自组装有序纳米银线表面增强拉曼光谱检测牛奶中三聚氰胺

制备具有表面增强拉曼散射(SERS)增强效果的基底是获得灵敏SERS检测的基础.本研究以多元醇法合成、流体流动法组装制备的有序纳米银线作为三聚氰胺的SERS增强基底,实现了样品中痕量三聚氰胺的快速灵敏检测.通过理论计算及实验考察得到了三聚氰胺的拉曼特征峰,优化了三聚氰胺在有序纳米银线基底上的SERS检测条件.在pH=8、水为溶剂、溶剂挥发时间为14 min的最佳条件下,三聚氰胺特征峰强度与浓度在0.05 ～ 1.00 mg/L范围内呈现良好的线性关系,其线性相关系数R=0.997,检测限为0.05 mg/L.在牛奶中添加不同浓度的三聚氰胺,其回收率为89.7％～ 109.2％,相对标准偏差低于6.8％.本方法对三聚氰胺检测具有很好的灵敏度和稳定性,为其它小分子化合物的SERS检测提供技术支持.     

Au@SiO2核壳结构-表面增强拉曼光谱原位检测食品中的酸性橙Ⅱ

以具有核壳结构的Au@SiO2纳米颗粒为基底,建立了一种以表面增强拉曼(SERS)原位、快速检测食品中非法添加剂酸性橙Ⅱ的新方法.研究了活性硅加入量对所形成的Au@SiO2纳米颗粒的SERS活性的影响,制备了具有最佳SERS活性的Au@SiO2,并以此为SERS基底建立了酸性橙Ⅱ的分析方法,可实现0.17 mg/L酸性橙Ⅱ的SERS检测.将合成的Au@SiO2滴加到瓜子表面后,可以实现对瓜子表面酸性橙Ⅱ浓度为0.01 mg/g时的SERS检测,能够满足食品中酸性橙Ⅱ的测定要求,有望用于瓜子及其它可能被非法添加该物质的食品的现场、快速检测.     

TiN-Ag@Ag SERS基底制备及其对腺嘌呤的检测性能与增强机制研究

该文制备了TiN@Ag溶胶、TiN-Ag薄膜、TiN-Ag@Ag溶胶3种复合基底对腺嘌呤进行表面增强拉曼光谱(SERS)检测,并对拉曼增强效应进行研究。结果显示,与理论峰位相比,腺嘌呤的SERS图峰位发生偏移,可能是腺嘌呤吸附在增强基底上时分子构型和偶极距发生了改变(理论计算中过多的电子和外部溶剂的参与也会引起峰位偏移)。研究发现TiN-Ag@Ag溶胶基底上腺嘌呤的信号最强,这是因为该基底不仅具有TiN薄膜与Ag纳米颗粒发生共振耦合出现的可使SERS活性明显提高的“热点”,还存在Ag纳米颗粒聚集在Ag纳米棒之间形成的纳米间隙产生的更多“热点”。利用TiN-Ag@Ag溶胶基底对腺嘌呤进行灵敏检测,检出限可达10^-5 mol/L。并通过紫外光电子能谱结合高斯软件中密度泛函理论和时域有限分差法,对各基底的增强机制进行了分析。     

