可用于油田测试的金基纳米复合结构LSPR光学特性研究

发布时间：2018-03-31 12:37

本文选题：LSPR　切入点：纳米结构　出处：《东北石油大学》2017年博士论文

【摘要】：基于金属及其复合结构纳米颗粒局域表面等离子体共振(LSPR)特性的光学传感测试技术在石油勘探开发领域具有巨大的应用潜力,金属复合结构纳米颗粒的LSPR由于具有共振光谱可控性和功能多样化的特点获得广泛关注。为了给新型LSPR纳米复合结构的设计和“油气光学”新传感测试方法提供理论依据,本论文从局域表面等离子体共振基本原理出发,采用仿真方法对金基纳米复合结构LSPR光学特性进行系统研究。对具有不同中间层的Au-中间层-Ag三层核壳纳米颗粒的LSPR消光特性进行仿真分析。采用离散偶极近似方法和有限元数值方法,分析了中间层材料、核壳比以及外界介质折射率等结构参数对其消光效率和LSPR共振波长的影响;分析结果表明,消光峰峰位与各层厚度、外界介质折射率变化有关,对中间层材料的变化极为敏感。中间层材料对三层纳米核壳的LSPR特性有显著影响,当中间层为空腔时,消光光谱中存在三个共振吸收峰及法诺共振现象。Ni中间层抑制了金核对核壳结构LSPR的贡献,消光谱中只存在一个共振峰,未形成法诺共振。Si3N4中间层对表面等离子体共振具有明显的增强作用,导致消光谱中出现多个共振峰;通过改变金核的半径可优化LSPR法诺共振波长和强度,实现在600~1200nm波长范围内调控。提出了一种新型对称破缺型Au-ITO-Ag三层纳米核壳结构模型,采用有限元计算方法和等离激元杂化理论研究了入射光偏振方向和入射光频率等参数对LSPR共振能量模式及其远场分布的影响及变化规律;结果表明,当入射光偏振方向垂直和平行于对称轴方向时,Au内核能量模式与Ag外壳纳米杯能量模式的相互作用可产生多个偶极和高阶共振模式。入射光波频率在一定范围内变化时,实现了对横向和轴向两个耦合模式LSPR光谱的分别控制;与吸收和消光曲线相比,散射谱线的能量模式均发生蓝移,且吸收效率大于散射效率,共振吸收在消光性能中占主导作用。电场轮廓增强分析表明,Ag外壳纳米杯缺口部分具有最突出的电场强度和高度可调节的光学特性。设计了一种Au/石墨烯基底复合Ag纳米棒阵列结构,采用离散偶极近似算法研究了Ag纳米棒长轴方向、石墨烯层厚度、纳米棒高度、共振波长以及Ag纳米棒个数等参数对纳米复合结构共振波长和电场分布特性的影响。仿真结果表明,当Ag纳米棒长轴平行于y轴时,纳米复合结构消光光谱存在三个等离子体共振模式,且长波长共振模式随石墨烯层厚度的增大发生显著蓝移。石墨烯层厚度对LSPR特性有显著影响,纳米复合结构的共振特性可通过控制石墨烯厚度进行调整和优化。LSPR的能量模式所对应的共振峰峰位随Ag纳米棒的高度不同发生变化,且与Ag纳米棒的纵横比有密切关系。随着等离子体共振波长增大,电场强度大幅度增加;对于八个Ag纳米棒的复合结构,当波长为800nm时,电场强度比入射电场增强70倍。Ag纳米棒之间局域电磁场相互作用,导致Ag纳米棒具有极强的分子拉曼信号,该现象可用于近场信号的放大和检测。外界介质折射率的微小变化导致Au/石墨烯基底复合Ag纳米棒阵列结构的LSPR共振条件发生变化,该响应关系可为制备更高活性的SERS活性基底折射率传感器提供理论支撑。本文系统地研究了金基纳米复合结构LSPR光学特性,揭示了结构参数与消光效率及LSPR共振波长之间内在关系,提出了一种光学特性高度可调的新型对称破缺型Au-ITO-Ag三层纳米核壳结构模型,设计了一种新型Au/石墨烯基底复合Ag纳米棒阵列结构,本文的研究成果对光纤传感器表面功能化修饰及纳米复合光学传感器设计具有理论指导和实践意义。
[Abstract]:The metal nanoparticles and their composite structures based on localized surface plasmon resonance (LSPR) optical sensing technology characteristics have great potential applications in the field of petroleum exploration and development, metal composite structure LSPR nanoparticles because of the resonance spectrum of controllability and functional diversification gained wide attention. In order to design the new LSPR nano composite structure and "oil gas optical" new sense test methods provide a theoretical basis, the basic principle of localized surface plasmon resonance of the simulation method used to systematically study the gold based nano composite structure of LSPR optical properties. Simulation analysis of LSPR extinction characteristic of the middle layer of Au- -Ag three core-shell nanoparticles with different intermediate layer of using the discrete dipole approximation method and numerical method of finite element analysis, intermediate layer materials, core-shell ratio and external refractive index Influence of structural parameters on the rate of extinction efficiency and LSPR resonance wavelength; the analysis results show that the extinction peak position and thickness of each layer, the external refractive index changes, the change of interlayer material is very sensitive. LSPR significantly affected the properties of the intermediate layer material of three layer nanometer nuclear shell, when the middle layer as the cavity, the three resonance absorption peak and Fano resonance phenomenon of.Ni intermediate layer suppresses the gold to check the core-shell structure of LSPR with extinction spectrum, a resonance peak exists only in the extinction spectrum, intermediate Fano resonance.Si3N4 layer on surface plasmon resonance is greatly enhanced by the formation, resulting in multiple resonance peaks extinction spectrum; by changing the radius of the nucleus can optimize LSPR Fano resonance wavelength and intensity, realized in the wavelength range of 600~1200nm regulation. We put forward a new symmetry breaking type Au-ITO-Ag three layer core-shell