Improved surface-enhanced Raman scattering of patterned gold nanoparticles deposited on silicon nanoporous pillar arrays

Large-area silicon nanoporous pillar arrays (Si-NPA) uniformly coated with gold nanoparticles was synthesized, and surface-enhanced Raman scattering of rhodamine 6G adsorbed on these gold nanoparticles were studied and compared. It's found that Au/Si-NPA substrate has a significantly high Raman signal sensitivity and good homogeneity. These are attributed to gold nanoparticles with narrow particle-size distribution uniformly coated on the surface and to the enlarged specific surface area for adsorption of target molecules brought by the porous silicon pillars.     

表面增强拉曼散射光谱对人体尿液成份的初步研究

作为人体体液之一的尿液中含有多种人体新陈代谢的产物以及体内排出的毒素,如果能够对这些组分进行定性分析,就能够在一定程度上有效反映人体器官的健康状况,这是临床医学中重要的研究途径。该实验分别以785和1 030 nm激光作为源激发,以具有电磁场增强的金纳米粒子作为基底,利用表面增强拉曼散射光谱(SERS)对临床实验研究中所用的人体新鲜尿液的成份进行快速、无损分析。通过控制金纳米溶胶与尿液原液的混合比例从而来制备一系列具有不同配比的实验样品,并且通过实验我们获得其相应的SERS光谱。由实验结果分析可知,我们能够有效地得到尿液中尿酸、次黄嘌呤等多种成份的SERS光谱。与此同时,我们还研究了在不同波长激光条件下的尿液的SERS光谱。相较于1 030 nm的激光,785 nm的激光得到的SERS光谱具有较高的分辨率以及较低的背景值。与此同时,利用具有1 030 nm激光的便携式拉曼仪对实验样品进行快速、无损分析,有望为临床医学现场、快速分析诊断提供帮助和支持。而且相信,SERS能够在人类健康甚至生物组织的检测等方面提供更加详细的信息。     

硫氰根在金银复合基底上的表面增强拉曼光谱研究

采用自组装技术在硅基底卜进行金银纳米粒子的复合组装,通过控制组装溶液中金溶胶和银溶胶的体积比进而控制基底上金银纳米粒子的密度.采用紫外可见漫反射和SEM对复合基底进行了表征,结果显示硅基底上金银同时存在且呈亚单层均匀分布.以硫氰根为探针分子研究了纯金、纯银以及混合组装时复合基底的SERS效应.通过一系列的校正表明,在金银同时存在的复合基底上,硫氰根的三键伸缩振动频率和特征峰的形状相对于单组分基底而言都接近于在银基底上的特征谱峰.对实验结果进行分析后认为,当金银同时组装在基底上时,金和银之间有一定的耦合作用,这种耦合作用最终导致金的SERS效应逐渐趋向于银.     

金银复合体系表面增强拉曼光谱分离

采用传统自组装技术在硅片表面进行金银纳米粒子的复合组装.以吡啶为探针分子,利用金银在不同激发光线下增强效应的不同,研究了不同波长的激发光下纯金、银以及复合组装时体系的SERS效应.结果表明在金银同时组装时的增强效应强于金弱于银,同时还通过一系列校正以及差谱方法分离出金银共存时SERS中金的增强效应,并进行了相关分析,结果表明在金银同时组装的复合体系中,金银之间产生一定的耦合作用.     

表面增强拉曼光谱快速检测尿液中的尿酸

表面增强拉曼光谱是一种表面灵敏度极高的“指纹”光谱技术,检测限可达单分子级别。它可以实现痕量物质的特异性识别及快速、无损检测,广泛应用于生命科学、电化学、环境安全等领域以及人们的日常生活中。通过种子生长法成功地实现了形貌均匀、尺寸可调的球形金纳米粒子的制备,并以此作为增强基底进一步探索其粒径对尿酸拉曼谱峰强度的影响。结果表明,金纳米粒子的尺寸显著影响其拉曼增强能力。在研究范围内,随着金纳米粒子尺寸的增加,其拉曼增强能力逐渐增加。在激光波长为638 nm时,150 nm的金纳米粒子具有最优的拉曼增强能力。这使得它们可适用于尿酸溶液的快速高灵敏度分析,检测限可达0.01 mmol·L-1。进一步的研究还表明,该方法可用于痕量尿酸的定量检测。在0.01～0.5 mmol·L-1范围内,尿酸的浓度与其特征拉曼峰640 cm-1处的峰强度之间呈线性关系,线性相关系数达0.98。将该方法用于真实样品(正常人体尿液)的快速检测,发现该方法不受尿液中其他成分的干扰,可以实现人体尿液中尿酸含量的快速测定。研究结果表明,以金纳米粒子作为基底的表面增强拉曼光谱方法可方便、快速地对尿液中尿酸的含量进行分析,极大地拓展了表面增强拉曼光谱在临床上的应用与研究。     