Ag纳米粒子在TiO2四棱柱阵列上的可控生长及其SERS效应

采用水热法在导电玻璃FTO导电面上沉积TiO₂四棱柱阵列; 并以其为基体, 分别采用聚乙烯基吡咯 烷酮(PVP)还原Tollens试剂以及柠檬酸三钠(TSC)还原硝酸银溶液, 将Ag纳米粒子(AgNPs)沉积在TiO₂四棱柱阵列上形成TiO₂@AgNPs-PVP和TiO₂@AgNPs-TSC微纳结构作为表面增强拉曼散射(SERS)基底. 实验结果表明, Ag纳米粒子在TiO₂四棱柱阵列上的尺寸和分布可通过改变Tollens试剂的浓度和TSC还原硝酸银溶液的反应时间来调控, 进而优化基底的SERS灵敏度. TiO₂@AgNPs-PVP微纳结构对罗丹明6G(R6G)的检出限为10^-12 mol/L, 对低活性小分子三聚氰胺的检出限为0.01 mg/mL; TiO₂@AgNPs-TSC微纳结构对R6G的检出限为10^-10 mol/L, 对三聚氰胺的检出限为0.01 mg/mL. TiO₂@AgNPs-PVP和TiO₂@AgNPs-TSC微纳结构基底的SERS活性、 循环可回收性与还原剂种类紧密相关: 包覆在Ag纳米粒子上的PVP可以作为隔离层避免Ag纳米粒子直接接触, 防止电磁场耦合作用减弱, 增强基底的SERS活性; 同时, PVP是一种水性聚合物, 有较强的亲水性, 作为循环可回收SERS基底使用时, 吸附小分子物质清洗难度较大.     

基于MOF@TiN-Ag/银溶胶复合基底的茶碱表面增强拉曼检测

以制备的MOF@TiN-Ag/银溶胶复合基底为表面增强拉曼光谱(SERS)活性基底，对茶碱进行SERS检测，探讨了基于该复合基底的表面增强拉曼技术在药物检测方面的应用。首先，利用电化学阳极氧化结合氨气还原氮化法制备了氮化钛纳米管阵列，随后通过电化学沉积法制备TiN-Ag复合基底，并在其表面原位生长金属有机框架(MOF)包覆层得到MOF@TiN-Ag复合基底，将茶碱与银溶胶混合后滴加在该复合基底上进行表面增强拉曼光谱检测。结果表明，MOF@TiN-Ag/银溶胶复合基底中存在面心立方晶型TiN、金属单质Ag和MOF钴基3种物相；扫描电镜结果显示，TiN纳米管排列整齐，Ag纳米结构呈树枝状均匀分散在其表面；作为隔绝层的MOF粒子形状规整，覆盖在TiN-Ag表面；银溶胶纳米粒子呈圆球状分布在MOF@TiN-Ag复合基底表面。由于银纳米粒子与TiN-Ag复合基底可发生协同增强作用，加之MOF的富集特性，使得该复合基底具有优异的SERS性能，其对茶碱溶液的SERS检出限为1×10^-5 mol/L，检测性能良好。所制备的MOF@TiNAg/银溶胶复合基底拓宽了SERS在药物检测...     

g-C3N4/Ag纳米复合材料表面增强拉曼基底对婴幼儿糖果中的罗丹明B的痕量检测

近年来, 由婴幼儿食品中存在非法添加剂所引起的食品安全问题已经受到了广泛的关注. 表面增强拉曼散射(SERS)技术可以对食品中被禁止添加的常用染料分子罗丹明B (RhB)进行快速无损超灵敏的检测. 通过在类石墨相氮化碳(g-C₃N₄)纳米片上组装Ag纳米粒子的方式构筑了g-C₃N₄/Ag复合材料, 并采用透射电子显微镜(TEM)、紫外可见近红外分光光度计(UV-Vis)、X射线衍射仪(XRD)、荧光光谱仪和共聚焦显微拉曼光谱仪(Raman)对复合材料的形貌和结构进行了表征. g-C₃N₄纳米片不仅具有高度的离域π共轭体系和良好的吸附染料分子的性能, 而且可以作为Ag纳米粒子的载体, 使Ag纳米粒子均匀稳定地分散在其表面. 通过控制实验条件, 优化了测试过程中的pH及基底与RhB的结合时间, 详细探究pH对基底表面等离子共振的影响和对探针分子SERS强度的影响. 由于基底与探针分子之间的静电相互作用及π-π相互作用, 基底可以对阳离子染料进行大量地富集, 从而实现对其检测. 在最佳的实验条件下, 在1.0×10 ^–9~1.0×10 ^–6 mol/L浓度范围内, SERS强度与RhB浓度之间成线性关系, 最低检测限为0.39 nmol/L. 另外这种基底也可以对婴幼儿食用的棒棒糖中添加的RhB分子实现痕量检测. 总而言之, g-C₃N₄/Ag纳米复合物是一种均一、稳定、高灵敏的SERS基底, 可以简单快速地实现对罗丹明B的痕量检测.     

