基于AFM纳米氧化技术的金纳米粒子定点组装

二维纳米粒子矩阵列在纳米电子器件^[1,2]、表面增强喇曼活性基底^[3,4]、刻蚀掩模^[5]等领域具有广泛的应用前景。在这些纳米粒子阵列为内部,纳米粒子的排布是随机、无序的。这一缺点已经妨碍了纳米粒子阵列在上述领域中的进一步应用。基于此,人们开始关注纳米粒子的可控组装。传统的光刻技术^[6]、微接触印刷技术^[7]以及生物分子模板技术^[8]都被用来实现纳米粒子在固体表面上的可控组装,本实验室在纳米粒子的合成及可控组装方面也进行了研究^[7,9,11]。本文力图精确控制单个纳米粒子在基底表面上的组装位置。利用AFM纳米氧化技术。在硅表面构建了纳米级的化学图形化表面,通过不同的化学官能团,如甲基、氨基对金纳米粒子亲和性质的差异,实现了纳米粒子在固体表面的定点组装。     

金纳米粒子组装结构中的表面重组现象

以纳米粒子为基本结构单元构筑的各种二维或三维超晶格结构受到了广泛的重视［１］．人们的兴趣一方面来源于在纳米尺度上控制材料结构 ,另一方面则因为组织化的纳米材料或结构具有独特的性质 ,以期在非线性光学、纳米电子学等前沿领域得到应用［２］．当前研究最多的结构形式是固体表面上的纳米粒子阵列或单层薄膜 ,通常是胶体粒子靠某种特殊相互作用吸附或沉积在固体表面上（亦称为“纳米粒子在表面上的组装［３］”） ,因此对纳米粒子及固体表面进行功能化的修饰 ,从而控制纳米粒子在表面上的排列和聚集状态 ,是制备这类复合结构的核心问…     

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.     

一种简单组装纳米沸石粒子层的方法及其二次法成膜研究

使用一种简单、新颖的纳米沸石晶体自组装方法, 以γ-氨丙基三甲氧基硅烷(AP-TMS)为偶联剂, 成功地实现了纳米A型沸石粒子在多孔不锈钢、陶瓷以及单晶硅表面的沉积组装, 获得了覆盖度高的续、均匀的沸石粒子层. 组装过程在合成釜内分为载体功能化和晶种化两步. 以该沸石粒子层为晶种二次法成膜, 形成了交织生长的连续、均匀的沸石膜, 并用含少量水的苯甲醛混合液评价了微型膜的渗透蒸发性能, 水-苯甲醛分离系数超过10 000以上. 考察了使用γ-氨丙基三甲氧基硅烷(AP-TMS)、γ-氯丙基三甲氧基硅烷(CP-TMS)和γ-巯丙基三甲氧基硅烷(SP-TMS)三种不同偶联剂时, 纳米A型沸石晶体在多孔不锈钢、陶瓷以及单晶硅表面的自组装效果. 研究发现, 使用CP-TMS作为偶联剂时, 只在不锈钢载体上形成较为连续的粒子层, 而使用SP-TMS作为偶联剂时, 在三种载体上纳米A型沸石粒子均不能沉积形成粒子层. 对偶联剂的作用和粒子组装机制进行了讨论和预测.     

静电组装金纳米粒子制备局域表面等离子体共振传感膜

采用聚电解质自组装技术制备局域表面等离子体共振(LSPR)传感膜的方法, 在玻璃基片上依次沉积聚电解质PDDA, PSS和PVTC, 并通过静电吸附构建胶体金纳米粒子自组装膜形成LSPR传感膜. 利用扫描电镜对LSPR传感膜表面形貌以及膜中金纳米粒子的粒径进行了表征, 同时通过紫外-可见消光光谱对其灵敏度和渗透深度等重要参数进行检测. 研究结果表明, 所制备的LSPR传感膜粒子分布均匀、单分散性好、稳定性高、重现性好; 消光峰位对样品溶液折射率的检测灵敏度为71 nm/RIU, 相应的峰强检测灵敏度为0.21 AU/RIU, 对表面吸附层的渗透深度约为16 nm.     

基于表面增强拉曼光谱的重金属离子检测

以对巯基苯甲酸为拉曼标记和自组装修饰分子, 在光亮金基底上修饰后作为检测基底, 在金纳米粒子表面修饰后获得具有表面增强拉曼光谱信号的标记金溶胶. 修饰的基底及纳米离子通过重金属离子与羧基端的配位而发生相互作用, 最终形成“金属基底-对巯基苯甲酸/重金属离子/对巯基苯甲酸-金属纳米颗粒”的三明治结构. 采用扫描电镜表征纳米粒子的组装及以表面增强拉曼光谱检测表面标记分子的信号, 以此实现重金属离子的检测. 以强螯合剂EDTA溶液淋洗三明治结构, 使重金属离子与金属基底以及纳米颗粒上的羧基的配位作用断裂, 获得可再次利用的修饰金基底.     