Single‐molecule detection of thionine on aggregated gold nanoparticles by surface enhanced Raman scattering

We report observations of single‐molecule detection of thionine and its dynamic interactions on aggregated gold nanoparticle clusters using surface enhanced Raman scattering (SERS). Spectral intensities were found to be independent of the size of Au nanoparticles studied (from 17 to 80 nm) at thionine concentration below 10⁻¹² M or at single‐molecule concentration levels. Raman line separations and, in particular, spectral fluctuations and blinking were also observed, suggesting temporal changes in single molecular motion and/or arrangements of thionine on Au nanoparticle surfaces. In contrast, by using dispersed Au nanoparticles, only ensemble SERS spectra could be observed at relatively high concentrations (> 10⁻⁸ M thionine), and spectral intensities varied with the size of Au nanoparticles. Copyright © 2007 John Wiley & Sons, Ltd.     

两种纳米粒子的自组装及表面增强拉曼光谱研究

在氨基硅烷化的单晶硅片表面通过静电自组装技术组装上金和金核铂壳两种纳米粒子,通过改变基底浸泡在溶胶中的时间控制基底上纳米粒子的密度。用扫描电子显微镜(SEM)对基底表面上的形貌进行表征,结果表明纳米粒子呈亚单层二维阵列分布。以吡啶(Py)为探针分子,用波长为632.8 nm的激发光作为激发光源,研究纯金和金铂复合基底上的表面增强拉曼光谱(SERS)行为。数据显示在金纳米粒子之间引入金核铂壳纳米粒子后,Py的两个特征峰的频率没有明显变化,但谱峰的强度却变弱了,其SERS信号衰减最大可至原来的24%。这是由于引入的铂的d态电子使金的等离子体激发猝灭,从而破坏了电磁场增强,使金的SERS信号衰减。     

Surface‐enhanced Raman scattering and fluorescence emission of gold nanoparticle–multiwalled carbon nanotube hybrids

Multiwalled carbon nanotubes (MWCNTs) are grafted with gold (Au) nanoparticles of different sizes (1–12 and 1–20 nm) to form Au–MWCNT hybrids. The Au nanoparticles pile up at defect sites on the edges of MWCNTs in the form of chains. The micro‐Raman scattering studies of these hybrids were carried using visible to infrared wavelengths (514.5 and 1064 nm). Enhanced Raman scattering and fluorescence is observed at an excitation wavelength of 514.5 nm. It is found that the graphitic (G) mode intensity enhances by 10 times and down shifts by approximately 3 cm⁻¹ for Au–MWCNT hybrids in comparison with pristine carbon nanotubes. This enhancement in G mode due to surface‐enhanced Raman scattering effect is related to the interaction of MWCNTs with Au nanoparticles. The enhancement in Raman scattering and fluorescence for large size nanoparticles for Au–MWCNTs hybrids is corroborated with localized surface plasmon polaritons. The peak position of localized surface plasmons of Au nanoparticles shifts with the change in environment. Further, no enhancement in G mode was observed at an excitation wavelength of 1064 nm. However, the defect mode (D) mode intensity enhances, and peak position is shifted by approximately 40 cm⁻¹ to lower side at the same wavelength. The enhanced intensity of D mode at 1064 nm excitation wavelength is related to the double resonance phenomenon and shift in the particular mode occurs due to more electron phonon interactions near Fermi level. Copyright © 2012 John Wiley & Sons, Ltd.     

Rapid Preparation of Large-Area Densely Packed Plasmonic Hot-Spots for Reliable Sers Sensing

A facile, efficient and time-saving strategy is proposed to obtain large-area and reliable surface-enhanced Raman scattering (SERS) substrates via artificial heat-treatment of Au nanoparticles or ultrathin Au films sputtered on the silica substrates. Excellent Raman enhancements with the detection limitation down to 10^–9 mol/L are obtained due to the highly-dense plasmonic hot-spots and strong plasmons near-field coupling. Decreased intensity of Raman peaks with the increased sputtering time of Au nanoparticles or ultrathin films mainly originates from the excited and hybridized coupling of multiple surface plasmons. The simple fabrication strategy and superior performance make these substrates promising candidates for the development of inexpensive and reliable SERS substrates.

