Fe3O4@Au核-壳纳米复合材料的制备及对农药福美双的SERS检测研究

首先采用热分解法制备了Fe₃O₄纳米材料, 再将其作为磁性核, 分别采用种子沉积法和种子介导生长法制备了Fe₃O₄-Au核-卫星纳米复合材料和Fe₃O₄@Au核-壳纳米复合材料, 并对其形貌和性能进行了表征分析. 结果表明, 所制备的Fe₃O₄-Au核-卫星和Fe₃O₄@Au核-壳纳米复合材料粒径均匀, Au纳米颗粒均匀沉积/包覆在Fe₃O₄纳米材料表面, 且样品均具有良好的磁响应性. 使用4-氨基苯硫酚(4-ATP)作为拉曼探针分子, 对比了这两种纳米复合材料作为SERS基底时的拉曼信号增强效果. 结果显示, Fe₃O₄@Au核-壳纳米复合材料是更优秀的SERS基底, 且该SERS基底具有良好的信号再现性. 最后, 使用Fe₃O₄@Au核-壳纳米复合材料作为SERS基底, 成功地在苹果皮上检测出残留福美双的SERS信号.     

超顺磁性Fe3O4/Au@Ag复合材料的合成及其SERS性能研究

利用溶剂热法和种子生长法分别合成Fe₃O₄磁性纳米粒子和Au@Ag核壳纳米粒子, 利用静电吸附方法成功将聚乙酰亚胺(PEI)修饰到Fe₃O₄表面并通过N-Ag共价键将Au@Ag核壳纳米粒子组装到Fe₃O₄表面, 制备Fe₃O₄/Au@Ag复合材料. 通过控制Au@Ag复合粒子的加入量, 来调节Fe₃O₄/Au@Ag复合材料的表面增强拉曼(SERS)活性. 以对巯基苯胺(p-ATP)为拉曼活性探针分子来考察该复合纳米材料的SERS性能, 检测限可以低至2×10^-9 mol/L. 同时, 将该复合材料应用于农药分子福美双的检测, 检测限可以低至10^-6 mol/L. 这种功能性复合材料既具有良好的SERS活性, 又具有Fe₃O₄磁性内核, 可以通过外加磁场实现对待测分子的分离、富集, 具有更广泛的应用前景.     

铬酸根离子的SERS检测及磁分离研究

介绍了一种基于表面增强拉曼光谱技术(SERS)的简单快速检测低浓度铬酸根离子的方法. 通过介质中水与铬酸根离子以及修饰在金基底和金纳米粒子表面的羧酸根形成氢键而构建“巯基苯甲酸-金基底/铬酸根-水/巯基苯甲酸-金纳米粒子”三明治结构. 通过检测标记分子的SERS信号判断溶液中是否存在铬酸根离子. 研究表明标记分子的SERS强度与铬酸根离子的浓度有关, 随浓度增加SERS强度呈非线性增强, 在10^－9 mol/L出现转折点. 利用以上三明治结构, 通过引入功能化的Fe₂O₃@Au核壳磁性纳米粒子, 利用外加磁场可富集分离溶液中的铬酸根离子, 经SERS 检测表明10^－5 mol/L的铬酸根离子磁分离后其浓度降低了约4～6个数量级.     

微流控芯片结合表面增强拉曼光谱实时监测α-苯乙醇的微量合成反应

表面增强拉曼光谱（SERS）因极高的检测灵敏度且能够提供丰富的分子结构信息,可实现原位、实时监测等优点而成为广受关注的痕量分析工具.本文发展了基于微流控和SERS的联用技术,实现了微有机合成反应的现场监测.以磁性核壳纳米粒子Fe₃O₄@Ag为SERS基底,通过外加磁场调控富集实现连续的SERS检测;结合微流控反应器在有机合成中反应物用量少、效率高、易于实现在线检测和高通量筛选的优势,实现了α-苯乙醇的微量合成反应以及实时SERS监测.研究表明,Fe₃O₄@Ag核壳纳米粒子具备在微流控反应通道中的磁富集功能和SERS连续检测的性能.通过改变微流控通道中反应物的流速可调控反应速度,在固定时间内获得不同浓度的反应物,利用差谱技术消除反应物光谱的干扰,获得了产物α-苯乙醇的特征SERS光谱.结果表明微流控技术与SERS联用可发展成为微量有机反应的监测手段,在有机化学反应高通量筛选中具有潜在应用价值.     

