Proceedings of the 2025 International Conference on Engineering, Technology and Applied Science Innovations

DOI: http://dx.doi.org/10.15439/2025I14

Citation: Proceedings of the 2025 International Conference on Engineering, Technology and Applied Science Innovations, Gerasimos Pylarinos, Christos P. Antonopoulos, George Syrrokostas, Panteleimon Apostolopoulos, Stratos David (eds). ACSIS, Vol. 46, pages 29–32 (2025)

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Abstract. Iron oxides are promising materials for a wide range of applications including photocatalytic water splitting, energy storage, and heterogeneous catalysis. However, understanding the interaction between iron oxide nanoparticles (Fe₂O₃ nps) and liquid water at the molecular level remains challenging due to the limitations of conventional surface analysis techniques. In this study, we present an in-situ X-ray Photoelectron Spectroscopy (XPS) investigation of Fe₂O₃ nps suspended in aqueous solution using a custom-designed environmental cell (e-cell), sealed with ultrathin silicon nitride (SiN) membranes. The attenuation of Fe 2p photoelectrons through 3--5 nm thick membranes was modeled and experimentally verified, enabling successful detection of chemical states within the aqueous suspension. Depth relevant information revealed a layered structure of the nps, with surface hydroxide species, an Fe₂O₃ core, and an intermediate FeOx phase. Spectra close to the valence band region confirmed the liquid nature of the encapsulated solution via the detection of water molecular orbitals, while ionic Na⁺ signals further demonstrated the method's capability for detecting dissolved species. This approach provides a powerful platform for real-time chemical analysis of solid-liquid interfaces under ambient-like conditions, with broad implications for catalysis, electrochemistry, and environmental science.

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