金纳米棒:合成、修饰、自组装、SERS及生物医学应用

纳米颗粒作为信号感应单元在化学与生物传感应用中已引起广泛关注,这些功能和金属纳米结构与光相互作用时产生的表面等离子体共振密切相关.表面增强拉曼散射(SERS),是指吸附在粗糙的金属纳米结构表面的被分析物,在光照射下其拉曼光谱获得显著增强的异常表面光学现象,近年来.SERS技术已广泛用于物质检测和生物传感等研究,在生物医学领域表现出巨大的应用潜力并取得了令人瞩目的研究成果.本文阐述了金纳米棒的制备方法、表面修饰和共轭生物分子的方法.并从金纳米棒表面增强拉曼散射的角度系统阐述基于金纳米棒表面增强拉曼散射的1D,2D,3D自组装,并介绍了近期金纳米棒表面增强拉曼散射在生物医学检测与成像中最具有代表性的应用研究.     

金纳米棒——从可控制备与修饰到纳米生物学与生物医学应用

金纳米棒因其独特的光学活性(纵向和横向两个等离子体共振吸收峰,可调范围从可见光区到近红外区)、长径比可调,表面易于修饰,生物相容性良好而使得其在纳米生物学和生物医学等领域具有广泛的应用前景。金纳米棒的合成及表面修饰直接决定着其物理化学性质,进而影响其生物相容性及其在生物医学中的应用。本文综述了金纳米棒的可控制备方法(包括模板法、电化学法、光化学法和晶种法)、表面可控修饰方法及其在纳米生物学和生物医学中的应用新进展,重点总结了金纳米棒的表面可控修饰及其在分子探针、生物传感、生物成像、药物载体、基因载体和光热疗法的最新研究进展。最后针对金纳米棒在生物应用过程中的一些瓶颈问题(如:特异性识别能力需要增强和荧光量子产率尚待提高等)提出了将手性分子或智能聚合物引入到金纳米棒表面进行可控修饰,以期增强其特异性识别能力并提高荧光量子产率,为金纳米棒的发展提供了新的思路。     

金纳米棒的表面改性及其在生物医学领域的应用

各向异性的金纳米棒由于具有独特的光学性质,在生物医学领域得到了日益广泛的应用。本文综述了金纳米棒的表面改性及其在生物标记与识别、生物成像、癌症诊断和光热治疗等领域中的应用。     

大长径比金纳米棒的合成及其单细胞毒性研究

利用三步晶种生长法合成长径比约为14的大长径比金纳米棒(GNR),利用巯基十一酸(MUDA)对金纳米棒表面进行了生物适应性修饰,并在宏观水平上研究了修饰前后的金纳米棒在对细胞活性的影响。利用单细胞方法分别考察了修饰后的纳米金棒对细胞贴壁过程、增殖速率、细胞内ROS以及骨架排布的影响。虽然MTT细胞活性结果显示内吞后的金纳米棒对细胞无毒,但单细胞毒性分析方法发现,不同浓度纳米金棒对早期贴壁过程有较小的影响,且内吞的纳米金棒在一定程度上促进了细胞的增殖,而高浓度下纳米金棒引起了细胞内ROS含量的升高,并破坏了细胞内骨架纤维排布。本研究建立了用单细胞行为分析纳米颗粒对细胞毒性的方法,证明了以往仅仅利用MTT等宏观手段分析纳米材料生物适应性是不足的。纳米材料在生物医学领域的进一步应用还应考虑单细胞及分子水平上的毒性效应。     

单金纳米棒的光散射分析化学:径向比与分析灵敏度的关系

单纳米颗粒作为信号感应单元在化学与生物传感应用中已引起广泛关注.本文通过暗场显微成像(iDFM)研究了不同径向比金纳米棒的光散射性质.将iDFM与扫描电子显微镜(SEM)结合表征种子生长法制备的金纳米棒,结果发现,因局域表面等离子体共振而展示出的红色散射光随单个金纳米棒的径向比增大逐渐红移,且金纳米棒对其周围介质折光率(RI)变化的敏感程度随径向比增大而增大.这一结果对设计高灵敏的生物纳米传感器、提高分析检测的灵敏度具有很好的指导意义.     

