Size Dependent SERS Activity of Gold Nanoparticles Studied by 3D-FDTD Simulation
LI Li-mei1, FANG Ping-ping2, YANG Zhi-lin1*, HUANG Wen-da1, WU De-yin2, REN Bin2, TIAN Zhong-qun2
1. The School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen 361005，China 2. State Key Laboratory for Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005，China
Abstract：By synthesizing Au nanoparticles with the controllable size from about 16 to 160 nm and measuring their SERS activity，the authors found that Au nanoparticles film with a size in the range of 120-135 nm showed the highest SERS activity with the 632.8 nm excitation, which is different from previous experimental results and theoretical predictions. The three dimensional finite difference time domain (3D-FDTD)method was employed to simulate the size dependent SERS activity. At the 632.8 nm excitation, the particles with a size of 110 nm shows the highest enhancement under coupling condition and presents an enhancement as high as 109 at the hot site. If the enhancement is averaged over the whole surface, the enhancement can still be as high as 107, in good agreement with our experimental data. For Au nanoparticles with a larger size such as 220 nm, the multipolar effect leads to the appearance of the second maximum enhancement with the increase in particles size. The averaged enhancement for the excitation line of 325 nm is only 102.
Key words：Surface-enhanced Raman scattering(SERS);Au nanoparticles;3D-finite difference time domain(3D-FDTD)
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