Challenges in the study of chemistry and photochemistry at air–water interfaces: Toward <i>in situ</i> monitoring of reaction kinetics with spectroscopic techniques

Air-water interfaces, including those on droplet surfaces, have been the subject of many recent experiments due to their propensity for unique chemistry. Here, an overview of some recent advancements in understanding interfacial reaction kinetics is provided, highlighting non-surface-specific methods-such as mass spectrometry-compared with the advantages of surface-specific techniques-such as reflection-absorption spectroscopy, sum frequency generation, and photoelectron spectroscopy. This Perspective discusses the information depth and time constraints of common surface-specific spectroscopic methods that need to be addressed to monitor interfacial chemistry in situ and uses a few key examples from the literature as case studies. It concludes by advocating for the continued development of advanced spectroscopic methods to further investigate interfacial chemistry, underscoring the need for interdisciplinary collaboration to bridge the gap between molecular-level insights and macroscopic observations in future research.