Facile Fabrication of Amorphous Molybdenum Oxide as a Sensitive and Stable SERS Substrate under Redox Treatment

Amorphous MoO3-x nanosheets were fabricated by the room-temperature oxidation of molybdenum powder with H2O2, followed by light-irradiation reduction in methanol. When applied as a substrate for surface-enhanced Raman spectroscopy (SERS), these nanosheets exhibit higher sensitivity than the crystalline counterpart for a wide range of analytes. Moreover, the SERS activity remains stable on repeated oxygen insertion/extraction. In contrast, the performance of crystalline MoO3-x continuously deteriorates on successive redox treatments. This unique SERS activity allows the recycling of the substrate through an H2O2-based Fenton-like reaction. More importantly, the non-invasive SERS was unprecedentedly used for the self-diagnosis of amorphous MoO3-x as a more selective photocatalyst than its crystalline counterpart.