black electrochromism. The presented results are beneficial for understanding redox kinetics in WIS electrolytes, and inspire researches on batteries and electrochromism with multivalent-ions.     

Electrochemical synthesis of copolymers based on 2-(anthracen-9-yl)thiophene: A facile and efficient route to a series of multicolor electrochromic polymers

A monomer named 2-(Anthracen-9-yl)thiophene (An-Th) has been synthesized via Stille coupling reaction, while its homopolymer is difficult to prepare on the conducting electrode via electrochemical methods. However, it can be a good comonomer to obtain copolymers with other monomers such as thiophene (Th), selenophone (SePh), 3-methylthiophene (MeTh) and 3,4-ethylenethiophene (EDOT) via electrochemical copolymerization. The structures of the prepared copolymers are characterized via FTIR and XPS analysis. In addition, the spectroelectrochemical and electrochromic properties of these copolymers are also investigated. The derived copolymers present multicolor electrochromism, which can be tuned by the applied comonomer and polymerization solvent. Moreover, the copolymers have reasonable switching response and stability. All of these indicate that the synthesized Th-An can be applied as a good comonomer for preparation of electrochromic copolymers.     

基于LVDS的长线传输模块设计

针对并行长线数据传输速度过慢的实际情况,文中介绍了一种基于LVDS串行总线长线传输模块设计。系统采用FPGA作为主控芯片,采用高速串行数字接口自适应电缆均衡器和电缆驱动芯片,增强长线电缆驱动能力,提高了LVDS数据传送的距离。其中通过双绞线电缆、光纤,DS92LV1023和DS92LV1224型号的LVDS芯片与驱动芯片CLC001和CLC006相互配合能使数据传输100米。该系统已投入使用,其性能具有较高可靠性、很强的应用价值。     

局域单PT对称势中基态孤子的传输特性研究

具有Parity-Time (PT)对称性的光学系统是近年提出的一种新型光学结构,在光开关、光子信息处理器件等方面具有潜在的应用.文章数值研究了局域单PT对称光学系统中基态孤子的存在范围与稳定特性.研究结果表明:基态孤子存在一临界传播常数,该传播常数对应线性模下的本征值.孤子的能量随着传播常数的增加而增加,但随着PT对称势的调制深度的增加而减少.基态孤子在较深和较浅的PT对称势中都能稳定地传输.     

基于光学滤波的水面弱纹理提取方法研究

水下潜体运动产生的内波反映到水表会形成一定的红外弱纹理信号,这使得利用红外遥感手段探测成为可能。但是这种纹理信号的对比度很弱,而且往往和振幅很强的背景杂波混在一起,给信号的提取造成很大困难。比较了已有水面弱纹理探测方法的优缺点,提出光学滤波的方法增强水面弱纹理信号的信杂比,使这种信号的提取更容易。基于非相干光学滤波的原理和特定信杂比评估弱纹理信号提取性能的方法,对不同特定频率信号的光学滤波方法采用信杂比进行分析和评估,然后在此基础上,针对特定频率的信号优化了相应的非相干光学传递函数,通过仿真和实验验证了该方法的可行性,同时表明优化的双孔径非相干光系统对弱纹理模型和信号具有较好的提取能力,该优化的系统可以得到7%以上的信杂比增强,再结合后续的数字对比度增强技术可以进一步有效提高对弱纹理信号的提取能力。     

Phototunable Azobenzene Cholesteric Liquid Crystals with 2000 nm Range

Phototuning of more than 2000 nm is demonstrated in an azobenzene‐based cholesteric liquid crystal (azo‐CLC) consisting of a high‐helical‐twisting‐power, axially chiral bis(azo) molecule (QL76). Phototuning range and rate are compared as a function of chiral dopant concentration, light intensity, and thickness. CLCs composed of QL76 maintain the CLC phase regardless of intensity or duration of exposure. The time necessary for the complete restoration of the original spectral properties (position, bandwidth, baseline transmission, and reflectivity) of QL76‐based CLC is dramatically reduced from days to a few minutes by polymer stabilization of the CLC helix.     

