Octahedral Molybdenum Iodide Clusters Supported on Graphene for Resistive and Optical Gas Sensing

This paper reports for the first time a gas-sensitive nanohybrid based on octahedral molybdenum iodide clusters supported on graphene flakes (Mo-6@Graphene). The possibility of integrating this material into two different transducing schemes for gas sensing is proposed since the nanomaterial changes both its electrical resistivity and optical properties when exposed to gases and at room temperature. Particularly, when implemented in a chemoresistive device, the Mo-6@Graphene hybrid showed an outstanding sensing performance toward NO2, revealing a limit of quantification of about 10 ppb and excellent response repeatability (0.9% of relative error). While the Mo-6@Graphene chemoresistor was almost insensitive to NH3, the use of an optical transduction scheme (changes in photoluminescence) provided an outstanding detection of NH3 even for a low loading of Mo-6. Nevertheless, the photoluminescence was not affected by the presence of NO2. In addition, the hybrid material revealed high stability of its gas sensing properties over time and under ambient moisture. Computational chemistry calculations were performed to better understand these results, and plausible sensing mechanisms were presented accordingly. These results pave the way to develop a new generation of multi-parameter sensors in which electronic and optical interrogation techniques can be implemented simultaneously, advancing toward the realization of highly selective and orthogonal gas sensing.

Automated summary

This paper reports the development of a gas-sensitive nanohybrid based on octahedral molybdenum iodide clusters supported on graphene flakes. It shows that the nanomaterial can be integrated into gas sensing devices due to its ability to change electrical resistivity and optical properties when exposed to gases at room temperature. The results demonstrate excellent sensing performance of the Mo-6@Graphene hybrid for NO2 in a chemoresistive device, and outstanding detection of NH3 using an optical transduction scheme.