金核壳纳米粒子的控制合成及其生物复合(英文)

合成了一系列Au/SiO2核壳纳米粒子,并详细研究了Au纳米壳层的生长过程。发现在金纳米壳层形成的过程中存在着2个竞争反应。利用这一发现,可将金纳米壳层的吸收峰从524nm连续调谐至980nm处。恩度是一种临床抗癌药物,我们首次将其生物复合于吸收峰位于808nm的Au/SiO2壳层表面,得到Au/SiO2-Endo,通过FTIR测试证明该生物复合成功。将恩度特殊的饿杀肿瘤特性以及对肿瘤具有特异识别能力,与Au/SiO2纳米壳层结构的光学可调谐特性以及良好的光热转换能力复合于一体,我们期望得到一种治疗肿瘤效果更强的新型药物。     

Heteroepitaxial growth of high-index-faceted palladium nanoshells and their catalytic performance

The development of high-performance nanocatalysts relies essentially on the generation of stable and active surface sites at the atomic scale through synthetic control of the size, shape, and chemical composition of nanoscale metals and metal oxides. One promising route is to induce the exposure of catalytically active high-index facets of nanostructures through shape-controlled syntheses. We have designed and prepared two types of Pd nanoshells that are enclosed by high-index {730} and {221} facets through heteroepitaxial growth on high-index-faceted Au nanocrystals. The turnover numbers per surface atom of the high-index-faceted Pd nanoshells have been found to be 3-7 times those of Pd and Au-Pd core-shell nanocubes that possess only {100} facets in catalyzing the Suzuki coupling reaction. These results open up a potential for the development of inexpensive and highly active metal nanocatalysts.     

Silica-metal core-shell nanostructures

Silica-metal nanostructures consisting of silica cores and metal nanoshells attract a lot of attention because of their unique properties and potential applications ranging from catalysis and biosensing to optical devices and medicine. The important feature of these nanostructures is the possibility of controlling their properties by the variation of their geometry, shell morphology and shell material. This review is devoted to silica-noble metal core-shell nanostructures; specifically, it outlines the main methods used for the preparation and surface modification of silica particles and presents the major strategies for the formation of metal nanoshells on the modified silica particles. A special emphasis is given to the St?ber method, which is relatively simple, effective and well verified for the synthesis of large and highly uniform silica particles (with diameters from 100 nm to a few microns). Next, the surface chemistry of these particles is discussed with a special focus on the attachment of specific organic groups such as aminopropyl or mercaptopropyl groups, which interact strongly with metal species. Finally, the synthesis, characterization and application of various silica-metal core-shell nanostructures are reviewed, especially in relation to the siliceous cores with gold or silver nanoshells. Nowadays, gold is most often used metal for the formation of nanoshells due to its beneficial properties for many applications. However, other metals such as silver, platinum, palladium, nickel and copper were also used for fabrication of core-shell nanostructures. Silica-metal nanostructures can be prepared using various methods, for instance, (i) growth of metal nanoshells on the siliceous cores with deposited metal nanoparticles, (ii) reduction of metal species accompanied by precipitation of metal nanoparticles on the modified silica cores, and (iii) formation of metal nanoshells under ultrasonic conditions. A special emphasis is given to the seed-mediated growth, where metal nanoshells are formed on the modified silica cores with deposited metal nanoparticles. This strategy assures a good control of the nanoshell thickness as well as its surface properties.     

Differential SERS activity of gold and silver nanostructures enabled by adsorbed poly(vinylpyrrolidone)