Optimal design of periodic surface texture for thin‐film a‐Si:H solar cells

Optical analysis of hydrogenated amorphous silicon (a‐Si:H) solar cells with a periodic texture applied to the interfaces was carried out by two‐dimensional optical simulator. The optical simulator solves the electromagnetic wave equations by means of finite element method using triangular elements for the discretization of space. The periodic texture with rectangular‐like shape acts as a diffraction grating which scatters light into selective angles and thus gives a potential for significant prolongation of optical paths in thin absorber layers of the cells. Optimization of the geometrical parameters (period, height and duty‐cycle) of the periodic texture was carried out in order to obtain the highest photocurrent from a‐Si:H solar cells. The a‐Si:H solar cell with the optimal periodic texture parameters (period of 300 nm, height of 300 nm and duty cycle of 50%) and the absorber layer thickness of 300 nm generates up to 35% more photocurrent in comparison to the cell with flat interfaces. The optical analysis demonstrates that the optimal periodic texture in the a‐Si:H solar cell results in the best trade‐off between the antireflection effect at front interfaces, light scattering efficiency and the absorption losses at realistic metal back contact. Copyright © 2010 John Wiley & Sons, Ltd.     

Preparation,characterization and photocatalytic properties of polythiophene-sensitized zinc oxide hybrid nanocomposites

The composites of polythiophene (PT)/zinc oxide (ZnO) nanoparticles with different PT wt%, (2%, 4%, 6%, 10% and 20%), were synthesized by an in situ chemical oxidative polymerization method. Zinc oxide nanoparticles, prepared by polymer pyrolysis method, with average particle size of 30 nm were used as inorganic phase of these composites. The particle size of ZnO powder was measured by transmission electron microscopy (TEM). FTIR measurements and X-ray diffraction analyses showed that PT/ZnO composites were successfully synthesized. Optical properties of the prepared composites were investigated by diffuse reflectance spectroscopy (DRS) that showed a broad peak in the visible region. The morphologies of the obtained composites were studied by scanning electron microscopy (SEM). Also Barrett–Emmett–Teller (BET) technique was used to measure the specific surface area of the samples. The photocatalytic activities of the composites were evaluated by degradation of methyl orange (MO) aqueous solution under visible light (9 W LED lamp) and sunlight irradiation.     

Novel pulsed-laser-deposition—VO<Subscript>2</Subscript> thin films for ultrafast applications

VO₂ thin films deposited on fused quartz substrates were successfully fabricated by the pulsed-laser-deposition (PLD) technique. The obtained samples were examined by microscopy and x-ray diffraction (XRD). The films show a fast, passive thermochromic effect of semiconductor-to-metal phase transition (PT) with a characteristic hysterisis at ∼68°C. The thermochromic effect was measured as resistivity, optical transmission, and reflection versus temperature. Under pulsed laser excitation, an optically induced ultrafast PT of VO₂ thin film was observed. Using the degenerate-four-wave-mixing (DFWM) technique, it was found that excited state dynamics is responsible for the induced lattice reorientation polarization, which results in the ultrafast PT.     

Obtaining Reversible,High Contrast Electrochromism,Electrofluorochromism, and Photochromism in an Aqueous Hydrogel Device Using Chromogenic Thiazolothiazoles

There have been an increasing number of materials developed that show multifunctional chromogenic properties (such as electrochromism, electrofluorochromism, or photochromism), but to date, few materials have shown all three properties. Materials that are electrochemically and optically active are attractive for a diverse set of applications that include smart-windows, lighting, sensing, energy production, and conservation. This is especially attractive for building developers interested in adaptive or environmentally responsive façades. Achieving systems made from cost-effective, readily synthesized materials will make them easy to utilize in a variety of fields. Low-cost devices are developed using water-soluble, chromogenic thiazolo(5,4-d)thiazole (TTz) dyes that show high device performance in three areas: electrochromism, electrofluorochromism, and photochromism and are all contained within a highly fluorescent aqueous polyvinyl alcohol/borax hydrogel device. The dyes incorporate a rigid, heterocyclic TTz structure that enables the development of devices with excellent reversibility and stable cycling for 250 cycles. The TTz hydrogel-containing devices also exhibit photochromism under illumination, which can be electrochemically cycled back to the colorless state. In addition, coupling photochromism with electrochromism lowers the power necessary for a comparable electrochromic color change. Last, the hydrogel-containing devices also show electrofluorochromism, where fluorescence can be turned off by > 90%.     

