球形金纳米颗粒的消光特性及不同折射率环境下的共振波长

摘要

In order to study extinction characteristic of spherical Au nanoparticles and the relation between resonance wavelength and ambient refractive index,the extinction spectra of spherical Au nanoparticles in diameters of 20,40,60 and 80 nm in mediums with different refractive indexes were calculated with Mie theory.The absorbance of Au nanoparticles in the four particle sizes was measured in sweet water with different concentrations experimentally to obtain relation between refractive index of medium in sweet water and the concentration,dispersion law,extinction coefficient of Au nanoparticle and the variation of resonance wavelength with ambient refractive index.The results show that when concentration of sweet water in medium environment are constant while radius of Au nanoparticle is increasing,red shift of extinction peak can be discovered;when radius of nanoparticle is constant while concentration of sweet water in medium environment is increasing,red shift of extinction peak can be discovered.The resonance wavelength of Au nanoparticle is linear to the concentration of sweet water with linear slopes corresponding to Au nanoparticles in diameters of 20,40,60 and 80 nm are 0.106 0,0.135 5,0.193 8 and 0.265 8 respectively.The slope increases with the growth of particle size.These conclusions have laid the foundation for exploring the refractive index sensitivity of nanoparticles.%为了研究球形Au纳米颗粒的消光特性及共振波长与环境折射率的关系,采用Mie理论计算了直径为20,40,60和80 nm的球形Au纳米颗粒在不同折射率的介质环境中的消光谱,并利用消光法实验测量了这4种粒径的Au纳米颗粒在不同浓度糖水中的吸光度,取得了糖水介质环境的折射率与浓度之间的关系及其色散规律,以及Au纳米颗粒的消光系数及共振波长随环境折射率变化的数据.结果表明,介质环境糖水浓度一定时,Au颗粒半径增大,消光峰值红移;颗粒半径一定时,周围介质环境糖水浓度增大,消光峰值红移;Au纳米颗粒的共振波长与糖水浓度呈线性关系,20,40,60,80 nm的Au纳米颗粒对应的线性斜率分别为0.106 0,0.135 5,0.193 8,0.265 8,斜率随粒径尺寸的增大而增大.该结论为探索纳米颗粒的折射率敏感性奠定了基础.