直接测量大气细颗粒物pH值的原位表面增强拉曼光谱研究方法

In the formation process of haze in our country, the formation of fine particles is a kind of complex polution mechanism, which includes not only the response mechanism of London fog, but also the formation mechanism of photochemical smog in Los Angeles, and many interface reaction mechanisms. A core problem of these reaction mechanisms is the acid-base properties of particles. The reaction rates between particles and trace gases such as SO2, NOx, NH3 and VOC are greatly affected by the pH values of particles. Therefore, how to establish an on-line research technique to determine the pH values of particles in situ has been the core scientific problem of the research on the formation mechanisms of fine particles in the world at present. In view of the current technical problem of determining the pH values of particles, this project intends to establish a surface enhanced Raman scattering (SERS) method for the in-situ measurement of pH values of particles. By utilizing the high sensitivity of the technology to specific molecules, the surface enhanced Raman spectrum of endogenous diacids, aromatic organic acids, phenol, aniline and other organic molecules can be obtained to determine the quantitative relationship between surface enhanced Raman spectrum and pH values, relative humidity and inorganic salts. The pH values of particles can be determined according to the sensitivity of SERS spectrum of these molecules to the pH of particles.

我国雾霾形成过程中，细颗粒物的形成机制是一种复合反应机制，既包含伦敦雾的反应机制，也包含洛杉矶光化学烟雾形成机制，还有很多界面反应机制。这些反应机制中的一个核心问题，就是颗粒物的酸碱性问题，颗粒物的pH值极大地影响着颗粒物与痕量气体如SO2，NOx，NH3，VOC之间的反应速度。因此，如何建立一种在线研究方法，能原位确定细颗粒物的pH值，是目前国内外细颗粒物形成机制研究的核心科学问题。针对目前实验直接测量颗粒物pH的难题，本项目拟建立颗粒物pH值的表面增强拉曼散射（SERS）原位测量方法。利用该技术对特定分子的极高的灵敏度，获得内源性有机二酸、芳香有机酸、苯酚、苯胺等有机分子表面增强拉曼光谱，确定这些分子表面增强拉曼光谱与pH的定量关系，以及与相对湿度、无机盐种类之间的关系，根据这些分子SERS光谱对颗粒物的pH的敏感性，直接确定颗粒物的pH值。