1282 Acta Phvs. -Chim. Sin. 2012 VoL 28 bsorption profile bsorption profile absorption profile (b) 32 (d)a absorption profile absorption profile×101 2.5 -3.0 x/nm x/nm 7 FDTD模拟Au纳米棒单体和二聚体按照不同耦合方式的场增强分布 Fig 7 Simulated electric field enhancement using fdtD for a single Au nanorod and dimers Au nanorods dimer aligned end to end with spacing of 0. I nm(a), I nm(b), and 5 nm(c), Au nanorod monomer with aspect ratio of 3(d)and 6(e), Au nanorods dimer aligned side-by-side with spacing of I nm(f) 3.5 1.5 649nm 13 10 716nm 74 nm 60070080 monomer dimer monomer 图8(A)Au纳米棒二聚体不同耦合光散射谱;(B)不同构型二聚体耦合示意图;(O用DDA方法得到的耦合金 纳米棒二聚体表面电荷密度 Fig 8 (A)Scattering spectra of various Au nanorod dimers; (B)plasmon hybridization schemes for dimers in different geometric arrangements;(C)surface charge density of coupling gold nanorods dimer calculated using discrete dipole approximation (DDA) nset in Fig. (A): electron micrographs of the same dimers showing the different configurations, scale bar =100 nm; (B)red x means impossible configurations; (C)interparticle separations are all 1.5 nm 尺的数量级,只具有相对意义.一般,文献中采用1-4nm的要大一个数量级,说明间距非常小时,其 FDID方法模拟时,场增强没有数量级,只有颜色标耦合非常大相比于单棒的増强效应,双棒端-端间 尺)从图π(ab)中可以看出∷:端-端相对的双棒间距距为0.lnm时电场要增大4个数量级,即双棒端-端 为0.Inm时,两棒耦合的电场増强效应比间距为间距为0.nm时,拉曼散射增强因子增大8个数量Acta Phys. ⁃Chim. Sin. 2012 Vol.28 尺的数量级, 只具有相对意义. 一般, 文献中采用 FDTD方法模拟时, 场增强没有数量级, 只有颜色标 尺). 从图7(a, b)中可以看出: 端-端相对的双棒间距 为 0.1 nm 时, 两棒耦合的电场增强效应比间距为 1-4 nm的要大一个数量级, 说明间距非常小时, 其 耦合非常大. 相比于单棒的增强效应, 双棒端-端间 距为0.1 nm时电场要增大4个数量级, 即双棒端-端 间距为0.1 nm时, 拉曼散射增强因子增大8个数量 图7 FDTD模拟Au纳米棒单体和二聚体按照不同耦合方式的场增强分布图 Fig.7 Simulated electric field enhancement using FDTD for a single Au nanorod and dimers Au nanorods dimer aligned end to end with spacing of 0.1 nm (a), 1 nm (b), and 5 nm (c); Au nanorod monomer with aspect ratio of 3 (d) and 6 (e); Au nanorods dimer aligned side-by-side with spacing of 1 nm (f) 图8 (A) Au纳米棒二聚体不同耦合光散射谱; (B) 不同构型二聚体耦合示意图; (C) 用DDA方法得到的耦合金 纳米棒二聚体表面电荷密度83 Fig.8 (A) Scattering spectra of various Au nanorod dimers; (B) plasmon hybridization schemes for dimers in different geometric arrangements; (C) surface charge density of coupling gold nanorods dimer calculated using discrete dipole approximation (DDA)83 Inset in Fig.(A): electron micrographs of the same dimers showing the different configurations, scale bar =100 nm; (B) red × means impossible configurations; (C) interparticle separations are all 1.5 nm. 1282