(Au-Probe)@SiO_2单层纳米粒子膜制备及表面增强拉曼光谱研究

表面增强拉曼光谱(SERS)因其高达单分子检测的表面灵敏度而广受青睐,其增强机理主要包括电磁场增强效应(EM)和电荷转移增强(CT)。通常,前者占主导作用,且局域电磁场可极大地增强表面吸附分子的拉曼信号。而介质通常对局域电磁场和EM增强有一定影响,从而影响SERS检测,通过壳层隔绝纳米粒子(SHINs)可避免介质与SERS增强源间的直接接触。但迄今为止,几乎未见有关介质对其增强拉曼光谱(SHINERS)影响的研究,主要因SERS基底均匀性较差所致。制备了两种探针分子内嵌且Au核尺寸不同的核壳纳米粒子,即(55 nm Au-PNTP)@SiO_2和(110 nm Au-pMBA)@SiO_2,壳层厚度分别为3.5和4.0 nm,壳层结构连续且无针孔效应。采用液-液两相成膜法制备其单层膜,转移至固相基底上可作为SERS基底,(55 nm Au-PNTP)@SiO_2单层膜上SERS谱峰强度的相对标准偏差约为5.38%,(110 nm Au-pMBA)@SiO_2单层膜上相对标准偏差约为5.97%,其重现性及均匀性优良,符合作为SERS基底的要求。研究它们分别在空气和水两种介质中的SERS效应,结果表明Au核被致密无针孔效应的SiO_2壳层包裹,且探针分子内嵌其中,由此完全隔绝了电磁场增强源内核Au纳米粒子与介质的直接接触,当改变基底所处的环境时,其实际介质仍为SiO_2,因此在两种介质中SERS信号几乎不发生改变。内嵌探针分子的PNTP或pMBA被包裹在SiO_2壳层内,溶剂及氧气等均无法参与反应,因此探针分子未发生SPR催化反应,保持稳定的光谱特征。由此可见内嵌探针分子的SERS信号强度及光谱特征不受介质的影响,可望作为多介质环境使用的高灵敏度SERS检测以及稳定内标或标记的重要基底。     

可循环表面增强拉曼光谱基底的制备及其应用

以氨基硅烷为偶联剂,硅酸钠为硅源,合成了一种以金为核,二氧化硅为壳的核壳纳米粒子。通过调节硅酸钠的量,反应温度和反应时间控制二氧化硅壳层厚度,获得理想的表面增强效应。通过研究表面增强拉曼光谱(SERS)信号强度和二氧化硅层厚度之间的关系优化基底的制备条件。采用对巯基苯和联吡啶作为探针分子进行SERS实验,在一定浓度范围内得到SERS信号强度和浓度的对数之间的线性关系,实验结果表明此组装有Au@SiO2的ITO基底作为可循环利用基底可定量分析吸附物种的浓度。     

Au-TiO_2纳米复合基底的制备及其SERS研究

通过溶胶-水热法合成TiO_2纳米粒子,然后采用光催化还原法通过改变氯金酸(HAuCl4)水溶液浓度和光照时间等参数制备不同量Au沉积的TiO_2(Au-TiO_2)纳米复合体,并以其作为SERS活性基底对吸附在其表面的探针分子(4-MBA)进行SERS研究。与纳米TiO_2上本征的SERS增强相比,适量的Au沉积导致复合基底对4-MBA分子具有更强的SERS增强效应,4-MBA的SERS信号增强来源于贵金属和半导体的共同作用;制备复合基底的光还原时间和氯金酸的浓度对复合基底的SERS增强效应均具有重要的影响。     

一种用于现场快速检测的SERS基底的制备

利用化学自组装方法,首先在色谱玻璃小瓶的内壁吸附上一层PDDA阳离子聚电解质,然后通过静电吸附作用将带有负电荷的银纳米粒子组装到内壁;比较了不同色谱瓶作为吸附银纳米粒子的载体的优缺点;用紫外-可见吸收光谱监测吸附到玻璃瓶内壁的银纳米粒子的表面等离子体共振峰,跟踪银纳米粒子的组装情况;利用对-巯基苯胺作为探针分子研究了基底的表面增强拉曼散射(SERS)活性。结果表明：所制备的SERS小瓶基底具有良好的SERS活性,并且使用简单,保存时间长,适合SERS现场快速检测的需要。     