碳纳米管@SiO_2@Ag纳米复合材料的制备及其表面增强拉曼效应

本文以SiO2为中间层,在多壁碳纳米管(MWCNTs)表面负载Ag纳米粒子,制备出CNTs@SiO2@Ag纳米复合材料,并采用TEM、XRD、UV-Vis、XPS等对纳米复合材料的结构、形貌和成分进行了表征,同时对该纳米复合材料的表面增强拉曼散射(Surface-enhanced Raman scattering,SERS)效应进行了研究。结果显示,Ag纳米颗粒有效提高了CNTs的SERS活性,纳米复合材料的拉曼峰强度是单纯CNTs拉曼峰强的近5倍。进一步研究了吸附罗丹明6G生物染料分子的SERS光谱,结果表明R6G分子的拉曼信号的质量与强度得到显著提高。因此,所制备的CNTs@SiO2@Ag纳米复合材料有望作为SERS的活性基底,应用于生物无损检测领域。     

纳米Ag/TiO_(2)纳米管阵列基底构建及表面增强拉曼散射光谱检测与降解盐酸四环素北大核心CSCD

将阳极氧化与光还原法结合,在TiO_(2)纳米管阵列(TiO_(2)NTAs)表面修饰Ag纳米粒子,获得一种均匀有序、稳定性高且可循环的TiO_(2)NTAs/Ag活性基底。采用X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-Vis DRS)、表面增强拉曼散射光谱(SERS)和扫描电子显微镜(SEM)等手段对TiO_(2)NTAs/Ag的组成和结构进行了表征。进一步研究了该TiO_(2)-NTAs/Ag阵列对盐酸四环素(TC-HCl)的SERS响应,结果表明,该复合基底对TC-HCl具有较高的检测灵敏度,在水中检测限可达1×10^(−14) mol/L,而TiO_(2)-NTAs与Ag之间的协同效应对其检测性能的提高起着关键作用。此外,TiO_(2)NTAs/Ag基底在光照下对TC-HCl展示了优异的降解活性,且至少可循环使用8次。表明该TiO_(2)NTAs/Ag基底在环境中有机污染物的SERS检测和降解领域具有潜在的应用前景。     

基于贵金属纳米粒子的SERS活性基底研究进展

表面增强拉曼光谱(SERS)是一种新兴的分析技术,具有很高的检测灵敏度,可以实现单分子量级的检测,并且能够提供丰富的分子结构信息。将SERS发展成为一种具有实际应用意义的分析技术,其关键是制备灵敏度高、稳定性高、重现性好、选择性高的SERS活性基底。对贵金属纳米粒子表面进行分子修饰,或者将贵金属纳米粒子与基质材料进行复合,可以组成融合贵金属纳米粒子的SERS活性并弥补其缺陷的新型SERS基底材料。本文综述了近年来基于贵金属纳米粒子常见的分子修饰和基质复合型SERS活性基底的研究进展。     

碳纳米管@SiO2@Ag纳米复合材料的制备及其表面增强拉曼效应

本文以SiO₂为中间层,在多壁碳纳米管(MWCNTs)表面负载Ag纳米粒子,制备出CNTs@SiO₂@Ag纳米复合材料,并采用TEM、XRD、UV-Vis、XPS等对纳米复合材料的结构、形貌和成分进行了表征,同时对该纳米复合材料的表面增强拉曼散射(Surface-enhancedRamanscattering,SERS)效应进行了研究。结果显示,Ag纳米颗粒有效提高了CNTs的SERS活性,纳米复合材料的拉曼峰强度是单纯CNTs拉曼峰强的近5倍。进一步研究了吸附罗丹明6G生物染料分子的SERS光谱,结果表明R6G分子的拉曼信号的质量与强度得到显著提高。因此,所制备的CNTs@SiO₂@Ag纳米复合材料有望作为SERS的活性基底,应用于生物无损检测领域。     

