银纳米微粒对锌卟啉的荧光增强效用研究

采用波长为407 nm的激光照射以银纳米颗粒作为荧光增强剂的成人全血溶液,研究其对血液中锌卟啉(ZPP)的荧光增强作用。实验结果表明,胶体状态的银纳米颗粒可以显著增强锌卟啉的荧光强度,增强效果最大可以达到5.2倍,且荧光增强效率随银胶加入量的增加呈现先增后减的趋势。分析认为,当溶液中锌卟啉分子和银纳米颗粒之间的距离满足荧光增强条件时,引起荧光强度的增加。加入大量的银胶颗粒时,分子之间作用距离逐渐减小,增强效果发生变化。研究结果表明使用银纳米颗粒可以实现低浓度血样中锌卟啉荧光的增强效应,为提高锌卟啉检测的灵敏度和精度提供有价值的参考。     

基于荧光光谱技术的大肠杆菌活性及灭菌效应研究

在食品和环境监测中,大肠杆菌是一个重要指标细菌,因此,对大肠杆菌的监测和灭菌效果也引起了人们广泛的关注。基于荧光光谱检测技术具有的灵敏度高、速度快、稳定性强等优点,利用荧光光谱技术研究了大肠杆菌的发射峰强度与大肠杆菌浓度的内在变化规律,得到了一种更加方便、快捷、监测浓度更低的大肠杆菌计数方法。采用289 nm的激发光照射大肠杆菌水溶液,得到大肠杆菌的荧光发射光谱;改变大肠杆菌溶液的浓度,得到不同浓度大肠杆菌溶液的荧光光谱,并分析大肠杆菌特征峰强度与大肠杆菌浓度的关系。在此基础上,利用荧光光谱技术研究了银纳米颗粒对大肠杆菌荧光发射的影响,分析了银纳米颗粒对大肠杆菌的灭菌效果,结果表明：(1)当289 nm的激发光照射大肠杆菌水溶液时,大肠杆菌分别在332和425 nm两处有明显的荧光特征峰;荧光特征峰强度随着大肠杆菌浓度降低而降低;当大肠杆菌浓度小于20%时,332和425 nm处特征峰强度与大肠杆菌溶液的浓度均呈线性关系。(2)当大肠杆菌水溶液中加入银纳米颗粒时,在4个小时内,银纳米颗粒的作用时间越长,大肠杆菌的荧光特征峰越弱,即灭菌率越高;增加银纳米颗粒的浓度或者提高环境温度,均可提高银纳米颗粒对大肠杆菌的灭菌率。本文的研究结果对食品、环境等中大肠杆菌的计数和灭菌研究有参考意义。     

甲基橙-银胶体系pH和氯离子效应的光谱研究

研究了甲基橙-银胶体系的光吸收和光致发光信号随pH值和加入氯离子的变化规律.实验发现随着pH值的增加, 分子的荧光发射峰与银胶的光吸收峰的重叠增大, 引起体系中能量转移效率的增加, 即428 nm分子荧光峰的淬灭和560 nm聚集体的特征光致发光峰增强现象的加剧.另外, 不同pH值下氯离子的加入都会使染料分子更加密集的吸附在胶体银颗粒表面, 形成分子吸附更加紧密的聚集体, 造成体系中受表面吸附分子影响的光致发光峰获得了极大的增强.同时, 因聚集体表面吸附层染料分子对入射光的大量吸收, 导致到达内核银表面的入射光强度减弱, 致使体系能量转移通道在一定程度上受阻, 表现为428 nm荧光峰的淬灭幅度减小.参照分子聚集体的形成理论, 接合体系光谱的变化, 从pH值的改变和Cl^-的加入对分子结构及加剧聚集体的形成等方面的影响来解释发光和光吸收的显著变化.     

蛋白质对纳米铕岛膜表面荧光的增强作用

将经硫辛酸修饰的铕纳米颗粒和蛋白质固定在石英玻璃表面或胶原蛋白隔离的石英玻璃表面,研究蛋白质对纳米铕岛膜荧光的增强作用.研究结果发现,在275nm激发波长下,铕纳米岛膜的荧光光谱与铕纳米颗粒溶液的荧光性质相似,且微量蛋白质的加入可以使铕纳米岛膜的荧光强度增强,但被石英玻璃片吸附后,铕纳米岛膜以及铕-蛋白质体系的荧光发射峰的位置由378.8nm红移至420nm,且胶原蛋白隔离铕纳米岛膜和滴加微量BSA蛋白质的荧光光谱相似,但荧光强度没有发生明显变化.     

