基于T-Hg~(2+)-T结构的非标记共振光散射法检测汞离子

根据目标物诱导核酸分子构象发生变化,导致体系共振光散射强度增大的原理建立了检测Hg~(2+)的新方法。当溶液中有Hg~(2+)存在时,基于"T-Hg~(2+)-T"特异性结合作用,促使Hg~(2+)特异核酸探针的构象发生变化,由单链状态变为刚性双链结构,使体系共振光散射强度增大。在波长566nm处,当汞离子浓度在7.2×10~(-9)~9×10~(-8)mol·L~(-1)范围内时,体系的共振光散射增强程度ΔI与汞离子的浓度(c)具有良好的线性关系。其线性方程为ΔI=5.12c+3.55(r=0.999 5)。将该方法用于环境水样中汞离子的测定,相对标准偏差(RSD)小于1.9%;样品加标回收率为99.4%~104.3%。该方法以Hg~(2+)的高度特异性核酸探针作为识别元件,通过控制Hg~(2+)浓度的变化调节共振光散射强度的变化,将Hg~(2+)的检测转化为对DNA分子构象变化的检测,该转化有利于增强体系共振光散射强度,提高方法灵敏度,该共振光散射检测方法能检测到浓度为2.16×10~(-9)mol·L~(-1)的Hg~(2+)。同时,由于"T-T"错配碱基对对Hg~(2+)的特异结合能力,显著提高了该分析方法对Hg~(2+)的选择性。另外,该方法操作简便、不需标记。     

碳量子点-VB2荧光共振能量转移法测定VB2

用微波法合成了具有发光特性的CDs,以发射波长为447nm的CDs为供体,维生素B2 (VB2)为受体,建立了一种以十六烷基三甲基溴化铵(CTAB)为介质的荧光共振能量体系检测VB2含量的方法.结果表明:在pH=7.1时,VB2的浓度与Fa/Fd值在1.8×10-8-3.0×10-7mol/L范围内呈线性关系,其线性方程为Fa/Fd=0.0766C(×10-8mol/L)+0.5658,相关系数为0.9996,检出限为8.3×10-9 mol/L.     

基于Schiff碱结构的香豆素类荧光探针的合成及对Mg~(2+)的识别

以2-氨基苯并咪唑和7-羟基香豆素为基本原料制备了Mg~(2+)荧光探针,采用核磁共振谱与质谱等手段对产物的构成进行了详尽的表征。然后通过荧光发射光谱的测试分析,了解了探针的各项性能。结果显示,在MeOH∶H_2O=1∶1(V∶V)混合溶液中探针对Mg~(2+)具有良好的选择性而不受其他金属离子(Ca~(2+)、Na~+、Li~+、K~+、Cu~(2+)、Fe~(3+)、Zn~(2+)、Ni~(2+)、Mn~(2+)、Ba~(2+)、Cd~(2+)、Cr~(3+)、Ag~+、Al~(3+)、Hg~(2+)、Co~(2+)、Pb~(2+))的干扰。探针对Mg~(2+)具有可逆性,其检测限为7.3×10~(-8) mol/L。通过对探针的性能研究可知该探针能够完成对Mg~(2+)的检测,在生命医学、环境科学及分析化学等领域具有潜在的应用价值。     

钇(Ⅲ)-环丙沙星配合物的荧光性质及其应用

研究了稀土钇离子(Y3+)与环丙沙星(CPLX)体系的荧光特性,Y3+可使体系的荧光强度明显增强,由此建立测定环丙沙星药物的新方法。对CPLX-Y3+体系荧光增强的机理进行了初步探讨,并系统研究了CPLX-Y3+体系荧光强度的影响因素。在pH=5.5的Tris-HC1缓冲溶液中,Y3+浓度为5.0×10-5mol/L时,环丙沙星的浓度与体系的荧光强度呈良好的线性关系,线性范围为1.0×10-9~2.0×10-6mol/L,检出限为3.1×10-11mol/L(S/N=3)。该方法可用于人体尿药浓度和环丙沙星片剂的直接测定。     