金纳米棒在超疏水表面的组装行为研究

采用了"烟囱效应"以及超疏水表面作为基底这两项外力作用来将金纳米棒进行组装。借用"烟囱"技术的侧面向心力所产生的向心空气气流,以及超疏水表面上液滴收缩产生的应力对纳米粒子的向心挤作用,得到了金纳米棒垂直于基片致密排列的特殊的组装花样以及金纳米棒水平短程有序的致密排列的组装花样。这种简便的组装方法不仅对纳米器件的应用有着重要的影响,而且可以广泛地适用于其他的纳米粒子的二维有序组装以得到不同的功能性的纳米组装体。     

基于局域SPR传感器的免疫分析

局域表面等离子体共振(LSPR)是一种由入射光(电磁场)与金属纳米粒子表面自由电子间相互作用产生的物理光学现象,其性质与纳米粒子的组成、尺寸、形状、粒子间距和周围介质折射率等因素有关.溶胶LSPR传感已被成功地应用于免疫分析以及DNA检测等方面.应用聚电解质作为自组装材料,通过静电相互作用,将金纳米粒子组装于玻璃基片上制备LSPR传感膜.此种方法制备的LSPR传感膜中金纳米粒子的单分散性好,制备过程简单、组装时间短.同时,应用紫外.可见分光光度计进行检测,实验操作更加简便.     

复合Fe2O3纳米粒子的高分子微球的结构表征

近年来，复合有机、无机粒子的高分子微球及其特殊性质越来越引起人们的兴趣与关注［1］．获得有机、无机复合微球的方法很多，如在无机粒子存在下的乳液或无皂乳液聚会[2，3]，通过可聚合的表面活性剂在粒子表面形成胶囊化层[4]以及共沉淀法等[5]．这些无机粒子包括氧化钛、氧化铁、氧化铝及氧化硅等．Haga等[6]增发现包覆在聚合物粒子中的CdS与其本体的光电性质不同；单分散的聚合物微球可以在基片上被组装成二维乃至三维有序的结构[7]．这为信息存储、立体印刷等领域提供了新途径．因此，将无机粒子与聚合物复合成为功能化粒子是一项有…     

帽状铝纳米粒子的制备及表面等离子共振特性

金属纳米材料具有许多独特的物理和化学性质,其中一个重要的光学性质就是表面等离子共振,然而在大多数情况下,金属纳米粒子表面等离子共振所产生的吸收峰被限制在相对狭小的范围内,很难进行调谐。近年来,以电介质为核金属为壳的核壳结构复合纳米材料成功的解决了这一问题,通过设计和剪裁内核的直径与外壳层厚度的比值,可以实现光学性质可调的特性[1～5]。此类复合材料可被广泛应用于光催化、传感器、光信息存储、生物光子学、生物医学等领域[6～11]。美国莱斯大学及德州的研究人员利用这类核壳结构纳米材料成功地实现了对体外乳腺肿瘤的杀灭实验[12]。在这种类型的材料中,对称性降低的即不完全包裹的纳米粒子如杯状[13]、帽状[13,14]、半球壳状[15]、月牙状[16]等核壳结构复合粒子由     

Effect of Ag and Au nanoparticles on the SERS of 4-aminobenzenethiol assembled on powdered copper

Raman scattering measurements were conducted for 4-aminobenzenethiol (4-ABT) assembled on powdered copper substrates. Initially, very weak Raman peaks were detected, but upon attaching Ag nanoparticles probably via NH2 groups onto 4-ABT/Cu, distinct Raman spectra were observed. Considering the fact that no Raman peak was identified when Ag nanoparticles were adsorbed on 4-aminophenyl-derivatized silane monolayers assembled on silica powders, the Raman spectra observed for Ag@4-ABT/Cu should be surface-enhanced Raman scattering (SERS) spectra, occurring by an electromagnetic coupling of the localized surface plasmon of Ag nanoparticles with the surface plasmon polariton of Cu powders. The extra enhancement factor attainable by the attachment of a single Ag nanoparticle is estimated to be as large as 1.4 x 10(5) in the case when 632.8-nm radiation is used as the excitation source. When Au nanoparticles were attached onto 4-ABT/Cu, at least an order of magnitude weaker Raman spectra were obtained at all excitation wavelengths, however, indicating that the Au-to-Cu coupling should be far less effective than the Ag-to-Cu coupling for the induction of SERS.     

