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

Amorphous MoO 3− x nanosheets were fabricated by the room‐temperature oxidation of molybdenum powder with H 2 O 2 , 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 MoO 3− x continuously deteriorates on successive redox treatments. This unique SERS activity allows the recycling of the substrate through an H 2 O 2 ‐based Fenton‐like reaction. More importantly, the non‐invasive SERS was unprecedentedly used for the self‐diagnosis of amorphous MoO 3− x as a more selective photocatalyst than its crystalline counterpart.