基于纳米效应的in situ激光诱导击穿光谱（LIBS）增强特性的研究

Laser-induced breakdown spectroscopy (LIBS) has become an increasingly popular technique which enables one to carry out rapid and direct remote analysis without time consuming. However, one of the drawbacks of LIBS is its low sensitivity to perform the analysis of elements. Several methods have been developed to improve the sensitivity by enhancing the LIBS emission intensity, especially the using of nanoparticles, which can lead to a large electromagnetic field enhancement and an anomalous enhancement in LIBS emission spectra intensities. In the proposal, nanoparticles will be deposited on samples in ultra- high vacuum and then the laser pulse will be focused on the target. Hopefully, this study can provide more conclusive experimental evidence for revealing the relationship between laser pulse energy,morphologyof nanoparticles and enhancement of LIBS. The research of this project has important scientific and practical significance.

激光诱导击穿光谱技术（Laser-induced breakdown spectroscopy, 简写为LIBS）具有快响应、无需样品制备、多元素同时分析以及远程分析等优点。尽管LIBS技术已较为成熟，在众多领域有着广泛的应用，且卓有成效，但如何提高其灵敏度，极大地下延其探测下限仍是亟需解决的重要科学问题。由于纳米结构表现出强烈的表面等离子体共振特性，很大地增强电场，因此基于纳米技术的被测材料改性能导致其LIBS信号强度甚至增加几个量级。本项目拟利用现有的超高真空光谱测量系统，用蒸发镀膜法在被测样品表面生长纳米材料，进行激光照射样品实验研究，揭示入射激光功率密度、激光诱导等离子体、LIBS信号增强以及纳米材料形貌之间的相互关系，进一步探索基于纳米材料的LIBS信号增强机制，为提高LIBS的灵敏度提供更加可靠的机制、技术与实验数据支撑。

激光诱导击穿光谱(Lase induced breakdown spectroscopy, LIBS)是一种发射光谱检测技术，它通过测量高能激光烧蚀等离子体的发射谱线，得到样品中的元素成分和含量信息。LIBS技术具有快速响应、多元素分析、在线检测、远程检测等优点，因而在环境检测、材料分析、食品安全、空间探测、矿产冶金等领域应用广泛。通过对纳米增强LIBS（nanoparticle enhanced LIBS, NELIBS）的研究发现，其具有强烈依赖于特定的金属纳米结构的性质。本工作研究了（1）两亲性分子和金纳米粒子的库仑作用对NELIBS 的影响。实验发现，在硅基底上，使用阳离子型表面活性剂CTAB 和金纳米粒子时，K 原子的LIBS 信号显著增强，探测限由ppm 降低到ppb 量级。（2）银纳米团簇的沉积量对LIBS 信号增强的影响。使用磁控溅射镀膜的方法，在覆盖了有机硅胶的PET 薄膜表面沉积银纳米团簇，测量了Si 谱线受银纳米团簇尺寸的影响。研究发现，随着镀膜时间增加，银团簇尺寸增加，沉积量升高，LIBS 信号先升高，后饱和，最后降低，谱线的最大增强倍数为~15 倍。