HA/Ag纳米复合材料的制备与性能

采用一锅热熔胶法制备出多孔花状羟基磷灰石/银(HA/Ag)纳米复合材料。通过检测罗丹明B揭示了HA/Ag作为SERS活性底物的独特拉曼增强效应,其检测极限为10~(-8) mol·L~(-1)。在检测中,改变拉曼激光强度,取点位置等手段能有效提高检测的灵敏度。此外,所制备的多孔纳米复合材料HA/Ag作为对硝基苯酚(4-NP)还原为对氨基苯酚(4-AP)反应的催化剂,可以大大缩短反应时间40 min。     

Fabrication and Formation Mechanism of Ag Nanoplate‐Decorated Nanofiber Mats and Their Application in SERS

We report a new simple method to fabricate a highly active SERS substrate consisting of poly‐m‐phenylenediamine/polyacrylonitrile (PmPD/PAN) decorated with Ag nanoplates. The formation mechanism of Ag nanoplates is investigated. The synthetic process of the Ag nanoplate‐decorated PmPD/PAN (Ag nanoplates@PmPD/PAN) nanofiber mats consists of the assembly of Ag nanoparticles on the surface of PmPD/PAN nanofibers as crystal nuclei followed by in situ growth of Ag nanoparticles exclusively into nanoplates. Both the reducibility of the polymer and the concentration of AgNO₃ are found to play important roles in the formation and the density of Ag nanoplates. The optimized Ag nanoplates@PmPD/PAN nanofiber mats exhibit excellent activity and reproducibility in surface‐enhanced Raman scattering (SERS) detection of 4‐mercaptobenzoic acid (4‐MBA) with a detection limit of 10^?10 m , making the Ag nanoplates@PmPD/PAN nanofiber mats a promising substrate for SERS detection of chemical molecules. In addition, this work also provides a design and fabrication process for a 3D SERS substrate made of a reducible polymer with noble metals.     

ZnGa2O4 Nanorod Arrays Decorated with Ag Nanoparticles as Surface‐Enhanced Raman‐Scattering Substrates for Melamine Detection

The availability of sensitive, reproducible, and stable substrates is critically important for surface‐enhanced Raman spectroscopy (SERS)‐based applications, but it presently remains a challenge. In this work, well‐aligned zinc gallate (ZnGa₂O₄) nanorod arrays grown on a Si substrate by chemical vapor deposition were used as templates to fabricate SERS substrates by deposition of Ag nanoparticles onto the ZnGa₂O₄ nanorod surfaces. The coverage of the Ag nanoparticles on the ZnGa₂O₄ nanorod surfaces was easily controlled by varying the amount of AgNO₃. SERS measurements showed that the number density of Ag nanoparticles on the ZnGa₂O₄ nanorod surfaces had a great effect on SERS activity. The SERS signals collected by point‐to‐point and SERS mapping images showed that as‐prepared SERS substrates exhibited good spatial uniformity and reproducibility. Detection of melamine molecules at low concentrations (1.0×10^?7 M ) was used as an example to show the possible application of such a substrate. In addition, the effect of benzoic acid on the detection of melamine was also investigated. It was found that the SERS signal intensity of melamine decreased greatly as the concentration of benzoic acid was increased.     

Visible‐light‐driven self‐cleaning SERS substrate of silver nanoparticles and graphene oxide decorated nitrogen‐doped titania nanotube array

