Synthesis and Optical Properties of Small Au Nanorods Using a Seedless Growth Technique
Synthesis and Optical Properties of Small Au Nanorods Using a Seedless Growth Technique
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DOI：
10.1021/la301387p
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发表时间：
2012-06-26
期刊：
影响因子：
3.9
通讯作者：
El-Sayed, Mostafa A.
中科院分区：
文献类型：
--
作者：
Ali, Moustafa R. K.;Snyder, Brian;El-Sayed, Mostafa A.
金纳米粒子在光热治癌和光电子技术中显示出潜力。在这两种应用中，需要小尺寸的纳米棒。在目前的工作中，一锅无籽合成技术已被开发用于制备相对较小的单分散金纳米棒，其平均尺寸（长x宽）为18 x 4.5 nm、25 x 5 nm、15 x 4.5 nm和10 x 2.5 nm。在这种方法中，pH值被发现在纳米棒的单分散性中起着至关重要的作用，当生长溶液的NaBH 4浓度被调节以控制金离子的还原速率时。在优化的pH值和NaBH4浓度下，通过调节生长溶液中CTAB的浓度，可以得到较小的金纳米棒。此外，发现生长溶液中银离子的浓度在控制纳米棒的纵横比方面是关键的。使用吸收光谱、尺寸分布和原子光谱分析数据来估计具有三种不同纵横比的小金纳米棒的消光系数值。先前接受的消光系数或纵向带波长值和纳米棒的长径比之间的关系发现的大纳米棒不延伸到小尺寸域中报告的本工作。在更大的尺寸上扩展这些关系的失败是光与大棒的相互作用的结果，大棒给出主要由散射过程引起的消光带，而小纳米棒的消光由吸收过程引起。
Gold nanoparticles have shown potential in photothermal cancer therapy and optoelectronic technology. In both applications, a call for small size nanorods is warranted. In the present work, a one-pot seedless synthetic technique has been developed to prepare relatively small monodisperse gold nanorods with average dimensions (length x width) of 18 x 4.5 nm, 25 x 5 nm, 15 x 4.5 nm, and 10 x 2.5 nm. In this method, the pH was found to play a crucial role in the monodispersity of the nanorods when the NaBH4 concentration of the growth solution was adjusted to control the reduction rate of the gold ions. At the optimized pH and NaBH4 concentrations, smaller gold nanorods were produced by adjusting the CTAB concentration in the growth solution. In addition, the concentration of silver ions in the growth solution was found to be pivotal in controlling the aspect ratio of the nanorods. The extinction coefficient values for the small gold nanorods synthesized with three different aspect ratios were estimated using the absorption spectra, size distributions, and the atomic spectroscopic analysis data. The previously accepted relationships between the extinction coefficient or the longitudinal band wavelength values and the nanorods' aspect ratios found for the large nanorods do not extend to the small size domain reported in the present work. The failure of extending these relationships over larger sizes is a result of the interaction of light with the large rods giving an extinction band which results mostly from scattering processes while the extinction of the small nanorods results from absorption processes.