     

Theoretical and experimental studies on the adsorption behavior of thiophenol on gold nanoparticles

FT‐Raman spectra were obtained for thiophenol (TP) and TP on gold nanoparticles. All vibrational fundamentals for the TP molecule are assigned on the basis of the scaled quantum force field procedure. Three model systems are studied and compared for the interactions of TP with the Au atom: (1) TP with a Au atom, C₆H₅SH Au; (2) TP anion with a Au atom, C₆H₅S⁻ Au; and (3) TP with a Au atom and subsequent formation of thiophenylate, C₆H₅SAu. The equilibrium structures and Raman spectra were calculated for the model systems using density functional theory (DFT) with the B3LYP functionals and the mixed basis set 6‐311 + G** (for C, S, H) and LANL2DZ (for Au), and theoretical Raman wavenumbers of C₆H₅SAu and C₆H₅S⁻ Au were assigned according to potential energy distributions. The third model system is shown to be preferred over the other two. The calculated binding energies are also shown to support the third model system. It is suggested that a simple model, such as the one used in the present study, is reasonable to describe surface‐enhanced Raman spectroscopy of thiophenol adsorbed on gold nanoparticles. Copyright © 2007 John Wiley & Sons, Ltd.     

The design of a peptide linker group to enhance the SERS signal intensity of an atto680 dye‐nanoparticle system

The Surface enhanced resonance Raman spectroscopy (SERRS) spectra of three modified atto680 dyes were recorded using Au nanoparticles and an excitation laser operating at 670 nm. The dyes were modified with linker groups based on the small peptides, Cys, Cys–Gly and Cys–Gly–Gly. The Cys thiol group acted as the coupling point to the Au surface and the Gly  NH₂ group used to attach the dye. The maximum signal was recorded for the Cys–Gly linker. This gave a signal intensity for the 577 cm⁻¹ Raman peak of the atto680 dye that was more than 27 times greater than the unmodified dye. The Au nanoparticles used had a diameter of 49.8 ± 1.2 nm and were synthesised by the citrate reduction method. The Raman dye‐AuNP probes were also used in an immunoassay to detect mouse IgG in the femto mole range. Copyright © 2010 John Wiley & Sons, Ltd.     

不同Ag壳厚度Au@Ag纳米粒子的调控制备表征及表面增强拉曼光谱的效应

采用化学还原法制备了以Au为核、包覆Ag的双金属核壳Au@Ag纳米粒子,并成功地用于表面增强拉曼光谱(SERS)分析测试。通过改变制备液中Ag/Au的量比来调控Ag壳包覆厚度。采用透射电子显微镜(TEM)和紫外-可见光谱仪(UV-Vis)对Au@Ag纳米粒子的构貌进行表征。TEM显示明显存在核壳结构,且Ag壳层随Ag/Au的量比的增加而逐渐变厚;UV-Vis表明随着Ag/Au的量比的增加,Au@Ag纳米粒子出现了Au核与Ag壳吸收峰的2个等离子体共振峰,同时伴随着Au峰的蓝移和Ag峰的红移。以双甲脒为分析物,考察了不同Ag/Au的量比时的Au@Ag纳米粒子的SERS活性。结果表明,SERS活性随Ag/Au的量比的增加先增大后减小,在6∶5时其SERS增强效应最佳,此时Ag壳厚度约为6 nm。以对巯基苯胺(4-ATP)、结晶紫(CV)和双甲脒为分析测试对象,对比了Au@Ag、Ag、Au 3种基底的SERS活性。结果表明,所制备的Au@Ag纳米粒子的SERS活性要明显优于单纯的Au、Ag纳米粒子。     

Individual SERS substrate with core–satellite structure decorated in shrinkable hydrogel template for pesticide detection

Individual Au@PNIPAM/Ag composite has been designed and fabricated as surface‐enhanced Raman scattering (SERS) substrate in this paper. Because of the high porosity of the polymer shell and the driving force of the Au core to Ag⁺(H₂O)_n (n = 1–4) in aqueous solution, chemical reactions can be carried out while aggregation is completely avoided. Also, this makes the formation of vast and monodisperse Ag nanoparticles within PNIPAM and increases the colloidal stability. The Au cores with different sizes and the vast Ag nanoparticles then form core–satellite structures that can generate plasmon resonance. Moreover, this kind of individual Au@PNIPAM/Ag composite can be seen directly through Raman optical microscope, and uncertain effects on SERS signals resulting from variability of the configurations are minimized because these individual composite particles are relatively uniform. Importantly, the gaps between the Au and Ag nanoparticles can decrease because the PNIPAM shrinks from swollen to collapse state, so the substrate can also be used for inspecting pesticide residues accurately and rapidly. Copyright © 2014 John Wiley & Sons, Ltd.     