Biosensor Array of Interpenetrating Polymer Network with Photonic Film Templated from Reactive Cholesteric Liquid Crystal and Enzyme‐Immobilized Hydrogel Polymer

A biosensor array is fabricated using an interpenetrating polymer network consisting of photonic film templated from reactive cholesteric liquid crystal (CLC) and enzyme‐immobilized polyacrylic acid (PAA). The solid‐state photonic film on the glass substrate is successfully templated by ultraviolet (UV) curing of the reactive CLC mixture of a reactive mesogen mixture of RMM 727 (from Merck) and a nonreactive chiral dopant of (S)‐4‐cyano‐4′‐(2‐methylbutyl)biphenyl following the extraction of the chiral dopant. The acrylic acid monomer mixed with a cross‐linker of tri(propylene glycol) diacrylate is infiltrated into the extracted space of the photonic film, and UV‐cured with a photomask to obtain a patterned array‐dot film. The interpenetrated cholesteric liquid crystal/hydrogel polymer network (CLC‐hydrogel‐IPN) array is further functionalized in the individual dots with urease, for a model study of biosensor array applications. The dots of the CLC‐hydrogel‐IPN array respond independently to the urea by a color change with high sensitivity and stability. Thus, the patterned CLC‐hydrogel‐IPN can be used as a new biosensor array for cost‐effective and easy visual detection without any sophisticated instruments.     

Sol–gel derived nanocrystalline TiO2 thin films: A promising candidate for self-cleaning smart window applications

In the present work, anatase TiO₂ films are prepared by sol–gel spin coating method. The structural and optical properties of the films have been studied at different post-annealing temperatures. The photocatalytic activity and electrochromic performance of the films are investigated. The films annealed at 400 °C exhibit the highest photocatalytic activity with a rate constant of 4.56×10⁻³ min⁻¹. The electrochromic performance for the films annealed at 400 °C expressed in terms of difference in optical density (ΔOD) at 550 nm between coloured and bleached state is 0.5493. This combination of photocatalysis and electrochromism makes the sol–gel derived titania thin films as promising candidates for self-cleaning smart window applications.     

Semiconductor-to-metallic phase transition of VO<Subscript>2</Subscript> by laser excitation

VO₂ thin films deposited on MgO and fused silica glass substrates were prepared by the pulsed laser deposition (PLD) technique, which shows phase transition (PT) from the monoclinic semiconductor phase to a metallic tetragonal rutile structure at temperatures over 68°C. The observed PT is reversible, showing a typical hysteresis. The PT can also be induced through optical pumping by laser excitation. In this case, it was found that the optically induced PT is ultrafast and passive, but not thermally initiated. In order to understand the PT mechanism, a study of transient holography using degenerate-four-wavemixing (DFWM) measurement was conducted. A Nd:YAG pulsed laser with pulse duration of 30 psec operating at 532 nm was employed as the coherent light source. This showed that the observed transient holography in VO₂ thin film is associated with the excited state dynamical process, which essentially causes the structural change, or so-called optically induced PT. The observed extremely large polarizability is believed to relate to the large offset in the potential well minimum between the ground state and excited state. Through an unidentified intermediate state, the transient lattice distortion triggered the structural change.     

Internal electrochromism in vanadium pentoxide xerogel films

We describe the internal electrochromic effect in V₂O₅ xerogel films caused by the redistribution of hydrogen ions inside the film, instead of insertion from the outside, i.e. from an electrolyte, as in the case of conventional electrochromism. A hypothesis is put forward according to which the mechanism of this electrochromic effect is associated with formation of red-colored hexa- and (or) deca-vanadic acid inclusions inside the vanadium pentoxide layers. This model is supported by the calculated data of energy characteristics of V–O chemical bonds in V₂O₅ octahedra layers of xerogel, as well as by the experimental results of XRD, FTIR, and optical spectroscopy.