金纳米棒的光学性质研究进展

金纳米棒在紫外-可见-近红外(UV-Vis-NIR)波段具有独特的可调节表面等离子体共振(SPR)光学特性,其良好的稳定性、低生物毒性、亮丽的色彩和在催化、信息存储、生物医学等领域广阔的应用前景受到相关研究领域的广泛关注.结合已有的研究基础,本文主要综述了金纳米棒光学性质的研究进展,包括表面等离子体共振、局域场增强效应、共振耦合效应及荧光特性,并对金纳米棒的应用做了展望.     

一种制备高长径比金纳米棒的新方法

报道了一种制备高长径比金纳米棒的新方法. 在25 ℃条件下, 采用种子介导生长法, 通过优化表面活性剂十六烷基三甲基溴化铵(CTAB)的浓度, 制备了长度(200±18.62) nm, 长径比大于10的金纳米棒, 并讨论了金纳米棒的形成机制. 结果表明, 金纳米棒的长径比和纵向吸收波长与CTAB的浓度有关. 此外, 通过提高反应液的离子强度, 利用制备的金纳米棒与球形颗粒不同的静电作用将金纳米棒分离纯化. 运用透射电子显微镜(TEM)和扫描电子显微镜(SEM)对金纳米棒的表面形貌进行表征.     

阴离子表面活性剂作为添加剂种子生长法制备尺寸可调的单分散金纳米棒

以不同阴离子表面活性剂作为添加剂种子生长法制备金纳米棒,并考察阴离子表面活性剂种类对金纳米棒形貌及光学性质的影响。在十二烷基苯基磺酸钠(SDBS)存在下,金纳米棒的产率明显高于使用十二烷基磺酸钠的反应体系。对添加SDBS的种子生长法制备金纳米棒的反应条件进行优化,得到十六烷基三甲基溴化铵、SDBS、抗坏血酸和硝酸银的最佳浓度分别为0.04 mol.L-1、2.4 mmol.L-1、1.2 mmol.L-1和0.08 mmol.L-1。在此条件下,金纳米棒的生长在30 min内完成,所制备的金纳米棒表面等离子共振吸收峰位于823 nm,其横纵比为(5±0.03)。当改变生长液中硝酸银浓度时,金纳米棒的尺寸也随之发生改变。此外,我们还探讨了SDBS的作用机理。相对于经典种子生长法,新方法制备纳米金棒在尺寸可调性、单分散性和生物毒性方面明显改善,可广泛应用于各种光学及生物分析。     

局域表面等离子体共振辅助的金纳米棒/聚合物纳米复合材料的双光子聚合

本文研究了金纳米棒的局域表面等离子体共振效应在双光子聚合过程中的作用,即当激发光与金纳米棒表面等离子体共振波长相匹配时,会在金纳米棒表面产生很强的局域电磁场,从而引发双光子聚合。通过采用与金纳米棒表面等离子体共振波长相同的飞秒激光,在低于光刻胶聚合阈值的功率下照射含有金纳米棒的光刻胶,制备聚合物包覆金纳米棒的纳米复合材料。透射电子显微镜结果表明,当飞秒激光功率为0.6 W、光斑直径为1.6 cm、照射时间为0.3 s时,金纳米棒表面成功聚合上厚度为5 nm左右的聚合物。本研究在制备聚合物/金属纳米粒子方面提供了一种简单可行的方法,有望在纳米光子学、纳米传感器等新兴领域得到应用。     

金纳米棒的偏光特性及其作为方向探针在单分子水平成像上的应用

随着生物医学的发展,对生物成像技术和成像分辨率的要求越来越高,纳米材料和技术被越来越多地应用到生物医学领域.各向异性的金纳米棒由于具有较高的电子密度、较大的吸收截面、特殊的表面等离子共振光学特性、优良的生物相容性和化学稳定性而被广泛应用于生物成像领域.复杂的活细胞组织内纳米级目标的位置和动态的空间构型对于我们理解很多生物物理学过程的细节问题至关重要.本文结合本课题组在该领域的研究经验,并从金纳米棒局部等离子共振特性和偏光特性出发,综述了金纳米棒作为方向探针的3D跟踪定位成像技术与手段.包括暗场成像技术、微分干涉成像、光热成像、共聚焦显微镜成像等生物成像技术和脱焦成像、全内反成像和双通道等生物成像手段.同时阐述了金纳米棒作为方向探针在生物成像领域中的应用进展.     