苯并噻唑类探针取代基结构对金属离子识别性能的影响

荧光探针对识别金属离子具有检测快、选择性好等特点,设计合成了两个苯并噻唑类探针分子6-(3,5-二甲基苯氧基)-5-胺基-2-苯基苯并噻唑(L4)和6-(3,5-二甲基苯氧基)-5-苯甲酰胺基-2-苯基苯并噻唑(L5),并通过探针分子的紫外可见光谱和荧光光谱的变化特征,详细研究了探针L4和L5对溶液中三价金属离子Al~(3+), Fe~(3+), Cr~(3+)和二价金属离子Cu~(2+)的识别性能。研究结果表明,当L4分子中的识别基团胺基与苯甲酰基键合形成L5分子结构时,会发生荧光猝灭,同时获得了开启式荧光探针L4和关闭式荧光探针L5。紫外可见光谱检测结果表明,在有机溶液中,探针L4选择性地识别出Al~(3+), Fe~(3+), Cu~(2+);在含水乙腈溶液中,探针L4高选择性地识别出Cu~(2+);通过紫外光照射下的裸眼检测,含探针L4的试纸有效地识别出纯水中的Cu~(2+);在有机溶液中,探针L5选择性地识别出Al~(3+)和Fe~(3+)。荧光光谱检测结果表明,当探针L4与Fe~(3+), Al~(3+), Cu~(2+)存在于有机溶液中时, L4将发生荧光猝灭;在含水乙腈溶液中,探针L4对Cu~(2+)具有高选择性识别作用;当探针L5与Cr~(3+), Fe~(3+), Al~(3+), Cu~(2+)存在于有机溶液中时, L5的荧光强度依次增强。利用溶液浓度对吸收强度作图,计算出了探针L4对Cu~(2+)的检出限为4.51×10~(-6) mol·L~(-1),络合常数Kα为1.12×10~3 M~(-1);探针L5对Al~(3+), Cr~(3+), Fe~(3+), Cu~(2+)的检测限分别为2.85×10~(-6), 4.79×10~(-6), 5.95×10~(-6)和3.23×10~(-6) mol·L~(-1),络合常数分别为:Kα(Al~(3+))=2.17×10~3 M~(-1),Kα(Cr~(3+))=2.06×10~3 M~(-1),Kα(Fe~(3+))=3.92×10~3 M~(-1),Kα(Cu~(2+))=4.43×10~3 M~(-1)。根据探针与识别金属离子的荧光滴定实验结果,推测出探针分子与金属离子之间形成了1∶1络合物。抗金属离子干扰实验结果表明,探针分子对特定金属离子的识别基本不受其他干扰金属离子的影响。~1H NMR滴定结果表明,探针L4分子结构中胺基和二甲基苯氧基,探针L5分子结构中的苯甲酰胺基和二甲基苯氧基取代基在识别金属离子过程中发挥了重要作用。探针L4在识别Cu~(2+)方面具有更广阔的应用前景。     

Cu~(2+)参与的N-乙酰基-L-半胱氨酸修饰的CdTe量子点用于测定D-/L-青霉胺

以N-乙酰基-L-半胱氨酸作为修饰剂,合成了高荧光产率的CdTe量子点。在pH为7.80的磷酸缓冲溶液中,Cu~(2+)可以显著猝灭量子点的荧光,有趣的是,在猝灭体系中加入手性青霉胺(PA)可使其荧光恢复。因此基于量子点的荧光变化,建立了快速检测D/L-青霉胺的方法。在最优的实验条件下,NALC-CdTe QDs-Cu~(2+)体系测定青霉胺的范围为2.0×10~(-7)～4.0×10~(-6) mol·L~(-1),检出限为5.8×10~(-8) mol·L~(-1).将该法成功用于实际样品中检测D/L-青霉胺,取得了满意的结果。     

