维生素K3的表面增强拉曼光谱研究

首次报道了维生素K3 (VK3 )分子的常规拉曼光谱 (NRS)及该分子在活性衬底银镜上的表面增强拉曼散射 (SERS) ,并对它的拉曼特征谱带进行了初步的指认和归属。通过对比VK3 的常规拉曼光谱和SERS谱 ,发现VK3 分子吸附在银表面后拉曼散射强度被大大增强了。另外 ,VK3 的羰基与银粒子发生电荷转移后形成负离子自由基 ,碳氧双键打开。受VK3 分子吸附在银镜表面的影响 ,萘环结构发生了很大的扰动 ,导致一些拉曼特征峰产生位移 ,环变形振动对应的拉曼散射强度得到了增强。这些研究结果为SERS技术今后对VK3进行药物检测以及痕量分析方面的应用提供了依据。     

Surface plasmon polariton contributions to strokes emission from molecular monolayers on periodic Ag surfaces

Surface enhanced Raman scattering from molecular monolayers adsorbed on a holographic grating and covered by Ag has been studied. The coupling of surface plasmon polaritons to light through the grating produces emission similar to the continuum observed in other surface Raman experiments. The angular dependence of the surface Raman scattering shows that enhanced Raman cross-sections can arise from scattering of surface plasmon polaritons into light by the localized molecular vibrations.     

The SERS phenomenon in light of recent excitation profile measurements

We have recently reported on the measurements of the ultra high vacuum (UHV) surface enhanced Raman scattering (SERS) excitation profile for pyridine and CO on two different kinds of silver surfaces prepared in situ (ref.1). The curves all show a maximum and the peak positions depend both on the adsorbed molecule and the preparation of the silver surface. The optical spectra of these systems have also been measured using an oscillating beam spectrometer which compares the difference in the reflected light at two adjacent areas with and without the adsorbed molecules. The SERS phenomenon investigated in UHV is viewed in light of these results.     

The role of direct surface interaction in surface enhanced Raman scattering by pyridine and CO on silver

The surface enhanced Raman scattering (SERS) phenomenon due to pyridine on silver and CO on silver in ultra-high vacuum (UHV) has been compared. The study was carried out for two different kinds of silver surfaces, island films and “cold” films on island films. We have reported earlier that it was necessary to warm the samples to about 70K in order to observe the full surface enhanced Raman spectrum when the pyridine was deposited on silver island films on sapphire substrates at liquid He temperatures. We call this the effect of a “low temperature anneal” and the present work indicates that this effect is more general than we originally thought. It has also been found that island films exhibit enhanced Raman scattering for pyridine but not for CO, although “cold” films enhance the Raman scattering of both CO and pyridine. This is the first clear indication that molecular specificity may be a part of the SERS phenomenon. The interpretation of these observations depends critically on our understanding of the SERS phenomenon.     

Effect of extended surface plasmons on surface enhanced Raman scattering

Surface enhanced Raman scattering of pyridine adsorbed to weakly roughened silver films is studied using a well-characterized extended surface plasmon excitation. We show that the additional increase in the Raman signal associated with the extended surface plasmon is fully accounted for by the enhancement in the average macroscopic field.     

硫脲吸附在电镀银表面的SERS

研究了在盐酸水溶中硫脲分子的表面增强拉曼散射。实验结果表明：硫脲分子倾斜吸附在银表面。当盐酸浓度增加时,硫脲分子平面更加偏离银表面的法线方向。     

Using surface enhanced Raman scattering to study vibrations of adsorbates on thin metallic overlayers on silver

We have studied the surface enhanced Raman scattering from molecules adsorbed on thin gold overlayers on silver island films. The Raman scattering of gold cyanide species adsorbed on gold overlayers decreases in intensity with gold overlayer thickness between 0.5 – 10 Å . This intensity decrease is consistent with a simple model which takes into account the damping of the electromagnetic resonances of the silver islands by the absorbing gold overlayer. Implications of these findings for the enhancement of Raman scattering from adsorbates on other metals deposited as overlayers on silver will be discussed.     

硫脲在酸性溶液中的表面增强拉曼光谱

本文在电镀沉积的银衬底上,研究了硫脲分子在酸性溶液中的表面增强拉曼散射。结果表明,硫脲分子是通过硫原子倾斜着吸附在银表面;当溶液中的ＨＣｌ浓度增加时,在银表面吸附的硫脲分子面更加偏离银表面的法线方向;实验结果还暗示,该体系存在着较强的化学增强机制。     

天线共振子理论对吡啶分子在铁钴镍衬底上SERS增强因子的计算

天线共振子模型是在研究表面增强拉曼散射增强机理过程中提出的理论.作为一项非常具有代表意义的工作,文章利用天线共振子模型计算了吡啶分子1010 cm-1特征振动模在过渡金属Fe,Co,Ni衬底上的表面增强拉曼散射增强因子:给出了共振时三种金属增强因子与激发光能量的依赖关系;研究了它们的表面粗糙度对增强因子的影响,计算了能量为0.89 eV的入射光在不同表面粗糙度的三种金属衬底上的增强因子.计算结果表明,它们在可见光范围增强因子不大,这与已报道的实验结果一致;但在红外波长却有大的增强因子,可以达到104～107,有待实验检验.     

