谷胱甘肽在金纳米粒子有序膜表面吸附的表面增强Raman光谱表征

将制备好的金纳米溶胶粒子组装在3-氨基丙基-三甲氧基硅烷(APTMS)修饰的ITO导电玻璃表面,形成金纳米粒子有序膜。FE-SEM电镜图显示金纳米粒子有序膜呈现出较为均匀的亚单层分布。同时利用电化学方法对有序膜进行了表征。将有序膜作为表面增强Raman光谱(SERS)基底应用于生物分子谷胱甘肽的SERS光谱表征与分析。研究表明,所制备的金纳米粒子有序膜可有效应用于谷胱甘肽分子的SERS光谱表征与分析。     

Au-TiO_2纳米复合基底的制备及其SERS研究

通过溶胶-水热法合成TiO_2纳米粒子,然后采用光催化还原法通过改变氯金酸(HAuCl4)水溶液浓度和光照时间等参数制备不同量Au沉积的TiO_2(Au-TiO_2)纳米复合体,并以其作为SERS活性基底对吸附在其表面的探针分子(4-MBA)进行SERS研究。与纳米TiO_2上本征的SERS增强相比,适量的Au沉积导致复合基底对4-MBA分子具有更强的SERS增强效应,4-MBA的SERS信号增强来源于贵金属和半导体的共同作用;制备复合基底的光还原时间和氯金酸的浓度对复合基底的SERS增强效应均具有重要的影响。     

新型膜状金纳米活性基底的制备及拉曼光谱增强研究

贵金属纳米粒子作为增强基底已经广泛应用于表面增强拉曼光谱(SERS)研究，传统的贵金属纳米基底在制备方法、增强能力、准确性等方面仍有待改进和提高。采用一种简易、高效的方法制备出了一种具有膜状结构的新型金纳米增强基底：以聚乙烯吡咯烷酮(PVP)作保护剂和粘结剂，通过化学还原法制备金纳米基底。实验考察了还原剂种类、反应温度、体系pH和柠檬酸钠浓度对反应的影响，制备出增强效果最佳的新型膜状金纳米基底。利用罗丹明B作为探针分子，考察基底的SERS特征，其增强因子可达6.5×105。利用扫描电镜(SEM)对纳米粒子的结构进行了表征，结果表明其具有膜状结构，且比表面积大，利于分子的吸附。相比于传统的贵金属纳米基底，该实验所制备的新型膜状金纳米基底增强效果更佳、灵敏度和准确度更高，具有很大的应用前景。     

水溶液银纳米晶聚集对表面增强拉曼散射的影响

由于贵金属纳米粒子独特的光学性质,基于衬底的贵金属纳米粒子薄膜表面增强拉曼散射技术在分子生物学和医学免疫分析等研究领域中显现出非常好的应用优势和潜力。本项研究工作应用柠檬酸纳作聚集剂诱导水溶液中对巯基苯甲酸修饰的Ag纳米粒子聚集,并应用以此形成的"热点"增强SERS光谱,获得了对巯基苯甲酸修饰的Ag纳米粒子聚集非常有效的4-MBA分子的SERS信号,为未来建立生物待测物的分析检测奠定前期基础。结果证明,水溶液中的Ag纳米粒子的聚集形成的"热点"具有非常好的SERS光谱增强效应。     

