金纳米双球系统的高灵敏光学传感与其消光系数及局域场增强之关联

Correlation of optical sensing with extinction coefficient and local field enhancement in gold nanosphere dimer

系统地研究了最基本的单/双金纳米球系统的共振峰移动、局域场增强和消光谱等光学响应行为.发现在双金纳米球系统中,入射光除了能激发每个金纳米球的局域表面等离激元共振模式外,调整金纳米球间隙可使共振模式间产生强烈耦合,使系统局域场增强因子进一步提升,并增强光学传感能力和消光系数.有趣的是,受限于有限的局域场增强体积,具有高局域场增强因子的间隙为2 nm的双金纳米球系统的消光系数大幅降低,其消光系数和光学传感能力均低于5 nm间隙的系统.研究表明,双金纳米球系统的光学传感灵敏度不是由局域场增强幅度直接决定的,而与系统消光系数有相似的变化行为.这些结果可指导金纳米双颗粒和多颗粒系统的设计,为表面拉曼散射增强和光学传感等方面的应用提供创新性思路和方案.

In this paper we systematically study the optical extinction,local field enhancement,and resonance peak shift of basic single/double gold nanosphere system.We find that in the double gold nanosphere system,the incident light can excite the coupled resonance modes when the two gold nanospheres are approaching to each other,leading the local field to be enhanced greatly.Interestingly,limited by the scant volume of local field,the extinction coefficient of the double gold nanosphere system of 2 nm gap with a high local field enhancement factor is greatly reduced,so that its optical sensing sensitivity and extinction coefficient are smaller than the 5 nm gap system’s.Studies show that the optical sensing sensitivity of the double gold nanosphere system is not directly determined by the local field enhancement amplitude,but has a similar change behavior to the extinction coefficient of the system.These results can offer us a useful route and hint for designing the gold nanoparticle systems used in the surface Raman scattering enhancement and high performance optical sensing.