一种基于光子晶体的雾霾检测仪的设计

为设计雾霾检测仪,由Si和LiF介质组成了一含缺陷层的光子晶体.在考虑两介质色散关系的基础上,利用传输矩阵法对其透射特性进行了研究.计算表明,此光子晶体在580 ～ 720 nm的范围内出现了一个透射率为1的缺陷模,此缺陷模有如下特征:缺陷层中折射率变化时,不影响缺陷模的透射率,只改变缺陷模的中心位置,且缺陷模的中心波长与缺陷层中的折射率有线性关系.两介质几何厚度分别增加时,缺陷模的透射率不变,但其中心位置红移.缺陷层的几何厚度单独变化时,仅影响缺陷模的中心位置,几何厚度增加,缺陷模中心红移,且移动率一定.缺陷模的以上特征为利用此类光子晶体设计雾霾检测仪提供了有益的指导.     

一维光子晶体结构参数的随机扰动对其光学特性的影响

用特征矩阵法研究结构参数存在随机扰动的情况下一维光子晶体的光学特性, 无论是加工过程中介质层几何厚度的误差, 还是介质层折射率的随机波动都会影响一维光子晶体的光学特性.随机扰动对一维光子晶体带结构高频部分影响较大, 造成带结构消失, 甚至全部变成禁带; 随机扰动对光子晶体缺陷模式的影响是使缺陷模的位置发生随机平移, 平移的程度与随机度有关, 介质层折射率的随机变化要比介质层厚度的随机变化对缺陷模位置的影响要大; 周期数目的增加可以部分地减小缺陷模的平移, 但同时会使缺陷模透射率减小,增加缺陷层厚度可以有效降低随机扰动对光子晶体缺陷模式的影响. 本文的研究将对一维光子晶体的设计工作提供有价值的参考.     

一种基于光子晶体的糖溶液检测仪的设计

为设计糖溶液浓度检测仪,由LiF和Si介质组成了一含缺陷层的光子晶体.在考虑两介质色散关系的基础上,利用传输矩阵法对其透射特性进行了研究,计算表明,此光子晶体在400～ 700 nm的范围内出现了一个透射率为1的缺陷模,此缺陷模有如下特征:缺陷层中糖溶液浓度变化,不影响缺陷模的透射率和半峰全宽度,只改变缺陷模的中心位置,且糖溶液浓度与缺陷模的中心波长呈线性关系.两介质几何厚度分别或同时增加,缺陷模的透射率和半峰全宽度均不变,但其中心位置红移,移动率分别保持不变;LiF单独变化时,中心位置的移动率最小,LiF和Si同时变化时,移动率最大.不同介质几何厚度变化时,糖溶液浓度与缺陷模的中心波长呈不同的线性关系,但可通过重新定标来确定.     

一种基于光子晶体的多通道倍频滤波器

本滤波器所用的光子晶体由ZnS和复折射率介质交替排列而成.利用传输矩阵法进行数值计算的结果表明,该光子晶体的透射谱具有以下特征:当两介质的光学厚度均为特征波长的四分之一时,在特征频率的偶数倍频附近出现了透射率为13.7的窄带透射峰,而其它位置均为禁带.周期数增加,透射峰位置稍有蓝移,峰值不变.入射角增大,透射峰位置不变,峰值下降.两介质的几何厚度同时变化时,透射峰的峰值保持不变,位置随之变化,几何厚度增加,透射峰位置蓝移,反之亦然.以上特征为此类光子晶体实现多通道倍频滤波提供了理论指导.     

基于含掺杂半导体复合光子晶体的太赫兹多通道滤波器

用n型掺杂GaAs和TiO2组成两个相同的光子晶体,并把它们串联成一个复合光子晶体.数值计算表明,复合光子晶体在0.1～6 THz的频段出现了数个相同的透射峰,这些透射峰有如下特征:当n型掺杂GaAs的掺杂浓度＞1020/m3并继续增加时,从高频到低频各透射峰的透射率依次下降直至消失.当周期数变化时,透射峰的个数M和周期数N间满足关系式M=N-1,且N一定时,各透射峰的形状和中心间距相同.入射角增加时,各透射峰中心的移动很小,且入射角越大,各透射峰的半峰全宽度越窄.介质的几何厚度增加时,各透射峰的透射率和半峰全宽度不变,仅是其中心位置红移.这些现象为此复合光子晶体实现太赫兹频段的多通道滤波提供了理论指导.     

