Constructing the MoC@MoO Heterostructure for Improved SERS Application.

Surface-enhanced Raman scattering (SERS) is a non-destructive spectra analysis technique. It has the virtues of high detectivity and sensitivity, and has been extensively studied for low-trace molecule detection. Presently, a non-noble-metal-based SERS substrate with excellent enhancement capabilities and environmental stability is available for performing advanced biomolecule detection. Herein, a type of molybdenum carbide/molybdenum oxide (MoC@MoO) heterostructure is constructed, and attractive SERS performance is achieved through the promotion of the charge transfer. Experimentally, MoC was first prepared by calcinating the ammonium molybdate tetrahydrate and gelatin mixture in an argon atmosphere. Then, the obtained MoC was further annealed in the air to obtain the MoC@MoO heterostructure. The SERS performance was evaluated by using a 532 nm laser as an excitation source and a rhodamine 6G (R6G) molecule as the Raman reporter. This process demonstrates that attractive SERS performance with a Raman enhancement factor (EF) of 1.445 × 10 (R6G@10 M) and a limit of detection of 10 M can be achieved. Furthermore, the mechanism of SERS performance improvement with the MoC@MoO is also investigated. HRTEM detection and XPS spectra reveal that part of the MoC is oxidized into MoO during the air-annealing process, and generates metal-semiconductor mixing energy bands in the heterojunction. Under the Raman laser irradiation, considerable hole-electron pairs are generated in the heterojunction, and then the hot electrons move towards MoO and subsequently transfer to the molecules, which ultimately boosts the Raman signal intensity.