腺嘌呤、嘌呤和四并苯的表面增强拉曼光谱随温度的可逆变化

用硝酸腐蚀法处理得到了具有表面增强拉曼光谱 (SERS)活性的银表面。在表面温度于 - 1 90℃～30℃变化时 (上升和下降 ) ,分别测定了吸附在银表面上的腺嘌呤、嘌呤和四并苯的表面增强拉曼光谱 ,观察到一系列有关拉曼峰频率和强度的可逆变化。结果表明 ,温度降低 ,吸附分子SERS中受电磁增强机制作用的振动的拉曼位移发生蓝移 ,同时峰强度也有变化 ;而受化学增强机制作用的振动的拉曼位移则不受温度的影响。温度的变化导致分子平面可弯曲分子在金属表面的取向发生变化 ,如腺嘌呤和嘌呤在高温下取直立态 ,而平面的对称分子 (如四并苯 )在表面上的取向则不受温度的影响。     

Surface Enhanced Raman Scattering on Self-assembled Nano Silver Film Prepared by Electrolysis Method

用一种廉价的电解方法制备了纳米银膜,并详细研究了在这种银膜上的表面增强拉曼散射效果．结晶紫为本实验的检测性分子．通过实验发现,这种银膜用便携式拉曼光谱仪测试并计算出的表面增强拉曼散射的增强因子为603,并对结晶紫的最小检出限为0.1 nmol/L     

An acoustically enhanced gold film Raman sensor on a lithium niobate substrate

The surface enhanced Raman scattering effect has shown immense potential for detecting trace amounts of explosive vapor molecules. To date, efforts to produce a commercially available, reliable SERS sensor have been impeded by an inability to separate the electromagnetic enhancement produced by the metallic nanostructure from other signal enhancing effects. Here, we show a new Raman sensor that uses surface acoustic waves (SAWs) to produce controllable surface structures on gold films deposited on LiNbO₃ substrates that modulate the Raman signal of a target compound (thiophenol) adsorbed on the films. We demonstrate that this sensor can dynamically control the Raman signal simply by changing the SAW's amplitude, allowing the Raman signal enhancement factor to be directly measured with no variation in the concentration of the target compound. The physically adsorbed molecules can be removed from the sensor without physical cleaning or damage, making it possible to reuse it for real‐time Raman detection. Copyright © 2014 John Wiley & Sons, Ltd.     

Single‐molecule surface‐enhanced Raman scattering of fullerene C60

We achieved single‐molecule surface‐enhanced Raman scattering (SM‐SERS) spectra from ultralow concentrations (10⁻¹⁵ M) of fullerene C₆₀ on uniformly assembled Au nanoparticles. It was found that resonant excitation at 785 nm is a powerful tool to probe SM‐SERS in this system. The appearance of additional bands and splitting of some vibrational modes were observed because of the symmetry reduction of the adsorbed molecule and a relaxation in the surface selection rules. Time‐evolved spectral fluctuation and ‘hot spot’ dependence in the SM‐SERS spectra were demonstrated to result from the single‐molecule Raman behavior of the spherical C₆₀ on Au nanoparticles. Copyright © 2010 John Wiley & Sons, Ltd.     

The relationship of angle resolved light scattering from surface optical resonances to the surface enhanced Raman effect

For a given mildly rough Ag surface, the angle resolved pattern bears the same shape for elastic light scattering, for Raman scattering from adsorbed pyridine or cyanide, or for the luminescence background. This result suggests that surface enhanced Raman scattering is closely related to topographically related surface optical resonances.     

Low-energy vibrational excitation cross section of multilayers of CO molecules on graphite using electron scattering

This paper presents a low-energy study of the vibrational excitation cross section of 50 layers of CO molecules on graphite at 23 K using the electron energy loss spectroscopy technique. The vibrational excitation cross section or the excitation curve is presented for two different scattering angles. The results show an energy dependence of the vibrational excitation cross section, at both angles, which indicates the formation of negative ion resonance in this adsorbed phase of CO on graphite. The data show an oscillatory structure in the region between 0.5 and 3 eV that is associated with the excitation of the ²Π state.     

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。     

聚集体分子的基频和高阶线性Raman散射研究

本文报道了2,2′菁染料的J聚集体吸附于银胶体的表面增强基频和高阶线性Raman散射效应,分析了基频和高阶线性Raman光谱随染料溶液浓度的变化关系。结果表明,J聚集体分子在银胶体表面具有一个稳定的吸附结构,且侧立吸附于表面,一些低波数振动模式起因于J聚集体分子。高阶线性Raman散射的增强与J聚集体分子的性质有关。 关键词：     

Surface enhanced Raman spectroscopy of palladium

Large enhancements in the Raman scattering signals have been observed from molecules and ions adsorbed on a palladium surface. The largest enhancement factor is in the order of 10⁵. Results will be discussed in terms of theoretical models on the surface enhanced Raman scattering process.     

多孔硅银淀积表面RhB染料分子的表面增强Raman散射

我们采用多孔硅和多孔硅银淀积表面作为衬底研究了ＲｈＢ染料分子的表面增强Ｒａ ｍａｎ散射。在多孔硅表面,ＲｈＢ染料分子的Ｒａｍａｎ散射有大约１０倍的表面增强效果;而在多孔硅的银淀积表面,表现出超过１０４表面增强。通过多孔硅表面银颗粒对ＲｈＢ染料分子荧光的抑制和对Ｒａｍａｎ散射的表面增强,我们获得了谱峰清晰的ＲｈＢ染料分子Ｒａｍａｎ散射谱     

Chemical contribution to surface-enhanced Raman scattering

We present a new mechanism for the chemical contribution to surface-enhanced Raman scattering (SERS). The theory considers the modulation of the polarizability of a metal nanocluster or a flat metal surface by the vibrational motion of an adsorbed molecule. The modulated polarization of the substrate coupled with the incident light will contribute to the Raman scattering enhancement. We show that for a metal cluster and for a flat metal surface this new chemical contribution may enhance the Raman scattering intensity by a factor of approximately 102 and approximately 104, respectively. The new SERS process is determined by the electric field parallel to the surface of the metal substrate at the molecular binding site.