TY - JOUR
T1 - Imaging of pH distribution inside individual microdroplet by stimulated Raman microscopy
AU - Gong, Kedong
AU - Ao, Jianpeng
AU - Li, Kejian
AU - Liu, Le
AU - Liu, Yangyang
AU - Xu, Guanjun
AU - Wang, Tao
AU - Cheng, Hanyun
AU - Wang, Zimeng
AU - Zhang, Xiuhui
AU - Wei, Haoran
AU - George, Christian
AU - Mellouki, Abdelwahid
AU - Herrmann, Hartmut
AU - Wang, Lin
AU - Chen, Jianmin
AU - Ji, Minbiao
AU - Zhang, Liwu
AU - Francisco, Joseph S.
N1 - Publisher Copyright:
Copyright © 2023 the Author(s). Published by PNAS. This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).
PY - 2023/5/16
Y1 - 2023/5/16
N2 - Aerosol microdroplets as microreactors for many important atmospheric reactions are ubiquitous in the atmosphere. pH largely regulates the chemical processes within them; however, how pH and chemical species spatially distribute within an atmospheric microdroplet is still under intense debate. The challenge is to measure pH distribution within a tiny volume without affecting the chemical species distribution. We demonstrate a method based on stimulated Raman scattering microscopy to visualize the three-dimensional pH distribution inside single microdroplets of varying sizes. We find that the surface of all microdroplets is more acidic, and a monotonic trend of pH decreasing is observed in the 2.9-μm aerosol microdroplet from center to edge, which is well supported by molecular dynamics simulation. However, bigger cloud microdroplet differs from small aerosol for pH distribution. This size-dependent pH distribution in microdroplets can be related to the surface-to-volume ratio. This work presents noncontact measurement and chemical imaging of pH distribution in microdroplets, filling the gap in our understanding of spatial pH in atmospheric aerosol.
AB - Aerosol microdroplets as microreactors for many important atmospheric reactions are ubiquitous in the atmosphere. pH largely regulates the chemical processes within them; however, how pH and chemical species spatially distribute within an atmospheric microdroplet is still under intense debate. The challenge is to measure pH distribution within a tiny volume without affecting the chemical species distribution. We demonstrate a method based on stimulated Raman scattering microscopy to visualize the three-dimensional pH distribution inside single microdroplets of varying sizes. We find that the surface of all microdroplets is more acidic, and a monotonic trend of pH decreasing is observed in the 2.9-μm aerosol microdroplet from center to edge, which is well supported by molecular dynamics simulation. However, bigger cloud microdroplet differs from small aerosol for pH distribution. This size-dependent pH distribution in microdroplets can be related to the surface-to-volume ratio. This work presents noncontact measurement and chemical imaging of pH distribution in microdroplets, filling the gap in our understanding of spatial pH in atmospheric aerosol.
UR - http://www.scopus.com/inward/record.url?scp=85158159310&partnerID=8YFLogxK
U2 - 10.1073/pnas.2219588120
DO - 10.1073/pnas.2219588120
M3 - Article
C2 - 37155894
AN - SCOPUS:85158159310
SN - 0027-8424
VL - 120
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 20
M1 - e2219588120
ER -