Au@SiO2核壳纳米粒子的制备及其表面增强拉曼光谱

采用柠檬酸钠还原氯金酸法制备金溶胶, 以正硅酸乙酯(TEOS)为硅源, 氨水作催化剂, 制备以金为核, 二氧化硅为壳的核壳纳米粒子. 金纳米粒子的粒径可以通过柠檬酸钠和氯金酸的比例控制, 通过调节TEOS的量和反应的时间可以控制二氧化硅壳层的厚度. 以苯硫酚为探针分子研究了核壳结构纳米粒子的表面增强拉曼散射(SERS)效应与二氧化硅壳层厚度之间的关系. 研究结果表明, 金内核电磁场增强效应随着二氧化硅壳层厚度的增加逐渐减弱, 且其衰减速度比具有相同尺度的双金属核壳结构纳米粒子的慢. 此外, 探针分子主要以物理作用吸附在二氧化硅的表面, 可通过洗涤方法将探针分子除去, 从而可使该复合结构基底用于循环SERS分析.     

磁性二氧化硅复合纳米粒子的合成及其与青铜器的相互作用研究

采用反相微乳液法, 合成了以PVP分散的磁性Fe₃O₄纳米粒子为核、SiO₂为壳并复合有荧光标记物钌联吡啶的核壳型复合功能纳米粒子. 在对该功能型二氧化硅复合纳米粒子进行TEM、荧光特性和磁性等特性表征的基础上, 重点研究了水溶性高聚物PVP溶液对Fe₃O₄纳米粒子的分散性, 并将其均匀的包入SiO₂壳中, 基于此研究了该功能型二氧化硅复合纳米粒子与青铜器之间的相互作用、以功能型复合纳米粒子为材料对青铜器腐蚀机理进行了在线、无损、实时监测以及将复合纳米材料从被分析体系中无损去除的方法, 发展了适合于去除吸附于青铜器文物表面的功能型纳米粒子的新方法. 这一研究结果为以该纳米粒子为基质构建适合于青铜器表面成分分析的纳米传感器奠定了基础.     

SiO2@Fe2O3核-壳结构催化剂的制备及表征

采用优化的Stöber法制备了平均粒径为230 nm的单分散球形SiO₂颗粒,并以此为内核,通过水解沉积法制备了不同壳层厚度的核-壳结构SiO₂@Fe₂O₃催化剂。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、N₂物理吸附和X射线衍射分析(XRD)等手段对催化剂进行表征,探讨了不同制备条件对SiO₂@Fe₂O₃催化剂形貌的影响。结果表明,通过水解沉积法制备的SiO₂@Fe₂O₃催化剂具有明显的核-壳结构,并且保持了原始SiO₂核的球形形貌,Fe₂O₃纳米粒子通过-OH的氢键作用连接在SiO₂表面,形成了2~10 nm厚的Fe₂O₃均匀连续包覆层。     

三组分抗原的磁分离及分离效率的SERS研究

利用种子生长法制备了磁性γ-Fe₂O₃@Au核壳纳米粒子, 通过修饰抗体实现表面功能化, 利用抗原抗体间的特异性作用, 通过外加磁场对三组分抗原进行了逐个以及双抗原的磁分离, 采用基于表面增强拉曼光谱(SERS)技术的免疫检测方法对磁分离效率进行了评价, 并且研究了该磁分离和效率评估方法的极限工作浓度. 研究结果表明, 该磁免疫分离法能对三组分混合抗原中的任意组分进行很好的选择性分离, 而不影响其它抗原的存在, 使其分离后溶液中被分离抗原的浓度降低到SERS免疫检测限, 分离所能达到的极限抗体浓度约0.1 pg/mL.     

表面分子印迹磁性纳米粒子的制备及其血红蛋白传感应用

以Fe₃O₄磁性纳米粒子为载体、多巴胺（DA）为功能单体、血红蛋白（Hb）为模板分子,用氯铂酸氧化DA生成聚多巴胺（PDA）,同时氯铂酸还原为铂纳米粒子（PtNPs）,与Hb一起负载于Fe₃O₄纳米粒子表面,洗脱Hb后合成了表面分子印迹磁性纳米粒子（印迹Fe₃O₄/PDA-PtNPs）. 将印迹Fe₃O₄/PDA-PtNPs修饰于磁性玻碳基底表面,制得印迹Fe₃O₄/PDA-PtNPs修饰电极. 实验结果表明,印迹Fe₃O₄/PDA-PtNPs具有良好的水溶性,粒径分布均匀,生成的PtNPs具有良好的导电性和刚性. 用印迹Fe₃O₄/PDA-PtNPs构建的传感器对Hb具有良好的识别性,在0.14 ~ 2.7 μg·mL^-1 Hb浓度范围与交流阻抗变化值呈良好的线性关系,检出限（S/N=3）为0.05 μg·mL^-1.     

