覆银银电极上哌啶分子的表面增强拉曼散射研究

通过改进电极修饰方法,在粗糙银电极上沉积银纳米颗粒,得到了哌啶分子吸附在覆银银电极上的高质量SERS谱,并研究了电位对哌啶分子在这种覆银银电极上SERS光谱的影响。实验表明,沉积有银纳米颗粒的粗糙银电极是一种新的高效SERS活性基底,分析并解释了覆银银电极能产生极强的增强效应的可能原因。     

非线性光散射、振荡与谐波产生

单壁碳纳米管表面增强喇曼散射的新方法=New technique in SERS study on single wailed carbon nanotubes[刊,中]/方炎(首都师范大学北京市纳米光电子学重点实验室.北京(100037)),欧阳雨∥光电子·激光.—2004,15(6).—731-733 依据碳纳米管独特的力学性能,在银表面直接研磨单壁碳纳米管(SWCNTs),在形成纳米级粗糙银表面的同时,SWCNTs管也吸附在银表面上,在银表面粗糙程度和SWCNTs厚度适中的区域得到了高质量的表面增强喇曼散射(SERS)谱。理论分析和实验结果表明,该方法是正确可行的。图2表1参10(于晓光)     

哌啶分子在两种不同银电极上吸附行为的实验和理论研究北大核心CSCD

分别在粗糙银电极和银纳米颗粒修饰银电极上得到了哌啶分子的表面增强拉曼(SERS)光谱.哌啶在银电极与银纳米颗粒修饰的银电极上的SERS谱有很大的区别,分析认为是由于哌啶在不同基底上的吸附方式不同所引起的,据此建立了哌啶吸附在银颗粒表面的两种模型,用DFT-B3PW91-lanl2dz方法计算了两种模型的拉曼频移,通过与实验结果比较说明了哌啶分子主要通过N原子的孤对电子竖直吸附在粗糙银电极表面,而在银纳米颗粒修饰的银电极上则以平行吸附方式为主.     

哌啶分子在两种不同银电极上吸附行为的实验和理论研究

分别在粗糙银电极和银纳米颗粒修饰银电极上得到了哌啶分子的表面增强拉曼（SERS）光谱。哌啶在银电极与银纳米颗粒修饰的银电极上的SERS谱有很大的区别,分析认为是由于哌啶在不同基底上的吸附方式不同所引起的,据此建立了哌啶吸附在银颗粒表面的两种模型,用DFT-B3PW91-lanl2dz方法计算了两种模型的拉曼频移,通过与实验结果比较说明了哌啶分子主要通过N原子的孤对电子竖直吸附在粗糙银电极表面,而在银纳米颗粒修饰的银电极上则以平行吸附方式为主。     

碳纳米管在银基底上的表面增强拉曼散射光谱研究(英文)

介绍了一种单壁碳纳米管表面增强拉曼散射的新方法。依据碳纳米管独特的力学性能,在银表面直接研磨单壁碳纳米管,在形成纳米级粗糙银表面的同时,单壁碳纳米管也吸附在银表面上。在银表面粗糙程度和单壁碳纳米管厚度适中的区域得到了高质量的单壁碳纳米管SERS谱。该方法消除了溶剂的干扰,保证了结果的准确性,理论分析和实验结果表明该方法是正确的、可行的     

二苯基乙二胺在银胶表面吸附的表面增强拉曼光谱研究

以银纳米粒子作为SERS活性基底,研究了二苯基乙二胺(DPEDA)在银表面的吸附行为,并研究了溶液的pH值和DPEDA的浓度对吸附构型的影响。对比DPEDA的Raman和SERS谱图,可以认为DPEDA是通过氮原子的孤对电子吸附在银胶表面。在酸性介质中DPEDA的氨基被质子化生成胺正离子,导致DPEDA不容易吸附到银胶表面,所以DPEDA的SERS信号强度随着溶液酸性的增加而减弱。DPEDA的浓度变化对其吸附构型中芳香环的取向影响不大,但是其C-N键与表面的角度会有一定的变化。从SERS光谱得到的信息可以加深我们对DPEDA修饰的金属催化剂的多相不对称催化机理的认识。     