We report that poly(vinylpyrrolidone) (PVP), a common stabilizer of colloidal dispersions of noble metal nanostructures, has a dramatic effect on their surface-enhanced Raman scattering (SERS) activity and enables highly selective SERS detection of analytes of various type and charge. Nanostructures studied include PVP-stabilized Au-Ag nanoshells synthesized by galvanic exchange reaction of citrate-reduced Ag nanoparticles (NPs), as well as solid citrate-reduced Ag and Au NPs, both before and after stabilization with PVP. All nanostructures were characterized in terms of their size, surface plasmon resonance wavelength, surface charge, and chemical composition. While the SERS activities of the parent citrate-reduced Ag and Au NPs are similar for rhodamine 6G (R6G) and 1,2-bis(4-pyridyl)ethylene (BPE) at various pH values, PVP-stabilized nanostructures demonstrate large differences in SERS enhancement factors (EFs) between these analytes depending on their chemical nature and protonation state. At pH values higher than BPE's pK(a2) of 5.65, where the analyte is largely unprotonated, the PVP-coated Au-Ag nanoshells showed a high SERS EF of >10(8). In contrast, SERS EFs were 10(3)- to 10(5)-fold lower for the protonated form of BPE at lower pH values, or for the usually highly SERS-active cationic R6G. The differential SERS activity of PVP-stabilized nanostructures is a result of discriminatory binding of analytes within-adsorbed PVP monolayer and a subsequent increase of analyte concentration at the nanostructure surface. Our experimental and theoretical quantum chemical calculations show that BPE binding with PVP-stabilized Au-Ag nanoshells is stronger when the analyte is in its unprotonated form as compared to its cationic, protonated form at a lower pH.     

Core-shell Ag-Au nanoparticles from replacement reaction in organic medium

The replacement reaction between hydrophobized Ag nanoparticles and hydrophobized AuCl4- in toluene has been examined in detail. The conclusions obtained under our experimental conditions are different from those reported in the literature in three aspects: (1) a detectable contraction of the Ag nanoparticle sacrificial templates during the course of the reaction is shown; (2) the deposition of Au on the shrunken Ag templates inhibits further Ag oxidation, resulting in the formation of core-shell Ag-Au nanoparticles instead of Au nanoshells; and (3) the significant red-shift in the surface plasmon resonance (SPR) band is more of a consequence of shape and chemical composition changes rather than as an indication of Au nanoshell formation. Solvent and temperature are influential environmental factors that determine the structure and composition of nanoparticles formed by the replacement reaction.     

Evolution of ultrafine gold seed nanoparticles with temperature and time and synthesis of plasmonic nanoshells

Features of the evolution of ultrafine gold nanoparticles synthesized by the Duff method with temperature and time have been studied in relation to their use as seeds for the formation of plasmonic nanoshells. A quantitative relation has been revealed between the duration of preheating of such particles at a preset temperature and their size. The obtained relation indicates that Au nanoparticles grow mainly via the Ostwald ripening mechanism. Using anisotropic composite FeOOH/Ag particles as an example, it has been shown that the obtained information may be used to substantially decrease the duration of the synthesis of metal nanoshells on diverse cores.     

Synthesis of Fe3O4@phenol formaldehyde resin core-shell nanospheres loaded with Au nanoparticles as magnetic FRET nanoprobes for detection of thiols in living cells

A magnetic, sensitive, and selective fluorescence resonance energy transfer (FRET) probe for detection of thiols in living cells was designed and prepared. The FRET probe consists of an Fe(3)O(4) core, a green-luminescent phenol formaldehyde resin (PFR) shell, and Au nanoparticles (NPs) as FRET quenching agent on the surface of the PFR shell. The Fe(3)O(4) NPs were used as the core and coated with green-luminescent PFR nanoshells by a simple hydrothermal approach. Au NPs were then loaded onto the surface of the PFR shell by electric charge absorption between Fe(3)O(4)@PFR and Au NPs after modifying the Fe(3)O(4)@PFR nanocomposites with polymers to alter the charge of the PFR shell. Thus, a FRET probe can be designed on the basis of the quenching effect of Au NPs on the fluorescence of Fe(3)O(4)@PFR nanocomposites. This magnetic and sensitive FRET probe was used to detect three kinds of primary biological thiols (glutathione, homocysteine, and cysteine) in cells. Such a multifunctional fluorescent probe shows advantages of strong magnetism for sample separation, sensitive response for sample detection, and low toxicity without injury to cellular components.     