基于金纳米棒的核壳纳米结构及其光学性质研究

以金纳米棒为核的核壳结构纳米粒子由于它独特的光学性质、结构特点以及在催化、表面增强拉曼散射方面的应用前景,成为目前纳米材料研究的热点之一。本文重点介绍以金纳米棒为核,包覆其他无机材料的核/壳结构之合成方法,同时阐述其结构特征、光学性质以及外界条件对结构和性质的影响。其中,由于金银纳米核壳结构的研究开始最早,研究最为深入,故对其进行重点阐述。最后对以金纳米棒为核的核壳结构未来研究进行了展望。     

Robust multilayer thin films containing cationic thiol-functionalized gold nanorods for tunable plasmonic properties

Gold nanorods have great potential in a variety of applications because of their unique physical properties. In this article, we present the layer-by-layer (LbL) assembly of thin films containing positively charged gold nanorods that are covalently functionalized by cationic thiol molecules. The cationic gold nanorods are uniformly distributed in ultrathin nanocomposite LbL thin films. We studied the collective surface plasmon resonance coupling in the LbL films via UV-visible spectroscopy and evaluated their application in the surface-enhanced Raman scattering detection of rhodamine 6G probe molecules. Furthermore, we successfully manufactured freestanding nanoscale thin films containing multilayers of gold nanorods with a total thickness of less than 50 nm. The surface morphology and their optical and mechanical properties were systematically investigated, and the polycationic gold nanorods were found to play an important role in manipulating the properties of the nanocomposite thin films. Our findings reveal that such nanorods are excellent building blocks for constructing functional LbL films with tunable plasmonic behavior and robust mechanical properties.     

Nanoplasmonic Nanorods/Nanowires from Single to Assembly: Syntheses,Physical Mechanisms and Applications

Gold nanorods are anisotropic and exhibit different optical characteristics in both transverse and longitudinal directions, so the plasmon resonance in the near‐infrared region will reflect two absorption peaks. Because of strong enhancements of electromagnetic fields of gold nanorods, gold nanorods are widely used in medical treatment, biological detection, sensors, solar cells and other fields. Since rapid developments of gold nanorods, it is necessary to sort out the recent achievements. In this review, we select three classifications of single nanorods/nanowires, dimers and assembled nanorods to introduce their syntheses methods, optical properties and applications respectively. We firstly overview the history of nanorods/nanowires syntheses and summarize the improvement of the commonly utilized seed‐mediated growth synthesis method; and then, physically, nano‐plasmonic and optical properties of single and assembled nanorod/nanowires are concluded in detail. Lastly, we mainly summarize the recent advances in applications and provide perspective in different fields.     

High-sensitivity biosensors fabricated by tailoring the localized surface plasmon resonance property of core-shell gold nanorods

An enhanced sensitive biosensor has been developed to detect biological targets by tailoring the localized surface plasmon resonance property of core–shell gold nanorods. In this new concept, a shell layer is produced on gold nanorods by generating a layer of chalcogenide on the gold nanorod surface after attachment of the recognition reagent, namely, goat IgG and antigen of schistosomiasis japonica. The bioactivity of these attached biomolecules is retained and the sensitivity of this biosensor is thus enhanced significantly. The plasmonic properties of the gold nanorods attached with the biomolecules can be adjusted and the plasmon resonance wavelength can be red-shifted up to several hundred nanometers in the visible or near infrared (NIR) region, which is extremely important to biosensing applications. This leads to a lager red-shift in the localized surface plasmon resonance absorption compared to the original gold nanorod-based sensor and hence offers greatly enhanced sensitivity in the detection of schistosomiasis japonica. The human serum infected with schistosomiasis japonica diluted to 1:50,000 (volume ratio, serum/buffer solution) can be detected readily. The technique offers enhanced sensitivity and can be easily extended to other sensing applications based on not only immuno-recognition but also other types of specific reactions.     