含左手材料的——维“啁啾”光子晶体的偏振特性

把“啁啾”函数引入含左手材料的一维光子晶体中,且左手材料的介电常数和磁导率采用Lossy Dryde model,利用传输矩阵法研究了其透射谱.结果表明:在“啁啾”函数对材料几何厚度调制较小时,该光子晶体有完整的禁带,随着调制的加强,禁带宽度增加,但底部逐步抬高.在相同的调制下,磁、电等离子体频率的比值越大,禁带宽度越宽.入射角增加,TE模的禁带宽度不变而TM模的禁带宽度变窄,TE模和TM模均产生了角度隙,此角度隙的宽度随入射角增加而变宽,且TM模的变化大于TE模的.周期数N变化时,角度隙基本不变.nR的变化对禁带和角度隙的位置没有影响,但nR越小,禁带底部越高且圆,角度隙中透射峰峰值越大.     

含缺陷的一维镜像光子晶体的量子理论

用量子理论新方法研究一维镜像光子晶体,将光的量子波动方程应用到一维光子晶体中,推导出量子传输矩阵,量子透射率和量子反射率公式.进一步研究缺陷层数目以及吸收介质和激活介质对一维光子晶体量子透射特性的影响,从而可以设计出光学滤波器、放大器和衰减器.当加缺陷层时,缺陷模出现尖锐峰,当缺陷层数目增加时,缺陷模个数增加,可设计为多通道光学滤波器.在缺陷层中加入吸收介质时,缺陷模强度减弱.在缺陷层中加入激活介质时,缺陷模强度增强,可设计为光学放大器和衰减器.     

一种基于复式光子晶体的多通道红外滤波器

用LiF和Si构成了一(ABBA)N型光子晶体,考虑到材料的色散关系,对其透射特性进行了研究,结果表明:在44~46μm的范围内出现了若干透射峰,透射峰的数目k与结构周期数N间满足k=N-1的关系。入射角增加,各透射峰的位置红移,长波端透射峰的红移量比短波端的稍大,当入射角θ≥45°时,短波端透射峰的透射率有所下降。两介质的几何厚度同时增加时,各透射峰的中心蓝移,对应的透射率不变;反之,其中心红移,且长波端透射峰的透射率下降。透射峰的以上特征为其实现多通道的红外滤波提供了理论指导。     

梳状光子晶体滤波器的设计

选用常见的LiF和Si为介质,并在考虑其色散关系的基础上,针对2000 nm的特定波长设计了一普通光子晶体,并将其串联成梳状光子晶体滤波器.数值计算表明该滤波器具有以下特征:在1800~2200 nm的波长范围内有多个滤波通道,普通光子晶体周期N增加,滤波通道数增加,间距变小.串联数M增加,通道位置和其透射率峰值均不变,透射谱原准禁带的底部逐渐下降.N或M增加,滤波通道对应的透射峰的半峰全宽变窄,滤波性能改善.入角度θ>10°时,各通道中心都有蓝移,原特定波长处的移动量较小,而两侧的移动量较大.入射角越大,这些变化越明显.     

吸收条件下光子晶体介观压光效应的研究

在考虑材料吸收的情况下利用传输矩阵的方法研究光子晶体介观压光效应.研究表明:当在光子晶体的轴向方向施加应力产生应变时,光子晶体缺陷模将向左(波长小的方向)移动;缺陷模透射峰的峰值和半高宽不随应变的变化而变化;当消光系数和有效弹光系数增大时,介观压光系数的绝对值将会减小,即缺陷模透射率对应力的变化越来越不敏感.这为高灵敏应力传感器的设计提供了理论参考.     