Hg~(2+)@CDs的荧光传感体系检测水质中的I~-

在人体内部环境中,碘是合成甲状腺激素的关键原料之一,而甲状腺激素主要功能是促进人体生长发育以及调节新陈代谢,因此碘对人体内部环境正常运转起到至关重要的作用。碘在人体内主要以碘化氨基酸的形式存在于甲状腺中,对其常用的检测手段有很多种。而这些方法虽然具有较高精度以及灵敏度高,但检测过程较为复杂且检测周期较长。因此,发展一种成本较低、操作简单、快速准确的I~-检测方法具有应用意义。研究设计一种简便且快速精准的I~-检测方法,利用荧光"Off-On"传感体系对溶液中I~-进行定量检测。以柠檬酸为碳源、乙二胺为氮源,通过水热法一步合成水溶性较好且具有良好荧光性质的碳点(CDs)。利用荧光光谱仪以及紫外-可见光光谱仪对该CDs的光学性能进行表征。通过分析CDs的光谱可知该CDs的激发波长为345 nm,发射波长为470 nm。另外,通过傅里叶-红外光谱仪以及高分辨紫外光电子能谱对该CDs表面的官能团以及元素进行分析检测。通过荧光光谱进行检测,可以发现当CDs溶液中存在Hg~(2+)时, CDs的荧光发生猝灭现象。其原因是CDs与Hg~(2+)的d轨道间非辐射电子转移或Hg~(2+)与CDs表面的氨结合形成非荧光复合物,导致CDs的荧光强度下降。通过将最佳浓度的Hg~(2+)与CDs溶液进行混合,来制备Hg~(2+)@CDs的荧光传感体系溶液。分析Hg~(2+)@CDs的荧光传感体系溶液的荧光光谱图可以发现,当Hg~(2+)@CDs的荧光传感体系溶液中存在I~-时,体系荧光强度随着I~-浓度的上升而逐渐增强。该原因可以归根于I~-与Hg~(2+)之间存在较强的相互作用可将Hg~(2+)从CDs表面脱附,使CDs的荧光重新恢复,从而实现I~-的荧光"Off-On"检测。利用该方法来检测溶液中的I~-,其检测范围在5.0～75μmol·L~(-1),而检测限为0.25μmol·L~(-1)。实验最后还利用荧光光谱仪对Hg~(2+)@CDs的荧光传感体系的选择性以及抗干扰能力进行分析,结果显示该荧光传感体系对I~-具有较好的选择性以及良好的离子抗干扰性能。     

氮掺杂碳量子点的合成及作为荧光探针对Hg~(2+)的检测

与传统量子点相比,碳量子点作为一种新型的荧光碳纳米材料,由于其良好的生物相容性、易于表面功能化、低毒性等优点受到了广泛关注。采用柠檬酸为碳源,氨水为氮源,热解法制备出水溶性好的氮掺杂碳量子点(NCDs)。透射电镜(TEM)观察NCDs的粒径在3nm左右;X射线光电子能谱(XPS)和傅里叶红外光谱(FIIR)证明NCDs的表面被羧基、氨基、羟基、羰基等官能团功能化,说明NCDs有很好的水溶性。研究还发现Hg~(2+)对NCDs的荧光有良好的猝灭作用,可作为荧光探针检测水中Hg~(2+)含量。在PBS缓冲液中(0.1mol·L~(-1) pH 7.0),NCDs的荧光猝灭率(F/F0)与汞离子浓度在0.001~0.1μmol·L~(-1)之间存在良好的线性关系,检出限为2.1nmol·L~(-1)。该方法灵敏度高、选择性好、方法简便,可应用于Hg~(2+)快速、灵敏的检测。     

CdTe量子点荧光猝灭法测定钴

以CdTe量子点作为荧光探针,基于荧光猝灭法对钴(Ⅱ)进行了定量检测,考察了缓冲溶液体系、量子点浓度、反应时间等多种因素的影响。实验结果表明,在pH8.0的0.2mol/LNa2HPO4-NaH2PO4缓冲液中,反应时间为10min,钴(Ⅱ)浓度为1.6×10-5—20×10-5mol/L范围时,其线性回归方程为F0/F=1.45+0.096Q(10-5mol/L),检出限为3×10-7mol/L。该方法检测范围宽,灵敏度高,为钴的测定提供了新的方法。     

