表面等离激元增强的拉曼光谱面直接成像

Raman spectrum is a nondestructive, non-contacting, and fingerprinting analysis method. Raman imaging technology simultaneously has the advantages of Raman spectrum and imaging technology which has high-throughput and direct-viewing character. It has outstanding superiority on the characterization of nano-patterned samples, such like cells, micro/nano devices, etc. However, the present Raman imaging which usually obtained by mapping has been seldom used due to its low spatial resolution, long mapping time and low sensitivity. In this research project, we propose a novel Raman imaging method with a high sensitivity and high throughput. Based on the propagating surface plasmons (PSPs), the electromagnetic (EM) fields on the surface of metal film will be enhanced uniformly. The Raman signal will be selectly transmitted through the narrow band filters and the F-P interference device. The matrix CCD will then detect the Raman signal in the whole view field and the Raman images could be directly obtained. This Raman imaging method which is analogous to the fluorescence imaging can reach a high spatial resolution closed to the light diffraction limit without mapping. By means of the uniform enhanced EM fields by PSPs, the Raman signal of the sample in the whole view field could be enhanced uniformly. The high spatial resolution images of molecules distribution on microscopic scale could be rapidly obtained by this method. It could be expected that this Raman imaging method would be a powerful analysis tool in nanotechnology and bioscience fields.

拉曼光谱成像兼备了拉曼光谱无损、非接触、指纹性的优点和成像技术大信息量、形象直观的特点，在表征具有微纳结构的样品时（如细胞、微纳器件等）具有突出优势，然而目前扫描式拉曼成像存在空间分辨率低、扫描时间长、灵敏度差等缺点，应用十分有限。本项目提出一种具有高灵敏度、大信息通量的新型拉曼成像方式，拟基于传播型表面等离激元（PSPs）增强的电磁场对金属膜表面的样品进行均匀的“面激发”、利用法-珀干涉器与滤光片共同实现窄带通滤光、面阵CCD对视野内的拉曼光谱进行“面收集”的方式实现特定拉曼峰的直接成像。该“面收集”的拉曼成像方法类似于荧光成像的方式，可不用扫描即获得接近光衍射极限的高成像分辨率。而利用PSPs电磁场分布均匀的特点，对整个面内的电磁场实现均匀的增强，可有效提高拉曼成像的灵敏度。通过该方法可快速获得高分辨率的分子微区分布图像，有望成为微纳科学和生命科学领域中有力的分析工具。

拉曼光谱成像兼备了拉曼光谱无损、非接触、指纹性的优点和成像技术大信息量、形象直观的特点，在表征具有微纳结构的样品时（如细胞、微纳器件等）具有突出优势，然而目前扫描式拉曼成像存在空间分辨率低、扫描时间长、灵敏度差等缺点，应用十分有限。本项目设计和研制了具有自主知识产权的高分辨率拉曼光谱面成像系统，在宽场拉曼光谱成像技术（wide-field Raman imaging）基础上，创造性的采用可调谐激光器扫描结合固定波长滤光片+法-珀干涉器的方式，大幅提升了光谱分辨率（达到1个波数左右）和通光效率（提高5-10倍），使该系统在成像速度、空间分辨率及光谱分辨率等关键指标上显著优于国内外同类系统。在此基础上，利用PSPs激发均匀的局域电磁场，对拉曼光谱成像实现了“面增强”，增强倍数达到10倍以上，该方法适用于表界面的研究（如细胞膜成分成像、自组装体系等）。此外，拉曼光谱成像技术的研究还带动了相关光谱检测技术的研究，将拉曼光谱用于核材料及模拟材料的氧化膜内应力表征、腐蚀产物现场分析、材料的氢化反应动力学及氧化反应动力学研究，对核材料腐蚀研究和国防大型试验实施起到了有力支撑作用。本项目发展的拉曼光谱成像技术拟用于核材料腐蚀机理相关研究，对科学认识核材料的氧化、氢化腐蚀行为，进而提出对应的防腐策略具有指导作用，或者推向市场实现产业化，预期在催化、生命科学、材料腐蚀、考古、微纳科学等领域均具有良好的应用前景。