新型冠状病毒S蛋白在金纳米粒子中的表面增强拉曼效应

表面增强拉曼光谱技术因其高灵敏度、操作简单、快速检测等优点,被广泛用于病毒检测方面。国内外的病毒拉曼检测研究主要集中在检测病毒核酸以及组成核酸的各种碱基的表面增强拉曼光谱(SERS),但少见对病毒蛋白的SERS检测。以新型冠状病毒（SARS-CoV-2）的S蛋白为检测对象,采用无标记SERS检测方法,对比SARS-CoV-2固态、饱和液态S蛋白的普通拉曼光谱和选用40 nm金纳米粒子为基底的SARS-CoV-2低浓度S蛋白SERS光谱。结果表明,以40 nm金纳米粒子为基底,采用SERS技术检测SARS-CoV-2的S蛋白是完全可行的。SARS-CoV-2的S蛋白分子中的羧基与金纳米粒子发生了分子增强,氨基与金纳米粒子发生了电磁增强,从而使得SARS-CoV-2的S蛋白拉曼效应得到了增强,并使得峰位发生一定移动。实验获得了较好的SARS-CoV-2低浓度S蛋白SERS光谱,为建立敏感、特异、快速的SARS-CoV-2检测新技术提供了一种方法。     

水溶液银纳米晶聚集对表面增强拉曼散射的影响

由于贵金属纳米粒子独特的光学性质,基于衬底的贵金属纳米粒子薄膜表面增强拉曼散射技术在分子生物学和医学免疫分析等研究领域中显现出非常好的应用优势和潜力。本项研究工作应用柠檬酸纳作聚集剂诱导水溶液中对巯基苯甲酸修饰的Ag纳米粒子聚集,并应用以此形成的"热点"增强SERS光谱,获得了对巯基苯甲酸修饰的Ag纳米粒子聚集非常有效的4-MBA分子的SERS信号,为未来建立生物待测物的分析检测奠定前期基础。结果证明,水溶液中的Ag纳米粒子的聚集形成的"热点"具有非常好的SERS光谱增强效应。     

气/液界面自组装金纳米粒子薄膜作为SERS基底检测三聚氰胺

采用气/液界面自组装方法制备金纳米粒子薄膜作为SERS基底,其结构规整、均匀,利用此基底对三聚氰胺实现高灵敏的半定量分析。此SERS基底的制备是直接于水相合成的金纳米粒子中加人正十二硫醇,金纳米粒子通过硫醇修饰后由亲水性转变成疏水性质,在相界面上自组装为致密金纳米粒子单层膜结构。这种SERS基底不仅制备方法简单,而且应用范围广,除了检测三聚氰胺还可以拓展到其他的非极性的分子如多环芳烃等高灵敏的半定量分析。     

Au@SiO_2单层膜间耦合效应的表面增强拉曼光谱研究

借助水/油两相界面自组装形成致密排列且有序稳定的Au@SiO2单层膜,通过膜层层转移到固相基底的方法制备了具有不同纳米粒子层数的SERS基底,成功在同一硅片上制备了六层Au@SiO2纳米粒子膜,研究了不同膜层数与SERS信号的关系,结合SERS成像技术可测定纳米粒子膜在基底上的层数。通过改变探针分子在多层纳米粒子膜上的位置,研究了纳米粒子膜间的耦合增强效应。研究表明,同一层膜表面探针分子的SERS信号分布均匀,随膜层数的增加,SERS信号明显增强,当膜层达到第五层时探针分子的SERS信号最强,之后几乎保持不变,说明SERS信号主要来源于表层的五层纳米粒子膜,位于五层以下纳米粒子对SERS效应并没有贡献。固定探针分子仅吸附于底层纳米粒子表面,当再覆盖一层裸露纳米粒子膜后,SERS信号达到最大,其主要源于热点的增强作用占主导地位,而覆盖至第三层时,SERS信号反而出现微小减弱,这是由于多层的Au@SiO2纳米粒子膜影响了激发光以及信号的传播,但粒子间产生的耦合效应仍对底层的探针分子起增强作用,当覆盖至五层Au@SiO2膜后,探针分子SERS信号完全消失,由此说明纳米粒子单层膜控制在三层以内可有效检测底层及以上所有纳米粒子上吸附分子的SERS信号,该结果为制备理想SERS基底提供了实验依据。     

