Improved sensing characteristics of methane over ZnO nano sheets upon implanting defects and foreign atoms substitution

Thanks to the growing interests of metal oxide sensors in environmental and industrial uses, this study presents the sensing mechanism of methane gas (CH₄) on recently synthesized two-dimensional form of ZnO, ZnO nano sheets (ZnO-NS). The adsorption energy of CH₄ on pristine ZnO-NS, calculated by means of van der Waals corrected first-principles calculations, is found to be insufficient restricting its application as an efficient nano sensor. However, the creation of (O/Zn) vacancies and the substitution of foreign dopants into ZnO-NS considerably intensify the binding energy of CH₄. Through a comprehensive energetic analysis, it is observed that among all the substituents, boron (B), sulphur (S) and gallium (Ga) improves the binding of CH₄ to 2.75, 6.1 and 7.5 times respectively than its values on pristine ZnO-NS. In addition to the CH₄ binding energies falling ideally between physisorption and chemisorption range, a prominent variation in the electronic properties before and after CH₄ exposure indicates the promise of substituted Zn-NS as a useful nano sensors.