Fe doped MoS₂/polypyrrole microtubes towards efficient peroxidase mimicking and colorimetric sensing application

Molybdenum disulfide (MoS₂) nanosheets have been found to exhibit intrinsic peroxidase-like activity that could be applied in colorimetric sensing platforms. However, their poor conductivity and few exposed edge sites often lead to poor catalytic activity, impeding the application of MoS₂ nanosheets in enzyme-like catalysis. Here, a novel strategy was developed to selectively deposit Fe-doped MoS₂ nanosheets on polypyrrole microtubes to obtain Fe-MoS₂@PPy microtubes to address these issues. In the synthesized Fe-MoS₂@PPy microtubes, PPy microtubes can not only be used as a conductive support to promote the electron transfer, but also greatly alleviate the aggregations of MoS₂ nanosheets, and thus improve the enzyme-like activity. Meanwhile, additional active sites, formed by Fe doping, also endow the catalyst with excellent activity in enzyme-like catalysis. Notably, in the process of sulfidation, the dissolution, redistribution and diffusion result in the disappearance of MoO₃@FeOOH cores and the formation of Fe doped MoS₂ nanosheets, which significantly facilitate the deposition of Fe-doped MoS₂ nanosheets on PPy microtubes. On the basis of the high peroxidase-like catalytic efficiency of the Fe-MoS₂@PPy microtubes, a simple and convenient colorimetric strategy for the rapid and sensitive detection of L-cysteine has been developed. This strategy introduces both the PPy layer and Fe doping to increase the conductivity and the density of active sites of MoS₂ nanosheets, thus enhancing the catalytic activity and stability. More importantly, Fe-MoS₂@PPy microtubes could be used as a good support for loading other materials such as Au and Ag nanoparticles (NPs), forming ternary Fe-MoS₂/Ag, Au@PPy nanotubes. This work offers an opportunity to develop low-cost and highly active MoS₂-based nanocomposites for promising potential applications in electrochemical energy conversion and medical diagnostics.