基于功能化Fe3O4@Ag纳米粒子快速检测H92+的SERS方法

近年来,汞作为一种重要的污染物引起了人们的广泛关注.迄今为止,基于表面增强拉曼光谱（Surface-enhanced Raman scattering,SERS）的Hg²⁺检测方法因其在不同的检测方法中具有高灵敏度而备受关注.基于“turn-off”机制,我们合成出一种磁性Fe₃O₄@Ag（FA）纳米材料用于Hg²⁺的SERS检测.磁等离子体共振纳米颗粒结合了磁共振和等离子体共振特性,可用于高灵敏度和高选择性的汞离子的SERS检测.通过修饰带正电的聚二烯丙基二甲基氯化铵（PDADMAC,PolyDADMAC,PDDA）层,Fe₃O₄@Ag表面吸附上带负电的甲基橙探针分子,在Hg²⁺存在的情况下,可以观察到SERS信号显著降低.由于Hg²⁺与Ag纳米颗粒会快速反应并在Ag纳米颗粒表面形成一层汞齐,从而影响了Ag纳米颗粒的表面等离子体共振（Surface Plasmon Resonance,SPR）性能,导致电磁场强度的减弱;同时,这样也会导致Ag纳米颗粒的表面Zeta电位的降低,并且影响拉曼探针分子在其表面的吸附,从而进一步导致SERS信号的降低.因此,在含有Hg²⁺的情况下,SERS强度的降低主要归因于Hg²⁺与AgNPs的相互作用.通过我们的实验可以证明,基于“turn-off”机制检测Hg²⁺的方法的检测限可以低至10^-10 mol/L.本实验设计的SERS纳米传感器可用于快速检测环境中Hg²⁺,为构建重金属离子SERS纳米传感器提供了巨大的潜力.     

单个Fe2O3@Au粒子的偏振表面增强拉曼光谱

本文首次报道了单个纺锤形Fe2O3@Au颗粒的偏振相关的SERS光谱, 为研究SERS机理提供了实验依据.     

双金属双硅层核-壳纳米结构Au@SiO2@Ag@SiO2用于葡萄糖检测

制备了一种灵敏度高、 稳定性强的双金属双硅层核-壳结构纳米材料Au@SiO₂@Ag@SiO₂. 由于双金属之间的硅层促进了远程等离子体的激发转移, 使该纳米粒子具有良好的表面增强拉曼散射(SERS)的特性及优异的稳定性. 利用这种SERS活性材料能直接检测出人体尿液的主要成分, 且该材料呈现出对低浓度(10^-6 mol/L)葡萄糖的无标记高效检出能力. 此外, 还实现了人工尿液中等浓度(10^-3 mol/L)葡萄糖和尿素分子的同时检测, 以及实际尿液中10^-3 mol/L葡萄糖的检测. Au@SiO₂@Ag@SiO₂纳米粒子具有在多种生物分子存在时快速检测葡萄糖的实际应用潜力.     

The effects of Au aggregate morphology on surface-enhanced Raman scattering enhancement

