Deposition of Ag nanoparticles on porous anodic alumina for surface enhanced Raman scattering substrate

Ag nanoparticles were exclusively deposited inside the pores of the porous anodic alumina (PAA) template through the deposition cycle including the incubation and the subsequent reduction of Ag(NH₃) . Both the density and size of the produced Ag nanoparticles increased as the deposition cycle number increased. A field‐emission scanning electron microscopeand an ultraviolet‐visible spectrometer were applied, respectively, to study the morphology and the extinction spectra of the Ag nanoparticles. The optimum deposition number was found from the scanning electron microscope (SEM) analysis. Surface enhanced Raman scattering (SERS) spectra of p‐aminothiophenol recorded on the Ag–PAA substrates prepared under increasing number of deposition cycles, manifested an enlarging trend of peak intensity. A point‐by‐point SERS mapping of p‐aminothiophenol on the Ag–PAA substrate was acquired to characterise the homogeneity of the substrate. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation of SERS active Ag nanoparticles encapsulated by phospholipids

A cost‐effective way of fabricating lipid‐coated surface‐enhanced Raman spectroscopy (SERS) substrate having reproducible high SERS activity was proposed. Ag nanoparticle embedded in 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPC) and 1,2‐dioleoyl‐3‐trimethylammonium‐propane (DOTAP) membranes was produced by direct deposition of a 5‐nm‐thick layer of Ag onto the solid‐supported phospholipid membrane, and subsequent dissolution of the Ag nanoparticle‐embedded membrane in iso‐octane allowed easy one‐pot fabrication of DOPC‐ or DOTAP‐coated Ag nanoparticles. In particular, DOTAP produced nearly monodisperse lipid‐encapsulated Ag nanoparticles (9 nm in diameter) exhibiting reproducible high SERS activity (detecting up to 10 nM of rhodamine 6G and 0.5 μM of glutathione). In addition, the process was modified to incorporate variety of Raman active molecules (rhodamine 6G, malachite green, 4‐aminothiopheonol, 4‐mercaptopyridine) into the particle‐encapsulating lipid bilayer. The DOTAP/Raman dye‐coated Ag nanoparticles also generated high SERS activity to enable potential application of the DOTAP/Raman dye‐coated Ag nanoparticles feasible in different areas. Copyright © 2014 John Wiley & Sons, Ltd.     

自组装银纳米粒子及其SERS增强效应

采用柠檬酸三钠还原硝酸银方法制备出银纳米粒子, 并通过在玻璃表面修饰3-氨基丙基-三乙氧基硅烷( APTES)对银纳米粒子进行自组装。利用紫外-可见(UV-Vis)吸收光谱和扫描电子显微镜(SEM)测试手段对样品进行分析和表征。由测试结果可知银纳米粒子的尺寸比较均匀, 组装致密度较高, 基本以亚单层的形式分布于基底表面。进一步研究了以结晶紫(CV)为探针分子的自组装基底的表面增强拉曼光谱(SERS), 计算发现该基底的拉曼增强因子数量级达106。结果表明: 银纳米粒子自组装基底具有良好的SERS增强效应, 为痕量CV的检测提供了有效的方法。     

纳米银粒子表面增强拉曼光谱在宠物饲料中三聚氰胺的速测研究

研究将制备的纳米银粒子作为表面增强拉曼光谱的增强试剂,实现对宠物饲料中三聚氰胺的快速定性定量分析。以709与1542cm-1处拉曼位移作为定性依据,以1149cm-1峰强度作为归一化标准,在1.0～10.0mg·kg-1浓度范围实现定量计算,检测限0.5mg·kg-1。研究发现,纳米银粒子对三聚氰胺具有较强的拉曼增强效应,特征峰信号强度与纳米银粒子加入时间,溶液涡旋强度有很大的关系,同时也受提取溶剂的种类、提取方式及样品加入量的影响。本方法中每个样品5min内完成分析,与现有方法相比,快速简便,对宠物饲料中三聚氰胺实现现场、快速检测。     

Research on the Raman properties of NiFe/cicada wing composite SERS platform modified by silver nanoparticles

Composite structures have been widely concerned in the preparation of surface enhanced Raman scattering (SERS) substrates. In this paper, by solving the problem that the magnetic material was difficult to glow in magnetron sputtering, ferro-nickel (NiFe) alloy was deposited on the cicada wing (CW) and the NiFe/CW substrate was obtained. The results of sliver nanoparticles (Ag NPs) modified on the substrate were subsequently compared, and the SERS properties of the new Ag/NiFe/CW substrate were analyzed. Obviously, the intensity of SERS signals has been greatly improved after the modification of Ag NPs, and the substrate exhibits excellent reproducibility. The Ag NPs modified substrates were also applied to the detection of toxic crystal violet (CV) solution, which showed remarkable SERS activity. It has been proved that the strategy of modifying Ag NPs on the substrate to form a composite structure has great potential for improving the SERS performance of the substrate.     

