In-situ synthesized gold nanoparticles modified Mo2C MXene for surface enhanced Raman scattering

Herein, we demonstrate a proof-of-concept of using Mo2C MXene and gold nanoparticles (NPs) hybrid as an efficient surface-enhanced Raman scattering (SERS) substrate for organic pollutants detection. Mo2C MXene/Au hybrid is synthesized by an in-situ reduction of Au3+ ions onto Mo2C MXene nanosheets and characterized for its optical and structural properties. For the hybrid structures, we first synthesized Mo2C MXene by hydrofluoric acid etching of Mo2Ga2C and subsequent delamination with dimethyl sulfoxide to obtain few-layered nanosheets. The concentration of HAuCl4 for in-situ formation of Au was optimized with UV–Vis spectroscopy and probed with high resolution transmission electron microscopy. X-ray diffraction confirms the presence of Au NPs and MXene, while scanning and transmission electron microscopy analyses reveal the loading of Au NPs with an average size of ~ 9 nm on MXene few-layer particles. Based on our X-ray photoelectron spectroscopy results, we proposed a synthesis mechanism in which the functional groups of Mo2C MXene take an active part in reducing the gold precursor to form gold NPs. The optimized Mo2C/Au hybrid was then coated onto silicon and studied as a potential SERS substrate utilizing methylene blue as a model dye. Further, the comparison of the studies with rhodamine 6G confirms and justifies the role of the Mo2C/Au hybrid in signal enhancement. The preliminary findings demonstrate an enhancement factor of 2.2 × 104 and a detection limit of 0.01 μM (10–8 M) for optimal Au loading for MB. The fabricated SERS substrate is stable for nearly 1 month and exhibits excellent signal reproducibility with ~ 88% retention of the signal. These findings can be further extended to other MXenes to obtain in-situ synthesized hybrid for SERS as well as other applications including sensors, photocatalysis, and electrocatalysis.