1-Hexadecylamine as both reducing agent and stabilizer to synthesize Au and Ag nanoparticles and their SERS application

1-Hexadecylamine (HDA)-capped Au and Ag nanoparticles (NPs) have been successfully prepared by a one-pot solution growth method. The HDA is used as both reducing agent and stabilizer in the synthetic process is favorable for investigating the capping mechanism of Au and Ag NPs’ surface. The growth process and characterization of Au and Ag NPs are determined by Ultraviolet–visible (UV–vis) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Experimental results demonstrate that the HDA-capped Au and Ag NPs are highly crystalline and have good optical properties. Furthermore, surface-enhanced Raman scattering (SERS) spectra of 2-thionaphthol are obtained on the Au and Ag NPs modified glass surface, respectively, indicating that the as-synthesized noble metal NPs have potentially high sensitive optical detection application.     

Au/TiN复合薄膜制备及其表面增强拉曼光谱研究

表面增强拉曼散射光谱(SERS)已用于环境监测、生物医药、食品卫生等领域,而高活性SERS基底是表面增强拉曼散射光谱技术应用的关键。TiN作为新型等离子材料具有较强的SERS性能,同时化学稳定性及生物相容性较好,但其SERS性能不如贵金属金强。该研究采用氨气还原氮化法和电化学沉积法,在TiN薄膜表面沉积贵金属Au纳米颗粒制备出Au/TiN复合薄膜。在Au/TiN复合薄膜中单质Au和TiN两种物相共存;随着电化学沉积时间延长,TiN薄膜表面单质金纳米颗粒数量逐渐增多,金纳米颗粒尺寸增大,颗粒间距减小。由于金与TiN两者的本征表面等离子共振耦合作用,Au/TiN复合薄膜的共振吸收峰发生了偏移。利用罗丹明6G为拉曼探针分子,对Au/TiN复合薄膜进行SERS性能分析,发现Au/TiN复合薄膜上的R6G探针分子的拉曼峰信号强度随沉积时间延长呈现先增大后减小的规律;当电化学沉积时间为5 min时,R6G拉曼信号峰较高,复合薄膜样品的SERS活性最大。将Au/TiN复合薄膜和Au薄膜分别浸泡在10-3,10-5,10-7,10-8及10-9 mol·L-1 R6G溶液5 min,进行检测限分析,发现Au/TiN复合薄膜检测极限达10-8 mol·L-1,增强因子达到8.82×105,与Au薄膜和TiN薄膜相比,Au/TiN复合薄膜上对R6G探针分子SERS活性最高。这得益于Au/TiN复合膜中表面等离子体产生的耦合效应,使得局域电磁场强度增强,从而引起R6G探针分子拉曼信号增强。通过2D-FDTD模拟电场分布发现Au/TiN,Au及TiN薄膜具有电场增强作用,其中Au/TiN复合薄膜的增强作用尤为显著,这也证实了氮化钛与金纳米颗粒之间存在耦合效应。另外发现TiN与Au之间可能存在电荷转移,促进了4-氨基苯硫酚氧化反应,进而证实了TiN与Au薄膜的协同作用。此外,Au/TiN复合薄膜均匀性较好,相对平均偏差仅为7.58%。由此可见,采用电化学沉积制备的Au/TiN复合薄膜具有作为SERS基底材料的应用潜力。     

量子点尺寸对量子点和金纳米粒子之间的荧光共振能量转移的影响

量子点（QDs）所具有的一元激发多元发射的特点预示着QDs在高通量的多元量化生物信息处理领域具有应用前景。采用柠檬酸钠直接还原法制备了粒径为15 nm的Au纳米粒子,利用静电自组装的方法构建了Au与QDs的荧光共振能量转移（FRET）系统。采用该系统研究了QDs的尺寸变化对FRET效率的影响,获得了FRET效率和给体与受体之间交叠积分的关系。结果证明,QDs是构建多元均相免疫检测技术的一个有效给体。     

An effective surface-enhanced Raman scattering template based on gold nanoparticle/silicon nanowire arrays

A large-scale Si nanowire array （SiNWA） is fabricated with gold （Au） nanoparticles by simple metal-assisted chemical etching and metal reduction processes. The three-dimensional nanostructured Au/SiNWA is evaluated as an active substrate for surface-enhanced Raman scattering （SERS）. The results show that the detection limit for rhodamine 6G is as low as 10-7 M, and the Raman enhancement factor is as large as 105 with a relative standard deviation of less than 25%. After the calibration of the Raman peak intensifies of rhodamine 6G and thiram, organic molecules could be quantitatively detected. These results indicate that Au/SiNWA is a promising SERS-active substrate for the detection of biomolecules present in low concentrations. Our findings are an important advance in SERS substrates to allow fast and quantitative detection of trace organic contaminants.     