Graphene oxide (GO) and silver nanoparticles (Ag NPs) sequentially decorated nitrogen‐doped titania nanotube array (N‐TiO₂ NTA) had been designed as visible‐light‐driven self‐cleaning surface‐enhanced Raman scattering (SERS) substrate for a recyclable SERS detection application. N‐TiO₂ NTA was fabricated by anodic oxidation and then doping nitrogen treatment in ammonia atmosphere, acting as a visible‐light‐driven photocatalyst and supporting substrate. Ag/GO/N‐TiO₂ NTA was prepared by decorating GO monolayer through an impregnation process and then depositing Ag NPs through a polyol process on the surface of N‐TiO₂ NTA, acting as the collection of organic molecule and Raman enhancement. The SERS activity of Ag/GO/N‐TiO₂ NTA was evaluated using methyl blue as an organic probe molecule, revealing the analytical enhancement factor of 4.54 × 10⁴. Ag/GO/N‐TiO₂ NTA was applied as active SERS substrate to determine a low‐affinity organic pollutant of bisphenol A, revealing the detection limit of as low as 5 × 10^?7 m . Ag/GO/N‐TiO₂ NTA could also achieve self‐cleaning function for a recycling utilization through visible‐light‐driven photocatalytic degradation of the adsorbed organic molecules. Ag/GO/N‐TiO₂ NTA has been successfully reused for five times without an obvious decay in accuracy and sensitivity for organic molecule detection. The unique properties of this SERS substrate enable it to have a promising application for the sensitive and recyclable SERS detection of low‐affinity organic molecules. Copyright © 2016 John Wiley & Sons, Ltd.     

Silver nanocubes monolayers as a SERS substrate for quantitative analysis

Surface-enhanced Raman scattering (SERS) is a powerful spectroscopic tool in quantitative analysis of molecules, where the substrate plays a critical role in determining the detection performance. Herein, a silver nanocubes/polyelectrolyte/gold film sandwich structure was prepared as a reproducible, high-performance SERS substrate by the water/oil interfacial assembly method. In addition to the hot spots on the nanocubes surface, the edge-to-edge interspace of the Ag nanocubes led to marked enhancement of the SERS intensity, with a limit of detection of 10^?11 mol/L and limit of quantitation of 10^?10 mol/L for crystal violet. When rhodamine 6G and crystal violet were co-adsorbed on the Ag nanocube surfaces, the characteristic SERS peaks of the two molecules remained well resolved and separated, and the peak intensities varied with the respective concentration, which could be exploited for concurrent detection of dual molecules. Results from this work indicate that organized ensembles of Ag nanocubes can serve as effective SERS substrate can for sensitive analysis for complex molecular systems.     

Surface-enhanced Raman scattering of 4-aminobenzenethiol on silver nanoparticles substrate

Active surface-enhanced Raman scattering (SERS) silver nanoparticles substrate was prepared by multiple depositions of Ag nanoparticles on glass slides. The substrate is based on five depositions of Ag nanoparticles on 3-aminopropyl-trimetoxisilane (APTMS) modified glass slides, using APTMS sol–gel as linker molecules between silver layers. The SERS performance of the substrate was investigated using 4-aminobenzenethiol (4-ABT) as Raman probe molecule. The spectral analyses reveal a 4-ABT Raman signal enhancement of band intensities, which allow the detection of this compound in different solutions. The average SERS intensity decreases significantly in 4-ABT diluted solutions (from 10⁻⁴ to 10⁻⁶ mol L⁻¹), but the compound may still be detected with high signal/noise ratio. The obtained results demonstrate that the Ag nanoparticles sensor has a great potential as SERS substrate.     

Dealloying Ag–Al Alloy to Prepare Nanoporous Silver as a Substrate for Surface‐Enhanced Raman Scattering: Effects of Structural Evolution and Surface Modification

Sensitive detection of molecules by using the surface‐enhanced Raman scattering (SERS) technique depends on the nanostructured metallic substrate and many efforts have been devoted to the preparation of SERS substrates with high sensitivity, stability, and reproducibility. Herein, we report on the fabrication of stable monolithic nanoporous silver (NPS) by chemical dealloying of Ag–Al precursor alloys with an emphasis on the effect of structural evolution on SERS signals. It was found that the dealloying conditions had great influence on the morphology (the ligament/pore size) and the crystallization status, which determined the SERS signal of rhodamine 6G on the NPS. NPS with small pores, low residual Al, and perfect crystallization gave high SERS signals. A high enhancement factor of 7.5×10⁵ was observed on bare NPS obtained by dealloying Ag₃₀Al₇₀ in 2.5 wt % HCl at room temperature followed by 15 min aging at around 85 °C. After coating Ag nanoparticles on the NPS surface, the enhancement factor increased to 1.6×10⁸ owing to strong near‐field coupling between the ligaments and nanoparticles.     

