银纳米粒子有序自组装体中偶联分子的表面增强拉曼光谱研究

采用自组装方法,分别以1,4-二巯基苯和对巯基苯胺为偶联分子,在光滑银基底表面上构筑了银纳米粒子的单层和双层有序结构.表面增强拉曼光谱研究表明,在有序银纳米粒子组装体中偶联分子的拉曼散射得到很大增强,其中1,4-对巯基苯的拉曼散射增强效应主要来自光滑银基底表面与单层银纳米粒子间的电磁耦合,而对巯基苯胺的拉曼散射增强效应则主要由两层银纳米粒子之间耦合作用所致.两种不同的耦合作用所产生的增强效应大致相近.     

银纳米粒子自组装结构的光谱性质研究

采用自组装方法在玻璃基底表面上构筑了银纳米粒子二维亚单层结构, 进而以对巯基苯胺为耦联分子进行银粒子的二次组装, 构成具有分子尺寸间隙的银粒子簇. 银粒子表面等离子体共振依赖于粒子间距、表面吸附分子和粒子组装方式. 同层内的银粒子相互间电磁偶合可导致银粒子偶极子等离子体共振蓝移; 对巯基苯胺的吸附则使得表面等离子体共振红移. 表面增强拉曼光谱结果表明, 具有分子尺寸间隙的银粒子簇对耦联于粒子间的对巯基苯胺分子的拉曼散射具有极大的增强效应, 同时也使耦联的对巯基苯胺与银粒子间产生更大程度的电荷转移.     

Au-Ag三角纳米环单层膜的原位转化制备及 SERS效应

利用模板牺牲氧化还原反应将自组装在基片上的三角板银纳米粒子(边长约为79.2 nm)与氯金酸溶液作用进而原位转化形成三角纳米环. 通过紫外-可见(UV-Vis)光谱实时监测基片上银三角板纳米粒子在反应不同阶段的消光特性; 扫描电子显微镜(SEM)显示了银三角板纳米粒子转化过程的形貌变化; 利用X射线光电子能谱(XPS)对其成分进行分析. 表征结果表明, 三角纳米环的成分为Au-Ag合金或复合物; 随着基片与氯金酸溶液作用时间的增加, 自组装膜的表面等离子体共振峰逐渐红移; Au-Ag三角环状纳米粒子的平均壁厚度从29.3 nm缩小至16.2 nm. 以4-巯基苯胺(4-ATP)为探针分子研究了该Au-Ag三角环状纳米粒子单层膜的表面增强拉曼(SERS)活性. 自组装单层膜基底的SERS信号随着Au-Ag三角纳米环平均壁厚度的增加逐渐增强.     

金纳米粒子在氨基表面上的组装-pH值的影响

用原子力显微镜（AFM）和表面增强喇曼光谱（SERS）研究了pH值对金纳米粒子在Au／巯基苯胺自组装膜表面上组装效果的影响．AFM结果表明，金纳米粒子在表面上的覆盖度随pH值表现出规律性的变化，巯基苯胺自组装膜的SERS强度随pH值的变化也有类似的趋势．在磁性环境下，氨基未质子化，金粒子难以组装上，而在酸性条件下，氨基质子化带正电，金粒子与基底容易结合．我们认为金纳米粒子和氨基之间的作用属于静电力，pH值同时影响膜表面氨基的质子化程度和金纳米粒子表面的带电量．     

银纳米粒子有序结构中电荷转移的表面增强拉曼光谱

对疏基苯胺;自组装阵列;银纳米粒子有序结构中电荷转移的表面增强拉曼光谱     

GaAs基底上金纳米粒子的二维组装及其表面增强喇曼散射活性

利用巯基苯胺作耦联分子,成功地将Au纳米粒子组装到GaAs(100)表面上,并且用TM-AFM观察了纳米粒子在表面上的分布情况.Raman研究表明,该基底显示出表面增强喇曼散射活性.     

