Khlebtsov Boris N, Khanadeev Vitaly A, Khlebtsov Nikolai G
Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences, 13 Prospekt Entuziastov, Saratov 410049, Russia.
Phys Chem Chem Phys. 2014 Mar 28;16(12):5710-22. doi: 10.1039/c3cp55414g. Epub 2014 Feb 13.
The experimental depolarized light scattering ratio IVH/IVV of plasmonic nanorods is strongly decreased by a co-polarized contribution from impurity particles inevitably presented in suspensions fabricated by common seed-mediated methods with a single surfactant [typically, hexadecyltrimethylammonium bromide (CTAB)]. We used a binary NaOL (sodium oleate) + CTAB surfactant method (Ye et al., Nano Lett., 2013, 13, 555) to dramatically decrease the percentage of impurity particles in suspensions of as-prepared and overgrown nanorods without any separation procedures. The as-prepared nanorods demonstrated a very high ratio of longitudinal to transversal plasmonic maxima (of about 7) and an unprecedented, extra-high depolarized light scattering ratio IVH/IVV (of about 60%). To the best of our knowledge, this is the first experimental demonstration of the depolarized light scattering ratio approaching the theoretical limit of 75%. The NaOL + CTAB growing solution was also used to increase the nanorod diameters and lengths by a controllable overgrowing process. Statistical TEM data for as-prepared and overgrown nanorods were used to solve a direct problem, i.e. for T-matrix simulation of the extinction and depolarized light scattering spectra. To solve an inverse problem, with the extinction peak wavelength and full width at half-maximum (FWHM) as the input parameters, we obtained calibration plots to quantify the aspect ratio distribution in terms of a simple two-parametric log-normal model. Simultaneous fitting of the T-matrix calculations of extinction and depolarized light scattering spectra to the experimental data enabled us to retrieve the aspect ratio distribution and the percentage of impurity particles, in excellent agreement with statistical estimations based on transmission electron microscopy images.
在采用单一表面活性剂（通常为十六烷基三甲基溴化铵，CTAB）的常见种子介导法制备的悬浮液中，不可避免地存在杂质颗粒，其共偏振贡献会使等离子体纳米棒的实验去偏振光散射比IVH/IVV大幅降低。我们采用二元油酸钠（NaOL）+CTAB表面活性剂法（Ye等人，《纳米快报》，2013年，第13卷，第555页），无需任何分离步骤，就能显著降低制备好的纳米棒和生长后的纳米棒悬浮液中杂质颗粒的百分比。制备好的纳米棒展现出极高的纵向与横向等离子体最大值之比（约为7）以及前所未有的超高去偏振光散射比IVH/IVV（约为60%）。据我们所知，这是去偏振光散射比首次实验证明接近75%的理论极限。NaOL+CTAB生长溶液还用于通过可控的过度生长过程增加纳米棒的直径和长度。利用制备好的纳米棒和生长后的纳米棒的统计透射电子显微镜（TEM）数据来解决一个直接问题，即对消光和去偏振光散射光谱进行T矩阵模拟。为了解决一个反问题，以消光峰值波长和半高宽（FWHM）作为输入参数，我们获得了校准图，以便根据一个简单的双参数对数正态模型来量化纵横比分布。将消光和去偏振光散射光谱的T矩阵计算结果与实验数据同时拟合，使我们能够获取纵横比分布和杂质颗粒的百分比，这与基于透射电子显微镜图像的统计估计结果非常吻合。