Development of nanofibrillated cellulose coated with gold nanoparticles for measurement of melamine by SERS

The objective of this study was to develop nanofibrillated cellulose (NFC)-based substrate for rapid detection of melamine in milk by surface-enhanced Raman spectroscopy (SERS). NFC were served as a highly porous platform to load with gold nanoparticles (AuNPs), which can be used as a flexible SERS substrate with nanoscale roughness to generate strong electromagnetic field in SERS measurement. The NFC/AuNP substrate was characterized by UV–Vis spectroscopy and electron microscopy. Milk samples contaminated by different concentrations of melamine were measured by SERS coupled with NFC/AuNP substrate. The spectral data analysis was conducted by multivariate statistical analysis [i.e. partial least squares (PLS)]. Satisfactory PLS result for quantification of melamine in milk was obtained (R = 0.9464). The detection limit for melamine extracted from liquid milk by SERS is 1 ppm, which meets the World Health Organization’s requirement of melamine in liquid milk. These results demonstrate that NFC/AuNP substrate has improved homogeneity and can be used in SERS analysis for food safety applications.     

Detecting trace melamine in solution by SERS using Ag nanoparticle coated poly(styrene-co-acrylic acid) nanospheres as novel active substrates

A systematic study for the preparation of Ag nanoparticle (Ag-NP) coated poly(styrene-co-acrylic acid) (PSA) composite nanospheres by in situ chemical reduction is reported. The experimental results showed that the reaction temperature and the surface coverage of the -COOH determined the surface coverage and grain size of Ag nanoparticles on the PSA nanospheres. The surface enhanced Raman spectroscopy (SERS) sensitivity was investigated using 4-hydroxythiophenol (4-HBT) as the model probe in the solution of composite nanospheres stabilized by polyvinylpyrrolidone (PSA/Ag-NPs/PVP), with the detection limit of about 1 × 10(-6) M. Potential application of the new SERS substrate was demonstrated with the detection of melamine, and the detection limit was about 1 × 10(-3) M. Chemical noises from PVP and other impurities were observed and attributed mainly to the competitive adsorption of PVP on the surfaces of Ag-NPs. After tetrahydrofuran washing of the PSA/Ag-NPs/PVP substrates that removed the PVP and other residuals, the signal/noise levels of SERS were greatly improved and the detection limit of melamine was determined to be 1 × 10(-7) M. This result indicated that the new PSA/Ag-NPs system is highly effective and can be used as the SERS-active substrate for trace analysis of a variety of drugs and food additives.     

3D aluminum/silver hierarchical nanostructure with large areas of dense hot spots for surface‐enhanced raman scattering

Plasmonic nanomaterials possessing large‐volume, high‐density hot spots with high field enhancement are highly desirable for ultrasensitive surface‐enhanced Raman scattering (SERS) sensing. However, many as‐prepared plasmonic nanomaterials are limited in available dense hot spots and in sample size, which greatly hinder their wide applications in SERS devices. Here, we develop a two‐step physical deposition protocol and successfully fabricate 3D hierarchical nanostructures with highly dense hot spots across a large scale (6 × 6 cm²). The nanopatterned aluminum film was first prepared by thermal evaporation process, which can provide 3D quasi‐periodic cloud‐like nanostructure arrays suitable for noble metal deposition; then a large number of silver nanoparticles with controllable shape and size were decorated onto the alumina layer surfaces by laser molecular beam epitaxy, which can realize large‐area accessible dense hot spots. The optimized 3D‐structured SERS substrate exhibits high‐quality detection performance with excellent reproducibility (13.1 and 17.1%), whose LOD of rhodamine 6G molecules was 10^?9 M. Furthermore, the as‐prepared 3D aluminum/silver SERS substrate was applied in detection of melamine with the concentration down to 10^?7 M and direct detection of melamine in infant formula solution with the concentration as low 10 mg/L. Such method to realize large‐area hierarchical nanostructures can greatly simplify the fabrication procedure for 3D SERS platforms, and should be of technological significance in mass production of SERS‐based sensors.