银纳米粒子修饰三维碳纳米管阵列SERS实验

为了使表面增强拉曼散射(SERS)基底的三维聚焦体积内包含更多的“热点”,能吸附更多探针分子和金属纳米颗粒,以便获得更强的拉曼光谱信号,提出了银纳米粒子修饰垂直排列的碳纳米管阵列三维复合结构作为SERS基底,并对其进行了实验研究。利用化学气相沉积(CVD)方法制备了垂直排列的碳纳米管阵列;采用磁控溅射镀膜方法先在碳纳米管阵列上形成一层银膜,再通过设置不同的高温退火温度,使不同粒径的银纳米粒子沉积在垂直有序排列碳纳米管阵列的表面和外壁。SEM结果表明：在有序碳纳米管阵列的表面和外壁都均匀地负载了大量银纳米粒子,并且银纳米颗粒的粒径、形貌及颗粒间的间距随退火温度的不同而不同。采用罗丹明6G(R6G)分子作为探针分子,拉曼实验结果表明：R6G浓度越高,拉曼强度越强,但是R6G浓度的增加与拉曼强度增强并不呈线性变化;退火温度为450 ℃,银纳米颗粒平均粒径在100～120 nm左右,退火温度为400 ℃,银纳米颗粒平均粒径在70 nm左右,退火温度为450 ℃的拉曼信号强度优于退火温度400和350 ℃。     

银电极表面上C60薄膜的表面增强拉曼光谱研究

在银电极表面形成一层C60薄膜,分别在乙腈溶液和水溶液中进行表面增强拉曼光谱(SERS)研究并将两者进行比较,从而消除了溶液中的C60干扰表面吸附C60的SERS谱图的可能性.研究结果表明,C60分子对称性的降低导致SERS谱峰发生了分裂;表面电磁场的作用使得光谱选律在SERS效应中被拓宽,产生了新的拉曼谱峰.该结果与团簇吸附在粗糙银电极表面的C60分子的研究结果相似.与之不同的是在乙腈溶液和水溶液中的SERS谱图的低波数区内分别在348和311 cm-1左右出现一个新峰,经过分析可认为该峰与C60-金属基底的相互作用有关.     

银纳米粒子/碳纳米管阵列SERS基底增强因子分析和实验

为了直观、准确地定量分析表面拉曼增强散射基底结构的拉曼增强,利用磁控溅射和高温退火的方法制备了银纳米粒子修饰垂直排列的碳纳米管阵列三维复合结构样品;实验采用罗丹明6G(R6G)溶剂作为探针分子,结合共聚焦显微拉曼系统,开展了表面增强拉曼增强因子(EF)分析计算的相关实验。SEM结果表明：在有序碳纳米管阵列的表面和外壁均匀地负载了大量银纳米粒子。对退火温度为450 ℃,退火时间为30 min的样品进行了EF计算,得到其增强因子约为2.2×103,并分析了EF值低的原因主要是：在碳纳米管上溅射的银膜膜厚不均匀,导致退火后银颗粒分布不均,使得样品粗糙度值偏大,EF值较低;实验中所用的激励光源并非银纳米颗粒的优化光源。     

SERS study of Ag nanoparticles electrodeposited on patterned TiO2 nanotube films

In this work, Ag nanoparticles (NPs) were deposited on patterned TiO₂ nanotube films through pulse‐current (PC) electrodeposition, and as a result patterned Ag NPs films were achieved. Scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and X‐ray diffraction (XRD) were used, respectively, to study the morphology, uniformity, and phase structure of the patterned Ag NP films. The size and density of the as‐deposited Ag NPs could be controlled by changing the deposition charge density, and it was found that the patterned Ag NP films produced under a charge density of 2.0 C cm⁻² gave intense UV–vis and Raman peaks. Two‐dimensional surface‐enhanced Raman scattering (SERS) mapping of rhodamine 6G (R6G) on the patterned Ag NP films demonstrated a high‐throughput, localized molecular adsorption and micropatterned SERS effect. Copyright © 2010 John Wiley & Sons, Ltd.     