We have identified empirically a relationship between the surface morphology of small individual aggregates (<100 Au nanoparticles) and surface-enhanced Raman scattering (SERS) enhancement. We have found that multilayer aggregates generated greater SERS enhancement than aggregates limited to two-dimensional (2D) or one-dimensional structures, independent of the number of particles. SERS intensity was measured using the 730 cm(-1) vibrational mode of the adsorbed adenine molecule on 75 nm Au particles, at an excitation wavelength of 632.8 nm. To gain insight into these relationships and its mechanism, we developed a qualitative model that considers the collections of interacting Au nanoparticles of an individual aggregate as a continuous single entity that retains its salient features. We found the dimensions of the modeled surface features to be comparable with those found in rough metal surfaces, known to sustain surface plasmon resonance and generate strong SERS enhancement. Among the aggregates that we have characterized, a three 75 nm nanoparticle system was the smallest to generate strong SERS enhancement. However, we also identified single individual Au nanoparticles as SERS active at the same wavelength, but with a diameter twice in size. For example, we observed a symmetric SERS-active particle of 180 nm in diameter. Such individual nanoparticles generated SERS enhancement on the same order of magnitude as the small monolayer Au aggregates, an intensity value significantly stronger than predicted in recent theoretical studies. We also found that an aspect of our model that relates the dimensions of its features to SERS enhancement is also applicable to single individual Au particles. We conclude that the size of the nanoparticle itself, or the size of a protrusion of an irregularly shaped single Au particle, will contribute to SERS enhancement provided that its dimensions satisfy the conditions for plasmon resonance. In addition, by considering the ratio of the generated intensities of typical 2D Au aggregates to the enhancement of individual SERS-active particles, a value of approximately 2 is determined. Its moderate value suggests that it is not the aggregation effect that is responsible for much of the observed SERS enhancement but the surface region associated with the SERS-active site.     

Characterization of the surface enhanced raman scattering (SERS) of bacteria

The surface enhanced Raman scattering (SERS) of a number of species and strains of bacteria obtained on novel gold nanoparticle (approximately 80 nm) covered SiO(2) substrates excited at 785 nm is reported. Raman cross-section enhancements of >10(4) per bacterium are found for both Gram-positive and Gram-negative bacteria on these SERS active substrates. The SERS spectra of bacteria are spectrally less congested and exhibit greater species differentiation than their corresponding non-SERS (bulk) Raman spectra at this excitation wavelength. Fluorescence observed in the bulk Raman emission of Bacillus species is not apparent in the corresponding SERS spectra. Despite the field enhancement effects arising from the nanostructured metal surface, this fluorescence component appears "quenched" due to an energy transfer process which does not diminish the Raman emission. The surface enhancement effect allows the observation of Raman spectra of single bacterial cells excited at low incident powers and short data acquisition times. SERS spectra of B. anthracis Sterne illustrate this single cell level capability. Comparison with previous SERS studies reveals how the SERS vibrational signatures are strongly dependent on the morphology and nature of the SERS active substrates. The potential of SERS for detection and identification of bacterial pathogens with species and strain specificity on these gold particle covered glassy substrates is demonstrated by these results.     

Surface-enhanced Raman scattering system of sample molecules in silver-modified silver film

Surface-enhanced Raman scattering (SERS) spectrum of very good quality of "silver nano-particles/sample molecules/silver film" system was reported by nesting the sample molecules to the gap of silver nano-particles and silver film, indicating that "silver nano-particles/sample molecules/silver film" is a highly SERS-active system. Not only was the number of the vibrational modes increased, but also were the frequencies of Raman bands up and down shifted. It is difficult to separate the contributions of the electromagnetic and chemical mechanisms to the great enhancement of the Raman signal. The shift by 5-30cm(-1) of the SERS bands and the change in their relative intensity compared with the ordinary Raman spectrum indicate the chemisorption of the sample molecules on the silver-modified silver surface. Furthermore, the silver nano-particles modified on the rough silver film surface play an important role in magnifying the surface local electric field near the silver surface through resonant surface plasmon excitation. From the rich information, obtained from high-quality SERS of PHBA in ternary system, we inferred that PHBA molecules in ternary system adsorb onto the metal surfaces through carboxyl at a perpendicular orientation.     

银－金红石复合纳米微晶的光谱性能

λ>330nm光照射含有金红石型TiO2微晶颗粒的AgNO3溶液,制备出了Ag-TiO2复合超微粒子,与纯的银溶胶相比,复合粒子上银的等离子体吸收峰宽化红移,位于400～600nm。这种复合超微粒子的溶胶,表现出表面增强拉曼散射(SERS)效应。吸附-共振增强可用来解释Ag-TiO2复合粒子的SERS效应。     

水汽界面二维银颗粒表面上的单分子拉曼光谱检测

随着各种超灵敏分析仪器的发展 ,已经可以在低温固体中、室温液体中和电介质表面检测、鉴定单分子及其动力学行为 .这种新进展为科学家在分析化学、分子生物学和纳米结构材料等各种学科的应用开辟了许多新的视窗 .单分子谱学的研究在基础科学和应用科学方面引起了人们广泛的兴趣 .人们不仅希望能够“看到”单分子 ,而且希望了解单分子的物理化学行为 .在各种超灵敏检测技术中 ,拉曼光谱成为一种重要的技术 .由于原子力显微等微区技术的发展 ,并结合高灵敏度检测技术的进步 ,拉曼光谱已经发展成为一种检测灵敏度可以达到分子级的检测技术 [1,…     

