基于纳米光学谐振增强电子隧穿的肝脏微结构质谱化学成像

The spatial resolution of Matrix Assisted Laser Desorption Ionization-Mass Spectrometric Imaging (MALDI-MSI) is mainly limited by laser beam size, uneven distribution of organic matrix materials co-crystalized with analytes of different shapes and sizes as well as background interferences. Moreover, the theoretical maximum of spatial resolution is also confined to optical diffraction limit. This work is aimed to break through the limit of the soft ionization technique of laser desorption ionization. The research will be focused on enhanced electron tunneling by nano optical resonant cavity of hexagonal ZnO as well as optical and electrical properties of Schottky junction. Through the control of kinetic energies of tunneling electrons, these hot electrons are exothermally captured by charge deficient atoms of adsorbed molecules without vibrational exciation. Resultant unpaired electrons then further initiate homolytic cleavages of α chemical bonds. In this technique, the nano-sized electron beam, optical resonant cavity enhancement and surface modification on Schottky junction play important roles in the improvement of resolution, signal-to-noise ratio and selectivity of mass spectrometric imaging. By using the proposed technique, it is expected to achieve high resolution mass spectrometric imaging of structural microdomains of liver that can characterize chemical compositions and physical shapes. Changes in these structural microdomains caused by environmental pollution will also be investigated.

激光光斑大小以及有机基质与样品形成大小、形状不均匀晶体和背景干扰是制约激光解析离解质谱成像技术（MALDI-MSI）分辨率的主要原因，不仅如此，其空间分辨率的理论极值还受制于光学衍射极限。本项目旨在突破激光解析离解软电离方法的局限，重点研究紫外激光诱导下半导体ZnO六方纳米谐振腔产生的增强隧穿电子束流以及肖特基势垒结的光电传输性质，通过控制隧穿电子束能量使这些隧穿电子被样品分子中的缺电子原子非振动激活俘获，并引发特异性α化学键断裂。该技术中纳米级电子束流、谐振增强和表面修饰诱导肖特基性能改变等特性是提高质谱图像分辨率、信噪比和选择性的关键，预期该技术可获得能够表征肝脏微区结构和化学组成的高分辨质谱图像，发现环境因素影响下这些微区结构的变化规律。

激光光斑大小、热效应以及有机基质与样品形成大小、形状不均匀晶体和背景干扰是制约常规激光解析离解质谱成像技术分辨率的主要原因。本项目研究了半导体材料表面光生电子与分子的相互作用和影响因素，建立了基于光电子转移俘获的软电离方法，旨在突破激光解析离解软电离方法的局限。这种图像采集方法以半导体薄膜取代了有机小分子基质，大大降低了背景干扰和结晶大小不均的问题。特别是激光热效应导致的光斑增大问题得到了有效解决，因为激光的热效应不足以激励电子能级的跃迁。重点研究了紫外激光诱导下半导体ZnO六方纳米谐振腔的制备和性质，探索了隧道电流与肖特基势垒结的关系。研究发现通过控制隧穿电子束能量可使这些隧穿电子被样品分子中的缺电子原子非振动激活俘获，并引发特异性化学键断裂。纳米级电子束流、谐振增强和表面修饰诱导肖特基性能改变等重要实验数据的获得对进一步深入研究奠定了基础。