Sensitive detection of As(III) on Fe3O4/MoS2 through interfacial engineering to accelerate the Fe2+/Fe3+ cycle: Identifying the dominant role of electron transfer induced by valence change in synergistic electroanalysis

Fe-based metal oxide nanomaterials have attracted significant attention as the electroanalytical sensing for heavy metal ions (HMIs) detection. It is recently found that their activities should be mainly ascribed to their valance change behavior (i.e. the Fe2+/Fe3+ cycle). However, how to promote the Fe2+/Fe3+ cycle to further increase their detection performance is highly desired yet challenging. Herein, the nanocomposite of Fe3O4/MoS2 is developed as a sensing for the electrochemical detection of the highly toxic As(III). Through a series of characterizations including the XPS and DFT, the Fe3O4/MoS2 shows an accelerated electron transfer induced by the valence change of Fe2+/Fe3+ cycle. The active Mo4+ on MoS2 can serve as electron doner to reduce the Fe3+ to Fe2+ on Fe3O4, and thus promotes the Fe2+/Fe3+ cycle. Moreover, the synergistic effect between the excellent adsorption ability of Fe3O4 towards As(III) and the good conductivity of MoS2 will further benefit to the detection. As expected, the Fe3O4/MoS2 reflects an outstanding detection performance to As(III) with a sensitivity of 4.16 mu A center dot ppb-1, which even much outperforms than that of noble-metal materials. Overall, these discoveries are expected to drive great advances in the application of the accelerated valence change behavior for electroanalysis.