Kim Kwan, Lee Hyang Bong, Lee Ji Won, Park Hyoung Kun, Shin Kuan Soo
Department of Chemistry, Seoul National University, Seoul 151-742, Korea.
Langmuir. 2008 Jul 15;24(14):7178-83. doi: 10.1021/la800733x. Epub 2008 Jun 20.
Branched poly(ethylenimine) (PEI)-capped Au nanoparticles are prepared at room temperature using PEI as the reductant of hydrogen tetrachloroaurate (HAuCl4). The size of Au nanoparticles, ranging from 10 to 70 nm, is readily controlled by varying the relative amount of PEI used initially versus HAuCl4. The PEI-capped Au nanoparticles are further demonstrated to be assembled into a large area of 2-D aggregates at a toluene-water interface either by heating the mixture or by adding benzenethiol to the toluene phase at room temperature. Both films are quite homogeneous, but Au nanoparticles appear to be more closely packed in the film assembled via the mediation of benzenethiol. The optical property of the PEI-capped Au films is controlled by the amount of benzenethiol added to the toluene phase. The obtained large area of PEI-capped Au film exhibits strong SERS activity of benzenethiol and also exhibits a very intense SERS spectrum of 4-nitrobenzenethiol via a place-exchange reaction that takes place between benzenethiol and 4-nitrobenzenethiol. Because the proposed method is cost-effective and is suitable for the mass production of diverse Au films irrespective of the shapes of the underlying substrates, it is expected to play a significant role in the development of optical nanotechnology especially for surface plasmon-based analytical devices.
以聚乙烯亚胺（PEI）为四氯金酸（HAuCl4）的还原剂，在室温下制备了PEI包覆的金纳米粒子。通过改变最初使用的PEI与HAuCl4的相对量，可以很容易地控制金纳米粒子的尺寸，其范围为10至70纳米。通过加热混合物或在室温下向甲苯相中添加苯硫醇，进一步证明PEI包覆的金纳米粒子在甲苯-水界面处组装成大面积的二维聚集体。两种薄膜都相当均匀，但在通过苯硫醇介导组装的薄膜中，金纳米粒子似乎堆积得更紧密。PEI包覆的金薄膜的光学性质由添加到甲苯相中的苯硫醇的量控制。所获得的大面积PEI包覆的金薄膜表现出苯硫醇的强表面增强拉曼散射（SERS）活性，并且通过苯硫醇与4-硝基苯硫醇之间发生的置换反应，还表现出4-硝基苯硫醇的非常强烈的SERS光谱。由于所提出的方法具有成本效益，并且适用于大规模生产各种形状的金薄膜，而与底层基板的形状无关，因此预计它将在光学纳米技术的发展中发挥重要作用，特别是对于基于表面等离子体的分析装置。