CsI-LiCl共晶材料的坩埚下降法生长与闪烁性能研究

本文采用坩埚下降法,在真空密封的石英坩埚中成功生长出CsI-LiCl与CsI-LiCl:Na共晶闪烁体。通过扫描电子显微镜(SEM)观察晶体微结构表明该共晶中LiCl相与CsI相存在周期性的层状排列,CsI相的厚度在5 μm左右。共晶样品的X射线激发发射谱显示在CsI-LiCl和CsI-LiCl:Na共晶样品存在缺陷发光,在CsI-LiCl样品中还观察到了纯CsI的自陷激子(STE)发光。CsI-LiCl样品在α粒子激发下的多道能谱中观察到明显的全能峰,这一结果证明CsI-LiCl共晶可用于热中子探测的潜力。     

静电纺丝法制备CeO2微纳米纤维及其除氟性能

以聚丙烯腈(PAN)为载体,六水合硝酸铈[Ce(NO₃)₃·6H₂O]为原料,采用静电纺丝法制备了Ce(NO₃)₃/PAN纤维,在空气中热处理得到CeO₂微纳米纤维,通过XRD、BET和SEM对CeO₂微纳米纤维进行表征。采用静态吸附实验探讨了CeO₂微纳米纤维去除水溶液中氟离子的性能,考察了溶液pH值、初始氟离子浓度及共存阴离子等对吸附性能的影响。结果表明,pH=3时,CeO₂微纳米纤维对F^-的吸附性能最佳,CeO₂吸附量随着F^-浓度的增大呈上升趋势。CeO₂微纳米纤维对F^-的吸附等温线遵循Langmuir模型,二级动力学模型能很好地描述CeO₂微纳米纤维对F^-的吸附过程。CeO₂微纳米纤维的除氟性能优良,可为其实际应用提供理论参考。     

X-ray analysis of sideroxol from <Emphasis Type="Italic">Sideritis leptoclada</Emphasis>

Sideroxol (1), a kaurane diterpene which has the ent-7α,18-dihydroxy-15β,16β-epoxykaurane structure (MW = 320.47, C₂₀H₃₂O₃) was obtained from the acetone extract of Sideritis leptoclada plant as well as from some other Sideritis species. It crystallizes in the orthorhombic space group P2₁, 2₁, 2₁ with a = 10.967(3), b = 24.555(5), c = 6.372(4) Å, Dc = 1.240 g cm⁻³, Z = 4, and refines to R = 0.065 for 721 independent reflections. The skeleton consists of three fused six-membered rings and a five-membered ring with fused epoxide. The six membered rings exhibited slightly distorted chair conformation. In addition to sideroxol, two kaurane and five kaurene diterpenes were isolated from the hexane and acetone extracts of the studied plant.     

Photoluminescence characteristics of Mg- and Si-doped GaN thin films grown by MOCVD technique

We have studied the optical, structural and surface morphology of doped and undoped GaN thin films. The p- and n-type thin films have been successfully prepared by low-pressure MOCVD technique by doping with Mg and Si, respectively. The different carrier concentrations were obtained in the GaN thin films by varying dopant concentrations. Photoluminescence (PL) studies were carried to find the defect levels in the doped and undoped GaN thin films at low temperature. In the undoped GaN thin films, a low intensity and broad yellow band peak was observed. The donor–acceptor pair (DAP) emission and its phonon replicas were observed in both the Si or Mg lightly doped GaN thin films. The dominance of the blue and the yellow emissions increased in the PL spectra, as the carrier concentration was increased. The XRD and SEM analyses were employed to study the structural and surface morphology of the films, respectively. Both the doped and the undoped films exhibited hexagonal structure and polycrystalline nature. Mg-doped GaN thin films showed columnar structure whereas Si-doped films exhibited spherical shape grains.     

New zeotype borophosphates with chiral tetrahedral topology: (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II))

Two new isostructural open‐framework zeotype transition metal borophosphate compounds, (H)_0.5M_1.25(H₂O)_1.5[BP₂O₈]·H₂O (M = Co(II) and Mn(II)) were synthesized by mild hydrothermal method. The structure of compounds were characterized by single‐crystal X‐ray diffraction which have ordered, alternating, vertex‐sharing BO₄, PO₄, and (MO₄)OM(H₂O)₂ groups with hexagonal, P 6₁ 2 2 (No 178) space group and unit cell parameters for Co a = 9.4960(6) Å, c = 15.6230(13) Å, for Mn a = 9.6547(12) Å, c = 15.791(3) Å, Z = 1 for both of them. TGA/DTA analysis, IR spectroscopy were used for characterization. Magnetic susceptibility measurements for both of the compound indicate strong antiferromagnetic interaction between metal centers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Solubility of Ag2O into the Na2O–B2O3–Al2O3 system