基于CdTe量子点荧光猝灭-恢复方法测定依诺沙星的研究

水相合成了巯基丙酸保护的CdTe量子点。根据在Cu2+存在的情况下,CdTe量子点荧光恢复程度与依诺沙星浓度成正比的现象,建立了基于CdTe量子点荧光猝灭-恢复测定依诺沙星的新方法。考察了溶液pH值以及Cu2+浓度等对检测体系的影响。在p H=10的硼砂缓冲溶液中,在Cu2+浓度为2.3×10-5mol/L的条件下,依诺沙星浓度在8.0×10-7~3.0×10-5mol/L范围内与量子点荧光恢复程度呈良好的线性关系,检出限为7.2×10-8mol/L。该方法用于实际样品中依诺沙星的检测,回收率为95.5%~105.0%。     

Speckle characteristics of a broad-area VCSEL in the incoherent emission regime

We present a technique to reduce the speckle contrast of a NIR broad-area VCSEL based on the spatially incoherent emission regime that can be obtained when using the proper driving conditions. We evaluate the efficiency of this technique to reduce the speckle contrast by comparing it with the speckle characteristics in multimode emission under cw operation. Depending on the illumination setup, the incoherent emission regime can lead to a strongly reduced speckle contrast down to 1.3%. This is in agreement with estimates of the expected speckle contrast reduction when three contrast reducing effects are taken into account. These low contrast values make the investigated sources attractive for several applications that suffer from speckle noise.     

XYZ particles at Belle

In this paper, I review recent progress in the study of the XYZ particles at Belle. I only focus on studies with charmonium and one or more light mesons in the final states. This covers the X(3872), X(3915),Y(4140), X(4350), and the charged Z states.     

Beyond the LAN: Ethernet’s Evolution into the Public Network

This article details the evolution of Ethernet into Gigabit Ethernet and how this LAN-based technology has undergone major transformations over time. From its data rates and distances to supported media and functionality, Ethernet has greatly improved, enabling it to surmount many of its former limitations and in so doing to expand beyond the LAN into the MAN and now even the WAN. In this article, Pioneer Consulting explores the evolution further by focusing on some of the major technological directions in the Ethernet equipment industry.     

Optical transmission through an interface between subwavelength slits

This paper studies optical transmission through an interface between two slits with different widths in a sheet composed of an ideal conductor. Such a structure is of potential use in fabricating optical diode and may be the simplest one compared to other designs. Our calculations show that there is a critical wavelength. When the light wavelength is below the critical wavelength, the transmissivity is unidirectional. The expression of the stable transmissivity as a function of the ratio of the widths of the two slits was obtained analytically. Particularly, at the critical wavelength, the transmissivities are zero. This phenomenon has great potential for application in the manufacture of wavelength blockers.     

Effect of swift heavy ion irradiation on photoluminescence properties of ZnO/PMMA nanocomposite films

We report a study on the SHI induced modifications on structural and optical properties of ZnO/PMMA nanocomposite films. The ZnO nanoparticles were synthesized by the chemical route using 2-mercaptoethanol as a capping agent. The structure of ZnO nanoparticles was confirmed by XRD, SEM and TEM. These ZnO nanoparticles were dispersed in the PMMA matrix to form ZnO/PMMA nanocomposite films by the solution cast method. These ZnO/PMMA nanocomposite films were then irradiated by swift heavy ion irradiation (Ni⁸⁺ ion beam, 100 MeV) at a fluence of 1×10¹¹ ions/cm². The nanocomposite films were then characterized by XRD, UV-vis absorption spectroscopy and photoluminescence spectroscopy. As revealed from the absorption spectra, absorption edge is not changed by the irradiation but the optical absorption is increased. Enhanced green luminescence at about 527 nm and a less intense blue emission peak around 460 nm were observed after irradiation with respect to the pristine ZnO/PMMA nanocomposite film.     