Self-assembled metal colloid films: two approaches for preparing new SERS active substrates

In this paper, we propose two new approaches for preparing active substrates for surface-enhanced Raman scattering (SERS). In the first approach (method 1), one transfers AgI nanoparticles capped by negatively charged mercaptoacetic acid from a AgI colloid solution onto a quartz slide and then deoxidizes AgI to Ag nanoparticles on the substrate. The second approach (method 2) deoxidizes AgI to Ag nanoparticles in a colloid solution and then transfers the Ag nanoparticles capped by negatively charged mercaptoacetic acid onto a quartz slide. By transfer of the AgI/Ag nanoparticles from the colloid solutions to the solid substrates, the problem of instability of the colloid solutions can largely be overcome. The films thus prepared by both approaches retain the merits of metal colloid solutions while they discharge their shortcomings. Accordingly, the obtained Ag particle films are very suitable as SERS active substrates. SERS active substrates with different coverages can be formed in a layer-by-layer electrostatic assembly by exposing positively charged surfaces to the colloid solutions containing oppositely charged AgI/Ag nanoparticles. The SERS active substrates fabricated by the two novel methods have been characterized by means of atomic force microscopy (AFM) and ultraviolet-visible (UV-vis) spectroscopy. The results of AFM and UV-vis spectroscopy show that the Ag nanoparticles grow with the increase in the number of coverage and that most of them remain isolated even at high coverages. Consequently, the surface optical properties are dominated by the absorption due to the isolated Ag nanoparticles. The relationship between SERS intensity and surface morphology of the new active substrates has been investigated for Rhodamine 6G (R6G) adsorbed on them. It has been found that the SERS enhancement depends on the size and aggregation of the Ag particles on the substrates. Especially, we can obtain a stronger SERS signal from the substrate prepared by method 1, implying that for the metal nanoparticles capped with stabilizer molecules such as mercaptoacetic acid, the in situ deoxidization in the film is of great use in preparing SERS active substrates. Furthermore, we have found that the addition of Cl- into the AgI colloid solution changes the surface morphology of the SERS active substrates and favors stronger SERS enhancement.     

Fabrication, Characterization, and Surface-Enhanced Raman Activity Study of Silver Coated Gold Nanoparticulate Films

This paper reports a study on the preparation of Ag-clad Au colloidal monolayer films by a combination of colloid self-assembly and liquid phase microwave high-pressure technique. Firstly, monodisperse Au nanoparticles prepared by microwave heating method were assembled onto a quartz slide. Then, these Au colloidal particles on the quartz surface acted as seeds for growing the Ag-clad Au composite particulate films. The obtained particulate films were characterized by UV-Vis spectra and atomic force microscopy. It was found that the thickness of the shell and thus the size of particles in the composite colloidal films could be controlled by deposition of Ag on the preformed Au colloidal particle film in the microwave reaction system, and such films significantly increased the surface-enhanced Raman scattering enhancement （SERS） ability compared with Au colloidal particle films. Their strong enhancement ability may mainly stem from relatively large particle consisting of Ag cladding as well as effective coupling among particles in the Ag-clad Au particle ftlms.     

Assembly of Multilayered Films on Core Substrate:Preparation and Characterization

Certain colloidal metals such as.silver (Ag), gold (Au) and copper, (Cu), when properly or assembled, display remarkable enhancement effect to the Raman scattering cross section of adsorbed molecules. This surface-enhanced Raman scattering (SERS) phenomenon has found wide applications in the study of interfacial chemical processes and is a potentially non-invasive technique in molecule-specific analysis. However, the SERS activity of metal colloids depends sensitively on both the synthetic method and the aggregation and assembly procedure, making it difficult to develop SERS into a reliable and quantitative analytical technique. To solve this problem, one needs to develop a substrate with a well-defined adsorption area and SERS activity. One approach to achieve this goal is to assemble a monolayer of uniform colloidal metals onto a well-defined secondary substrate. Here we report our effort in assembling monolayers of uniform Au nanoparticles on the well-defined optical-inactive microparticles in a layer-by-layer (LbL) manner and the use of such assembly as SERS-active substrate.     

Surface enhanced Raman scattering from layered assemblies of close-packed gold nanoparticles

A synthetic method of ordering hydrophilic gold nanoparticles into a close-packed two-dimensional array at a hexane-water interface and subsequent transferring of such structure onto a solid substrate is described. By repeating the transfer process, multilayered gold nanoparticle films are formed without need of linker molecules. Their surface enhanced Raman scattering (SERS) efficiencies are compared as a function of the number of layers. It is shown that both the number of layers and the particle size contribute to SERS phenomenon. Judging from the noticeable dependence of SERS efficiency on the nanometer scale architecture, the close-packed nanoparticle formation at an immiscible interface presents a facile route to the preparation of highly active and relatively clean SERS substrates by controlling both the particle size and the film thickness. Among the investigated samples, the gold nanoparticle film assembled with quintuple layers of 30 nm diameter particles showed the maximum SERS efficiency.     