Preparation and optical properties of worm-like gold nanorods

A type of worm-like nanorods was successfully synthesized through conventional gold nanorods reacting with Na2S2O3 or Na2S. The generated worm-like gold nanorods comprise shrunk nanorod cores and enwrapped shells. Therefore, a gold-gold sulfide core-shell structure is formed in the process, distinguishing from their original counterparts. The formation of the gold chalcogenide layers was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy. Experimental results showed that the thickness of the gold chalcogenide layers is controllable. Since the increase of shell thickness and decrease of gold nanorod core take place simultaneously, it allows one to tune the plasmon resonance of nanorods. Proper adjustment of reaction time, temperature, additives and other experimental conditions will produce worm-like gold nanorods demonstrating desired longitudinal plasmon wavelength (LPW) with narrow size distributions, only limited by properties of starting original gold nanorods. The approach presented herein is capable of selectively changing LPW of the gold nanorods. Additionally, the formed worm-like nanorods possess higher sensitive property in localized surface plasmon resonance than the original nanorods. Their special properties were characterized by spectroscopic methods such as Vis-NIR, fluorescence and resonance light scattering. These features imply that the gold nanorods have potential applications in biomolecular recognition study and biosensor fabrications.     

Plasmonic gold-superparamagnetic hematite heterostructures

Bifunctional heterostructures composed of gold nanorods and hematite nanoparticle aggregates are prepared facilely through the hydrothermal decomposition of ferric acetylacetonate on the surface of the nanorods. The gold nanorod in the heterostructure is partially coated with the hematite nanoparticle aggregates. The hematite coating is porous. These heterostructures exhibit both plasmonic and superparamagnetic properties. They are well-dispersed in aqueous solutions. Such heterostructures will be potentially useful for many biotechnological applications.     

Recent advances in analytical and bioanalysis applications of noble metal nanorods

In the last decade the use of anisotropic nanoparticles in analytical and bioanalytical applications has increased substantially. In particular, noble metal nanorods have unique optical properties that have attracted the interest of many research groups. The localized surface plasmon resonance (LSPR) generated by interaction of light at a specific wavelength with noble metal nanoparticles was found to depend on particle size and shape and on the constituting material and the surrounding dielectric solution. Because of their anisotropic shape, nanorods are characterized by two LSPR peaks: the transverse, fixed at approximately 530 nm, and the longitudinal, which is in the visible–near infra-red region of the spectrum and varies with nanorod aspect ratio. The intense surface plasmon band enables nanorods to absorb and scatter light in the visible and near infra-red regions, and fluorescence and two-photon induced luminescence are also observed. These optical properties, with the reactivity towards binding events that induce changes in the refractive index of the surrounding solution, make nanorods a useful tool for tracking binding events in different applications, for example assembly, biosensing, in-vivo targeting and imaging, and single-molecule detection by surface-enhanced Raman spectroscopy. This review presents the promising strategies proposed for functionalizing gold nanorods and their successful use in a variety of analytical and biomedical applications.     

Advances and Prospects of Gold Nanorods

With the development of nanotechnology, many novel nanomaterials with unique properties such as magnetic, electronics, and photonics are increasingly being exploited. Gold nanorods, which are rod‐shaped nanomaterials, show powerful potential in biological/biomedical fields, especially photothermal therapy, biosensing, imaging, and gene delivery for the treatment of cancer. Many scientific groups have shown strong interests in gold nanorods and have attempted to push them towards possible clinical applications. However, owing to the quantum‐size effects of nanomaterials, people have also raised some concerns about the potential toxicity hazards. Therefore, it is becoming urgent to study and exploit the biological effects of gold nanorods for benefit in the near future.     

Plasmonic response of ordered arrays of gold nanorods immersed within a nematic liquid crystal

We study theoretically the optical properties of a two-dimensional lattice of metallic (gold) nanorods immersed within a nematic liquid crystal (NLC) strongly anchored to the surface of the nanorods. The distribution of the director field of the NLC is found by minimising the corresponding total free energy via simulated annealing. Optical properties such as transmittance, reflectance and absorbance of the structure are found by employing a hybrid discrete-dipole approximation/layer-multiple-scattering technique. We show, in particular, that when the NLC is strongly anchored to the nanorods, light absorbance is more efficient compared to the case where the liquid crystal (LC) is aligned by application of an external field. Also, the alignment of the LC molecules via an external field leads to a significant shift of the surface-plasmon resonance of the gold nanorods relative to the strong-anchoring case, an effect which can be exploited in switching applications. We also report that the rate of light absorption is a non-monotonic function of the height of nanorods due to the guiding of EM waves taking place for long enough nanorods.