带有碳杂质的钨中氢稳定性的第一性原理研究

应用第一性原理计算方法研究了碳(C)原子对钨(W)中氢(H)原子稳定性的影响. 本征W中, 当C-H间距离为～2.5 Å时, H的溶解能出现最低值, 此时为H最稳定的位置. W中存在空位时, 由于C的影响, H占据的最佳电子密度面值为0.10 Å^-3. 研究发现, W中单空位最多能容纳10个H原子, 且不能形成H分子, 不同于没有C存在的情况, 表明C对W中H稳定性存在很大影响. 此外, 当两个C原子存在于空位中时, H占据的最佳电子密度面值变为0.13 Å^-3.     

Grain boundary potential and charge density at grain boundaries of chemically prepared thin silver sulfide films

The grain boundary potential and interface state charge density at the grain boundaries of silver sulfide (Ag₂S) thin films prepared by chemical conversion of cadmium sulfide (CdS) films have been determined from the dc resistance of the material and are found to be sensitive to annealing. A reduction in the grain boundary potential and the grain boundary charge density of the film has been noticed when the source CdS film is annealed at different temperatures prior to chemical conversion. The variation in the grain boundary charge density of the grown Ag₂S film with source annealing temperature has been found to be similar to that of thin cadmium sulfide film, reported earlier. An additional low temperature heat treatment of the sample results in an enhancement in the charge density at the grain boundaries. The change in the silver vacancy and/or oxygen and sulfur content of the films as revealed from the energy dispersive spectra of the films suggests possible role of film composition on the grain boundary charge density.     

Reflections from polished single mode fiber ends

Abstract

The performance of a wavelength division multiplexing (WDM) system with optical cross-connects (OXCs) and in the presence of polarization and nonlinear effects was analyzed. We determined the effect of PMD and PDL; nonlinearity such as XPM, SPM, and FWM; and CD on the system performance. We found that the system outage probability is highest at DGD threshold for the respective maximum eye closure (EC). We showed that the allowable DGD depends on the time slot for one bit T, which is the inverse of the network bit rate. Wider T is more immune to large PMD with the EC still maintained at the same level since DGD/T is unchanged. Our analysis also indicated that as DGD increases, BER increases. The BER also increases with increase in PDL and further increases with the presence of XPM, SPM, FWM, and CD.     

The Effects of Polarization and Non-Linearity on the Performance of WDM System with Optical Cross-Connects

The performance of a wavelength division multiplexing (WDM) system with optical cross-connects (OXCs) and in the presence of polarization and nonlinear effects was analyzed. We determined the effect of PMD and PDL; nonlinearity such as XPM, SPM, and FWM; and CD on the system performance. We found that the system outage probability is highest at DGD threshold for the respective maximum eye closure (EC). We showed that the allowable DGD depends on the time slot for one bit T, which is the inverse of the network bit rate. Wider T is more immune to large PMD with the EC still maintained at the same level since DGD/T is unchanged. Our analysis also indicated that as DGD increases, BER increases. The BER also increases with increase in PDL and further increases with the presence of XPM, SPM, FWM, and CD.     

化学发光法测定巯嘌呤的含量

在流动注射系统中,利用巯嘌呤在碱性Luminol-K₃Fe(CN)₆化学发光体系中发光信号强的特点,建立了一种测定巯嘌呤的新方法。在优化条件下,方法的线性范围是1.02×10-7～1.02×10-9mol·L-1, 回归方程是Y=36.315c+140.72(Y是相对发光强度,c是巯嘌呤浓度与10-8 mol·L-1的乘积), 相关系数是0.998 2,检出限(S/N=3)是6.33×10-10mol·L-1,RSD为3.54%（c_i=2.0×10-9mol·L-1, n=12）。该法用于合成样品的测定,简便、灵敏、快速,结果令人满意。文章简要地探讨了巯嘌呤在碱性Luminol-K₃Fe(CN)₆化学发光体系中的化学发光机理：在反应过程中,产生大量的过氧自由基和羟基自由基,自由基与鲁米诺反应,形成激发态的鲁米诺分子,鲁米诺分子由激发态回到基态产生化学发光现象。