AgNPs/MIL-101(Cr)纳米复合材料的制备及其SERS光谱应用

金属有机框架(Metal Organic Frameworks,MOFs)是一类新型的多孔状的高结晶性材料。MOFs借助于过渡金属离子和有机配体的有序组装,以配位作用构筑起晶体结构。MOFs材料可作为纳米粒子的稳定载体用于与金属纳米粒子组合形成新型的纳米复合材料。这一新型的纳米复合材料可作为SERS基底应用于SERS光谱分析研究。我们将Ag纳米粒子封装在MIL-101(Cr)这种MOFs材料中,MOFs材料所具备的大的比表面积和多孔状的结构可使分析物分子预富集且更加接近金属银纳米粒子表面,从而有助于改善SERS光谱分析与检测性能。借助于多种表征手段与数据分析,我们对此纳米复合材料的制备条件进行了优化。以对巯基吡啶为光谱探针表征了该纳米复合材料的SERS光谱活性,计算了增强因子。在此基础上,将该纳米复合材料用于水溶液中超痕量葡萄糖的SERS光谱检测,探讨了应用SERS光谱技术对葡萄糖进行定量分析的可行性。     

不同粒径、超均匀球形金纳米粒子合成及其表面增强拉曼散射效应研究

以氯金酸为原料,抗坏血酸为还原剂,柠檬酸钠为保护剂,用化学还原(种子生长)法制备了不同粒径、超均匀的球形金纳米粒子溶胶,并通过紫外可见吸收光谱(UV-Vis)和扫描电子显微镜(SEM)进行表征。结果表明,随着金纳米粒子粒径的增大,其UV-Vis光谱中的吸收峰发生红移并出现四极峰。为进一步研究金纳米粒子表面增强拉曼散射(SERS)效应的作用机理并优化其灵敏度,我们以罗丹明6G(R6G)为探针分子,对不同粒径的金纳米粒子进行SERS表征,发现R6G的SERS信号随着金纳米粒子的增大先增强后减弱。当金纳米粒子的平均粒径达到120nm时,产生最强SERS信号增强,增强因子约为1.1×10~7。三维时域有限差分法(3D-FDTD)理论模拟纳米粒子阵列电磁场分布结果与实验数据的趋势一致。     

Surface enhanced Raman scattering monitoring of chain alignment in freely suspended nanomembranes

The molecular chain reorganization in freely standing membranes with encapsulated gold nanoparticles was studied with surface enhanced Raman scattering (SERS) in the course of their elastic deformations. The efficient SERS was enabled by optimizing the design of gold nanoparticle forming chainlike aggregates, thus creating an exceptional ability to conduct in situ monitoring. Small deformations resulted in the radial orientation of side phenyl rings of polymer backbones while larger deflections led to the polymer chains bridging adjacent nanoparticles within one-dimensional aggregates.     

Tailor-made metal nanoparticles as SERS substrates

In this contribution we summarize recent experiments with the objective to generate optimized substrates for surface-enhanced Raman spectroscopy (SERS). For this purpose, the well-established laser-assisted growth technique has been applied, which relies on a precise control of the growth kinetics of supported metal nanoparticles. With this method reproducible and stable SERS substrates with tailor-made optical properties possing best field enhancements were produced for specific excitation wavelengths and detection ranges. Optimization of the SERS substrates has been achieved by stabilizing the localized surface plasmon polariton resonance (SPR) of gold nanoparticles in the vicinity of the laser wavelength of λ=647 nm and λ=785 nm used for SERS excitation. After nanoparticle preparation, SERS spectra of pyrene were obtained using naturally grown nanoparticles and nanoparticles prepared by laser-assisted growth. The most important result is that the optimized substrates prepared by laser-assisted growth exhibit a significantly higher signal-to-noise ratio as compared to naturally grown nanoparticles. They are even better than substrates whose SPR has been tuned to the excitation wavelength by an elevated temperature during preparation. Another important observation is that all SERS spectra exhibit excellent reproducibility and the substrates do not show degradation during the measurements. Finally, the SERS enhancement factors due to the optimized substrates have been estimated and are on the order of 10⁵ to 10⁶.     