C60空心纳米壳的制备及研究

利用超声技术, 选择间二甲苯溶液和乙腈两种不互溶的溶剂, 首次成功地制备了C60的空心纳米壳. 选择扫描电镜(SEM), 透射电镜(TEM)等对所制得的C60的空心纳米壳的形貌及结构进行表征. C60空心纳米壳的外直径为300～400 nm, 内直径为200～300 nm, 壁厚约100 nm. X射线衍射光谱(XRD)、傅里叶红外光谱检测结果表明其为C60分子组成的单晶结构. 利用电泳方法制备了均匀的C60的空心纳米壳膜电极, 并利用电沉积方法在所制备的C60的空心纳米壳电极表面沉积了金(Au)纳米颗粒. 为进一步沉积其它金属, 研究其在生物传感器及燃料电池方面的应用提供了基础.     

一种简易合成具有近红外吸收的纳米金壳球体方法

对经典的合成方法进行了详细的系统性的研究,通过改变合成过程中各反应物的参数,简易地得到了稳定的具有近红外吸收的纳米金壳球体。利用紫外可见光谱、动态光散射仪和透射电镜研究了制备过程中的各个参数对纳米金壳球体光学性质的影响。实验结果显示胺化试剂的用量以及先导试剂的预处理等在制备过程中都是重要影响因素。由改进方法所制备的纳米金壳球体具有很窄的粒径分布,并能在没有外加表面活性剂的条件下稳定地单分散于水溶液中。这些方法的改进提供了一种简易制备具有近红外吸收的纳米金壳球体的方法,从而有利于拓展此类纳米粒子在生物医学领域中的应用研究     

Spiky gold nanoshells

We report a high-yield synthetic method for a new type of metal nanostructure, spiky gold nanoshells, which combine the morphological characteristics of hollow metal nanoshells and nanorods. Our method utilizes block copolymer assemblies and polymer beads as templates for the growth of spiky nanoshells. Various shapes of spiky metal nanoshells were prepared in addition to spherical nanoshells by using block copolymer assemblies such as rod-like micelles, vesicles, and bilayers as templates. Furthermore, spiky gold shells encapsulating magnetic nanoparticles or quantum dots were prepared based on the ability of block copolymers to self-assemble with various types of nanoparticles and molecules. The capability to encapsulate other materials in the core, the shape tunability, and the highly structured surface of spiky nanoshells should benefit a range of imaging, sensing, and medical applications of metal nanostructures.     

Light-induced release of DNA from gold nanoparticles: nanoshells and nanorods

Plasmon-resonant nanoparticle complexes show highly promising potential for light-triggered, remote-controlled delivery of oligonucleotides on demand, for research and therapeutic purposes. Here we investigate the light-triggered release of DNA from two types of nanoparticle substrates: Au nanoshells and Au nanorods. Both light-triggered and thermally induced release are distinctly observable from nanoshell-based complexes, with light-triggered release occurring at an ambient solution temperature well below the DNA melting temperature. Surprisingly, no analogous measurable release was observable from nanorod-based complexes below the DNA melting temperature. These results suggest that a nonthermal mechanism may play a role in plasmon resonant, light-triggered DNA release.     

有序Au/Ag纳米碗阵列的简易制备及其表面增强拉曼散射性能

通过湿法化学合成基于SiO₂胶体晶体的大面积有序Au/Ag纳米碗(Au/AgNB)阵列。首先,在玻璃基板上以3D SiO₂胶体晶体作为模板。然后,在Au纳米颗粒(AuNP)种子的帮助下,通过原位生长方法在模板上沉积一层Au纳米壳(AuNS)。再通过HCHO还原Ag⁺使AuNS表面进一步沉积Ag纳米壳,形成Ag/Au双纳米壳(Ag/AuNS)阵列。通过丙烯酸酯改性双向取向聚丙烯(BOPP)方便地获得了单层有序反转Ag/AuNB阵列。这种有序Au/AgNB阵列具有更佳的表面增强拉曼散射(SERS)活性,其SERS分析增强因子(AEF)可达2.23×10⁷。     

Facile Synthesis of AuPd Nanochain Networks on Carbon Supports and Their Application as Electrocatalysts for Oxygen Reduction Reaction

