金纳米棒二聚体结构的Fano共振  

Fano Resonance of Gold Nanorod Dimers

作　　者：李星童 陈昱 马强[1] 琚志平 李康 陈梦迪 吴伯涛[1] 武愕[1,2,3] LI Xing-tong;CHEN Yu;MA Qiang;JU Zhi-ping;LI Kang;CHEN Meng-di;WU Bo-tao;WU E(State Key Laboratory of Precision Spectroscopy,East China Normal University,Shanghai 200241,China;Chongqing Key Laboratory of Precision Optics,Chongqing Institute of East China Normal University,Chongqing 401120,China;Collaborative Innovation Center of Extreme Optics,Shanxi University,Taiyuan 030006,China)

机构地区：[1]华东师范大学精密光谱科学与技术国家重点实验室,上海200241 [2]重庆市精密光谱重点实验室华东师范大学重庆研究院,重庆401120 [3]山西大学极端光学协同创新中心,山西太原030006

出　　处：《量子光学学报》2023年第2期82-90,共9页Journal of Quantum Optics

基　　金：上海自然科学基金(22ZR1421100)。

摘　　要：等离激元金属纳米结构中的Fano共振,由于其在超灵敏传感、超材料、光开关和非线性光学器件等方面的潜在应用而引起了广泛的关注。但在单颗粒尺度下单个金属纳米二聚体结构的Fano共振的实验研究仍然很少。本研究基于单颗粒光谱技术从实验上探讨了二聚体结构产生的Fano共振现象。利用种子生长法制备了等离激元共振峰分别在1 060 nm和700 nm的一长一短金纳米棒,通过L-半胱氨酸分子的静电吸附自组装构建首尾相连的金纳米棒二聚体结构,在暗场显微系统中表征了金纳米棒二聚体耦合前后的散射光谱。结果表明,短金纳米棒的明偶极模式与长金纳米棒的暗四极模式间的相消干涉在660 nm处产生了明显的Fano共振谷,同时基于有限差分时域(FDTD)方法的理论模拟散射光谱与实验结果能够较好地符合。这种自组装金纳米棒二聚体在等离激元传感和探测等方面具有广阔的应用前景。Due to its potential applications in ultra-sensitive sensing,metamaterials,optical switches,and nonlinear optical devices,Fano resonance in plasmonic metal nanostructures has attracted extensive attention.However,experimental studies on the Fano resonance of metal nanodimers at a single particle scale are stll scarce.In this paper,Fano resonance phenomenon in Au-Au nanorod dimers is investigated experimentally using single-particle spectroscopy.The long and short Au nanorods with resonance peaks at 1060 nm and 700 nm in water are synthesized by the seed growth method,their average lengths are 110 nm and 55 nm,corresponding to average diameters of 17 nm and 20 nm respectively,and the Au-Au nanorod dimers are constructed by electrostatic adsorption self-assembly of L-cysteine molecules.When mixed short and long gold nanorods solution is added with 0.9 mmol/L L-cysteine,the cysteine preferentially binds to the ends of the gold nanorods through the sulfydryl group,and due to the mutual attraction of positive and negative charges,the amphoteric ionic groups assist the two nanorods to interconnect through end-toend electrostatic adsorption,thus forming a dimer.Scattering spectra of a single Au-Au nanorod dimer before and after coupling are measured by dark-field microscopy and theoretically simulated by the finite difference time domain(FDTD)method.The near-field electromagnetic distribution images of nanodimers are also analyzed.Dark-field scattering spectrum shows that the destructive interference between the bright dipole mode of a short Au nanorod and the dark quadrupole mode of a long Au nanorod produces an obvious Fano resonance dip at 660 nm,and the theoretical simulated scattering spectrum is in good agreement with the experimental one.The electromagnetic distribution images show that the electric field enhancement of the bright dipole mode of a short Au nanorod is descend at the Fano dip(656 nm),while the dark quadrupole mode of a long Au nanorod is enhanced,which is also the result of the destructive interfer

关 键 词：Fano共振 二聚体 金纳米棒 散射 

分 类 号：O433.4[机械工程—光学工程]