Surface‐enhanced Raman scattering investigations on silver nanoparticles deposited on alumina and titania nanotubes: influence of the substrate material on surface‐enhanced Raman scattering activity of Ag nanoparticles

Silver nanoparticles deposited on various ‘inert’ porous materials (mainly Al₂O₃ and TiO₂) are often used as substrates for surface‐enhanced Raman scattering (SERS) measurements. In this study, we used the sputter deposition technique to cover tubular arrays of Al₂O₃ and TiO₂ with Ag nanoparticles. Raman spectra of pyridine (as a probe molecule) and of two selected dyes (5‐(4‐dimethylaminobenzylidene)rhodanine and 5‐(4‐(dimethylamino)benzylidene)‐3‐(3‐methoxypropyl)rhodanine) adsorbed on fabricated Ag/TiO₂‐n/Ti and Ag/Al₂O₃‐n/Al substrates were measured. We found that the SERS spectra of pyridine adsorbed on Ag nanoparticles deposited on an Al₂O₃‐n/Al substrate are distinctly different from those measured for an Ag/TiO₂‐n/Ti composite. Similar effects were observed for dyes adsorbed on the surface of both composites. The spectral differences between two kinds of composites (Ag/TiO₂‐n/Ti and Ag/Al₂O₃‐n/Al) are discussed in terms of (1) the modified electronic structure of the Ag nanoparticles due to their interaction with different substrate materials and (2) the different atomic topology of the metal particles thus deposited on the surfaces of the substrates. Composite samples were also studied with the aid of scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) to reveal their characteristic morphological and chemical features. Copyright © 2012 John Wiley & Sons, Ltd.     

Ultrathin silver‐coated gold nanoparticles as suitable substrate for surface‐enhanced Raman scattering

Surface‐enhanced Raman scattering (SERS) is an extremely powerful tool for the analysis of the composition of bimetallic nanoparticle (BNP) surfaces because of the different adsorption schemes adopted by several molecules on different metals, such as Au and Ag. The preparation of BNPs normally implies a change in the plasmonic properties of the core metal. However, for technological applications it could be interesting to synthesize core–shell structures preserving these original plasmonic properties. In this work, we present a facile method for coating colloidal gold nanoparticles (NPs) in solution with a very thin shell of silver. The resulting bimetallic Au@Ag system maintains the optical properties of gold but shows the chemical surface affinity of silver. The effectiveness of the coating method, as well as the progressive silver enrichment of the outermost part of the Au NPs, has been monitored through the SERS spectra of several species (chloride, luteolin, thiophenol and lucigenin), which show different behaviors on gold and silver surfaces. A growth mechanism of the Ag shell is proposed on the basis of the spectroscopic and microscopic data consisting in the formation and deposit of Ag clusters on the Au NP surface. Copyright © 2009 John Wiley & Sons, Ltd.     

TiO_2/石墨烯/Ag复合结构SERS实验

基于氧化物半导体的光催化特性,能够降解有机物分子,使表面增强拉曼散射基底得以重复使用。提出了银纳米颗粒有效修饰覆盖有石墨烯的二氧化钛纳米棒阵列(TiO_2/石墨烯/Ag)复合结构作为表面增强拉曼散射基底,并对其进行了实验研究。利用水热法制备了二氧化钛纳米棒阵列;采用湿法转移石墨烯和光照还原方法制备了TiO_2/石墨烯/Ag复合结构。用罗丹明6G(R6G)分子作为探测分子,结果表明:随着紫外光照沉积时间增加,探针分子的拉曼信号先增强后减弱;计算得到最大增强因子值约为2.6×106。此外,还对TiO_2/石墨烯/Ag复合结构的紫外自清洁特性进行了初步实验,结果表明,紫外光照射20min后,其拉曼强度下降到42.3%,具有一定的紫外清洁效果。     

Ag纳米粒子聚集体的SiO2包覆及其SERS效应

为实现表面增强拉曼散射（SERS）信号的快速检测分析,报道了一种简单的利用SiO₂包覆对巯基苯甲酸（4MBA）修饰的Ag纳米粒子形成核壳结构纳米颗粒SERS标记物的方法。通过调控溶液中硝酸钠的浓度来控制4MBA-Ag的聚集程度,获得不同的“热点”效应,然后利用SiO₂包覆实现对聚集体的固定。扫描电镜结果证实此种方法非常有效。该体系中SERS的信号强度依赖于4MBA-Ag的聚集程度。该研究结果有助于实现聚集体SERS标记物在生物成像、检测和传感等方面的应用。     