The present work reports the facile synthesis and characterization of carbon‐supported porous Pd shell coated Au nanochain networks (AuPdNNs/C). By using Co nanoframes as sacrificial templates, AuPdNNs/C series have been prepared by a two‐step galvanic replacement reaction (GRR) technique. In the first step, the Au metal precursor, HAuCl₄, reacts spontaneously with the formed Co nanoframes through the GRR, resulting in Au nanochain networks (AuNNs). The second GRR is performed with various concentrations of Pd precursor (0.1, 1, and 10 mM PdCl₂), resulting in AuPdNNs/C. The synthesized AuPdNNs/C series are investigated as electrocatalysts for oxygen reduction reaction (ORR) in alkaline solution. The physical properties of the AuPdNNs/C catalysts are characterized by scanning electron microscopy (SEM), high‐resolution transmission electron microscopy (HRTEM), UV‐vis absorption spectroscopy, and cyclic voltammetry (CV). Rotating disk electrode (RDE) voltammetric studies show that the Au_0.8Pd_0.2NNs/C (prepared using 1 mM PdCl₂) has the highest ORR activity among all the AuPdNNs/C series, which is comparable to commercial Pt catalyst (E‐TEK). The ORR activity of AuPdNNs/C is presumably due to the enhanced Pd surface area and high porosity of Pd nanoshells.     

Nanoshell magnetic resonance imaging contrast agents

Nanocontrast agents have great potential in magnetic resonance (MR) molecular imaging applications for clinical diagnosis. We synthesized Au(3)Cu(1) (gold and copper) nanoshells that showed a promising MR contrast effect. For in vitro MR images, the large proton r1 relaxivities brightened T(1)-weighted images. As for the proton-dephasing effect in T(2), Au(3)Cu(1) lightened MR images at the low concentration of 0.125 mg mL(-1) (3.84 x 10(-7) mM), and then the signal continuously decreased as the concentration increased. For in vivo MR imaging, Au(3)Cu(1) nanocontrast agents enhanced the contrast of blood vessels and suggested their potential use in MR angiography as blood-pool agents. We propose that (1) the cooperativity originating from the form of the nanoparticles and (2) the large surface area coordinated to water from their porous hollow morphology are important for efficient relaxivity. In a cytotoxicity and animal survival assay, Au(3)Cu(1) nanocontrast agents showed a dose-dependent toxic effect: the viability rate of experimental mice reached 83% at a dose of 20 mg kg(-1) and as much as 100% at 2 mg kg(-1).     

有序Au/Ag纳米碗阵列的简易制备及其表面增强拉曼散射性能

通过湿法化学合成基于SiO₂胶体晶体的大面积有序Au/Ag纳米碗(Au/AgNB)阵列。首先,在玻璃基板上组装3D SiO₂胶体晶体作为模板。然后,以Au纳米颗粒(AuNP)为种子,通过原位生长法在SiO₂模板上沉积一层Au纳米壳(AuNS)。再通过HCHO还原Ag⁺成Ag⁰,进一步在AuNS表面沉积Ag纳米壳,形成Ag/Au双纳米壳(Ag/AuNS)阵列。最后通过丙烯酸酯改性双向取向聚丙烯(BOPP)膜方便地获得了单层有序反转Ag/AuNB阵列。这种有序Au/AgNB阵列具有更佳的表面增强拉曼散射(SERS)活性,其SERS分析增强因子(AEF)可达2.23×10⁷。     

金纳米壳球体的制备及其潜在的生物学应用

利用分子自组装和胶体还原化学制备出具有核-壳结构的金纳米壳球体Au@SiO₂; 通过透射电子显微镜(TEM)、X射线光电子能谱 (XPS)和紫外-可见分光光度计对Au@SiO₂的制备过程及其在全血中的光学特性进行了研究. 结果表明, 通过改变复合颗粒Au-APTES-SiO₂的浓度, 可以得到具有合理核-壳比例的Au@SiO₂, 其等离激元共振峰位于光谱的近红外区, 这使得具有红外消光特性的金纳米壳球体具有潜在的生物学应用价值.     