新型磁性纳米金修饰过氧化氢生物传感器的研制

利用共沉淀法合成纳米Fe3O4颗粒,将半胱氨酸吸附到纳米Fe3O4微粒表面,借助半胱氨酸的巯基(-SH)对纳米金的强烈吸附,使纳米金自组装到磁性颗粒上,再通过静电吸附作用自组装辣根过氧化酶(HRP),合成了Fe3O4/Cys/Au/HRP纳米复合粒子,最后通过磁力将其修饰到固体石蜡碳糊电极表面,制得新型过氧化氢生物传感器.以对苯二酚作为电子媒介,用计时电流法对H2O2进行测定,线性范围为2.4 X10-3～6.0×10-6mol/L,检出限(S/N=3)为2.5 X 10-6mol/L,响应时间小于10 s.磁性纳米微粒Fe3O4/Cys/Au能够高效地保持HRP的生物活性.该新型传感器已用于实际样品测定.     

用简便方法组装二维模板银纳米阵列

通过制备甲基和羧基混合自组装单层膜, 然后在羧基基团上选择性地生长银制备二维模板银纳米阵列. 利用微接触印刷在金膜上制备模板自组装单层膜, 也就是利用具有二维微米图案的弹力印模把有机巯基化合物转移到金膜上. 改善的银镜反应被用来制备银纳米结构, 银纳米粒子选择性地生长在二维模板有机单分子层的羧基位置. 甲醇作为还原剂具有高的选择性和原子经济性, 一分子甲醇可以还原六个银离子. 利用原子力显微镜和扫描电子显微镜确定了银纳米结构的形貌, 用拉曼光谱研究银纳米结构的光学性质.     

复合SERS基底的构建及性质

通过自组装方法以对巯基苯胺(PATP)为偶联分子, 在石英基片上构筑了多种形貌的银钠米粒子单层结构和三明治结构. 研究了组装膜在不同激发线下表面增强拉曼散射(SERS)的增强差异. 研究结果表明, 单层基底和三明治基底中偶联分子的SERS信号因银纳米粒子间的电磁场耦合而显著增强, 且在三明治结构中增强更加明显. 对复合SERS基底增强因子进行计算可知, 复合SERS基底的表面等离子体共振(SPR)峰与激发线的匹配程度越好, 其增强因子越大. 在三明治结构中更易发生PATP分子转变为对巯基偶氮苯(DMAB)分子的激光诱导催化偶联反应. 另外, 该激光诱导催化偶联反应与激发波长密切相关.     

免标记地检测二元磷脂膜中磷脂分布的表面增强拉曼成像方法

以银纳米粒子自组装层为增强基底,我们报道了一种用于检测二元磷脂膜中具有相似结构磷脂分布的表面增强拉曼成像方法,这种方法具有免标记及花费低廉的优点.对探针分子对巯基苯胺（p-aminothiophenol）,实验中所用的银纳米粒子自组装层表现出强的表面增强拉曼活性及良好的重现性.原子力显微镜表征结果证明了完整的磷脂膜在银纳米粒子自组装层上的形成.以这种银自组装层为基底,我们得到了磷脂膜中二肉豆蔻酰磷脂酰甘油（DMPG）和二肉豆蔻酰磷脂酰胆碱（DMPC）的表面增强拉曼光谱,并且利用DMPG的光谱特征峰,1482cm-1,区分这两种磷脂.而通过1482cm-1和1650cm-1的峰强比（R1482/1650）,可以同时得知在混合磷脂膜上某点这两种磷脂所占的比例：R1482/1650值的增加意味着DMPG的增加和DMPC的减少.磷脂膜的表面增强拉曼成像则是由R1482/1650值和对应的位置信息组合而得到,其成像结果表明了带电的磷脂DMPG在混合磷脂膜中的聚集.我们所报道的基于表面增强拉曼成像技术的方法提供了一种便利的、免标记的和花费低廉的途径来研究磷脂膜的结构,例如磷脂域和脂阀.     

Contribution of charge-transfer mechanisms to surface-enhanced Raman scattering with near-IR excitation.

