Qian Yuqin, Brown Jesse B, Huang-Fu Zhi-Chao, Zhang Tong, Wang Hui, Wang ShanYi, Dadap Jerry I, Rao Yi
Department of Chemistry and Biochemistry, Utah State University, Logan, UT, 84322, USA.
Department of Chemistry, Fudan University, Shanghai, 200433, China.
Commun Chem. 2022 Apr 29;5(1):58. doi: 10.1038/s42004-022-00674-8.
Understanding the chemical and physical properties of particles is an important scientific, engineering, and medical issue that is crucial to air quality, human health, and environmental chemistry. Of special interest are aerosol particles floating in the air for both indoor virus transmission and outdoor atmospheric chemistry. The growth of bio- and organic-aerosol particles in the air is intimately correlated with chemical structures and their reactions in the gas phase at aerosol particle surfaces and in-particle phases. However, direct measurements of chemical structures at aerosol particle surfaces in the air are lacking. Here we demonstrate in situ surface-specific vibrational sum frequency scattering (VSFS) to directly identify chemical structures of molecules at aerosol particle surfaces. Furthermore, our setup allows us to simultaneously probe hyper-Raman scattering (HRS) spectra in the particle phase. We examined polarized VSFS spectra of propionic acid at aerosol particle surfaces and in particle bulk. More importantly, the surface adsorption free energy of propionic acid onto aerosol particles was found to be less negative than that at the air/water interface. These results challenge the long-standing hypothesis that molecular behaviors at the air/water interface are the same as those at aerosol particle surfaces. Our approach opens a new avenue in revealing surface compositions and chemical aging in the formation of secondary organic aerosols in the atmosphere as well as chemical analysis of indoor and outdoor viral aerosol particles.
了解颗粒的化学和物理性质是一个重要的科学、工程和医学问题，对空气质量、人类健康和环境化学至关重要。特别令人感兴趣的是悬浮在空气中的气溶胶颗粒，它们在室内病毒传播和室外大气化学中都起着重要作用。空气中生物气溶胶颗粒和有机气溶胶颗粒的增长与化学结构及其在气溶胶颗粒表面和颗粒内部气相中的反应密切相关。然而，目前缺乏对空气中气溶胶颗粒表面化学结构的直接测量。在此，我们展示了原位表面特异性振动和频散射（VSFS）技术，以直接识别气溶胶颗粒表面分子的化学结构。此外，我们的装置还允许我们同时探测颗粒内部的超拉曼散射（HRS）光谱。我们研究了丙酸在气溶胶颗粒表面和颗粒内部的偏振VSFS光谱。更重要的是，发现丙酸在气溶胶颗粒上的表面吸附自由能比在空气/水界面处的吸附自由能负性更小。这些结果挑战了长期以来的假设，即空气/水界面处的分子行为与气溶胶颗粒表面的分子行为相同。我们的方法为揭示大气中二次有机气溶胶形成过程中的表面成分和化学老化以及室内外病毒气溶胶颗粒的化学分析开辟了一条新途径。
Zotero 插件