Molecular crystallization of rubrene thin films assisted by gold nanoparticles

We demonstrate that crystalline organic rubrene thin films can be obtained by a facile spin-coating method using gold (Au) nanoparticles (NPs). Dodecanethiol-functionalized Au NPs were dissolved with rubrene molecules in solvent and a thin film of Au/rubrene was prepared by a simple spin coating process. The results of confocal photoluminescence (PL) and absorption spectral mapping confirmed the local formation of orthorhombic crystalline structures of the Au/rubrene hybrid film, in contrast to the monoclinic structure of plain rubrene films. Further, the results of transmission electron microscopy (TEM) and X-ray diffraction analysis, as well as Raman spectroscopy measurements of the rubrene and Au/rubrene films suggested the formation of high crystalline Au/rubrene film. The molecular crystallization of the Au/rubrene hybrid film is attributed to the nucleation effect of the Au NPs.     

基于金/银纳米三明治结构SERS特性的超灵敏前列腺特异性抗原检测

基于金/银纳米三明治结构的表面增强拉曼散射(SERS)特性, 实现了前列腺特异性抗原(PSA)高灵敏度免疫检测, 检测结果具有特异性。采用化学还原法制备金、银纳米粒子, 用4-巯基苯甲酸(4-MBA)及前列腺特异性抗体(Anti-PSA)链接金、银纳米粒子制备免疫探针, 在硅片表面原位生长金、银纳米粒子并链接Anti-PSA制备得到免疫基底。将免疫探针、免疫基底以及PSA组成三明治结构, 进行基于SERS特性的免疫检测。实验结果表明, 纳米银免疫探针与纳米银免疫基底组成的三明治结构具有最佳的检测效果, PSA的检测灵敏度低至1.8fg/mL(3.490吆^-18mol/L), 可应用于前列腺癌症的早期检测与诊断。     

具有双共振吸收峰的Au纳米粒子制备及其拉曼表征

表面增强拉曼散射(SERS)很大程度的弥补了拉曼散射强度弱的缺点,迅速成为科研工作者们的研究热点,在食品安全、环境污染、毒品以及爆炸物检测等领域应用广泛。纳米技术的发展使得目前对于SERS的研究主要集中于金属纳米颗粒基底的制备,金属纳米粒子的种类、尺寸及形貌对SERS增强和吸收峰峰位均有影响,要获得好的增强效果,需要对金属纳米结构进行工艺优化。特别是,需要结合金属纳米粒子的结构和激励光波长,以期获得更好的增强效果。为了研究SERS增强和吸收峰之间的关系,开展了具有双共振吸收峰的金属纳米粒子的研究。首先利用FDTD Solutions仿真建模,主要针对金纳米颗粒直径、金纳米棒长径比及分布状态对共振吸收峰进行仿真,得到金纳米球理论直径在50 nm左右,金纳米棒理论长径比在3.5~4.5左右时,吸收峰分别分布在532及785 nm附近,符合多波段激励光拉曼增强条件;对于激励光偏振方向,其沿金纳米棒长轴方向偏振时吸收峰位于785 nm附近,沿金纳米球短轴方向偏振时吸收峰位于532 nm附近。然后采用种子生长法,制备了可用于多种波长激励光的双吸收峰表面增强拉曼散射基底。通过改变硝酸银用量(5,10,20,30和40 μL)、盐酸用量(0.1和0.2 mL)以及其生长时间(15,17,21和23 h)等多种工艺参数来控制金纳米棒含量,得到了同时含有金纳米球及金纳米棒的双吸收共振峰金纳米粒子。最后用该样品作为基底,罗丹明6G(R6G)作为探针分子,分别测试其在532,633和785 nm激励光入射时的SERS表征,对分析物R6G最低检测浓度均达到了10-7 mol·L-1,增强因子达到了~105,满足了多波段SERS检测的需要。