Ni Weihai, Kou Xiaoshan, Yang Zhi, Wang Jianfang
Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, P. R. China.
ACS Nano. 2008 Apr;2(4):677-86. doi: 10.1021/nn7003603.
Tailoring the longitudinal surface plasmon wavelengths (LSPWs), scattering, and absorption cross sections of gold nanorods has been demonstrated by combining anisotropic shortening and transverse overgrowth and judiciously choosing starting Au nanorods. Shortening yields Au nanorods with decreasing lengths but a fixed diameter, while overgrowth produces nanorods with increasing diameters but a nearly unchanged length. Two series of Au nanorods with LSPWs varying in the same spectral range but distinct extinction coefficients are thus obtained. The systematic changes in the LSPW and extinction for the two series of Au nanorods are found to be in good agreement with those obtained from Gans theory. Dark-field imaging performed on two representative nanorod samples with similar LSPWs shows that the scattering intensities of the overgrown nanorods are much larger than those of the shortened nanorods. The experimental results are found to be in very good agreement with those obtained from finite-difference time-domain (FDTD) calculations. FDTD calculations further reveal that the scattering-to-extinction ratio increases linearly as a function of the diameter for Au nanorods with a fixed aspect ratio.
通过结合各向异性缩短和横向过度生长，并明智地选择起始金纳米棒，已证明可定制金纳米棒的纵向表面等离子体波长（LSPW）、散射和吸收截面。缩短会产生长度减小但直径固定的金纳米棒，而过度生长则产生直径增加但长度几乎不变的纳米棒。由此获得了两个系列的金纳米棒，其LSPW在相同光谱范围内变化，但消光系数不同。发现这两个系列金纳米棒的LSPW和消光的系统变化与从甘斯理论获得的结果非常吻合。对具有相似LSPW的两个代表性纳米棒样品进行的暗场成像表明，过度生长的纳米棒的散射强度远大于缩短的纳米棒的散射强度。发现实验结果与从时域有限差分（FDTD）计算获得的结果非常吻合。FDTD计算进一步表明，对于具有固定纵横比的金纳米棒，散射与消光比随直径呈线性增加。
