大气可吸入颗粒物中锐钛矿的发现及意义

激光拉曼微探针(laser Raman microprobe，简称LRM)能将激光聚焦在1 μm2的极小区域进行分子成分和结构的微区分析，是一种可靠的物相鉴定手段，非常适用于单个微小颗粒物的物相鉴定。文章利用LRM对北京市大气可吸入颗粒物(PM₁₀)进行单颗粒物相分析 将实验图谱与Renishaw矿物与无机材料拉曼光谱数据库中标准图谱进行对比，通过简正坐标分析对谱带进行指认和对各谱峰分子类型及振动模进行归属，首次在PM₁₀中发现了锐钛矿型TiO₂,其实验图谱具有638 cm-1处的较强峰以及398和517 cm-1处中等强度峰，为O—Ti—O特征振动，确认了大气中富Ti颗粒的矿物物相为锐钛矿型TiO₂。锐钛矿型TiO₂是一种重要的光催化剂，锐钛矿与其他矿物颗粒(尤其是含Ca碳酸盐)的聚集能够加剧非均相反应的发生。锐钛矿的晶体结构及所处大气环境的相对湿度和pH值对其光催化反应有重要影响。

Discovery of Anatase in Atmospheric Inhalable Particles and Its Significance

Laser Raman microprobe (LRM) is a reliable technique for phase identification to analyze the molecular composition and microstructure on 1 μm2 area of samples, and therefore, it is well-suited for identifying the mineral phases of single fine particles. In the present paper, we utilized LRM to identify the mineral phases of the single inhalable particles (PM10) from samples in Beijing City and compared the Raman microscopic spectra of samples with the standard spectra of mineral and inorganic material of Renishaw’s database. Then we confirmed, for the first time, that the mineral phase of Ti-rich particles in the environmental atmosphere is the anatase TiO2, whose Raman spectrum has a strong O—Ti—O band at 638 cm-1 and two medium O—Ti—O bands at 398 and 517 cm-1 respectively. Thus it ensures the existence of TiO2 particles in PM10. Anatase is an important photocatalyst which can speed up the heterogeneous reaction between mineral particles, especially the calcium carbonates, when carried by these particles. Furthermore, the crystal structure of anatase, relative humidity of environment and the surface pH value can significantly influence the photocatalysis of anatase in atmosphere.