structure. Type, plasmon hybridization theory on the polarization direction of the incident light and incident light frequency parameters of LSPR resonance energy mode and the far field distribution of influence and change law of the finite element method and etc.; results show that when the polarization direction of the incident light parallel and perpendicular to the direction of the symmetry axis, the interaction energy of Au kernel mode with the Ag shell nano cup pattern of energy can produce a plurality of dipole and higher order resonance modes. The incident wave frequency changes within a certain range, can control the transverse and axial two coupling modes in LSPR spectra; compared with the absorption and extinction curves, scattering spectrum energy patterns are blue shifted, and the absorption efficiency is larger than the scattering resonance absorption efficiency, which plays a dominant role in the extinction performance. Field contour enhancement analysis showed that the Ag shell nano gap cup portion has electric field strength of the most prominent and highly adjustable Optical characteristics. The design of a Au/ graphene composite substrate Ag nanorod array structure, using the discrete dipole of Ag nanorods long axis algorithm approximate, graphene layer thickness, nanorod height, parametric resonance wavelength and the number of the Ag nanorods nanocomposite structure resonance wavelength and field distribution characteristics were investigated. The simulation results show that when the Ag nanorods long axis parallel to the Y axis, there are three modes of plasmon resonance extinction spectra and nano composite structure, the long wavelength resonant mode with increasing graphene layer thickness has a significant blue shift. The graphene layer thickness on the characteristics of LSPR have a significant effect, resonance peak resonance characteristics of nano composite structure can be controlled by graphene the thickness of the adjustment and optimization of the.LSPR energy model corresponding to the level of different Ag nanorods changed, and the aspect ratio of the Ag nanorods have a close relationship with. The plasmon resonance wavelength increases, the electric field strength increased greatly; for the composite structure of eight Ag nanorods, when the wavelength is 800nm, the electric field strength than the incident electric field enhanced 70 times between.Ag nanorods localized electromagnetic interaction, resulting in Ag nanorods have strong molecular Raman signal, this phenomenon can be used for near-field signal amplification and detection of small changes in the outside world. The refractive index of the medium lead to changes in the LSPR resonance conditions of Au/ graphene composite substrate Ag nanorod array structure, the response relation for the preparation of SERS active substrate reflects a high activity rate sensor provides theoretical support. This paper systematically studied the optical properties of gold based nano composite structure of LSPR revealed the relationship between the structure parameters and the extinction efficiency and LSPR resonance wavelength, proposes a novel symmetrical optical characteristics of height adjustable breaking type Au-ITO-Ag three nanometer nuclear shell A new type of Au/ graphene based composite Ag nanorod array structure is designed. The research results in this paper have theoretical guidance and practical significance for the functional modification of optical fiber sensor and the design of nano composite optical sensor.

【学位授予单位】：东北石油大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TE151;O657.3

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