Effect of Al- And Ga-doping on the adsorption of H₂SiCl₂ onto the outer surface of boron nitride nanotube

Abstract

There is a compelling reason to design cost-effective sensors to detect and measure harmful molecules such as dichlorosilane (H₂SiCl₂) in the air. In this work, density functional theory (DFT) has been used to study the nature of the intermolecular interactions between the H₂SiCl₂ gas molecule with a single-walled pristine, Al-doped, and Ga-doped boron nitride nanotubes (BNNT, BNAlNT, and BNGaNT, respectively) to investigate their potential in gas-sensing applications. Full-dimensional geometry optimization and adsorption energies were calculated with four functionals: PBE0, M06-2X, ωB97XD, and B3LYP-D3 with a 6-311G(d) basis set. We find that the B, Al, or Ga atoms provide the most favorable sites for adsorption of the H₂SiCl₂ molecule. The adsorbate is more tightly bound to the surface of the doped rather than of the pristine BNNT nanotubes, demonstrating a larger energy gain due to adsorption. This is due to the fact that H₂SiCl₂ interacts with pristine BNNT through weak Van der Waals forces but seemingly has stronger ionic interactions with the doped variants. In general, introducing impurities can improve the selectivity and reactivity of the BNNT toward H₂SiCl₂. Among all of the absorbents, we find that BNGaNT exhibits the highest affinity toward H₂SiCl₂, and therefore holds a higher potential compared to the rest of the nanotubes investigated here for designing materials for dichlorosilane sensors.