Optical properties of hBN quantum dots for ammonia gas detection.

Detecting ammonia gas in low concentration with proper selectivity is crucial due to its harmful effects on human health and industry. Even low ammonia concentrations can cause a rapid burning sensation in the eyes, nose, and throat. In addition, it can react with copper, silver, and other heavy metals. Hence, it is essential to detect low concentrations of ammonia gas with proper selectivity. Hexagonal boron nitride quantum dots have introduced new properties and potentials for engineering applications and gas-sensing devices. A small perturbation from gas molecules can drastically alter the band structure of quantum dots. When NH3 is attached to BNQD, under the influence of the Coulomb force created between the gas and the quantum dot, the length of the bonds varies, and then the energy levels change, resulting in the band gap reduction. These changes in sub-bands can be easily detected using the optical absorption spectrum. In the present study, the changes in the optical properties of hexagonal boron nitride quantum dots in the presence of ammonia gas molecules are studied, Using density functional theory. Results show that different ammonia concentrations can alter the maximum optical absorption to higher energies. In addition, a few peaks are observed related to the transitions due to ammonia molecules in the system. The selectivity of the different gas molecules is also investigated. Moreover, the size of quantum dots was increased from 32 to 168 atoms, and it was concluded that by increasing their size, similar properties could be achieved. As a result, the present paper not only provides insight into the optical properties of hexagonal boron nitride quantum dots, but also brings up the novel idea of designing gas sensors based on such structures. [ABSTRACT FROM AUTHOR]