Preparation of polymer-coated functionalized silver nanoparticles
Preparation of polymer-coated functionalized silver nanoparticles
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DOI：
10.1021/ja992088q
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发表时间：
1999-11-17
影响因子：
15
通讯作者：
Chumanov, G
中科院分区：
文献类型：
--
作者：
Quaroni, L;Chumanov, G
近年来，纳米级无机晶体粒子的研究和制备在基础研究和应用研究方面都引起了广泛的关注。1金属纳米颗粒，特别是银、金和铜，由于其独特的光学性质而成为人们极大兴趣的焦点，这些光学性质由称为等离子体激元的电子密度的集体振荡决定。2.金属纳米颗粒对光的吸收和散射效率可以超过任何分子发色团。3这种与光相互作用的高效率，以及对光降解的极端抵抗力，正在刺激纳米颗粒在光化学，分析过程以及作为电子和光子器件组件的新应用的发展。耐化学性和改性金属表面的能力是许多潜在应用的重要先决条件。例如，在Ag+的强配体（例如氯离子）存在下氧驱动的银蚀刻限制了颗粒在富氯生物环境中的使用。银纳米颗粒也可以在硫醇的存在下被蚀刻，特别是当暴露于可见光时。与此同时，功能化硫醇的吸附是一种有效的方法，金属表面的剪裁，最近证明了金纳米粒子。4未保护的银和金颗粒的水悬浮液也易发生不可逆的聚集。这种聚集通常通过聚合稳定剂在颗粒表面上的自发吸附来克服。6然而，该方法需要在悬浮液中存在大浓度的稳定剂，这可能干扰表面官能化;在较低浓度下，悬浮液的稳定性受到稳定剂从表面解吸的限制。乳液聚合以前已经应用于微米和亚微米尺度上的有机和无机颗粒的涂层7。该方法具有生产稳定且致密的聚合物层、完全包围颗粒并提高其耐化学性的潜力。在此，我们报道了通过乳液聚合将银纳米颗粒封装到聚合物壳中以产生化学稳定的系统。该涂层是通过苯乙烯和/或甲基丙烯酸在油酸乳液中的聚合而产生的。在该系统中，银颗粒被涂覆有均匀的、明确定义的层，并且处于非聚集的悬浮液中，与先前报道的银颗粒似乎被嵌入聚合物基质中的系统相反。该层的厚度可以通过改变单体的浓度来容易地控制。在浓氯化物溶液中测试涂覆的颗粒，并显示出对蚀刻的强抗性。这些也可以通过过滤和/或沉淀有效地纯化，并重新分散在不同的介质中用于进一步的化学改性。作为颗粒表面化学剪裁的一个例子，我们将牛血清白蛋白（BSA）连接到来自甲基丙烯酸单体的羧酸酯官能团上。未涂覆和涂覆有聚合物的100 nm银颗粒的TEM照片如图1所示。聚合物层的电子密度不足以通过TEM直接观察到，并且通过用磷钨酸负染色实现涂层的可视化。聚合物在深色银核和颗粒周围染色剂的灰色晕圈之间显示为白色层。不同厚度的层，范围从2纳米到约10纳米，生产和检查...
In recent years, the study and preparation of inorganic crystalline particles on the nanometer scale has attracted considerable attention from both fundamental and applied research. 1 Metal nanoparticles, particularly silver, gold, and copper, have been the focus of great interest because of their unique optical properties, determined by the collective oscillations of electron density termed plasmons. 2 The efficiency for the absorption and scattering of light by metal nanoparticles can surpass that of any molecular chromophores. 3 Such a high efficiency for interaction with light, together with an extreme resistance to photodegradation, is stimulating the development of new applications of nanoparticles in photochemistry, analytical procedures, and as components of electronic and photonic devices. Chemical resistance and the ability to modify the metal surface are important prerequisites for many potential applications. For example, oxygen-driven etching of silver in the presence of strong ligands for Ag+, such as chloride ions, constrains the use of the particles in chloriderich biological environments. Silver nanoparticles can also be etched in the presence of thiols, particularly when exposed to visible light. At the same time, the adsorption of functionalized thiols is an efficient method for the tailoring of metal surfaces, as was recently demonstrated for gold nanoparticles. 4 Aqueous suspensions of unprotected silver and gold particles are also susceptible to irreversible aggregation. 5 This aggregation is traditionally overcome through the spontaneous adsorption on the particle surface of polymeric stabilizers. 6 However, this method requires the presence in the suspension of a large concentration of stabilizers which can interfere with surface functionalization; at lower concentrations, the stability of the suspension is limited by desorption of the stabilizers from the surface. Emulsion polymerization has been previously applied to the coating of organic and inorganic particles7 on the micrometer and submicrometer scale. The method has the potential for producing a stable and compact polymer layer, completely enclosing the particle and improving its chemical resistance. Herein, we report the encapsulation of silver nanoparticles into a polymer shell via emulsion polymerization to produce a chemically stable system. The coating was produced by the polymerization of styrene and/or methacrylic acid in emulsions of oleic acid. In this system, silver particles are coated with a uniform, well-defined layer and are in a nonaggregated suspension, contrary to previously reported systems in which silver particles appeared to be imbedded into a polymer matrix. The thickness of the layer can be readily controlled by changing the concentration of monomers. The coated particles were tested in concentrated chloride solutions and exhibited a strong resistance toward etching. These can also be efficiently purified by filtration and/or precipitation, and redispersed in different media for further chemical modification. As an example of chemical tailoring of particle surface, we attached bovine serum albumin (BSA) to the carboxylate functionalities derived from methacrylic acid monomers. TEM pictures of 100 nm silver particles uncoated and coated with the polymer are shown in Figure 1. The polymer layer has insufficient electron density to be directly observed by TEM and visualization of the coating was achieved through negative staining with phosphotungstic acid. The polymer appears as a white layer between the dark silver core and the gray halo of the stain surrounding the particles. Layers of varying thickness, ranging from 2 nm to about 10 nm, were produced and examined by …