金纳米-Nylon柔性膜基底的制备及其SERS性能研究

表面增强拉曼光谱（SERS）是目前最灵敏的分析技术之一,广泛应用于生命科学、材料科学、环境科学及分析化学等领域。SERS基底的特性决定了该技术的实际应用范围,是推动该技术发展的关键,高活性SERS基底的制备已经逐渐成为SERS研究领域的热点。为了获得最佳的拉曼信号,对具有特殊特性的SERS活性基底的需求一直很大。柔性SERS基底因具有良好的柔韧性,3D支架结构和表面可控的孔径大小等独特优势,在检测化合物和细菌等方面有很好的应用价值。Nylon(尼龙)柔性膜表面具有分级及多孔交错排列3D结构的特点,将固相萃取装置与特殊材料Nylon柔性膜相结合,通过改变金纳米颗粒的附着量以及金纳米颗粒与膜结合次数,制备了高SERS活性的金纳米-Nylon（Au-Nylon）柔性膜基底。研究表明,金纳米颗粒能很好地附着在Nylon纤维上,纳米颗粒与Nylon柔性膜表面等离子共振耦合作用,形成金纳米颗粒与Nylon纤维的复合体,Au-Nylon柔性膜基底的等离子共振吸收峰发生蓝移。首次处理后的Nylon纤维与其所附着的金纳米颗粒形成新的活性截留层,有助于使再次处理时金颗粒更好地附着在柔性膜表面,产生SERS“热点”效应,提高其SERS性能。利用结晶紫（CV）作为SERS探针分子,对Au-Nylon柔性膜基底SERS性能进行分析,发现CV探针分子在Au-Nylon柔性膜基底上的SERS强度随金纳米颗粒的附着量以及金纳米颗粒与膜结合次数而变化。对于面积为1 cm2的Au-Nylon柔性膜基底,当单次过滤金溶胶1 mL,与膜结合2次,总结合量2 mL时,CV探针分子的SERS信号最强,SERS活性最强。采用Au-Nylon柔性膜基底对浓度为2.5×10-5,1×10-5,1×10-6,5×10-7及1×10-7 mol·L-1的CV溶液进行的SERS检测,发现Au-Nylon柔性膜基底对CV探针分子检测极限达1×10-6 mol·L-1,增强因子达到1.0×104。此外,Au-Nylon柔性膜基底均匀性较好,相对平均偏差为11.8%。Au-Nylon柔性膜基底在微生物检测中,仍具有良好SERS活性,对金黄色葡萄球菌的SERS增强效果优于金溶胶。由此可见,研究中制备的Au-Nylon柔性具有良好的均一性,并具有较好的SERS活性,该方法简单且易批量制备,无论在化合物检测还是微生物检测中都具有良好的实际应用价值。     

双金属掺杂改进纳米二氧化钛的SERS性能

通过溶胶-水热法合成了Ni和Zn双金属共掺杂的TiO_2纳米粒子,并以其作为SERS活性基底对吸附在表面的4-巯基苯甲酸(4-MBA)探针分子进行了SERS研究。结果显示,吸附在Ni和Zn共掺杂TiO_2表面上的4-MBA分子展现了不同程度的SERS增强;适当比例的双金属掺杂有利于TiO_2基底对吸附分子的SERS增强。此工作将有助于进一步扩展纳米TiO_2作为SERS活性基底的研究及其应用。     

挥发性有机物的非接触SERS检测

挥发性有机物在自然环境中普遍存在,对人体健康造成显著影响,为此亟待发展高灵敏度的快速识别和检测技术。本文通过制备和优化表面增强拉曼散射(surface-enhanced Raman scattering,SERS)基底,实现了强吸附和弱吸附型挥发性有机物的检测。首先利用化学方法合成了粒径约为30nm的均匀准球形金纳米粒子,该粒子具有SERS效应以及良好的化学稳定性,以该纳米粒子为单元,通过气液两相界面自组装技术制备增强性能好、SERS信号均匀的金纳米粒子单层膜(Au MLF),并以此为SERS基底对挥发性有机物苯硫酚进行了检测。为了实现弱吸附挥发物质的检测,对Au MLF表面进行了修饰,构建了聚二甲基硅氧烷(PDMS)-Au MLF复合基底,实现了苯及二甲苯等弱吸附型挥发性有机物的检测。     

金纳米粒子自组装膜制备及苏丹红Ⅰ的分子SERS光谱研究

调节纳米颗粒相邻间距和排列方式,可以得到宏观有序纳米结构,其具有新的光、电性质,可作为研究亲脂性分子的表面增强拉曼光谱(SERS)基底。首先制备了直径为16 nm的金纳米粒子,通过界面自组装方法制得金纳米粒子膜,并利用扫描电镜、紫外-可见吸收光谱仪等对其进行了表征,结果表明其有两种膜结构,一种是均匀分布的单层膜,另一种是多层膜结构,它们的吸收峰在590 nm处。将其作为SERS基底,研究了相同条件下苏丹红Ⅰ分子在不同膜结构的谱学变化,发现单层和多层膜上苏丹红Ⅰ的SERS信号有明显差异。最后,初步探究了苏丹红Ⅰ分子随浸泡时间的吸附动力学。     

银纳米立方体的合成及其SERS活性研究

用乙二醇还原硝酸银,以聚乙烯吡咯烷酮作表面活性剂合成了银纳米立方体晶粒,并以吡啶和SCN-作为探针分子初步研究了银纳米立方体晶粒组装体系的SERS活性。当探针分子吸附于银纳米立方体晶粒上时,吡啶和SCN-的谱峰强度明显增强,表明银纳米立方体晶粒可望作为SERS活性基底。通过研究探针分子的SERS强度与粒子尺度关系,也有望用于表征银纳米立方体晶粒的光学性质。     

一种新型的通用的SERS基底-核壳结构纳米子

为了进一步来提高SERS基底和分子的普适性,本文采取了一种"借力"的方法,设计合成了金核过渡金属薄壳(Au@Pd,Au@Pt,Au@Ni,Au@Co)的核壳结构纳米粒子,借用底层高SERS活性的金核强的电磁场来增强过渡金属表面吸附分子的SERS信号,使得过渡金属表面的增强因子可达104-105。系统地开展了不同壳层厚度及相同壳层厚度下金核大小对SERS活性影响的研究,发现随着壳层厚的增加SERS活性迅速衰减,而且当金核为120-140 nm时可以得到最强的增强。     

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.     

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.     

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.     

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.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.