Study of tryptophan assisted synthesis of gold nanoparticles by combining UV–Vis, fluorescence, and SERS spectroscopy

We developed a rapid and non-toxic method for the preparation of colloidal gold nanoparticles (GNPs) by using tryptophan (Trp) as reducing/stabilizing agent. We show that the temperature has a major influence on the kinetics of gold ion reduction and the crystal growth, higher temperatures favoring the synthesis of anisotropic nanoparticles (triangles and hexagons). The as-synthesized nanostructures were characterized by UV–Vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), fluorescence, and surface-enhanced Raman scattering (SERS) spectroscopy. The UV–Vis measurements confirmed that temperature is a critical factor in the synthesis process, having a major effect on the shape of the synthesized GNPs. Moreover, fluorescence spectroscopy was able to monitor the quenching of the Trp fluorescence during the in situ synthesis of GNPs. Using Trp as molecular analyte to evaluate the SERS efficiency of as-prepared GNPs at different temperatures, we demonstrated that the Raman enhancement of the synthesized gold nanoplates is higher than that of the gold spherical nanoparticles.     

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。     

SERS enhancement of gold nanospheres of defined size

Monodisperse, citrate‐stabilized gold nanoparticles of sizes ranging from 15 to 40 nm were synthesized and characterized by small angle X‐ray scattering and UV‐vis experiments. Identical surface properties of nanoparticles of different sizes to avoid variation in the chemical surface‐enhanced Raman scattering (SERS) enhancement, as well as selection of experimental conditions so that no aggregation took place, enabled the investigation of enhancement of individual nanospheres. Enhancement factors (EFs) for SERS were determined using the dye crystal violet (CV). EFs for individual gold nanospheres ranged from 10² to 10³, in agreement with theoretical predictions. An increase of the EFs of individual spheres with size can be correlated to changes in the extinction spectra of nanoparticle solutions. This confirms that the increase in enhancement with increasing size results from an increase in electromagnetic enhancement. Beyond this dependence of EFs of isolated gold spheres on their size, EFs were shown to vary with analyte concentration as a result of analyte‐induced aggregation. This has implications for the application of nanoparticle solutions as SERS substrates in quantitative analytical tasks. Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of solid substrate on the SERS‐based immunoassay: a comparative study

A comparative study of the solid substrates used in surface‐enhanced Raman scattering (SERS) based immunoassay is made in this paper. Five different substrates were prepared and divided into two groups with and without SERS activity. They are (1) a poly‐L ‐lysine slide, (2) a glutaraldehyde (GA)‐aminosilane slide, (3) a substrate assembled with silver nanoparticles, (4) a substrate assembled with silver nanoparticles and functionalized with GA–aminosilane and (5) a substrate assembled with gold nanoparticles, of which the first two are substrates are without SERS activity and the latter three are with SERS activity because of the existence of the metallic nanoparticles. The SERS experimental results show that the immunoassay performed on an SERS‐active substrate is more effective than that employing the inactive substrate. Among the inactive substrates, the GA–aminosilane slide with a better ability for antibody immobilization leads to a more sensitive immunoassay than the poly‐L ‐lysine slide. Moreover, for SERS‐based immunoassay, the substrate with assembled silver nanoparticles has an advantage of higher SERS enhancement capacity over the substrate assembled with gold nanoparticles. This work indicates that SERS‐active substrates play important and positive roles in sensitive SERS‐based immunoassay. Copyright © 2010 John Wiley & Sons, Ltd.     

Gold aggregates on silica templates and decorated silica arrays for SERS applications

In this work, we report the fabrication and characterization of size controllable gold nanoparticles (NPs) aggregates for their application in surface enhanced Raman scattering (SERS). Aggregates were prepared using two methodologies: (i) by using silica particles arrays as a template to agglomerate gold NPs between the inter-particle interstices, and (ii) by functionalizing silica particles to be used as support to graft gold nanoparticles and thus to form decorated silica particle arrays. These substrates were used in the detection of Rhodamine 6G producing an enhancement factor (EF) from 10⁴ to 10⁶ that is associated to the increment of hot spot (HS) sites, and the fact that plasmon resonance from aggregates and absorption wavelength of test molecules are closely in resonance with excitation wavelength. The EF was also reduced when the plasmon resonance was red-shifted as a result of the increment of aggregate size. In spite of this, the EF is high enough to make these SERS substrates excellent candidates for sensing applications.     

