基于光诱导力和等离激元共振的亚单层分子高灵敏超分辨红外光谱研究

在中红外波段，分子吸收光后膨胀产生范德华力，称为光诱导力。利用原子力显微镜测量波长相关的光诱导力，可以实现超分辨红外光谱检测，进而在亚波长尺度下从结构功能、化学键变化等不同层面研究物质的物理和化学性质。现阶段，在纳米空间尺度下提高光谱获取的灵敏度，实现亚单层分子级别分析是该技术所面临的最前沿挑战之一。本项目提出利用等离激元共振提高分子所处位置的电磁场强度实现高灵敏超分辨红外光谱的获取方法。拟通过理论模拟精确设计制备中红外等离激元共振结构，调制其共振与目标分子红外吸收匹配，实现固气界面纳米尺度分辨的高灵敏红外光谱采集及成像。结合同步的原子力显微镜形貌分析，在针尖空间分辨率、亚单层分子灵敏度水平上揭示目标分子的物理化学特征及与等离激元共振结构的光质作用机制，进而研究生命过程中重要反应的物质交换、电子传递和能量转移机理。该研究有望为推进超高分辨光谱学在亚单层尺度的前沿研究提供理论支撑和实验基础。

Absorption of molecules in mid-infrared (mid-IR) region leads to the molecular expansion, resulting to the measurable Van der Waals force defined as photoinduced force. Using the atomic force microscopy (AFM) to detect the wavelength dependent photoinduced force, IR spectroscopy with hypersensitivity and super resolution can be achieved, which allows subwavelength scale analysis of the chemical and physical properties of molecules such as chemical bond, structure and function variations. Nowadays, one of the cutting edge challenge is to improve the sensitivity up to molecular monolayer level at nanoscale. In this project, we have proposed a plasmon enhanced strategy to achieve IR spectroscopy with hypersensitivity and super resolution with the highly confined and enhanced electromagnetic (EM) field on the plasmonic structures. Mid-IR resonant structures are fabricated with the guidance of numerical simulation. The plasmon resonance are tuned to match the molecular absorption, allowing the nanoscale IR spectra collection and imaging at solid/gas interfaces. Combining with the simultaneous AFM imaging, the physical and chemical properties of objective molecules as well the light-matter interactions on plasmonic structures can be revealed at sub molecular monolayer level sensitivity and tip apex radius scale resolution, which can be used for the in-depth investigations of the basic process of mass distribution, energy and electron transfer during specific reactions. This technique can be applied in frontier application based on super resolution optical technique such as interfacial sciences, catalysis sciences and nanooptics.