纳米银对表面吸附核黄素分子光谱性质的影响

采用氧化还原法制备了纳米尺寸的银溶胶,研究了纳米银粒子对核黄素(Riboflavin,Ri)水溶液吸收光谱和荧光光谱的影响.Ri溶液中加入纳米银粒子,随着纳米银浓度的增大,吸收强度不断增强,372 nm处吸收峰红移,而444 nm处吸收峰蓝移,同时发生荧光猝灭现象.从无辐射通道增强、纳米银表面局域场减弱及Ri分子第一激...     

表面荧光机制的理论研究

本文研究了 Rh B分子的 539.0 nm和 572 .5nm两荧光峰在表面增强活性银胶颗粒表面上的增强和淬灭效应 :在同一分子体系中同时观察到 530 .0 nm荧光峰的增强和 572 .5nm荧光峰的淬灭 ,并对其进行了理论计算。结果表明这两个荧光峰的增强或淬灭主要取决于局域电磁场增强和分子到金属表面无辐射能量转移衰减过程的竞争效应。当满足吸收共振增强和辐射共振增强时 ,荧光被增强 ;反之 ,荧光被淬灭。计算表明 ,荧光增强因子最高为 1     

激光拉曼光谱研究苏丹红Ⅲ分子的吸附方式

用近红外傅里叶拉曼光谱研究了苏丹红Ⅲ分子在覆银纳米颗粒的抛光铝片表面上的吸附行为,得到了一系列高质量的增强拉曼散射（SERS）谱图。对苏丹红Ⅲ分子在银胶溶液、覆银滤纸、覆银粗糙铝片上的SERS谱进行比较,结果表明苏丹红Ⅲ分子在各基底上与银纳米颗粒表现出不同的吸附行为。在银胶溶液中,苏丹红Ⅲ分子主要是通过N=N双键吸附在银纳米颗粒上的;在沉积了银纳米颗粒的滤纸表面,同样地,主要是由N=N双键吸附;而在沉积了银纳米颗粒的抛光铝片表面,不仅N=N双键参与了吸附,苏丹红Ⅲ分子中的羟基与银颗粒有相互作用,并且铝片上的氧化铝颗粒也可能吸附了苏丹红Ⅲ分子。     

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。     

纳米银胶中PVP和Alq3的荧光猝灭研究

本文通过湿法化学还原法合成了平均粒径为4.42nm、标准差为0.98nm的球形银纳米颗粒,并研究了在不同反应时间后获得的银纳米颗粒对PVP和Alq3的荧光猝灭效应。通过深入研究发现,PVP的荧光猝灭效应主要由于其分子链上的酮基与Ag颗粒之间发生了静电吸附,进而导致处在激发态的PVP分子与银颗粒之间产生电子或者能量转移(即非辐射弛豫),猝灭了PVP的荧光发光;而Alq3的荧光猝灭效应则主要归因于银纳米颗粒的欧姆损耗。通过采用时域有限差分法进行模拟发现,溶液中随机分布的银纳米颗粒,不仅能够吸收激发电磁波,削弱激发场强度,而且能够吸收荧光分子辐射的电磁波,进而猝灭了Alq3分子的荧光效应。这些研究成果将有利于了解金属纳米颗粒与PVP及Alq3分子荧光发光之间的关系,为调控荧光发光提供指导。     

表面增强机制中反常光吸收效应的理论研究

本文改进了银胶的制备方法 ,采用机械方法使银胶体系发生凝聚效应 ,其吸收峰位于435nm附近。当加入其他分子时 ,该吸收带没有明显移动 ,而在 435nm吸收带之外又出现了通常熟知的新的吸收带 ,其峰位随着加入其他分子的量的增加而向长波方向移动 ,本文的量子理论表明 ,435nm附近的吸收带是由银胶体系凝聚效应引起的 ,它应归属于银胶的凝聚特征峰。而在 435nm以外长波方向出现的吸收带 ,分析表明 ,它与银颗粒表面的化学吸附有关。     

甲基橙溶液的pH值对纳米银荧光增强效应的影响

研究了甲基橙溶液的pH对纳米银荧光增强效应的影响.当pH 1.5和2.1时,纳米银对溶液的吸收光谱影响甚小.当pH 3.1时,吸收峰蓝移26 nm,且强度明显降低.当pH值在3.8～8.2范围时,不仅吸收峰蓝移而且在426～456 nm出现宽吸收带.在任何pH值的甲基橙溶液中加入纳米银,S2→S0跃迁荧光发射带强度下降,但下降比率受pH值影响不大;S1→S0跃迁荧光发射带强度增强,其增强比率受pH值影响较大.当pH 2.1时,荧光增强比率最大;当pH 4.8时,荧光增强比率最小.分析认为,pH值对甲基橙溶液光谱性质的影响与不同pH值条件下甲基橙分子结构的改变以及分子在纳米银粒子表面不同的吸附方式、介质环境等因素相关,尤其与甲基橙分子与纳米银粒子间的距离密切相关.     

