【作者】 张乐；

【导师】 张强；

【作者基本信息】 太原理工大学 ， 电子信息（集成电路工程）（专业学位）， 2024， 硕士

【摘要】 贵金属纳米颗粒能够与光场发生相互作用产生局域表面等离激元共振(Localized Surface Plasmon Resonances,LPRs)。基于LSPRs,贵金属纳米颗粒诸多独特且优异的光学性质,例如显著增强光的吸收和散射作用,强烈的光场局域和强度放大。另外,LSPRs的共振特性还密切依赖于材料组分,结构形貌、尺寸及周围环境。表面增强的拉曼散射(Surface Enhanced Raman Scattering,SERS)光谱学在分子探测、生物诊断、成像等方面受到了极大的关注。特别是近年来科研人员提出了将信号分子嵌入到纳米颗粒内部,制备成所谓的金球-分子-金壳纳米颗粒。这种类型的颗粒有效的解决了信号分子受外部环境的影响,近年来在光学传感、生物诊断学等领域受到了青睐。然而,目前已报导的金球-分子-金壳纳米颗粒多分散在溶液中进行储存,在后续的使用中实际上也大多都是利用了单颗粒的光学性质,颗粒与颗粒之间的作用并没有被充分利用。于此同时,利用分子自组装技术制备的金属纳米颗粒超晶格结构能提供高密度的颗粒-颗粒耦合作用,显著地提升了SERS的性能,但目前的超晶格结构都只利用了简单的实心金属纳米颗粒。为了解决分散金球-分子-金壳纳米颗粒在SERS性能方面的不足,本论文提出了将金球-分子-金壳纳米颗粒制备成超晶格结构,并研究其光学特性尤其是SERS光谱性质。论文的具体内容依次为:(1)采用理论和数值计算研究了金球-分子-金壳纳米颗粒超晶格的光学响应。基于Mie理论及时域有限差分法的电磁模拟,获取了独立金球-分子-金壳纳米颗粒的散射和吸收谱,结合近场分析了其中的LSPR杂化规律;进一步,计算了金球-分子-金壳纳米颗粒超晶格的透、反射谱线随体系结构参数的变化规律,分析了导电和绝缘分子体系的不同特征。(2)研究了金球-分子-金壳纳米颗粒超晶格的自组装制备方法。首先,采用种子介导生长的溶液滑雪法合成了液相分散的金球-BDT分子-金壳纳米颗粒;然后,采用表面活性剂替换法将金球-分子-金壳纳米颗粒改性为油相分离;最后,采用气-液界面自组装法合成了金球-分子-金壳纳米颗粒超晶格并对其形貌进行了表征。(3)对合成的金球-分子-金壳纳米颗粒超晶格的光学响应进行了实验表征。采用显微光学系统测量了不同层金球-分子-金壳纳米颗粒超晶格的透射、反射谱,发现实际结构的光学响应与高导电分子的预测一致,表明BDT分子是一种再光频下具有高电导的分子;进一步,采用激光共聚焦系统测量了金球-BDT分子-金壳纳米颗粒超晶格的SERS光谱,发现BDT分子的振动模式拉曼信号有显著提高。本论文的研究结果为基于核-壳类金属纳米颗粒超晶格的近场增强光谱学提供了有价值的参考,有望应用于纳米集成光子器件、超灵敏传感、单分子探测、非线性光学器件、量子光学器件等领域。更多还原

【Abstract】 Noble metal nanoparticles can interact with the optical field,generating localized surface plasmon resonances(LSPRs).Based on LSPRs,noble metal nanoparticles exhibit unique and superior optical properties,such as significantly enhanced light absorption and scattering,strong field localization,and intensity amplification,etc.Moreover,the resonant characteristics of LSPRs are closely related to the material composition,structural morphology,size,and surrounding environment.Surface-enhanced Raman scattering(SERS)spectroscopy based on noble metal nanostructures has received great attention in molecular detection,biomedical diagnostics,and imaging.In recent years,researchers have proposed embedding signal molecules into nanoparticles,creating gold core-molecule-gold shell nanospheres.This type of nanoparticle effectively mitigates the effects of the external environment on signal molecules and has been favored in optical sensing and biomedical diagnostics.However,the reported gold core-molecule-gold shell nanoparticles are mostly dispersed in solutions for storage,and their optical properties are predominantly based on individual nanoparticles,with limited utilization of particle-particle interactions.At the same time,metal nanoparticle superlattice structures prepared using molecular self-assembly techniques provide high-density particle-particle coupling,significantly enhancing the performance of SERS.However,current superlattice structures only utilize simple solid metal nanoparticles.To address the limitations of dispersed gold core-molecule-gold shell nanoparticles in terms of SERS performance,this thesis proposes the fabrication of the nanoparticles into a superlattice structure and investigates their optical properties,particularly their SERS spectroscopic properties.The specific contents of the thesis are as follows:(1)The optical response of the gold core-molecule-gold shell nanoparticle superlattice is studied using theoretical and numerical calculations.Based on Mie theory and finite difference time domain simulations,the scattering and absorption spectra of individual gold core-molecule-gold shell nanoparticles are obtained,and the hybridization of LSPRs is analyzed in conjunction with near-field analysis.Furthermore,the transmission and reflection spectra of the gold core-molecule-gold shell nanoparticle superlattice are calculated,exploring the variations in the spectra with respect to the structural parameters of the system and analyzing the distinct characteristics of conductive and insulating molecular systems.(2)The self-assembly fabrication method of the gold core-molecule-gold shell nanoparticle superlattice is studied.Firstly,liquid-dispersed gold core-BDT molecule-gold shell nanoparticles are synthesized using a solution-based c高能模式ical method with seed-mediated growth.Then,the gold core-molecule-gold shell nanoparticles are modified into oil-dispersed form using surfactant displacement.Finally,the gold core-molecule-gold shell nanoparticle superlattice is synthesized using a gas-liquid interface self-assembly method,and its morphology is characterized.(3)The optical response of the synthesized gold core-molecule-gold shell nanoparticle superlattice is experimentally characterized.The transmission and emission spectra of different layers of the superlattice are measured using a micro-optical system,and it is found that the optical response of the actual structure is consistent with the prediction for the highly conductive molecule BDT,indicating that BDT is a molecule with high electrical conductivity at optical frequencies.Furthermore,the SERS spectrum of the gold core-BDT molecule-gold shell nanoparticle superlattice is measured using a laser-combined scanning system,and it is observed that the vibrational mode Raman signals of the BDT molecule are significantly enhanced.The research results of this thesis provide valuable references for near-field enhanced spectroscopy based on core-shell metal nanoparticle superlattices and hold promise for applications in nanoscale integrated photonic devices,ultra-sensitive sensing,single molecule detection,nonlinear optical devices,and quantum optical devices,among others.更多还原