Surface-enhanced Raman scattering under near-IR excitation is investigated for p-aminothiophenol (PATP) molecules that are either adsorbed on an electrochemically roughened silver electrode or embedded in an Au/PATP/Ag molecular junction assembled on an indium-doped tin oxide electrode. The contribution from chemical enhancement can be amplified relative to the contribution from electromagnetic enhancement, because the energy of the near-IR excitation is far from the surface plasmon resonance of the nanosized metal particles. The energy required for the charge-transfer process for the Au/PATP/Ag molecular junction is much lower than that of the PATP molecules adsorbed on the electrochemically roughened silver electrode. Coadsorption of chloride ions on the metal nanoparticles may result in an alteration of the local Fermi level of the metal nanoparticles, thus leading to better energy matching between the energy level of the interconnecting PATP molecules and the Fermi level of the metal nanoparticles.     

Ag_核Au_壳金属复合纳米粒子的制备及表面增强拉曼光谱研究

在已制备好的Ag纳米粒子表面,通过化学还原的方法沉积生长Au包裹层,制备了粒子尺寸为50-70nm的Ag核Au壳复合纳米粒子.通过改变AuCl₄^-量,使Ag_100-xAu_x中Au的含量由x=0变为x=30.用UV-Vis吸收光谱和透射电子显微镜(TEM)对该结构纳米粒子进行了表征,并以对巯基苯胺(PATP)为探针分子进行表面增强拉曼光谱(SERS)研究.表面拉曼光谱表明,该结构的纳米粒子具有比Ag更强的SERS活性,随着Au:Ag比例的逐渐增加,其活性呈现先增大后减小的趋势,其最大增强约为Ag纳米粒子的10倍.     

Highly sensitive Raman spectroscopy using a gap mode plasmon under an attenuated total reflection geometry

We investigated a gap mode plasmon under an attenuated total reflection (ATR) configuration toward realization of near-field Raman spectroscopy with a single molecule sensitivity and spatial resolution. Additional enhancement in Raman scattering at a nanogap was obtained by a coupling of a propagating surface plasmon (PSP) of Ag films on a prism, and a gap mode between Ag films and Ag nanoparticles (AgNPs). Immobilization of AgNPs on Ag films through thiol-SAM slightly up-shifted the resonance angle of a PSP, which broadened the reflectivity dip owing to an increased out-coupling of a PSP. Raman enhancement factor at a nanogap increased with decreasing surface coverage of AgNPs, albeit the enhancement factor averaged over illuminated area in Ag films decreased, ensuring the largest enhancement factor in tip-enhanced Raman scattering. This is due to increased efficiency for a PSP excitation at lower coverage of AgNPs in consistent with that in theoretical evaluation using finite difference time domain calculations. A gap mode under an ATR configuration was applied to elucidate a plausible photochemical reaction of p-amino thiophenol (PATP) adsorbed on Ag films on a prism. Spectral changes in Raman scattering under laser illumination were observed for PATP with a deuterated amino group, but suppressed by a dimethyl amino group owing to steric hindrance, supporting the photochemical dimerization.     

Fabrication of small-sized silver NPs/graphene sheets for high-quality surface-enhanced Raman scattering

In this paper, small-sized and highly dispersed Ag nanoparticles (NPs) supported on graphene nanosheets are fabricated via a strategy for etching a copper template with Ag(+). Firstly, big-sized Cu NPs are supported on graphene, and then the small-sized and highly dispersed Ag NPs are supported on graphene by replacement reaction, mainly making use of graphene passing electrons between Cu and Ag(+). The graphene used in the experiment is prepared by in situ self-generating template and has good dispersion, excellent crystallinity and little defects. Thus, in the process of Ag/graphene synthesis, there is no any intervention of surfactant, which ensures that SERS activity sites have not been passivated. And, the little defects of graphene benefit the excellent conductivity of graphene and ensured the replacement reaction between Cu and Ag(+). The obtained material exhibits significant high-quality and distinctive SERS activity. Especially, a serial new peak of p-aminothiophenol (PATP) is observed, this is suggested two reasons: one is "surface geometry" of the PATP on small-sized Ag NPs and another is the charge-transfer between Ag and graphene.     

Adsorbed state of p-mercaptobenzoic acid on silver nanoparticles

To exploit a gap mode plasmon in flocculates of metal nanoparticles most efficiently, the interaction between adsorbed chemical species and metal nanostructures were adjusted. We successfully formed flocculates of Ag nanoparticles (AgNPs) using electrostatic interaction between dissociated p-mercaptobenzoic acid (PMBA), protonated p-aminothiophenol (PATP) and their counter ions (Mⁿ⁺, X^m−), as well as van der Waals force between neutral PMBA, PATP and AgNPs. Detailed adsorbed state of PMBA and PATP in addition to trapped counter ions was characterized using enormous SERS enhancement in a flocculation method.     