Ag nanoparticles obtained by pulsed laser ablation in water: surface properties and SERS activity

We studied the surface properties and reactivity of silver nanoparticles obtained by picosecond or nanosecond pulsed laser ablation in water and with 1064‐nm wavelength. Ultraviolet–visible spectroscopy results and subsequent modelling by Mie theory indicated the presence of an oxide layer on the nanoparticle surface, which favours the colloidal stability, but reduces the interaction with the environment. The oxide layer is also responsible for the reduced surface enhanced Raman spectroscopy (SERS) activity of these colloids with respect to those obtained by chemical reduction. However, SERS activation can be efficiently obtained by addition of chloride ions to the colloids, leading to SERS enhancement factors that are comparable with those of the chemically prepared counterparts. Copyright © 2015 John Wiley & Sons, Ltd.     

SERS activity and stability of the most frequently used silver colloids

Single‐molecule detection by surface‐enhanced resonance Raman scattering (SERRS) spectroscopy has been demonstrated for a variety of molecules. The detection of single molecules that do not have a resonance contribution, SERS, has been shown in the case of adenine. However, when colloidal particles isolated on planar substrates are used as the enhancing medium, the presence of anomalous signals significantly complicates the analysis of the spectra. Selection of a silver colloid that minimizes these spurious signals should improve the ultra‐sensitive detection of non‐resonant single molecules by SERS. A range of silver colloids, prepared by different methods, were investigated with respect to their activity and stability. Minimal anomalous signals were obtained from hydroxylamine‐reduced silver colloids, which suggests that this colloid will be better for ultra‐sensitive SE(R)RS experiments compared to the more common citrate‐ and borohydride‐reduced silver colloids. Copyright © 2011 John Wiley & Sons, Ltd.     

Integral fluorescence enhancement by silver nanoparticles controlled via PMMA matrix

The metal-enhanced fluorescence is measured with different thickness of emission film. Silver nanoparticles are immobilized on glass slide by chemical self-assembly method. Rhodamine B molecules are dispersed in the polymer matrix of Poly(methyl methacrylate) (PMMA), then spin coated on prepared silver particles substrate with different thickness from 15 nm to 70 nm. The enhanced fluorescence is observed depending on the thickness of emission film since the average distance between rhodamine B molecules and silver nanoparticles is altered by the PMMA matrix. The 5-fold enhancement is attained. The experiment was explained qualitatively by an integral fluorescence enhancement.     

Surface‐enhanced Raman spectroscopy for quantitative measurement of lactic acid at physiological concentration in human serum

Lactic acid is a simple and effective indicator for estimating physiological function. Rapid and sensitive detection of lactic acid is very useful in clinical diagnosis. However, the concentration of lactic acid in the physiological state is too low to be detected using traditional Raman spectroscopy. We applied silver colloidal nanoparticles‐mediated surface‐enhanced Raman spectroscopy (SERS) for rapid identification and quantification of lactic acid. The standard SERS spectra of lactic acid were defined and the 1395 cm⁻¹ band intensity was used for quantification from 0.3 to 2 mM (R² = 0.99). In clinical blood sample measurement, the ultrafiltration (cutoff value 5 kDa) can efficiently reduce background fluorescence to improve SERS performance. We established identical and optimal procedure by adjusting reaction time and volume ratio of serum and nanoparticles to obtain high SERS reproducibility. Finally, we showed that silver colloidal nanoparticles‐mediated SERS technique was successfully applied to detect lactic acid at physiological concentrations in the blood. Copyright © 2010 John Wiley & Sons, Ltd.     

