金属/石墨烯纳米天线探针SERS与SEIRA光谱双增强机理及关键技术研究

The precise detection of the change of the polarizability and dipole in the biomolecular structure plays an extremely important role in the early discovery of the pathological biomolecular and cells. To address this increasing significant demand, we propose a novel approach to excite the surface plasmons of the metal /graphene nano antenna probe in both the visible and the infrared waveband, combining the free electron gas of metal and the two-dimensional electron gas of graphene. By this way, the Surface-enhanced Raman Scattering (SERS) and the Surface-enhanced Infrared Absorption (SEIRA) spectroscopies of the biomolecular can be greatly enhanced at the same time by the confined electromagnetic field. Firstly, the excitation mechanism of both the metal surface plasmons and the graphene surface plasmons is investigated employing the finite element method, and a physical model is built to implement the enhanced function of metal/graphene nano antenna probe for both SERS and SEIRA spectroscopies. Secondly, a new method is developed to design the metal/graphene nano antenna probe that can effectively excite the surface plasmons in both visible and infrared waveband, which facilitates the design of the chip. Finally, an experimental set up that beyond the diffraction limits is established to verify the feasibility of the proposed method by detecting the SERS and SEIRA spectroscopies of the typical biomolecular in the same chip. The proposed enhanced method for both SERS and SEIRA spectroscopies based on metal/graphene nano antenna probe offers a novel solution to breakthrough the insurmountable technical bottleneck encountered by the traditional metal nano structures, which lays a foundation for the next generation molecular spectroscopy detection technology with ultra high sensitivity.

在早期诊断生物分子和细胞病变过程中亟需全面精确地探测分子极化率和偶极矩变化信息。面向这一重大需求，提出将金属自由电子气与石墨烯二维电子气有机结合，通过激发金属/石墨烯纳米天线探针的可见及红外表面等离激元混合模式，实现对被测分子SERS与SEIRA光谱双增强的新方法。首先，采用有限元法研究金属表面等离激元与石墨烯表面等离激元的双激发机理，建立SERS和SEIRA光谱双增强物理模型；其次，发展双波段金属/石墨烯纳米天线探针的设计方法，突破纳米天线探针及双增强光谱芯片的关键加工工艺；最后，构建突破衍射极限的SERS与SEIRA光谱双增强实验及典型生物分子探测实验。本项目发展的金属/石墨烯纳米天线探针SERS与SEIRA光谱双增强方法，为突破传统金属纳米结构所存在的频率无法动态调谐和带宽限制等瓶颈提供了新思路，为实现下一代超高灵敏度的分子光谱检测技术奠定了基础。

面向分子探测领域亟需全面精确地探测分子极化率和偶极矩变化信息的重大需求，本项目提出了一种利用金属/石墨烯微纳探针结构实现对被测分子表面增强拉曼光谱（SERS）与表面增强红外吸收光谱（SEIRA）光谱双增强的新方法，突破了传统方法中SERS与SEIRA难以同时得到高增强因子的难题。紧密围绕SERS与SEIRA光谱双增强机理及痕量分子探测实验开展研究，取得了一些创新性的研究成果：.（1）建立了双波段表面等离激元模式的激发物理模型，分析了分子与表面等离激元模式的耦合关系。设计了可以实现SERS与SEIRA光谱双增强的金属纳米颗粒/石墨烯多层谐振结构和金属纳米颗粒/石墨烯纳米天线探针结构。.（2）在铜箔上实现了大面积单层石墨烯薄膜生长，并成功地转移到二氧化硅基底上。制备了金属纳米颗粒/石墨烯多层谐振结构光谱双增强器件，实现了对分子浓度低至10-12 M的R6G溶液拉曼光谱的检测，计算得到的最大增强因子约为7.0×106。设计了不同结构参数的谐振结构对双增强基底的红外光谱进行宽波段调控，实现了15nm PEO分子振动模式的选择性增强，计算得到最高增强因子最大可达9.3×104。.（3）利通电子束光刻加工了石墨烯纳米天线，并制备了金属纳米颗粒/石墨烯纳米天线探针结构光谱双增强器件，实现了对分子浓度低至10-10 M的 R6G溶液拉曼光谱的检测，计算得到双增强基底的拉曼增强因子约为7.5×105。设计了不同结构参数的石墨烯纳米带天线结构，实现了对15nmPEO分子红外振动光谱的检测，计算得到双增强基底对PEO红外光谱信号的增强倍数最高可达80倍。.在本项目的资助下，发表与项目相关、已经标注本项目的学术论文6篇，其中SCI收录5篇，EI收录1篇；培养研究生2名；申请发明专利3项。本项目的研究工作为探索新型双增强光谱技术奠定了理论及实验基础。