The sensing mechanism of pristine and transition metals doped Zn₁₂O₁₂, Sn₁₂O₁₂and Ni₁₂O₁₂nanocages towards NH₃and 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, Sn₁₂O₁₂and Ni₁₂O₁₂nanocages towards NH₃and PH₃. Based on the analysis of adsorption energy, charge transfer and the nearest intermolecular distance, Zn₁₂O₁₂, Sn₁₂O₁₂and Ni₁₂O₁₂nanocages exhibit excellent sensitivity toward NH₃with respect to PH₃. Meanwhile, the gas sensing performance of the NH₃adsorption 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 NH₃on Ti, Cr and Fe-doped nanocages were also analyzed. The cohesive energies are obtained to confirm the stability of doped Zn₁₂O₁₂, Sn₁₂O₁₂and Ni₁₂O₁₂nanocages. The results show that Zn₁₁TiO₁₂and Sn₁₁TiO₁₂exhibit a more desirable adsorption performance with respect to NH₃compared with pure Zn₁₂O₁₂and Sn₁₂O₁₂, along with larger adsorption energy and significant charge transfer. Therefore, Ti doped Zn₁₂O₁₂and Sn₁₂O₁₂can be considered as potential candidates for NH₃detection. 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.