金银纳米粒子的电化学性质及联苯胺的SERS研究

采用柠檬酸钠还原氯金酸,硼氢化钠还原硝酸银分别制备了较小粒径的金、银纳米粒子。运用紫外可见吸收光谱(UV-Vis)、扫描电子显微镜(SEM)、循环伏安法(CV)对金、银纳米粒子进行了表征。结果表明：所得金、银纳米粒子粒径分别约为16和10 nm,并能以亚单层形式组装于导电玻璃(ITO)表面;CV图显示金、银纳米粒子分别有一对不对称的氧化还原峰,而且纳米粒子的浓度对其氧化还原电位存在一定的影响。采用自组装方法,以联苯胺为偶联分子, 在粗糙金基底表面构筑了金/银纳米粒子的双层有序结构。表面增强拉曼光谱研究表明, 在有序金银纳米粒子组装体中偶联分子的拉曼散射得到了增强。     

Electromagnetic interaction of fluorophores with designed two-dimensional silver nanoparticle arrays

We study the fluorescence enhancement of dye molecules adsorbed on regular two-dimensional arrays of designed silver nanoparticles. The silver particles show two orthogonal optical resonances at different wavelengths because of their elongated shape. The short-wavelength resonance was designed to fit to the absorption maximum of the fluorophore. When the excitation light drives the short-wavelength resonance, the measured fluorescence intensity is strongly enhanced compared to that for the orthogonal particle orientation. This shows directly a strong electromagnetic coupling between the nanoparticles and the fluorophore. Additionally enhanced photochemical bleaching is observed due to the interaction of fluorophores with the particles. Using a rate model describing the fluorescence enhancement and the bleaching enhancement, an average value for the particle-induced increase in the radiative fluorescence rate is obtained, together with a lower limit for the averaged particle-induced field intensity enhancement factor. Received: 3 July 2001 / Revised version: 3 September 2001 / Published online: 15 October 2001     

纳米增强激光诱导击穿光谱的苹果表面农药残留检测

水果表面的农药残留严重危害身体健康,而常规检测方法需要采样处理,耗时、费力。激光诱导击穿光谱技术具有多元素分析和原位测量的能力,在水果表面农药残留检测方面潜力巨大。但是较差的检测灵敏度,限制了此技术在水果表面微量有害元素检测方面的应用。提高激光诱导击穿光谱系统的检测能力是目前的研究热点领域,研究了纳米粒子表面增强技术对苹果表面残留的毒死蜱农药的激光诱导击穿光谱信号的增强效果。通过在被测样品表面涂抹币族金属纳米粒子,然后利用激光诱导击穿光谱激发样品表面,对诱导出的原子发射光谱信号进行测量,实验结果表明,苹果表面涂抹金属纳米粒子后毒死蜱农药中磷元素的特征峰有4倍的增强。此方法的应用对提高果蔬表面微量有害元素的检测能力具有重要意义。然后我们对币族金属纳米粒子的增强效果进行了优化。研究了金纳米粒子和银纳米粒子的增强能力,同时对纳米粒子的粒径的增强效果进行了比较,通过对20 nm的金纳米粒子、20 nm的银纳米粒子和80 nm的银纳米粒子的增强效果比较,发现80 nm的银纳米粒子对苹果表面毒死蜱农药光谱的增强效果最好。研究了信号采集延时时间对光谱信噪比的影响,确定了0.2 μs的延时时间可以获得较为理想的信噪比。在以上研究的基础上,采用最优的实验参数(80 nm银粒子增强、0.2 μs的延时时间),以毒死蜱中磷元素在213.62,214.91,253.56和255.33 nm处的特征峰峰强作为依据,对苹果表面残留的毒死蜱农药进行了定量化分析。分别采集了毒死蜱残留浓度分别为30,20,15,12,10和6 μg·cm-2的苹果表面的LIBS光谱,然后分别利用磷元素的四个特征峰峰强进行了定量化曲线拟合,结果发现LIBS对残留的毒死蜱具有很好的定量化预测能力,R2在0.89以上。根据定量化拟合曲线,探讨了纳米增强LIBS的检测限,计算得到,利用纳米增强LIBS技术测量苹果表面的毒死蜱农药最低可以做到1.61 μg·cm-2的检测限。研究证明了金属纳米粒显著提高了LIBS对苹果表面农药残留的检测灵敏度。     

Nonlinear Excitation of Tryptophan Emission Enhanced by Silver Nanoparticles

We measured and analyzed the behavior of the fluorescence of tryptophan water solutions with and without silver nanoparticles, excited by one, two and three photon processes. Two different colloids with silver nanoparticles with distinct diameters (0.65 nm and 9 nm) were used in the experiments. Fluorescence quenching was observed with one and two photon excitation. However, upon three-photon excitation, significant fluorescence enhancement was observed in the colloid. In this case excitation of the amino acid is assisted by the nonlinear absorption of infrared light by the silver nanoparticles. In this paper we are proposing a new way to explore metallic nanoparticles to enhance autofluorescence of biomolecules.