The solubility of Ag₂O was measured for the Na₂O–B₂O₃ and Na₂O–B₂O₃–Al₂O₃ system with the rotating crucible method and static method, respectively, under air atmosphere at temperatures ranging from 1273 to 1423 K. The contamination of melts from crucibles could be avoided by the rotating crucible method, with which it became possible to measure the solubility of Ag₂O for the Na₂O–B₂O₃ system above the melting point of Ag for the first time. It was found that the addition of Na₂O decreases the solubility of Ag₂O while the addition of Al₂O₃ had little effect on the solubility. The effect of Na₂O and Al₂O₃ on the solubility of Ag₂O is expressed by interaction coefficients and is analyzed in terms of the basicity of melts. The solubility of Ag₂O in Na₂O–B₂O₃–Al₂O₃ melts increased with increased temperature. This phenomena was explained by a small enthalpy change in oxidation of silver.     

Selinidin: Crystal structure generated by C–H···O, C–H···π and π-π interactions

The title compound, 9,10-dihydro-8,8-dimethyl-2-oxo-2H,8H-benzo[1,2-b:3,4-b']dipyran-9-yl-2-methyl-2-butenoate, C₁₉H₂₀O₅, was isolated from the roots of Selinum vaginatum. The compound crystallizes into monoclinic space group P2 ₁ with unit cell parameters: a = 12.830(2) Å, b = 9.041(1) Å, c = 14.983(1) Å, β = 95.09(1)°, Z = 4. The crystal structure has been determined using direct methods and refined by full-matrix least-squares to a final R value of 0.0529 for 3142 observed reflections. There are two independent molecules, A and B, per asymmetric unit. In both the molecules, the coumarin nucleus is planar. However pronounced differences are observed in the conformation of dihydropyran ring which has a half-chair conformation with an 8β-9α orientation in molecule A and is intermediate between half-chair and sofa in molecule B. Differences also occur in the conformation of the 2-methylbutenoyloxy side chain at C9 due to the different geometry of C–H···π interactions in molecules A and B. Molecules A and B are connected by π–π interactions between their coumarin fragments forming dimers. The dimers interact through C–H···O and C–H···πhydrogen bonds.     

Chromene and Imidazole Based D-π-A Chemosensor Preparation and Its Anion Responsive Effects

We have designed and synthesized the colorimetric chemosensor through the reactions of 2-(4H-chromen-4-yildene)malonitrile and 4-imidazolecarboxaldehyde. Due to its well conjugated D-π-A system and the existence of NH- fragment in structure, we expected that the chemosensor can detect anion using NH- fragment in the imidazole moiety of the structure. In this regard, UV-Vis absorption spectra were measured to investigate sensing properties of the probe toward different anions in DMSO. This chemosensor can detect both fluoride and cyanide ion with absorption change in intensity. In addition, pH sensing property was also investigated upon the addition of hydroxide ion. These properties are related to the deprotonation effect. The ICT system in this molecule was also observed by the computational approach using Material Studio 4.3 package.     

电子显微分析在表征纳米晶体化学组分中的应用

纳米材料的化学组分及含量影响其光、电、声、热、磁等物理性能,电子显微分析是表征纳米晶体化学组分的重要方法之一.本文综述了X-射线能谱(EDS)、X-射线波谱(WDS)、电子能量损失谱(EELS)和选区电子衍射(SAED)等现代电子显微分析技术在表征纳米晶体化学组分、形貌、尺寸和结构等方面的应用及其研究进展,并比较了这些分析方法存在的差异,提出了其应用中存在的不足及今后的研发方向.     

Considerations on the structure and physical properties of B2O3-SiO2 and GeO2-SiO2 glasses

Data of density, refractive index and thermal expansion coefficient for B₂O₃-SiO₂ and GeO_2-SiO₂ glasses have been analyzed. The volumes of the structural units are the same found for the vitreous B₂O₃, GeO₂ and SiO₂. The volume of any structural unit is constant over the entire composition region of the glass system. The same has been found for the differential refraction and unit refraction of the structural units in these glasses. Different features are observed for the differential expansion of the structural units. There is a considerable change with composition in the differential expansion of BO₃, GeO₄ and SiO₄ units. The effect is attributed to a change in the asymmetry of vibrations with the number of Si-O-B or Si-O-Ge linkages in the matrix. The thermal expansion coefficient is mainly determined by the contribution of B₂O₃ or GeO₂ in the concerned glasses.