Fluorescence properties of Ag nanoparticles in water, methanol and hexane

Ag nanoparticles, synthesized employing the electro-exploding wire technique, are reported. Absorption in the UV-visible region by these particles is characterized by the features reported in the literature, namely, a possible plasmon peak at ∼404 nm. For Ag nanoparticles dispersed in water, photo-excitation in the ranges 210-235 and 255-280 nm produces similar fluorescence emission at ∼300 nm, whose corresponding resonant absorption takes place at 215 and 270 nm in the excitation spectra. Further, we study the effect of the surrounding medium (solvent effect) on fluorescence from these nanoparticles by comparing fluorescence emission in methanol and hexane for photo-excitation in the same range. Compared to water, fluorescence emission in methanol is observed red-shifted at ∼310 nm, which further red-shifts to ∼325 nm in hexane. The corresponding resonant absorptions in methanol are at 225 and 275 nm. Consequence of this red-shift in a less polar solvent is discussed.     

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.     

Surface plasmon resonance of Ag nanoparticles in the vicinity of a high impedance surface

Surface Plasmon resonance of Ag nanoparticles in the vicinity of a high impedance surface is investigated. Mushroom-like nanostructures were vertically grown on silicon substrate to form a high impedance surface operating in the range of optical frequencies. Formation of Ag nanoparticles on the fabricated high impedance surface was realized using plasma bombardment process. Optical measurements show an enhancement in the surface plasmon resonances of Ag nanoparticles. Also it was shown that the plasmon resonance peak of the Ag nanoparticles shifts to blue when Ag nanoparticles approach to the high impedance surface.     

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。     

ZnO/Ag纳米复合物的制备及光学性质

采用ZnO纳米晶表面还原Ag+的方法合成了ZnO/Ag纳米复合物,并研究了其光学性质.透射电镜和XRD谱表征了ZnO/Ag纳米复合物的晶体形貌和结构,吸收光谱和荧光光谱证明ZnO和Ag之间存在电子传递.在325 nm激光激发下观察到了ZnO/Ag纳米复合物的表面增强共振拉曼散射.     

Structural properties of core and surface of silica nanoparticles investigated by Raman spectroscopy

We studied the experimental Raman spectra of various commercial silica nanoparticles of average diameter from 7 to 40 nm and specific surface from 50 to 380 m²/g. We found that the peculiarities of the particles Raman spectra systematically depend on their specific surface. In detail, the peak position of the R band at about 440 cm⁻¹ shifts towards high wavenumbers following an almost linear dependence on the specific surface. Similarly, the amplitudes of the D1 and D2 bands, at about 495 and 605 cm⁻¹, respectively, increase linearly with the same quantity. Our results are interpreted in the frame of the shell model for the nanoparticles clarifying that the network of the core of the nanoparticles is comparable to the bulk silica materials, whereas the surface shell has a ring statistic shifted to the low member rings and features an higher density. Copyright © 2013 John Wiley & Sons, Ltd.     

静电纺丝法制备聚丙烯腈/银纳米粒子复合纳米纤维及其SERS特性

利用静电纺丝技术制备了一种聚丙烯腈/银纳米粒子复合纳米纤维的表面增强拉曼光谱基底。通过调节聚丙烯腈溶液的浓度可得到不同直径、不同厚度的纤维薄膜,将聚丙烯腈的N,N-二甲基甲酰胺溶液与硝酸银溶液混合得到聚丙烯腈/Ag种子溶液,然后利用静电纺丝技术制备聚丙烯腈/Ag种子/AgNO₃复合纳米纤维;加入AgNO₃并利用水合肼二次还原后可制备适合拉曼检测的聚丙烯腈/Ag纳米粒子复合纤维膜,聚合物纤维表面和内部的金属纳米粒子的密度可调节。通过调节不同的纳米粒子的密集程度,可构筑出具有较高的电磁场增强效果的特殊的“热”结构(高局域强电磁场的亚波长区域)。而聚合物纤维内部的银纳米粒子可通过溶胀作用吸附更多的探针分子,提高拉曼检测的灵敏度。该基底有很好的SERS信号,并且可大规模制备。