基于DDA和FDTD算法的银纳米球及其阵列LSPR现象分析

Analysis of Ag Nanosphere and Array's LSPR Phenomena Based on DDA and FDTD Method

目的:分析不同半径的银纳米球及其组合阵列的消光现象和耦合现象,探索局域表面等离子体共振(localized surface plasmon resonance,LSPR)发生的原因。方法:采用离散偶极近似(discrete dipole approximation,DDA)得到不同半径银纳米球及其阵列的消光光谱及其消光效率(Q_ext)、吸收效率(Q_abs)和散射效率(Q_sca)等;在此基础上,利用时域有限差分(finite difference time domain,FDTD)方法研究了双纳米球阵列的耦合作用及其电场分布。结果:对于单纳米粒子,随着半径的增大,散射效率占总的消光效率的比重增加。对于2个纳米颗粒,当入射光垂直于轴线,且纳米颗粒之间间距较小时,耦合的作用较大。对于纳米颗粒阵列,消光光谱的灵敏度与纳米颗粒的大小以及间距有关,当颗粒间距很小的时候会出现多峰形式的消光谱。结论:LSPR与纳米颗粒的种类、大小、形状、阵列及所处的介质环境等有关。

Objective To explore the reason of LSPR by analyzing different radiuses of silver nanoparticles and their couples and arrays.Methods Discrete Dipole Approximation （DDA） method was used for simulating different radius and the array of silver nanoparticles＇ extinction spectra and extinction efficiency （Q_ext）,absorption efficiency （Q_abs） and scattering efficiency （Q_sca）.FDTD （Finite Difference Time Domain） method was used for the coupling of two nanoparticles and simulating their around electric field distribution.Results For single nanoparticle,with the increase of radius,the Q_sca of Q_ext generally increased the proportion.For both nanoparticles,when the incident light was perpendicular to the axis,smaller spacing between nanoparticles had strong coupling effect.For nanoparticle arrays,the sensitivity of extinction spectra had relationship with the size and spacing of nanoparticles,and there would be multimodal forms of extinction spectrum when the particle spacing was small.Conclusion By analyzing and comparing,it＇s concluded that LSPR phenomenon is related to nanoparticle species,size,shape,the array and the media environment.