Enabling photoemission electron microscopy in liquids via graphene-capped microchannel arrays
Hongxuan Guo, Evgheni Strelcov, Alexander Yulaev, Jian Wang, Narayana Appathurai, Stephen Urquhart, John T. Vinson, Subin Sahu, Michael P. Zwolak, Andrei A. Kolmakov
Photoelectron emission microscopy (PEEM) is a powerful tool to spectroscopically access dynamic surface processes at the nanoscale but is traditionally limited to ultra-high or moderate vacuum conditions. Here, we develop a novel graphene-capped multichannel array platform that extends the capabilities of photoelectron spectro-microscopy, allowing for routine liquid and atmospheric pressure studies with standard PEEM setups. At the water-graphene interface, the XAS spectra at the oxygen K edge reveals that graphene has only a minor influence on the electronic structure of water in the first few layers, an ideal scenario for examining unperturbed aqueous-phase dynamics at the interface. Similar to microarray screening in biomedical research, our platform is suitable for application in tandem with large-scale data mining, pattern recognition, and combinatorial methods for spectro-temporal and spatiotemporal analyses at solid-liquid interfaces. Using these algorithms, we characterize the behavior of radiolysis products in water and observe a metastable wetting water layer during the late stages of bubble formation.