Silver Nanostructures on Graphene Oxide as the Substrate for Surface-Enhanced Raman Scattering (SERS)

Nanosized surface-enhanced Raman scattering (SERS) substrates fabricated by the controlled growth of metal nanostructures on water-dispersed two-dimensional nanomaterials can open a new avenue for SERS analysis of liquid samples in biological fields. In this work, regular and uniform Ag nanostructures were grown on the surface of graphene oxide (GO) through a microwave-assisted hydrothermal method. Polyamidoamine (PAMAM) dendrimers were assembled on the surface of GO to form GO/PAMAM templates for growing Ag nanostructures, which are primarily comprised of Ag dimers and trimers. The prepared Ag/GO nanocomposites are highly dispersed and stable in aqueous solution and may be used as substrates for enhanced Raman detection of rhodamine 6?G (R6G) in aqueous solution. This special substrate provides high-performance SERS and suppresses R6G fluorescence in aqueous solution and is promising as a nanosized material for the enhanced Raman detection of liquid samples in biological diagnostics.     

Surface-enhanced raman scattering of p-nitrothiophenol molecular vibrations of its silver salt and the surface complex formed on silver islands and colloids

The interpretation of the surface-enhanced Raman scattering (SERS) spectra of p-nitrothiophenol (p-NTP) is reported. SERS spectra were obtained by vacuum evaporation and casting of p-NTP onto silver island films, and also from colloidal silver solutions. The vibrational spectra of the silver salt (p-NTP-silver) were obtained for a direct comparison with the SERS of p-NTP chemically adsorbed onto Ag. Chemisorption of p-NTP through S-Ag bonding is indirectly proven by the disappearance of the S-H stretching mode. The Raman scattering spectrum of the silver salt is in good agreement with the SERS spectra of the silver surface complex. The spectral interpretation was aided using density functional theory calculations of the molecular spectra of p-NTP and that of the Ag-p-NTP.     

Surface-enhanced Raman scattering characteristics of 4-nitrobenzenethiol adsorbed on palladium and silver thin films

Palladium is an important catalytic metal, and it is desirable to develop a surface-enhanced Raman scattering (SERS) technique to investigate the reagent and product species adsorbed on its surface. Unfortunately, Pt-group metals, e.g., Pt and Pd, have been commonly considered as non- or weak-SERS-active substrates. In this work, Ag and Pd thin films were deposited very efficiently and evenly onto the surface of glass substrates by using only corresponding metal nitrate salts (AgNO₃ and Pd(NO₃)₂) with butylamine in ethanolic solutions. In this process, pure ethanol was used for Ag deposition, while an ethanol–water (8:2) mixture was used for Pd deposition. The as-prepared Ag and Pd films exhibited SERS activity over a large area. The surface-induced photoconversion capabilities of these Ag and Pd films were then tested on 4-nitrobenzenethiol by means of SERS. It was found that at least under visible laser irradiation, the surface-catalyzed photoreaction occurs more readily on a Ag film than on a Pd film for the conversion of 4-nitrobenzenethiol to 4-aminobenzenethiol, even though Pd is known to be an important transition metal with high catalytic activity.     

Surface-enhanced Raman scattering and micro-Raman imaging of Langmuir-Blodgett films of rhodium phthalocyanine

Rhodium phthalocyanine (RhPc) was synthesized and ultra thin Langmuir-Blodgett (LB) films of RhPc were successfully fabricated. The LB film characterization was carried out using both UV-vis absorption spectra and Raman scattering. The Raman spectroscopy was carried out using 633 and 780 nm laser lines. LB films were deposited onto Ag nanoparticles to achieve the surface-enhanced pre-resonance Raman scattering (pre-SERRS) and surface-enhanced Raman scattering (SERS) for both laser lines, respectively, which allowed the characterization of the RhPc ultra thin films. The morphology of the LB RhPc neat film is extracted from micro-Raman imaging.     

Designed fabrication of ordered porous au/ag nanostructured films for surface-enhanced Raman scattering substrates

This article reports the designed preparation of two different kinds of novel porous metal nanostructured films, namely, an ordered macroporous Au/Ag nanostructured film and an ordered hollow Au/Ag nanostructured film. Different from previous reports, the presently proposed method can be conveniently used to control film structures by simply varying the experimental conditions. The morphology of these films has been characterized by scanning electron microscopy (SEM), and their performance as surface-enhanced Raman scattering (SERS) substrates has been evaluated by using rhodamine 6G (R6G) as a probe molecule. We show that such porous nanostructured films consisting of larger interconnected aggregates are highly desirable as SERS substrates in terms of high Raman intensity enhancement, excellent stability, and reproducibility. The interconnected nanostructured aggregate, long-range ordering porosity, and nanoscale roughness are important factors responsible for this large SERS enhancement ability.