金纳米-Nylon柔性膜基底的制备及其SERS性能研究

表面增强拉曼光谱（SERS）是目前最灵敏的分析技术之一,广泛应用于生命科学、材料科学、环境科学及分析化学等领域。SERS基底的特性决定了该技术的实际应用范围,是推动该技术发展的关键,高活性SERS基底的制备已经逐渐成为SERS研究领域的热点。为了获得最佳的拉曼信号,对具有特殊特性的SERS活性基底的需求一直很大。柔性SERS基底因具有良好的柔韧性,3D支架结构和表面可控的孔径大小等独特优势,在检测化合物和细菌等方面有很好的应用价值。Nylon(尼龙)柔性膜表面具有分级及多孔交错排列3D结构的特点,将固相萃取装置与特殊材料Nylon柔性膜相结合,通过改变金纳米颗粒的附着量以及金纳米颗粒与膜结合次数,制备了高SERS活性的金纳米-Nylon（Au-Nylon）柔性膜基底。研究表明,金纳米颗粒能很好地附着在Nylon纤维上,纳米颗粒与Nylon柔性膜表面等离子共振耦合作用,形成金纳米颗粒与Nylon纤维的复合体,Au-Nylon柔性膜基底的等离子共振吸收峰发生蓝移。首次处理后的Nylon纤维与其所附着的金纳米颗粒形成新的活性截留层,有助于使再次处理时金颗粒更好地附着在柔性膜表面,产生SERS“热点”效应,提高其SERS性能。利用结晶紫（CV）作为SERS探针分子,对Au-Nylon柔性膜基底SERS性能进行分析,发现CV探针分子在Au-Nylon柔性膜基底上的SERS强度随金纳米颗粒的附着量以及金纳米颗粒与膜结合次数而变化。对于面积为1 cm2的Au-Nylon柔性膜基底,当单次过滤金溶胶1 mL,与膜结合2次,总结合量2 mL时,CV探针分子的SERS信号最强,SERS活性最强。采用Au-Nylon柔性膜基底对浓度为2.5×10-5,1×10-5,1×10-6,5×10-7及1×10-7 mol·L-1的CV溶液进行的SERS检测,发现Au-Nylon柔性膜基底对CV探针分子检测极限达1×10-6 mol·L-1,增强因子达到1.0×104。此外,Au-Nylon柔性膜基底均匀性较好,相对平均偏差为11.8%。Au-Nylon柔性膜基底在微生物检测中,仍具有良好SERS活性,对金黄色葡萄球菌的SERS增强效果优于金溶胶。由此可见,研究中制备的Au-Nylon柔性具有良好的均一性,并具有较好的SERS活性,该方法简单且易批量制备,无论在化合物检测还是微生物检测中都具有良好的实际应用价值。     

Surface-enhanced Raman scattering effect of gold nanoparticle arrays: The influence of annealing temperature,excitation power and array thickness

Gold nanoparticle arrays are fabricated for surface-enhanced Raman scattering (SERS) and the effect of the annealing temperature, the thickness of nanoparticle array and the exciting power on the SERS signals are investigated. The particle distribution and particle size are dense and uniform on the glass substrate when the 10 nm gold film was annealed at 250 °C and strong SERS signals for Rhodamine 6G were achieved via a 532 nm excitation with a 10 mW power. The SERS signal at 1650 cm⁻¹ is enhanced more than 10 times as compared to that of the gold film without annealing. The strong SERS behavior of gold nanoparticle arrays may broaden the SERS applications in biomedical and analytical chemistry.