聚乙二醇功能化程度对纳米金壳夹心二氧化硅载药量及稳定性影响研究

本文系统研究了不同聚乙二醇(PEG)功能化程度对纳米金壳夹心二氧化硅(GSNs)载药量及稳定性的影响.透射电子显微镜(TEM)观察结果表明,GSNs表面经修饰分子量为5 KDa的α-甲氧基-ω-巯基聚乙二醇(mPEG-SH)分子后,PEG分子层平均厚度约为4 nm;随PEG化程度增加,GSNs聚集沉降速度改善,稳定性提高,久置后(35 d)稳定性良好;电感耦合等离子体发射光谱(ICP-OES)测试表明,当PEG与Au反应摩尔比为0.24时,PEG分子层在金壳表面接近饱和;不同PEG化程度对GSNs载药量基本无影响.本研究可为优化无机纳米材料表面PEG修饰过程,发展无机纳米载体材料体内应用提供理论依据.     

Observation of a Quadrupole Surface Plasmon Mode for Au Nanorods: Effects of Surface Roughness and Crystal Facets

This paper describes how the surface roughness and synthetic methods of Au nanorods affect the optical properties that are often associated with localized surface plasmon resonances. We synthesized Au nanorods with different aspect ratios and surface roughness by using two different synthetic strategies to observe surface plasmon resonance bands. One set of nanorods was prepared in high yield by using a seed‐mediated dropwise‐addition method with a growth‐directing surfactant in aqueous solution (Au nanorods in aqueous phase, GNRA). The other set of Au nanorods were synthesized by the electrochemical deposition of Au onto an anodized aluminum oxide (AAO) template (Au nanorods by AAO template, GNRT). The length of the nanorods was controlled by changing the total charge that was passed through the cell and their diameter was monitored by changing the diameter of the template channel. The as‐prepared Au nanorods were optimized to observe a quadrupole mode, which is one of the higher‐order surface plasmon bands. Our results showed differences between the optical properties of GNRA and GNRT. The roughness and crystal structure of the Au nanorods affected their optical properties. Smooth and single‐crystal surface on GNRA had larger and sharper peaks than GNRT. The discrete dipole approximation (DDA) method was used to calculate the optical properties of the Au nanorods and these results were in good agreement with our experimental results.     

Synthesis and optical properties of nanorattles and multiple-walled nanoshells/nanotubes made of metal alloys

The galvanic replacement reaction between silver and chloroauric acid has been exploited as a powerful means for preparing metal nanostructures with hollow interiors. Here, the utility of this approach is further extended to produce complex core/shell nanostructures made of metals by combining the replacement reaction with electroless deposition of silver. We have fabricated nanorattles consisting of Au/Ag alloy cores and Au/Ag alloy shells by starting with Au/Ag alloy colloids as the initial template. We have also prepared multiple-walled nanoshells/nanotubes (or nanoscale Matrioshka) with a variety of shapes, compositions, and structures by controlling the morphology of the template and the precursor salt used in each step of the replacement reaction. There are a number of interesting optical features associated with these new core/shell metal nanostructures. For example, nanorattles made of Au/Ag alloys displayed two well-separated extinction peaks, a feature similar to that of gold or silver nanorods. The peak at approximately 510 nm could be attributed to the Au/Ag alloy cores, while the other peak was associated with the Au/Ag alloy shells and could be continuously tuned in the spectral range from red to near-infrared.     

Plasmonic Nanorattles as Next‐Generation Catalysts for Surface Plasmon Resonance‐Mediated Oxidations Promoted by Activated Oxygen

Nanorattles, comprised of a nanosphere inside a nanoshell, were employed as the next generation of plasmonic catalysts for oxidations promoted by activated O₂. After investigating how the presence of a nanosphere inside a nanoshell affected the electric‐field enhancements in the nanorattle relative to a nanoshell and a nanosphere, the SPR‐mediated oxidation of p‐aminothiophenol (PATP) functionalized at their surface was investigated to benchmark how these different electric‐field intensities affected the performances of Au@AgAu nanorattles, AgAu nanoshells and Au nanoparticles having similar sizes. The high performance of the nanorattles enabled the visible‐light driven synthesis of azobenzene from aniline under ambient conditions. As the nanorattles allow the formation of electromagnetic hot spots without relying on the uncontrolled aggregation of nanostructures, it enables their application as catalysts in liquid phase under mild conditions using visible light as the main energy input.