氯离子对固定银纳米颗粒SERS活性的影响

通过在硅片上修饰聚乙烯吡咯烷酮(PVP)对银纳米粒子进行组装,得到均一的表面增强拉曼光谱(SERS)基底。借助于此基底,在水溶液环境中,以异烟酸(INA)和罗丹明6g(R6g)作为探测分子,研究了氯离子(Cl-)对SERS增强的影响。结果表明,对于不同的探针分子,Cl-对银颗粒SERS活性的影响存在选择性。对于INA分子,在溶液中没有Cl-的情况下,分子通过羧基以锐角吸附在银颗粒表面,具有良好的SERS谱。在加入Cl-后,由于竞争吸附,INA分子脱附,SERS信号消失。R6g分子在银颗粒表面没有特异吸附,Cl-的加入并没有影响其与银颗粒的作用状态,在加入Cl-后SERS光谱没有发生显著变化。     

苯甲酸的羟基取代物在银纳米颗粒表面的吸附行为的研究

分别以覆银滤纸和银胶溶液中的银纳米颗粒为基底,对苯甲酸的三种羟基取代物(n-HBA,n=P,M,O)进行了表面增强拉曼散射(SERS),发现PHBA分子在覆银滤纸上的SERS光谱和银胶中的SERS光谱明显不同,而MHBA分子和OHBA分子在两种基底上的SERS光谱却很相近。分析表明这些变化都来源于分子在银纳米颗粒表面吸附行为的变化,基底的表面特性和分子的表面构型对分子在基底表面的吸附行为会产生很大的影响。     

单壁碳纳米管的场发射特性研究

利用场发射显微镜(FEM)和四极质谱计分别研究了经过热处理的单壁碳纳米管的场发射图像和热处理过程中样品脱附的残气质谱.当热处理温度达到1000℃左右时得到了单壁碳纳米管的场发射像,此像可能是顶端开口的单根(16,0)锯齿形单壁碳纳米管的具有原子可分辨的场发射图像.四极质谱分析结果表明,在此温度范围W针尖晶粒间隙中有O原子和C原子释放出来.它们对单壁碳纳米管顶端的修饰是我们能观察到这些碳纳米管场发射像的可能原因. 关键词： 单壁碳纳米管(SWCNTs) 场发射显微镜(FEM) 四极质谱     

基于纳米锥森林结构的表面增强拉曼散射透明器件研究

具有无损、超灵敏和实时检测优点的表面增强拉曼散射(SERS)器件具有重要研究意义。目前,针对SERS器件的大部分研究都围绕着非透明的器件展开。使用此类器件检测高浓度试剂时,激光只能从正面入射。这意味着入射激光需要穿透被测试剂分子层才能到达位于其下方的金属纳米结构表面,因此用于激发金属纳米结构表面等离子体共振(SPR)的激光能量被减弱,相应地,SERS光谱信号也被减弱;此外,SERS光谱信号因被测试剂分子层的遮挡,无法高效返回到电荷耦合元件(CCD)中,再次被大幅度减弱,甚至有可能完全无法被检测到。相比之下,如果使用透明SERS器件,检测过程中将被测试剂分子置于器件正面,激光从器件背面入射,此时高浓度被测试剂分子层对入射激光和SERS光谱信号的干扰最小。这种情况下,可以得到较好的光谱信号。通过在石英基底上旋涂聚酰亚胺(PI)层,然后通过氧等离子体对PI层进行无掩模轰击,在石英基底上自行生成纳米纤维掩模,配合反应离子刻蚀工艺(RIE)制备了石英纳米锥森林结构。之后,通过金属纳米颗粒溅射工艺,得到SERS透明器件。对于该SERS透明器件,在测试过程中,拉曼激光可从器件的正面以及背面分别入射。初步的测试结果表明,对于罗丹明6G(R6G)在10^-3~10^-6 mol·L^-1这一浓度范围内,背面入射方式收集的SERS光谱信号强度高于正面入射方式。另外,进一步研究了该SERS透明器件背面检测的一致性,得到了良好的结果,证明了其在实际生化检测中的可行性。这一工作有望扩展SERS在分析物检测领域中的应用。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.