利用离散偶极近似(discrete dipole approximation,DDA)的方法,系统研究壳层的材料、尺寸及形貌等因素对Au@Ag核-壳纳米光学吸收谱的峰值、峰位的影响。研究表明在液体环境中金球颗粒计算的结果与Mie理论计算的结果吻合,表明光学常数三次样条插值后DDA计算Au@Ag核-壳层纳米粒子的光学性质是准确可靠的。随着Ag壳层厚度增加,Au@Ag核-壳层球形纳米颗粒的吸光谱线形成与金球颗粒谱线不同的肩峰,然后主峰红移、肩峰蓝移消失合并为一条吸收峰,光学吸收谱线强度明显增强。Au@Ag核-壳层纳米立方体的光学吸收谱线在<450 nm时出现了许多次级吸收峰,随着Ag壳层厚度增加,主、次吸收峰增强,主吸收峰出现明显的蓝移。银壳层厚度的变化不仅改变光学吸收强度和峰值的位置,还在Au@Ag核-壳层纳米颗粒的尖端形成了很强的表面等离子体振荡(surface plasma resonance，SPR),提高Ag对光学吸收的影响。

Based on discrete dipole approximation(DDA),the effect of peak value and the peak position of optical absorption spectrum of Au@Ag core-shell nanostructure was systematically studied by the factors such as shell material,size and morphology.The results show that the calculations of Au spherical nanoparticles in the liquid environment are in agreement with the results calculated by the Mie theory,indicating that the optical properties of the Au@Ag core-shell nanoparticles after the cubic spline interpolation of the optical constants are accurate and reliable.With the increase of Ag shell thickness,the absorption spectrum of Au@Ag core-shell spherical nanoparticles forms different acromion with the spectrum of gold spheres,then the main peak shifts to red and the blue-shift of acromion vanishes,which becomes an optical absorption peak,and the intensity of optical absorption peak is enhanced.The optical absorption spectra of Au@Ag core-shell nanocube shows many secondary absorption peaks at <450 nm.With the growth of Ag shell thickness,the primary and secondary absorption peaks enhance,and the main absorption peak shows obvious blue-shift.The Ag shell not only changes optical absorption intensity and the location of peak value,but also forms strong surface plasma resonance (SPR) at the tip of Au@Ag core-shell nanoparticles,and improves the effect of Ag on optical absorption.