The sensing mechanism of pristine and transition metals doped Zn12O12, Sn12O12 and Ni12O12 nanocages towards NH3 and PH3: a DFT study

From the perspective of environmental safety and human health, it is crucial to develop high-performance sensitive materials that can effectively monitor ammonia (NH3) and phosphine (PH3) toxic gases. In this study, we first investigated the adsorption performance of Zn12O12, Sn12O12 and Ni12O12 nanocages towards NH3 and PH3. Based on the analysis of adsorption energy, charge transfer and the nearest intermolecular distance, Zn12O12, Sn12O12 and Ni12O12 nanocages exhibit excellent sensitivity toward NH3 with respect to PH3. Meanwhile, the gas sensing performance of the NH3 adsorption system can be improved by applying a positive electric field. Additionally, a humid environment has a great negative impact on the detection of PH3. Next, the sensing mechanisms of NH3 on Ti, Cr and Fe-doped nanocages were also analyzed. The cohesive energies are obtained to confirm the stability of doped Zn12O12, Sn12O12 and Ni12O12 nanocages. The results show that Zn11TiO12 and Sn11TiO12 exhibit a more desirable adsorption performance with respect to NH3 compared with pure Zn12O12 and Sn12O12, along with larger adsorption energy and significant charge transfer. Therefore, Ti doped Zn12O12 and Sn12O12 can be considered as potential candidates for NH3 detection. This work would be meaningful to reveal a gas sensing mechanism and provide theoretical guidelines for experimentalists to design and synthesis high sensitivity sensors for detecting toxic gases.