Local and average electromagnetic enhancement in surface-enhanced Raman scattering from self-affine fractal metal substrates with nanoscale irregularities

We study the electromagnetic mechanism in surface-enhanced Raman scattering (SERS) from random self-affine fractal metal substrates with nanoscale irregularities by means of the rigorous Green’s theorem integral equation formulation. The SERS enhancement factor is calculated from the numerical results for the surface electric field intensity at the pump frequency for ensembles of self-affine fractal realizations a few microns wide with decreasing lower scale cutoff. We observe a dramatic increase of the local and average SERS enhancement factors throughout the visible and near infrared when the size of surface irregularities is diminished to a few nanometers.     

Probing silver nanoparticles during catalytic H2 evolution

Employing silver nanoparticles from a recently developed synthesis [Evanoff, D. D.; Chumanov, G. J. Phys. Chem. B 2004, 108, 13948] and a well-studied probe molecule, p-aminothiophenol, we follow changes at the surface of the particles during the conditioning and eventually the catalytic production of hydrogen from water using strongly reducing radicals. Injection of electrons into the particles causes pronounced variations in the intensity of the surface enhanced Raman scattering (SERS) spectrum of the probe molecule. These spectral changes are caused by changes in the Fermi-level energy that are in turn caused by changes in the silver ion concentrations or in the pH, or by changes in electron density in the particle. This correlation highlights the effect of the chemical potential on the SERS enhancement at the end of the particles synthesis. The intensity of the SERS spectra increases in the presence of the silver ions when excitation at 514 nm is utilized. When the Ag(+) ions in the colloidal suspension are completely reduced by the radicals and the particles operate in the catalytic mode, the SERS spectrum is too weak to record, but it can reversibly be recovered upon the addition of Ag(+). The effect of pH on the SERS intensity is similar in nature to that of the silver ions but is complicated by the pKa of the aminothiol and the point of zero charge (pzc) of the particles. It is hypothesized that as the particles cross the pzc (around neutral pH) the electrostatic interaction between the protonated amine headgroup of the probe and the positively charged surface increases the density of probe molecules in the perpendicular orientation at the expense of a competing species. This conversion results in enhanced SERS signals and is observable during the preconditioning stage of the particles. Indeed, adsorption isotherms of the probe indicate the presence of two species. In analogous previous observations these two species have been attributed to perpendicular and flat adsorption orientations of the deprotonated probe molecule relative to the particle surface. However, preliminary density functional calculations on relevant prototypes raise the possibility that the two species may be the probe molecule and a cationic form produced by charge transfer in the ground state from the chemisorbed probe to the metal. These two forms of the probe have differing electronic structures and vibrational frequencies, with perhaps differing orientations relative to the surface. Whichever is the correct interpretation, a neutral molecule in a flat orientation or a radical cation, this species is easier to replace than the other in competitive adsorption by ethanethiol.     

Surface-enhanced Raman scattering of p-aminothiophenol on a Au(core)/Cu(shell) nanoparticle assembly.

Surface-enhanced Raman scattering (SERS) of p-aminothiophenol (PATP) molecules adsorbed onto assemblies of Au(core)/Cu(shell) nanoparticles is reported. We compare it with the SERS spectrum of PATP adsorbed onto gold nanoparticles: both the absolute and relative scattered intensities of various bands in the two spectra are very different. The difference in relative intensity can be ascribed to chemical effects; the chemical enhancement ratio of the two substrates is approximately 3-5. A theoretical analysis based on a charge-transfer model is carried out, which yields a consistent result and shows that the difference in chemical enhancement is mainly due to the state densities and Fermi levels of the substrates. The difference in absolute intensity originates from electromagnetic (EM) enhancement. EM enhancement of Au(core)/Cu(shell) nanoparticles is unlike that of single-component gold or copper SERS-active substrates. The core/shell particle size for optimal enhancement is about 20 nm in the case of a 632.8 nm incident laser (the size ratio of the core and shell layers is about 0.6).