Ag纳米粒子修饰光纤探针在等离激元催化反应中的应用

本文发展了一种基于Ag纳米粒子(AgNPs)修饰的局域表面等离激元共振(LSPR)光纤探针,作为等离激元催化反应基底同时原位检测表面增强拉曼光谱(SERS)信号,实现反应与检测一体化。本文使用(3-氨基丙基)三甲氧基硅烷(APTMS)分子将AgNPs组装到光纤探针表面。通过调控自组装时间,可形成AgNPs均匀分布的探针。以对巯基苯胺(PATP)作为反应的模型分子,获得了较好的等离激元催化及信号检测效果。在相同光源条件下,从光纤内部激发收集所得产物的SERS信号强度为外部激发收集的12.8倍,表明内激发收集方式在反应及信号检测方面具有优势;在一定浓度范围(10~(-4)–10~(-8)mol·L~(-1))内可用该光纤探针对PATP溶液进行定量分析;运用该光纤探针开展了等离激元催化PATP分子偶联反应的原位动力学研究。该LSPR光纤探针具有较高灵敏度,对样品损伤小,可在多场合下实现原位检测,且制备简便、成本较低。还有望结合近场扫描光学显微技术进一步对样品表面进行微区等离激元催化反应及检测并得到反应的二维分布图。     

A displacement principle for mercury detection by optical waveguide and surface enhanced Raman spectroscopy

A novel displacement principle of metal nanoparticles for target analysis, differing from the usual target-induced aggregation principle, was proved feasible by the use of para-aminothiophenol coupled Au nanoparticles (PATP-Au) multilayer as probes to detect Hg(2+). The PATP-Au multilayer was fabricated through layer-by-layer assembly of Au nanoparticles on optical waveguide (OWG) chip surface using para-aminothiophenol (PATP) as coupling molecules. The localized surface plasmon resonance (LSPR) extinction from Au nanoparticles and the PATP as a Raman reporter enable to easily capture changes in PATP-Au multilayer by OWG and of surface enhanced Raman spectroscopy, respectively. The introduction of the Hg(2+), which has a higher binding affinity to the thiol group of PATP, greatly destroyed the multilayer structure, and produced a large change, several folds higher than the noise, in LSPR features and Raman signals of PATP-Au multilayer probes, and resulted in an excellent selectivity for Hg(2+) detection at a low level of 1nM. This investigation provides us more ideas on the future development of surface analysis techniques for the detection of various target analytes.     

Effect of substrate on surface-enhanced Raman scattering of molecules adsorbed on immobilized silver nanoparticles

Silver nanoparticles were assembled on polyvinylpyridine (PVP) derivatized glass slides. Charge transfer between the adsorbed 4-aminothiophenol (PATP) and the immobilized silver nanoparticles was studied by surface-enhanced Raman spectroscopy with 1064 nm excitation, and compared with that of the silver nanoparticles in the colloid. It was demonstrated that the positive charges of the PVP layer could alter the charge distribution in the immobilized nanoparticles and induce the formation of the dipole in the nanoparticles, leading to less charge transfer from the metal to the adsorbed molecules. The coadsorption of chloride ions on the surface of the immobilized silver nanoparticles resulted in the redistribution of the charges in the nanoparticles and, in turn, altered the charge transfer between the adsorbed PATP molecules and the silver nanoparticles.     

金纳米粒子组装体系SERS化学增强的研究

Gold nanoparticles were assembled on gold substrates with the self-assembled monolayer(SAM) of p-minothiophenol(PATP). AFM measurements disclose that gold nanoparticles are scattered over the surface of the substrate with a submonolayer coverage. The Raman signal of the coupling layer, the SAM of PATP, can be well observed. Potential-dependent measurements were performed to study the chemical enhancement in SERS of such a system. Based on the supposition that the direction of charge transfer is from gold nanoparticles to PATP, it is deduced that Herzberg-Teller contribution has ruled in the SERS of such a system.