等离激元纳米结构辅助激光解吸附与电离的研究

Molecules can be desorbed and ionized when being illuminated by strong laser pulses. This Laser Desorption Ionization (LDI) process has a broad range of applications, such as laser spectroscopy, fabrication, and mass spectrometry. Particularly, LDI is one of the most important ionization methods for Mass Spectrometry (MS), playing a key role in proteomics, metabolomics, and pharmaceutical industry. In current LDI-MS techniques, special small organic molecules are commonly used as the sample matrix to absorb the excitation light and assist the desorption/ionization processes. However, the small molecules in the matrix can also be ionized together with sample molecules, and introduce strong background noises, making it impossible to analyze low mass biomolecules with this matrix-assisted LDI-MS. To solve this issue, we propose a plasmonic nanostructure assisted LDI technique. With the extraordinary light absorption capability, a thin plasmonic nanostructure film can be heated up to an extremely high temperature when being excited by a laser pulse, promising a superb desorption/ionization efficiency for organic molecules on its surface without introducing any background noises. In this project, we will design and fabricate novel 2D plasmonic structures, and investigate the LDI processes in both theory and experiment. It will not only deepen our understanding of light-matter interactions at the nanoscale, but also will lead to important applications in many fields, such as nanomaterial, analytical chemistry and biology.

当固体被强激光脉冲激发时，吸附在表面上的分子可被解吸附并离子化，这一过程被称为激光解吸/电离，或Laser Desorption Ionization (LDI)。它在质谱分析领域中是最重要的一种离子化技术，被广泛应用于蛋白组学和药物研发中。LDI质谱的核心是样品基质，它决定了质谱的性能。基质通常由几种特殊有机小分子构成，能有效辅助解吸/电离过程。但这些有机小分子也带来了高背景噪音的缺点，极大的限制了LDI质谱的应用。本项目将研发新型的无机纳米结构来取代传统基质，解决背景噪音问题，并提高离子化效率。新型的纳米结构基质将利用等离激元振荡实现高效的激发光吸收与加热,从而有效地解吸/电离待测分子。我们将设计、加工不同的结构，系统地研究纳米结构辅助LDI过程；开发高效、零背景的LDI质谱技术。此项研究不仅能加深对纳米尺度内光和物质相互作用的理解，还将对相关的材料、化学、生物领域产生推动作用。

本项目的研究主要集中在等离激元纳米结构衬底的调控与其在基底辅助激光解吸/电离中的应用。项目执行期间，基本按申请书中所列的研究内容开展,并且根据目前国内外的研究发展状况以及项目中的新发现进行了多个拓展性研究。（1）通过对等离激元纳米结构基底的光吸收与热学性质的调控，增强了其光致升温效应，实现了有机分子激光解吸/电离效率>30倍的提高，并有效的解决了困扰传统基质辅助激光解吸/电离技术的低质荷比区的背景噪音问题。（2）理论上给出了构建超薄宽带光吸收器所需材料的性质，并利用等效介质理论，给出了该种材料的制备方案，为设计高效能等离激元基底提供了理论基础；（3）利用牛顿环实验演示了等离激元纳米薄膜间的近场等厚干涉效应，为实现连续可调的等离激元纳米光学腔提供了便捷的方案，并将基于等厚干涉的距离测量技术的精度提高到3皮米；（4）在伯格曼（Bergman）表象下，利用微扰理论给出了等离激元纳米传感器的一般规律，指出当前广泛使用的基于无损介质共振腔的传感理论对强色散介质并不适用，该工作被选为ACS Editor’s Choice。项目执行期间，在Adv. Mater.，Light Sci. & Appl.，Chem.Rev.，ACS Photonics，Optics Express等SCI期刊上发表与项目相关论文9篇，申请专利3项。此外还有一篇文章已被Phys. Chem. Chem. Phys.接收并在线发表。